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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Latest Posts


Rob Painting

Rob is an environmentalist, scuba diver, spearfisherman, kayaker and former police officer. Has researched climate science, in an amateur capacity, for 4 years. A long-time reader of Skeptical Science and now contributor.


Recent blog posts

Ocean Heat Comes Back to Haunt Coral Reefs

Posted on 9 June 2016 by Rob Painting

As I predicted in August last year, the powerful El Niño of 2015-2016, in tandem with global warming, has seen a worldwide coral bleaching event unfold across the tropics. On Australia's Great Barrier Reef the bleaching is easily the worst on record with 93% of reefs experiencing bleaching ranging from minor to severe. However we won't know the full extent of  this global event until the end of the year, or perhaps 2017, when the bleaching is expected to have ended. Reports throughout the Pacific and Indian Ocean, however, hint that it could be the worst global bleaching event on record too, with a high rate of mortality likely. 

My prediction was rather stating the obvious as the oceans are warming and research in the last few decades has established that reef-building corals are near a high temperature tolerance threshold. Summer, combined with El Niño, is when sea surface temperatures in the tropics of each hemisphere tend to peak. As explained in my previous post, this has to do with year-to-year fluctuations in the rate at which the subtropical cell in the ocean transports heat poleward (meridionally) out of the tropics. The relaxation of the westward blowing trade winds, which accompanies El Niño, also allows heat buried in the subsurface ocean of the western tropical Pacific to surface and become entrained in the ocean's surface circulation. Accordingly, the climate model-based projections at NOAA's Coral Reef Watch were warning of thermal stress on the Great Barrier Reef, and elsewhere, as early as November 2015.

Figure 1 - Projected coral reef thermal stress (60% probability) for the period Dec 2015 to March 2016. Image from NOAA's Coral Reef Watch.

Although it only extends up to December 2014, and therefore excludes the 2015-2016 El Niño, the quality-controlled data provided by the Argo system of autonomous floats is able to provide a clearer picture of how this ENSO fluctuation affects the surface layers in the latitudes where almost all coral reefs reside - 30°N to 30°S. See Figure 2. 



Industrial-era ocean heat uptake has doubled since 1997

Posted on 4 February 2016 by Rob Painting

The oceans are by far the largest heat reservoir in the Earth's climate system, so much so that they make up a whopping 93% of global warming. Thus global warming is really the story of ocean warming. In many blog posts in recent years (see, here, here and here for example) Skeptical Science has consistently drawn attention to the fact that the oceans are continuing to accumulate heat and therefore, despite short-term fluctuations in both surface and atmospheric temperatures, global warming is proceeding largely as anticipated by the scientific community. 

A recent paper, Gleckler et al [2016], manages to put the recent warming of the ocean into a broader, longer-term, perspective. Using ocean temperature measurements obtained from various sources and methods, and utilizing data from the pioneering HMS Challenger expeditions of the late 19th century (Roemmich et al [2012]), the researchers were able to compare the observations stretching back to the mid-1800's with climate model simulations. They found the model simulations were consistent with this diverse collection of ocean temperature data. Perhaps the most startling result of this analysis is just how much the oceans have warmed in recent decades, with the recent acceleration so pronounced that the rate of ocean heat uptake in the industrial-era has doubled since 1997.

Figure 1 - The CMIP5 multi-model mean ocean heat content change from 1865 to 2015 expressed as a percentage for 3 ocean depth layers. The gray bars indicate the 1-standard deviation uncertainty and the black triangles along the bottom denote simulated large volcanic eruptions (which disperse light-scattering sulfate particles). Gray triangles show the many unsimulated small & moderate volcanic eruptions after 2000. Image from Gleckler et al (2016).

Adding greenhouse gases to the atmosphere makes the ocean warmer 

How additional greenhouse gases in the atmosphere cause the ocean to grow warmer is not generally well-known, so it's useful to provide some background context for this new research paper. In a similar vein to the warming of the atmosphere, the warming of the oceans occurs in response to the slowing of heat loss. It works like this: highly energetic solar (shortwave) radiation enters the surface layers and warms the ocean. The overlying air is typically cooler than the sea surface, so some ocean heat is lost to the atmosphere and any surplus is eventually radiated away to space high up in the atmosphere. The amount of heat in the ocean is therefore a balance between solar radiation entering the ocean and the energy which leaves it - mainly through evaporation. The oceans can warm through an increase in solar output (the sun has actually cooled in recent decades, thereby eliminating that as a potential cause) or by reducing the rate of heat loss to the atmosphere. This is where additional atmospheric greenhouse gases come in.



Why were the ancient oceans favorable to marine life when atmospheric carbon dioxide was higher than today?

Posted on 12 November 2015 by Rob Painting

When we look back through the geological record, we see that for much of the last 500 million years there was an abundance of life in the oceans and that atmospheric carbon dioxide was much higher than today for the vast majority of that time. Though it may seem counterintuitive, especially considering that ocean pH was lower than present-day, the ancient oceans were generally more hospitable to marine calcification (building shells or skeletons of calcium carbonate) than they are now [Arvidson et al (2013)].

Numerous examples exist to support this, such as the enormous coccolith deposits that make up the White Cliffs of Dover in England. These tiny coccolith shells are made of calcium carbonate (chalk) and date from the Cretaceous Period (Cretaceous is Latin for chalk) about 145 to 65 million years ago - when atmospheric CO2 concentration was several times that of today. So conducive to marine calcification was the Cretaceous ocean that it also saw the emergence of giant shellfish called rudists as a major reef-builder.


Figure 1 - Rudist fossils dating from the Cretaceous Period. Marine calcification during this time of higher-than-present atmospheric CO2 concentrations was very clearly not a problem for this marine organism. Image from Schumann & Steuber (1997).

Given the relationship between the concentration of carbon dioxide in the atmosphere and the pH of the ocean, why are scientists concerned about falling ocean pH when it was lower for much of the last 500 million years?  The simple answer is that these were not times of ocean acidification per se, and the key difference is in understanding the time scales and chemical processes involved. Ocean acidification only occurs when atmospheric carbon dioxide increases in a geologically-rapid manner because pH and carbonate ion abundance decline in tandem, and it’s the decrease in carbonate ions that makes seawater corrosive to calcium carbonate forms [Kump et al (2009)] . While the increase in dissolved CO2 and hydrogen ion concentration (falling pH) would have proven stressful for some ancient marine life, such as coral [Cohen & Holcomb (2009), Cyronak et al (2015)], the corrosive state of surface waters likely delivered the decisive blow. 

A perfect illustration of the marked difference between high and low carbonate saturation states is shown in Figure 2. Both marine fossils (discoaster) are from ancient periods of high atmospheric CO2 (i.e. low pH), however the fossil on the left pre-dates the Paleocene-Eocene Thermal Maximum (PETM) some 55-56 million years ago. Carbonate ions were abundant prior to the PETM, however a geologically-rapid pulse of CO2 entered the atmosphere during the PETM, and thus lowered the abundance of carbonate ions. The fossil on the right dates from the PETM and shows clear signs of dissolution, indicating that the oceans back then were corrosive to marine calcifiers, as we'd expect, because ocean acidification was underway (Penman et al (2014).



2015: Still No Let Up in Ocean Warming

Posted on 7 October 2015 by Rob Painting

Ocean warming has made up 93% of global warming in the last 5 decades (IPCC AR5 Chapter 3) and the first six months of ocean heat data for 2015 are now available from the National Centers for Environmental Information (NCEI). Armed with the knowledge that increasing industrial greenhouse gas emissions trap ever more heat in the atmosphere and ocean, it will come as no surprise whatsoever to learn that the strong ocean heating of recent years has continued into 2015. 

Figure 1 - Ocean heat content data up to June 2015 for the 0-2000 meter layer of the global ocean. Image from NOAA's National Center for Environmental Information.   

In contrast to the Northern Hemisphere, the surface area of the Southern Hemisphere is dominated by the ocean and it's therefore the end of Southern Hemisphere summer, when that hemisphere is closest to the sun, that ocean heat uptake is strongest. Loeb et al (2012), however, demonstrated that outgoing longwave radiation (heat loss) from the Earth increases during El Niño, so it will be interesting to see how things pan out over the next 6-8 months given that we have a powerful El Niño still developing in the Pacific Ocean. We may see a temporary reduction in the rate of ocean warming as the El Niño discharges a greater-than-normal amount of tropical ocean heat to the atmosphere. Inevitably, much of this surplus heat will be radiated out to space.  



A Powerful El Niño in 2015 Threatens a Massive Coral Reef Die-off

Posted on 13 August 2015 by Rob Painting

Key Points:
  • A powerful El Niño event continues to strengthen in the Pacific Ocean. During El Niño the poleward transport of warm surface water out of the tropics slows down dramatically and generally results in anomalous short-term heating of the tropical ocean - home to the world's coral reefs).
  • Because of the long-term warming of the oceans by industrial emission of greenhouse gases, the temporary surge in tropical sea surface temperatures associated with El Niño now threatens large-scale coral bleaching episodes - times when the maximum summer water temperatures become so warm that coral die in large numbers.
  • The powerful El Niño now forming, combined with the ongoing ocean warming, suggests that we are likely to see a mass coral bleaching episode that approaches, or exceeds, the large-scale bleaching that came with the Super El Niño years of 1982/1983 and 1997/1998. The 1997/1998 Super El Niño saw 16% of the world's coral bleach, the largest die-off ever observed, and some of this coral has never recovered.


Figure 1 - Coral bleaching outlook for August-November 2015 based on climate model forecasts. The figure is a from an new experimental product at NOAA's Coral Reef Watch.

Some Don't Like it Hot

The great irony of ocean warming and coral is that, until the late 20th century, it was actually beneficial to coral growth rates. Now, however, warming of the tropical ocean has progressed to a point where natural fluctuations of water temperature over summer months can now exceed an upper thermal tolerance threshold and which can often result in the death of coral reef communities. This is commonly known as mass coral bleaching, and takes place when coral have been subjected to water temperatures 1-3 degrees celsius above the normal summer maximum for several weeks or more.

Figure 2 - an example of coral bleaching. The loss of coloured pigments produced by the symbiotic algae makes the white coral skeleton visible beneath the coral polyp's translucent skin tissue.  Image from NOAA's Coral Reef watch.

Coral reefs consist of colonies of individual coral polyps which build their skeletons together so that they form massive structures capable of providing habitat for hundreds of thousands of marine species. Symbiosis is the term which describes the mutually beneficial relationship between the coral polyp and photosynthetic algae that live within its skin tissue. Through photosynthesis the algae provide food, in the form of sugars, to the polyp and also boost its immune system. In return the polyps provide safe lodgings for the algae. When this relationship breaks down, as it can do for a number of reasons but especially so when water temperature becomes too warm, the coral polyps expel the algae. Because the algae produce the pigments which give coral its colour, the loss of the algae results in the white coral skeleton becoming visible through the polyps transparent skin tissue - it appears to have been bleached.

Given sufficient time, most reefs can re-colonize areas that have been killed through bleaching, although some areas in the Galapagos Islands have never done so. But the issue with a warming ocean is that, eventually, the frequency and severity of bleaching will become so intense that coral reefs never recover (Hooidonk et al [2013]).



A Southern Hemisphere Booster of Super El Niño

Posted on 30 June 2015 by Rob Painting

Key Points:
  • Hong et al (2014) looked at global observations and model simulations to find out what sets a super El Niño apart. They discovered that a prerequisite condition was a circulation in the Southern Hemisphere, associated with a persistent high pressure system situated over Southern Australia and a low pressure system in the South Pacific, that fed surface winds back to the equator and therefore boosted anomalous westerly winds along the equator between the critical June to November development stage.

Figure 1 - Anomalous sea level pressure (colours) and surface winds (black arrows) for June-November for the 3 Super El Niño identified in the observational record. The strong equatorward wind flow around the edge of the Australian high pressure system feeds into and augments the anomalous westerly wind flowing along the equator - boosting super El Niño development. These large-scale features are absent from standard El Niño events. Image adapted from Hong et al (2014)

El Niño on my mind

The largest year-to-year variation in global weather results from the El Niño-Southern Oscillation (ENSO). At one extreme we have La Niña, a time when the normal easterly trade winds in the tropics intensify, and at the other extreme we have El Niño, a time when the trade winds weaken or even reverse. These winds are important because their persistence effects change, albeit temporary in this case, in the large-scale circulation of the ocean and atmosphere.

The near-permanent nature of the easterly tropical trade winds are largely a consequence of the strong warming of the ocean at the equator and Earth's rapid rate of rotation. Intense solar heating of the Pacific ocean drives strong evaporative uplift and cooler air near the surface moves into replace the vertically displaced warm air. As it does so, the incoming air is 'steered' toward the west by the Coriolis force (to its right in the Northern Hemisphere, and toward its left in the Southern Hemisphere). This really isn't a force in the strictest sense, but a useful mathematical construct to understand motion in a rotational frame of reference. In reality, due to its rotation, the Earth beneath is moving at a different speed to the loosely gravitationally-bound air above it.  



Hotspot Found Again: Warming of the Tropical Troposphere Confirms Climate Model Prediction

Posted on 20 May 2015 by Rob Painting

Key Points:
  • As the Earth warms, the lower atmosphere (troposphere) in the tropics is expected to warm at a faster rate than at the surface. The development of this so-called 'hotspot' is an expectation based on principles of atmospheric physics and is therefore also predicted by climate model simulations.
  • This hotspot in the tropical troposphere is not specific to the increased greenhouse effect resulting from industrial carbon dioxide emissions. It would, for example, also be expected in a hypothetical scenario where warming was due to increased solar output.
  • Despite obvious warming of the atmosphere, it had been difficult to confirm the existence of this hotspot primarily due to analytical deficiencies in accounting for temperature data quality and sampling, i.e. it's suspected to have been a 'measurement problem'.
  • Sherwood & Nishant (2015) is the latest scientific paper published in recent years to resolve this issue. By employing an improved analysis method to remove inherent biases in the data, these researchers have once again confirmed the existence of the tropical tropospheric hotspot. 

Figure 1 - Temperature of the atmosphere, by latitude and atmospheric pressure, from 1959-2012. Units are in degrees C per decade. Lower pressure corresponds to greater height in the atmosphere. Note the 'hotspot' above the equator centred about 300 hPa (about 9 km from the surface). The blue region at the top is the cooling stratosphere - confirmation of another prediction of the increased greenhouse effect. Image from Sherwood & Nishant (2015). 

Why should there be a 'hotspot' in the atmosphere above the tropics?  

Because most of Earth's incoming energy from the sun is received in the tropics, strong evaporation there removes a lot of heat from the ocean surface. This heat is hidden (latent) as it is used to convert water from a liquid to a gaseous form. Readers are probably familiar with this process as it is the same one in which we are cooled when sweat evaporates off our bodies during strenuous exercise. Our skin cools as heat is used up in the act of evaporating away the sweat.   

Strong evaporative uplift occurs near the equator due to the intense solar heating of the ocean there, and this forces the evaporated water (water vapour) to ascend up through the atmosphere. Because the temperature in the atmosphere decreases with increasing height (known as the lapse rate), this has the effect of cooling water vapor until it reaches a point where it condenses back into a liquid form (forming clouds and rainfall) - liberating the hidden (latent) heat into the upper atmosphere. With the great bulk of atmospheric moisture being concentrated in the tropics, this ongoing process should lead to greater warming in the tropical troposphere than at the surface.

Mark Richardson has a nice video animation of this process at about the 3 minute mark in his University of Queensland Massive Open Online Course (MOOC) Denial 101 lecture on the structure of the atmosphere.



Sea Level Rise is Spiking Sharply

Posted on 31 March 2015 by Rob Painting

Global sea level is rising because of warming from the industrial greenhouse gas emissions we humans keep pumping into the atmosphere. The expansion of seawater as it warms, and the addition of meltwater from disintegrating land-based ice, enforce a relentless rise in sea level. Despite this ongoing rise, there are significant year-to-year fluctuations due to variations in the volume of water equivalent stored (predominantly) in the tropical land basins, and as snowfall on the gigantic ice sheets of Antarctica and Greenland.

Figure 1 - Global sea level rise from 1993-2015 as measured by satellite altimetry. The surge in sea level rise at the end of 2014 is likely to be temporary, but may signal the drying out of the major continental basins in the tropics. Image from AVISO.  

As explained in the SkS sea level in 2010 rebuttal, El Niño is a time when anomalous warming occurs on the surface of the eastern tropical Pacific Ocean. This happens in response to weaker-than-normal trade winds which blow westward near the equator. Because the Coriolis Force, which typically deflects objects in motion at an angle to their path of travel, is negligible near the equator, warm water is dragged along in the same direction as the wind and piles up in the tropical western Pacific Ocean.

Figure 2 - Upwelling at the equator. The trade winds result in a net flow of water away from the equator due to the Coriolis Force. At the equator subsurface water is drawn up to the surface to replace it. The shallow thermocline (a result of water displacement to the west in the thin equatorial strip where the Coriolis Force drops to zero) in the east enables nutrient rich cold water from the deep to be drawn up to the surface, whereas in the west the deep thermocline results in recirculation within the layer above the thermocline. Image by jg.



Corrosive Seawater, Not Low pH, Implicated As Cause of Oyster Deaths

Posted on 12 January 2015 by Rob Painting

Key Points:
  • Because of the geologically-rapid emission of carbon dioxide into the atmosphere by human industrial activities, and the subsequent dissolution of this CO2 into the global oceans, ocean pH and carbonate saturation state are currently declining in tandem - a process known as ocean acidification.
  • Over geological timescales, however, ocean pH and carbonate saturation (corrosiveness) tend to become disassociated. This explains why the ancient oceans were highly saturated with carbonates and therefore conducive to calcification (calcium carbonate shell formation) at times of high CO2 in Earth's past even though ocean pH was lower than it is today. 
  • Waldbusser et al (2014) conducted a series of experiments with oyster and mussel juvenile life stages (larvae) which enable them to distinguish between the individual responses to carbonate saturation and ocean pH, something not done in typical ocean acidification laboratory experiments
  • The authors surprisingly found that, except at extremely low concentrations, ocean pH by itself had little impact on larvae growth. As expected though, low carbonate saturation was very detrimental to larvae growth and thus survival. This work implicates carbonate undersaturation as the key mechanism responsible for the large-scale die-off of oyster larvae along the North American Pacific coastline over the last decade.

Figure 1 - Images of the ancient fossil calcifier Discoaster before (left) and during (right) the Paleocene-Eocene Thermal Maximum (PETM) about 56 million years ago. Both creatures lived at times when the atmospheric concentration of CO2 was much higher than present-day and ocean pH was lower, but the fossil in the right-hand image lived when carbonate ion abundance (and carbonate saturation) was also low. This was due to a rapid increase in atmospheric CO2, which caused seawater to become corrosive to calcium carbonate forms. Image courtesy of Professor Patrizia Ziveri.



Record-Breaking Sea Surface Temperatures in 2014: Has the Climate Shifted?

Posted on 22 December 2014 by Rob Painting

The record for the warmest monthly global sea surface temperature (SST) has been broken three times this year and the five warmest months of sea surface temperature ever recorded have all taken place in 2014. Although the year is not yet over, 2014 looks set to break the annual SST record too. This record warming of the ocean surface has, not surprisingly, had a big impact on global surface temperatures as well with 2014 currently on track to beat 2010 as the warmest year recorded in several data sets.


Figure 1. Monthly global sea surface temperature (SST) anomaly (ERSST v3b) from 1990-October 2014. June through to October 2014 has seen the 5 warmest months of SST ever recorded. Image based on data from NOAA's National Climatic Data Center.



Mercury Rising: 2014 Likely to Surpass 2010 as Warmest Year on Record

Posted on 27 November 2014 by Rob Painting

The monthly global analysis for October has been released at NOAA's National Climatic Data Center (NCDC) and it reveals that global surface temperature for October 2014 is the warmest October in 135 years of record-keeping. This follows on from the 2nd warmest April, and the warmest May, June, August, and September, ever recorded. In fact the first 10 months of 2014, January to October, are the warmest such period ever recorded, and 2014 is very likely to end up as the warmest year - taking over the title from the previous record year in 2010. Other surface temperature data sets, such as NASA GISTEMP and the Japan Meteorological Agency, also have 2014 on pace to break the annual record.


Figure 1 - Global surface temperature anomalies for January-October from 1880-2014. As indicated, 2014 is now the warmest January-October period on record - beating out 1998 and 2010 (tied) by 0.02°C. Image from NOAA NCDC.

With two complete months of data yet to come, it may appear premature in declaring 2014 a likely record-breaker, but 2014 is different to the evolution in surface temperature during 2010 - the previous record holder. Record warm years are typically associated with the development of El Niño events, whereas in 2014 El Niño is yet to even put in an appearance. 



Ocean Warming has been Greatly Underestimated

Posted on 14 October 2014 by Rob Painting

Key Points:
  • The oceans are by far the largest heat reservoir on Earth, absorbing 93% of global warming. Because of this, accurate assessments of heat uptake are essential to balance the sea level budget, and for observationally-based estimates of climate sensitivity.     
  • Prior to 2005, when the Argo global array of submersible floats became operational, ocean temperature was much more sparsely sampled, especially in the southern hemisphere, leading to larger uncertainty over the evolution of ocean warming through time.
  • Durack et al (2014) analyse the period from 1970-2004 combining ocean temperature and sea surface height measurements with climate model simulations, and find that sparse sampling in the southern hemisphere oceans, and limitations of previous analytical methods, has led to a substantial underestimate of warming in the 0-700 metre layer*.
  • When corrected for this bias, Durack (2014) find that the top 700 metre layer of ocean, over the period 1970-2004, has warmed some 24-58% more than previous analyses have indicated. 

Figure 1 - Observed (coloured bars) and modelled (grey bars) upper ocean heat content changes for the period 1970-2004 from previous analyses. Top coloured segments are the adjustments based on the Durack (2014) study. Units are x1022 joules 35 yr-1 and MMM = multi model mean. Image adapted from Durack et al (2014). 

The Oceans Have Warmed, But How Much?

The Argo system of automated floats was constructed in order to provide more reliable and robust measurements of ocean temperature, and other quantities such as salinity and current velocity. Although they only measure down to typical depths of 2000 metres, and still exclude regions such as the Arctic and Indonesian Throughflow, the 3000+ floats represent a major step up in accuracy over older methods.

Figure 2 - typical Argo cycle.



Rising Ocean Temperature: Is the Pacific Ocean Calling the Shots?

Posted on 5 September 2014 by Rob Painting

Key Points:
  • Even though the ocean has warmed strongly, global 'surface' warming in the 21st century has been slower than previous decades. One of the prime suspects for this has been an increase in trade winds which help to mix heat into the subsurface ocean - part of a natural oscillation known as the Interdecadal Pacific Oscillation (IPO).
  • A recently published research paper, Chen & Tung (2014), claim that changes in the saltiness (salinity) of seawater in the North Atlantic is responsible for the decadal-scale variation in ocean heat uptake, rather than the IPO, as increased saltiness makes surface water denser and therefore facilitates the sinking of water transported poleward.
  • Chen & Tung's  own analysis, however, shows that North Atlantic Ocean warming peaked in 2006 and has declined since that time whereas deep ocean warming, as a whole, has not. 
  • This new research affirms earlier work (Meehl et [2011] & Meehl et al [2013]) implicating the increased, albeit likely temporary, mixing of heat down into deeper ocean layers as a key contributor to the slower rate of surface warming in the 21st century.


Figure 1 - Ocean heating rates for the global ocean and individual ocean basins down to 1500 metres. The coloured lines represent the various ocean layers. Notably the observations show greater warming in the deeper layers, with the strongest deep ocean warming occurring in the Atlantic & Southern Ocean. Image from Chen & Tung (2014)

Ocean Warming: Background Context

The oceans are currently warming because of the extra greenhouse gases that human industrial activity has added to the atmosphere. Not only do greenhouse gases trap heat in the atmosphere, but they alter the gradient in the cool-skin layer of the ocean, which results in less heat escaping the ocean and thus warming over time.

Despite this increasing greenhouse gas-induced warming of the oceans, the ocean doesn't warm in a linear manner due to a number of factors, one of these being a natural decadal-scale variation in the way heat is mixed into the oceans by winds - the Interdecadal Pacific Oscillation (IPO). The IPO is, essentially, an oscillation in the strength of winds (primarily the tropical Trade Winds) which promote the mixing of heat down into the ocean interior and thus affect sea surface temperatures.

The main mechanism for wind-driven mixing into the deep ocean (down to around 2000 metres) is via convergence of warm tropical surface water in the subtropical ocean gyres. These subtropical ocean gyres are large rotating masses of surface water which occupy the mid-latitudes of each ocean basin. Surface water is transported to the subtropical gyres because of the winds drag on the sea surface. Rather than travelling in the same direction as the trade winds, the net flow of water in the surface layers affected by the wind are 90 degrees to the direction of travel - to the right in the Northern Hemisphere, and to the left in the Southern Hemisphere. This occurs because the Earth is rapidly rotating beneath the surface currents and results in an 'apparent deflection'. The impact this has is very real however.

Figure 2 - annual wind stress (i.e. the average wind) for the global oceans between 1982-2004. The lime green splotches near the equator in each hemisphere depict the trade winds, and the areas from about 35° poleward show dominant mid-latitudes westerlies. From the location and direction of these dominant winds we get convergence of ocean currents at around 30-40° in each hemisphere. Image from NOAA GODAS. 

As the warm tropical surface waters travel poleward they encounter an equatorward flowing current created by the mid-latitude westerlies and this surface convergence causes the centre of the gyre to pile up water mass. With nowhere else to go, the surface convergence forms a vertical current known as Ekman pumping (Ekman [1905]) which transports heat down to the depths. In order to maintain a balance, there is a return flow of water, at depth, back toward the equator and poles. Note that there is also poleward transport in the shallow currents at the western edge of each subtropical ocean gyre - known as western boundary currents.     

Figure 3 - A strengthening of the gyre circulation between 2004-2008 is indicated by the gain in steric height for the 500 decibar pressure level (near 500m) relative to 2000 decibar (near 2000m). Image adapted from Roemmich & Gilson (2009).       

The Atlantic Ocean: A Driver, or a Passenger?

Chen and Tung (2014) analyse the ocean heat content data maintained by a Japanese research group, Ishii et al (2005), and make a number of statements about the cause of multi-decadal fluctuations in ocean heat mixing rates. Chief among these claims is that the change in salinity in the North Atlantic ocean is responsible for the decadal fluctuations, not changes in the trade winds and mid-latitude westerlies (the IPO) - as suggested by Meehl et al (2011), Meehl et al (2013) and England et al (2014) for instance. One of the rationales given by Chen & Tung for dismissing the role of the IPO in deep ocean warming is the expectation that the Pacific Ocean basin should have warmed more during the current (2000-to present) IPO negative phase. In a press release Tung states:



A Relentless Rise in Global Sea Level

Posted on 5 August 2014 by Rob Painting

Key Points
  • One of several confounding influences on global sea-level rise is natural multi-year, and decadal-scale, variation in water mass exchange between the oceans and land. This is due to weather patterns which affect the amount of rainfall and snow falling over the oceans and land surfaces. Weather-related variations in precipitation alter the volume of water in the ocean, but they are only temporary.
  • Global sea level continues to rise, but in the last decade the rate of this rise has been slower than that of the previous decade.This slowdown has occurred despite an increase in the amount of heat entering the ocean, and a growing contribution of glacial meltwater from disintegrating land-based ice - creating an apparent paradox.
  • A recent study, Cazenave et al (2014), reveals that sea level over the last two decades has in fact risen at an almost constant rate, but that this has been obscured by the temporary effect of smaller-than-average continental water mass storage from 1994-2002, and greater-than-average continental water mass storage from 2003-2011.


Figure 1 - 1993-2014 global sea-level rise from the AVISO data set (top) with 1994-2002 shaded blue and 2003-2011 shaded red. The lower figure (from Cazenave [2014]) shows a) the measured sea level trends of the five satellite altimetry data sets and their mean for the two periods, and b) the 'actual' sea level trend once corrected for weather-related ocean mass change (and thermal expansion fluctuations). The right-hand bars in b) demonstrate a near-constant rate of 'actual' sea-level rise over the two decades.

Some Background Context: Sea-Level Since the 19th Century

After the start of the Industrial Revolution, and due to the geologically-rapid increase in planet-warming gases such as carbon dioxide that accompanied it, global sea level began to rise. This most probably wasn't the case before the onset of human industrial activity, as a wealth of scientific evidence suggests the ocean volume was (effectively) static for 4-5000 years before this.

The reason for the rise in sea level since the 19th century is rather obvious - increased concentrations of greenhouse gases trap heat in the atmosphere and ocean. Seawater expands as it grows warmer, and extra water volume is being added to the oceans through the global-scale disintegration of land-based ice from warming. Not so obvious, however, is the fact that there is a large year-to-year variation in sea level due to fluctuations in the storage of water on land - be it as water or in the form of snow or ice.

Wrinkles in Sea-Level Rise

These annual fluctuations in continental water storage are largely driven by the El Niño-Southern Oscillation, as this coupled ocean-atmosphere phenomenon determines whether the bulk of precipitation falls over land or ocean. This topic is dealt with in more detail in the SkS Sea Level Fell in 2010 rebuttal, but briefly; during La Niña periods anomalous precipitation typically falls over land, and during El Niño it falls over the ocean.  



El Niño in 2014: Still On the Way?

Posted on 9 July 2014 by Rob Painting

Key Points:

  • Development of El Niño in 2014 continues to edge closer with sea surface temperatures (SST) in the key indicator equatorial regions approaching El Niño thresholds.
  • The discharge of ocean heat to the atmosphere associated with the build-up of the El Niño phenomenon has predictably seen a rise in global surface temperatures, resulting in May 2014 being the warmest May ever recorded.
  • Despite the strong initial build-up of a large warm water volume anomaly (WWV) in the equatorial subsurface ocean earlier in the year, the atmosphere has so far not provided sufficient reinforcement to maintain this large pool of warmer-than-average water and a substantial portion has been eroded.
  • The last half-century of observations, however, still favour the development of an extreme El Niño event, but the substantial reduction of the warm water volume anomaly (thankfully) diminishes the odds of a powerful event rivaling that of 1997-1998 from taking hold.

Figure 1 - global sea surface temperature (SST) anomalies (departures from the long-term average) as at 26th June 2014. Strong equatorial SST warming off the coast of South America (shown in red rectangle) is a tell-tale signature of El Nino conditions beginning to form. Image from NOAA Coral Reef Watch.  

El Niño on the Wane?.......

The intensity of El Niño is determined by a number of factors but, as discussed in the previous 2014 El Niño post, the size of the equatorial warm water volume (WWV) anomaly is a crucial ingredient because the heat from this warm water volume is discharged to the atmosphere as El Niño matures.

Earlier this year we saw the largest March WWV anomaly ever recorded. This warm anomaly exceeded even that of the monster El Niño of 1997-1998, raising fears of a similarly devastating El Niño in 2014. Fortunately, the chances of a repeat of 1997-1998 appear to have greatly diminished. The atmosphere needs to provide reinforcement in order for El Niño to fully take hold,  and although there have been brief episodes of westerly wind bursts, which allow near-surface warm ocean currents to flow back toward the east and shut off the upwelling of cold water there, these have not been of sufficient strength, or persistence, to shut off the upwelling entirely. As a result, the anomalous pool of warm water sitting beneath the eastern Pacific Ocean has been eaten away (moved out of the equatorial region)  and is now substantially smaller than before - see Figure 2.

Figure 2 - Global ocean temperature anomaly for the period 29th March-17th June 2014 (the Pacific Ocean is in the centre frame). Note that these are anomalies, not absolute temperatures, so the warmest water is still at the surface. The decline in the equatorial WWV anomaly is obvious as time progresses. Image adapted from CPC GODAS. 



Mercury Rising: 2014 Sees Warmest May Ever Recorded Following on From 2nd Warmest April

Posted on 1 July 2014 by Rob Painting

Increasing greenhouse gases in the atmosphere, from human industrial activity, are trapping ever more heat in the atmosphere and ocean. This is causing the Earth to warm regardless of a downturn in solar radiation over the last 3-4 decades. Despite this long-term warming of the background climate state, especially the warming of the ocean, global surface temperatures exhibit fluctuations from year-to-year because the Earth's weather is never the same in each year.

Figure 1 - global surface temperature anomalies for the month of May since 1880. 2014 is, globally, the warmest May in 135 years of observation. Image from NOAA NCDC.



97% - A Statistically Representative Debate On Global Warming

Posted on 13 May 2014 by Rob Painting

In a hilarious and insightful comedy skit on HBO's show, Last Week Tonight, John Oliver cuts straight to the heart of the scientific consensus on global warming and features the Skeptical Science research paper on this subject - see below. Oh, and be warned, make sure you're not drinking anything hot before clicking on the video.   

A research paper by the Skeptical Science team - Cook et al (2013) - Quantifying the consensus on anthropogenic global warming in the scientific literature - was an assessment of the level of consensus on the matter of human-caused global warming in the peer-reviewed scientific literature. Based on the abstracts (a short summary at the beginning of a research paper) of almost 12,000 papers, what we found was that, of those that expressed a view as to the cause, 97.1% of the scientific literature indicated that human activity was largely responsible for global warming. We also invited the authors of the papers we assessed (expressing a view as to cause) to rate their own papers (not abstracts) and based on those ratings it was determined that 97.2% of the author's papers attributed global warming to human activity.



Is a Powerful El Niño Brewing in the Pacific Ocean?

Posted on 23 April 2014 by Rob Painting

Key Points:
  • El Niño puts in an appearance every two to seven years, and involves the abrupt discharge of heat from the tropical ocean to the atmosphere - often resulting in years with warmer-than-average global surface temperatures.
  • Every now and then a very large event occurs, such as the one in 1997-1998 which broke surface temperature records at the time and caused worldwide disruption and damage.
  • The current large build-up and eastward movement of heat in the equatorial subsurface ocean strongly hints at a powerful El Niño developing this year.
  • A powerful El Niño is by no means guaranteed, but should one develop mid-2014 to mid-2015 would likely be the hottest 12 months ever recorded. Unfortunately widespread weather-related chaos and mass coral bleaching is almost certain to follow.

Figure 1 - Ocean temperature vs depth anomalies for the equatorial Pacific in 2014. Image from NOAA CPC.



Climate Models Show Remarkable Agreement with Recent Surface Warming

Posted on 28 March 2014 by Rob Painting

Key points:
  • Despite warming over the last 16 years, global surface temperatures have warmed at a slower rate than the previous 16 years and, at first glance, it appears that the climate models may have overestimated the amount of surface warming over this period.
  • Climate models, however, cannot predict the timing and intensity of La Niña and El Niño, natural cycles that greatly affect global temperature in the short-term by dictating the amount of heat available at the ocean surface.
  • Nor can the climate models predict the timing and duration of volcanic eruptions and industrial pollution, both of which eject light-scattering aerosols into the atmosphere and therefore reduce surface warming.
  • By failing to account for these and other factors, the CMIP5 collection of climate models erroneously simulate more warming of Earth's surface than would be expected.
  • When the input into the climate models is adjusted to take into consideration both the warming and cooling influences on the climate that actually occurred, the models demonstrate remarkable agreement with the observed surface warming in the last 16 years.

Figure 1 - The animation shows the CMIP5 model simulations compared to the HADCRUT4 surface temperature dataset. As allowances are made for better global coverage of temperature observations, El Niño/La Niña, solar radiation, and volcanic aerosols, the simulated surface temperature moves back toward the actual measured temperature over this period. Animation by Kevin C.



The Oceans Warmed up Sharply in 2013: We're Going to Need a Bigger Graph

Posted on 31 January 2014 by Rob Painting

Because the oceans cover some 71% of the Earth's surface and are capable of retaining heat around a thousand times that of the atmosphere, the oceans are where most of the energy from global warming is going - 93.4% over recent decades. So greenhouse gases emitted by human industrial activity not only cause more heat to become trapped in the atmosphere, they also cause more of the sun's energy to accumulate in the oceans.

Long-term the oceans have been gaining heat at a rate equivalent to about 2 Hiroshima bombs per second, although this has increased over the last 16 or so years to around 4 per second. In 2013 ocean warming rapidly escalated, rising to a rate in excess of 12 Hiroshima bombs per second - over three times the recent trend. This doesn't necessarily mean we are entering a period of greatly accelerated ocean warming, as there is substantial year-to-year variation in heat uptake by the oceans. It does, however, once again dispel the persistent myth of a pause in global warming, because the Earth has actually continued to warm faster in the last 16 years than it did in the preceding 16 years.

As can be seen in Figure 1 below, the global oceans have warmed so quickly in 2013 that the National Oceanographic Data Center (NODC) is going to need a bigger graph.         


Figure 1 - Ocean Heat Content data  for the 0-2000 metre layer (based on Levitus [2012]) for the period 1957-2013. The orange band highlights the interval falsely labelled as a 'pause' in global warming. Further ocean warming will necessitate the vertical axis being extended. Image adapted from the National Oceanographic Data Center (NODC).



Corrections to Curry's Erroneous Comments on Ocean Heating

Posted on 30 January 2014 by dana1981

Committed to the Cause Pause

Recently, Georgia Tech climate scientist Judith Curry, along with Texas A&M climate scientist Andrew Dessler, testified before a US Senate committee on the subject of climate change.  While Dessler's testimony was excellent and well-supported by the body of scientific evidence, Curry's contained a number of errors (i.e. see the Guardian on global warming attribution, Eli Rabett on Antarctic sea ice, and Tamino on Arctic warming and sea level rise, for starters).

Curry's main and most flawed argument was that information in the latest IPCC report should decrease our confidence in human-caused global warming; an argument she based in large part on the supposed global warming 'pause', which is itself a fictional creation.  While the warming of average global surface temperatures has slowed (though not nearly as much as previously believed), the overall amount of heat accumulated by the global climate has not, with over 90 percent being absorbed by the oceans.

A few days after her Senate testimony, Curry took to her blog to dispute these data, essentially arguing that the amount of heat absorbed by the oceans has also 'paused', which would then support her arguments.  However, in evaluating the ocean heat content data and scientific literature, Curry made a number of mistakes.  This gives us an excellent opportunity to properly evaluate the science on rising ocean heat content and see what it tells us.  The key points are:

  • The deep oceans are warming rapidly in every data set that measures them (including those referenced by Curry).
  • Sea levels are rising consistent with rapid ocean warming.
  • The rate of ocean warming is consistent with the global energy imbalance.
  • The geographic distribution of ocean warming is consistent with natural variability superimposed on a warming background state forced by the increased greenhouse effect.
  • The global warming 'pause' is a fictional product of wishful thinking.



Warming oceans consistent with rising sea level & global energy imbalance

Posted on 29 January 2014 by dana1981

Key Points:
  • The ocean is quickly accumulating heat and is doing so at an increased rate at depth during the so-called “hiatus” – a period over the last 16 years during which average global surface temperatures have risen at a slower rate than previous years.
  • This continued accumulation of heat is apparent in ocean temperature observations, as well as reanalysis and modeling experiments, and is now supported by up-to-date assessments of Earth's energy imbalance. 
  • Another key piece of evidence is rising global sea level. The expansion of the oceans (as they warm) has contributed to 35–40% of sea level rise over the last two decades - providing independent corroboration of the increase in ocean temperatures.

The Deep Ocean Layers are Quickly Accumulating Heat

Recently there have been some widespread misconceptions about heat accumulation in the oceans, particularly in the deeper layers below 700 meters.  Balmaseda et al. (2013) was a key study on this subject, using ocean heat content data from the European Centre for Medium-Range Weather Forecasts' Ocean Reanalysis System 4 (ORAS4).  A reanalysis is a climate or weather model simulation of the past that incorporates data from historical observations.  In the case of ORAS4, this includes ocean temperature measurements from bathythermographs and the Argo buoys, and other types of data like sea surface height and surface temperatures.  Their study concluded that heat has increased in the deep oceans at an unprecedented rate in recent years, with approximately 30 percent being sequestered below 700 meters since the year 2000.




2013 was Australia's Hottest Year, Warm for Much of the World

Posted on 10 January 2014 by Rob Painting

The following article was written by scientists from the Australian Bureau of Meteorology and originally appeared at The Conversation.

By Blair Trewin, Australian Bureau of Meteorology; David Jones, Australian Bureau of Meteorology; Karl Braganza, Australian Bureau of Meteorology; Neil Plummer, Australian Bureau of Meteorology, and Rob Smalley, Australian Bureau of Meteorology

The Bureau of Meteorology has confirmed 2013 as Australia’s hottest year since records began in 1910.

Average temperatures over the continent have been 1.2C above the 1961-1990 average, breaking the previous record set in 2005 by 0.17C. It was also the hottest year on record for South Australia, Western Australia and the Northern Territory. The other states - Queensland, New South Wales, Victoria and Tasmania – recorded above-average temperatures that rank in their top four hottest years.

Off to a hot start, and no El Niño

The year got off to an exceptionally hot start with a heatwave that spanned most of the continent during the first three weeks of January. Numerous locations experienced their highest temperatures on record during this period, including Hobart (41.8C on January 4) and Sydney (45.8C on January 18).

Moomba’s 49.6C on January 12 was the highest recorded temperature anywhere in Australia since 1998 and the highest in South Australia since 1960.

Nationally, January 7 was Australia’s hottest day on record. January was the hottest month on record and the summer of 2012-13 was the nation’s hottest summer.



New Study Suggests Future Global Warming at the Higher End of Estimates: 4°C Possible by 2100

Posted on 8 January 2014 by Rob Painting

In everyday terms, climate sensitivity refers to the amount of warming of global surface temperatures with a doubling of atmospheric carbon dioxide - a potent planet-warming greenhouse gas emitted by human industrial activity. In practice, establishing Earth's actual climate sensitivity has proven very problematic. A large part of this likely stems from the emerging realisation that climate sensitivity is not a fixed value, but varies with the background state of the planet (Armour [2012], Meraner [2013]).

The recent (2013) AR5 Intergovernmental Panel on Climate Change (IPCC) Report published a summary of peer-reviewed research on climate sensitivity and found that the likely values (greater than 66% probability) ranged from 1.5°C-4.5°C (for a doubling of atmospheric CO2). This range was lower than the previous (AR4) IPCC assessment because it included climate model/observationally-based research which implied a lower climate sensitivity (see Otto [2013] for example).

However, a research paper just published, Sherwood (2014), suggests that climate sensitivity of relevance today is in excess of 3°C - near the upper range of estimates from the latest IPCC report. Climate models exhibit a large range of climate sensitivities and the main reason for this is down to the way that each model handles cloud feedback. In brief: an increase in cloud cover in response to global warming would act as a negative (counteracting) feedback - reflecting more sunlight back out to space and thereby cooling the Earth, whereas a decline in cloud cover would act as a positive (reinforcing) feedback - as more sunlight reaches the Earth's surface and this leads to greater warming.



Climate Change: Years of Living Dangerously

Posted on 5 December 2013 by Rob Painting

James Cameron, the creator and director of many smash hit movies, has teamed up with producer Jerry Weintraub to make a television series on climate change for the Showtime television channel. The series, according to the promotional trailer below, seems to focus of the human story of climate change - how climate has already begun to impact the lives of people all around the world.

In the trailer, James Cameron says:

"Everybody thinks this is about melting glaciers and polar bears. I think it's a big mistake. This is one hundred per cent a people story"

I believe he's right. Even though Skeptical Science's core message is about the observational evidence underpinning the science of climate change, facts alone are unlikely to be enough to turn public opinion around. People remember human stories better than facts and figures, so examining the impacts of climate change on people around the world may leave a longer-lasting impression on viewers.

Indeed, if there's one thing that is guaranteed to shift public opinion into combating climate change, it's the warm, clammy, hand of reality intruding upon your own personal life. Whether that's in the form of more frequent and extreme heat waves, more extreme downpours, more intense drought and bushfires, or rising sea levels amplifying current flood risk many times over. Whatever form it takes, climate change is going to, at some point, intrude upon all our lives in a very detrimental way.

Sure, SkS regulars may take issue with the 99% analogy used by James Cameron, rather than the 97% which frequently appears in the scientific literature, including our study, Cook et al (2013). And with the claim by Weintraub that hurricanes are twice as bad as they ever were (they're not). Aside from these slight flaws it is encouraging to see one of the greatest filmakers of our time turn his talents toward communicating the urgency of combating climate change. 



Global Warming Paws Fails to Materialise: Earth Still Warming and Global Sea Level Rising Like Gangbusters

Posted on 19 November 2013 by Rob Painting

Human industrial activity burns fossil fuels which then release planet-warming greenhouse gases into the atmosphere thereby causing the Earth to warm. Most of this "extra" heat goes into the ocean (some 93.4% over the last few decades) and the rest goes into heating the land, global ice, and atmosphere (2.3%)

All these Earthly heat reservoirs are warming, resulting in the global-scale loss of land-based ice from mountain glaciers and the polar ice sheets, and the rise of global sea level. Indeed the rate of sea level rise, although complicated by a handful of factors, has risen at a much greater rate over the last two decades (the period of satellite-based observation) than it did during the rest of the 20th century.

Despite these observations clearly indicating ongoing heat accumulation by the Earth's climate system, climate science contrarians and some mainstream media have been hard out propagating the myth that global warming has paused. This, of course, relies on the time-honoured contrarian tradition of cherry picking - one of the five characteristics of scientific denial.

Surface air temperatures have recently warmed at a slightly slower rate partly due a temporary increase in tropical and mid-latitude wind strength which mixes more heat down into the ocean. Contrarians and some media outlets have misconstrued this slower warming of surface air temperatures for a pause in global warming. The ocean is by far the largest heat reservoir on Earth and the stronger ocean warming means, counterintuitively, that global warming has increased at a faster rate in recent times. Unsurprisingly, contrarians and like-minded media studiously avoid mentioning this highly relevant fact. Or if they do, a lot of hand-waving often ensues in an attempt to dismiss the inconvenient truth. 

Josh Willis is an oceanographer at NASA JPL who has published a lot of peer-reviewed scientific research on the current warming, and rise, of the global oceans. In the NASA: Ask a Climate Scientist video below he gives his uniquely humorous take on the frequently asked question on whether there has been a pause in global warming. Like Josh says, when the world is still warming and global sea level is rising "like gangbusters", pawses are strictly for kitty cats and puppy dogs.



The Sun Has Cooled, So Why Are The Deep Oceans Warming?

Posted on 28 October 2013 by Rob Painting

Key Points:

  • In keeping with scientific expectations, the ongoing emission of greenhouse gases from human industrial activity is causing the Earth to build up heat - a process known as the increased (enhanced) greenhouse effect.
  • Though this is not widely-known, the increased greenhouse effect traps more of the sun's energy in the ocean, causing the upper ocean to grow warmer over time.
  • Despite a much smaller increase in warming of the global atmosphere since the year 2000, the ocean, and the deep ocean in particular, has warmed rapidly.
  • The following series of posts will explain the fundamentals of the wind-driven ocean circulation, including a natural multidecadal oscillation in the circulation that, when it intensifies, is responsible for removing heat from the surface ocean and mixing it into deeper layers below.
  • The combination of the greenhouse gas-forced warming of the surface ocean, and the intensified (but temporary) vertical mixing of heat into the deeper layers, is consistent with the deep ocean warming which has been measured.

Figure 1 - Spin-up of the South Pacific subtropical ocean gyre centered near New Zealand between 1995-2004. As the wind-driven ocean circulation intensifies surface water is pushed toward the centre of the gyre where it piles up and raises the local sea surface height (anomalies shown are in cm). With the gyre spinning faster, and nowhere else to go, the water is pumped down into the ocean interior by a process known as Ekman pumping, and thereby warms the deep ocean. Animation created from images in Roemmich (2007).



Ocean Acidification: Eating Away at Life in the Southern Ocean

Posted on 7 August 2013 by Rob Painting

Key Points:

  • Ocean acidification is occurring as a result of carbon dioxide emissions from industrial activity dissolving into the oceans, and involves a fundamental change in the chemistry of the global oceans.
  • Perhaps the greatest challenge it presents to marine life that make their shells of calcium carbonate (chalk) is that it can make seawater so corrosive that their shells/skeletons begin to dissolve.
  • Bednarsek (2012) examined the shells of pteropods (sea butterflies) captured live from waters around Antarctica and found that, in low pH seawater, the shells of the creatures exhibited marked corrosion.
  • The presence of such highly corrosive water near the surface around Antarctica is a window into the future. Ocean acidification there will grow worse in time given current CO2 emission trends, and will pose a significant threat to the Antarctic marine ecosystem because the pteropod is a keystone species of the local food web.     

Fig 1 - animation of microscope images (with outermost organic layer removed) taken of juvenile pteropod shells retrieved from waters around Antarctica in 2008. In line with theoretical expectations, pteropods taken from areas of low carbonate ion abundance (aragonite undersaturation) exhibit obvious signs of corrosion. 100 micrometres (µm) = 0.1 millimetres). Images taken from Bednarsek (2012).   



A Looming Climate Shift: Will Ocean Heat Come Back to Haunt us?

Posted on 24 June 2013 by Rob Painting

Key Points:
  • Despite a large increase in heat being absorbed by the Earth's climate system (oceans, land & ice), the first decade of the 21st century saw a slowdown in the rate of global surface warming (surface air temperatures).
  • A climate model-based study, Meehl (2011), predicted that this was largely due to anomalous heat removed from the surface ocean and instead transported down into the deep ocean. This anomalous deep ocean warming was later confirmed by observations.
  • This deep ocean warming in the model occurred during negative phases of the Interdecadal Pacific Oscillation (IPO), an index of the mean state of the north and south Pacific Ocean, and was most likely in response to intensification of the wind-driven ocean circulation.
  • Meehl (2013) is an update to their previous work, and the authors show that accelerated warming decades are associated with the positive phase of the IPO. This is a result of a weaker wind-driven ocean circulation, when a large decrease in heat transported to the deep ocean allows the surface ocean to warm quickly, and this in turn raises global surface temperatures.
  • This modelling work, combined with current understanding of the wind-driven ocean circulation, implies that global surface temperaures will rise   quickly when the IPO switches from the current negative phase to a positive phase.      


Figure 1 - average sea surface temperature trends from the climate model simulations for a) 'hiatus' decades, i.e. decades with no warming of global mean surface temperatures, and b) 'accelerated' decades, i.e. decades with greater-than-average rises in global surface temperatures. The subtropical ocean gyres (green ellipses) are key players in the downward transport of heat. The stippling  indicates areas where this trend is statistically significant. From Meehl (2013).

Even with Global Dimming, Still Lots of Warming Down Below

The way that global warming has progressed in the 21st century has probably been a great surprise to many people, no doubt a few climate scientists among them. Despite a strong increase in planet-warming greenhouse gas emissions, warming of global surface temperatures has been rather muted. Surface temperatures have warmed, but at a slower rate than the last two decades of the 20th century.

Of course, the 2000's doesn't strictly qualify as a hiatus decade as defined in Meehl (2013) - where hiatus decades are described as negative global surface temperature trends - but it is, nevertheless, a suitable analogue.



Global Warming is Accelerating, but it's Still Groundhog Day at the Daily Mail

Posted on 17 April 2013 by Rob Painting

Key Points
  • Global warming has accelerated, however most of this warming (over 93%) has gone into the ocean - the Earth's largest heat reservoir. An important development has been the uprecedented warming of the deep ocean in recent years.
  • Most of the remaining global heat reservoirs also exhibit the same accelerated warming, and this accelerated warming is consistent with the observed acceleration in planet-warming greenhouse gas emissions from fossil fuel burning in the last two decades (Raupach [2007]).
  • The rate of surface air temperature warming during the last decade has been small however, and is slower than the previous decade. But this is consistent with at least one climate model which predicts this behaviour when anomalous heat is being deposited into the deep ocean during periods dominated by La Niña (Meehl [2011]).
  • If this is demonstrated to be the case with other climate models then we would expect the rate of surface warming to be at the lower end, or perhaps even drop below the 5-95% range, of climate model projections, even while the Earth is strongly warming.
  • Non-expert opinion in the mainstream media, such as the Daily Mail, often demonstrates a poor understanding of climate science, and conveniently omit the relevant points raised above. 

Figure 1 - A visual depiction of how much global warming heat is going into the various components of the climate system for the period 1993 to 2003, calculated from IPCC AR4 versus where skeptics/contrarians seem to think it's going. Note the graphic totals 99.9%, so 0.1% is unaccounted for.



Earth Encounters Giant Speed Bump on the Road to Higher Sea Level

Posted on 29 March 2013 by Rob Painting

The Earth is warming which is driving the ongoing thermal expansion of sea water and the melt of land-based ice. Both processes are raising sea level, but superimposed upon this long-term sea level rise are what scientists at  NASA JPL (Jet Propulsion Lab) have coined, "potholes and speed bumps on the road to higher seas". (See their follow-up paper - The 2011 La Niña: So strong, the oceans fell, Boening [2012]). 

Since mid-2011 a giant "speed bump" has been encountered. In roughly the last two years the global oceans have risen approximately 20 millimetres (mm), or  10 mm per year. This is over three times the rate of sea level rise during the time of satellite-based observations (currently 3.18 mm per year), from 1993 to the present.  

Figure 1 - mean sea level (in centimetres) since 1993 obtained by satellite altimetry observations. Annual and semi-annual signals have been removed to reveal the long-term trend. The glacial isostatic adjustment (GIA) of 0.3mm per year is added to account for the slumping of ocean basins. Image from the AVISO website.

So does this mean land-based ice is undergoing a remarkably abrupt period of disintegration? While possible, it's probably not the reason for the giant speed bump.



Carbon Dioxide the Dominant Control on Global Temperature and Sea Level Over the Last 40 Million Years

Posted on 5 March 2013 by Rob Painting

Key Points:

  • Because the water contained in land-based ice sheets is ultimately derived from the ocean, over long (geological) timescales global sea level is largely determined by global temperature and, consequently, the temperature-dependent volume of ice stored on land.
  • Since the concentration of carbon dioxide in the atmosphere (The Greenhouse Effect) exerts such a powerful influence on global and polar temperature, it therefore follows that it should also exhibit a strong relationship with global sea level over geologic intervals of time.
  • Foster & Rohling (2013) examined time slices of paleo data covering the last 40 million years to uncover the details of this carbon dioxide-sea level relationship. Surprisingly, they found a consistent and robust relationship between carbon dioxide and sea level irrespective of other contributing factors.
  • Based on the concentration of carbon dioxide in the atmosphere as of 2011, the authors estimated that future sea level is committed to rise  24 metres (+7/-15 m) above present-day once the land-based ice sheets have fully responded to the warming and the Earth is once more in equilibrium. 
  • The authors estimated that this sea level rise will likely take place over many centuries, if not several thousand years, but it nevertheless represents the long-term consequences of human industrial activity, and is  further evidence that CO2 is the Earth's "main control knob" for global temperature. 

Figure 1(a) - Relationship between atmospheric CO2 (in parts per million) and global sea level (in metres) over the duration of the ice core record. The dashed horizontal line depicts the pre-industrial state for comparison (b) Shows the cross-plot of CO2 versus sea level rise over this period. CO2/Co on the horizontal axis is the CO2 ratio relative to the pre-industrial where 0.0 respresents the pre-industrial, with negative values (below) and postive values (above) relative to pre-industrial. From Foster & Rohling (2013) 

Background Context: Greenhouse Gases and Planetary Warming

Carbon dioxide is the most significant of the greenhouses gases, gases that trap heat in Earth's atmosphere and reduce the rate of heat loss to space in the upper layers of the atmosphere. As a result the temperature of the planet's surface and ocean is largely dependent upon the concentration of greenhouse gases in the atmosphere. Generally-speaking; increase the concentration of greenhouse gases and the planet traps more heat, reduce them and the planet cools. Because of this behaviour, renowned glaciologist, Richard Alley, has dubbed carbon dioxide Earth's biggest temperature control knob



Australia's Great Barrier Reef: Last Chance to See?

Posted on 29 January 2013 by Rob Painting

Key Points

  • Coral cover was estimated at 28% in 1985 and it has now fallen to 13.8%. 
  • Two-thirds of of this decline has occurred in the period from 1998 onwards.
  • The three principal causes of this coral dieback over the 27-year period are; increased storm damage from cyclones (48%), population outbreaks of coral-eating Crown-of-Thorns starfish (42%), and mass coral bleaching brought about by marine heat waves (10%).
  • On current trajectory living coral cover on the Great Barrier Reef is likely to plunge to 5-10% within the next decade.

Figure 1 - Trends in coral cover, and annual mortality due to Crown-of-Thorns starfish (orange bars), cyclones (olive green), and mass coral bleaching (dark green) for the whole Great Barrier Reef (A&E), northern (B&F), central (C&G) and southern (D&H) GBR regions. From De'ath (2012).

Last Chance to See?

Last Chance to See, was the title of a 1989 BBC radio documentary series and subsequent book. The series featured reknowned author, Douglas Adams, and zoologist Mark Carwadine - both staunch and passionate environmentalists. The 2nd iteration of the series featured Carwadine and the ever-brilliant actor/writer, Stephen Fry. The plot of the series and book involves travelling to extinction hotspots to bring public attention to species on the brink of extinction.



Ocean Heat Came Back to Haunt Australia

Posted on 15 January 2013 by Rob Painting

Over the last 50 years an enormous amount of energy, equivalent to two Hiroshima bombs per second, has gone into heating the global oceans. Because of their much greater mass, the oceans have a thermal capacity roughly one thousand times greater than the atmosphere. This means that despite this huge increase in accumulated energy, the change in upper ocean temperature is small compared to that of global surface air temperatures.

Upper ocean heat buried beneath the surface layers doesn't necessarily remain in the ocean though. For instance, the largest year-to-year fluctuation in global temperature generally occurs in response to the Pacific Ocean phenomenon called the El Niño-Southern Oscillation (ENSO). Variation in ocean circulation and surface winds typically expose warmer-than-average sea surface water to the atmosphere during El Niño, and cooler-than-average sea surface water during La Niña episodes (check out this brilliant animation to understand the fundamental process). The resultant ocean-to-atmosphere heat exchange has a major influence on global surface temperature in any given year, and this works to obscure the long-term surface global warming trend when viewed at short intervals

Due to the huge difference in heat capacities between the ocean and atmosphere, what may in fact be a small amount of ocean heat transforms into a major bout of atmospheric warming when this heat is transferred from the ocean to atmosphere. A poignant example is the record-breaking heat wave which has recently enveloped all of Australia.

A heat wave requires a number of 'weather fluctuation stars to align', so-to-speak, but the role of the ocean in this heat wave is demonstrated in the animation below - where a pulse of oceanic heat rapidly accumulates in the surface Indian Ocean around Western Australia and propagates eastward.

Figure 1 - Global sea surface temperature anomalies (departures from the average) for the period 17th December 2012 to 10th January 2013. The maps are from the US-based National Oceanic and Atmospheric Administration (NOAA). The temperature bar is in °C and the anomalies are relative to the long-term average at each location for that time of year.



Observed Warming of the Ocean and Atmosphere is Incompatible with Natural Variation

Posted on 9 January 2013 by Rob Painting

Key points:

  • Sedláček & Knutti (2012) uses a simple analysis of the patterns of combined ocean and atmosphere warming in climate model simulations to ascertain whether recent global warming is consistent with natural variability, or with external forcing (i.e unrelated to internal variability of the climate system).
  • They accomplish this by comparing model simulations of natural variability only, with simulations of the early and late 20th century, which include natural and human contributions to climate. 
  • The authors found that the smoothly progressing pattern of warming, at the ocean surface and with increasing ocean depth, observed in the 20th century simulations is highly consistent with a smoothly increasing and externally-driven forcing.
  • Natural variability, on the other hand, exhibited a much smaller magnitude of warming and was characterized by a very patchy  distribution of temperatures at the surface and at depth. 
  • The smoothly progressing pattern of warming in the model simulations is similar to historical measurements of sea surface temperatures and  ocean heat content observations.
  • These simulations and historical observations are incompatible with natural variability as a possible cause of ocean warming.  

Figure 1 - Sea surface temperature trends scaled with global surface air temperature trends for half the climate models used in the study. First three columns are control (internal variability only) simulations. E20=early 20th century, and L20=late 20th century, simulations. The historical observations from Hadley Centre & Simple Ocean Data Assimilation (SODA) datasets are at the bottom. From Sedláček & Knutti (2012).



Frequently Asked Questions About Ocean Acidification

Posted on 4 January 2013 by Rob Painting

Skeptical Science is rather fortunate to have had three experts on ocean chemistry write an entire series (OA not OK) about ocean acidification (OA). Now the Woods Hole Oceanographic Institute (WHOI) has released a FAQ document, prepared by some of the world's foremost ocean acidification researchers, which answers many of the frequently asked questions about OA.

Figure 1 - A scanning electron microsope image of the pteropod (marine snail) Limacina helicina antarctica showing acute levels of shell dissolution. This species is a cornerstone of the Antarctic marine food web and is at imminent risk due to ocean acidification. Despite possessing a highly corroded shell, the  pictured specimen was alive at point of capture. Image courtesy of the British Antarctic Survey.  

As the above image graphically demonstrates, ocean acidification is not some far-flung future problem, it is a dire threat to many marine organisms that is happening in our oceans right now, and will progressively get worse with continued fossil fuel emissions.



Past 150,000 Years of Sea Level History Suggests High Rates of Future Sea Level Rise

Posted on 7 December 2012 by Rob Painting

Key points
  • An accurately dated, near-continuous, history of sea level variations for the last 150,000 years has been compiled.
  • Comparison with ice core data reveals that major global ice volume loss, as implied by sea level rise,  has followed relatively quickly after polar warming. The Greenland ice sheet responding virtually straight away (0-100 years lag time), and a 400-700 lag for the Antarctic ice sheet.
  • These response times are much faster than was previously commonly suspected, and implies that once sufficient polar warming is underway, future ice sheet collapse may be unavoidable.
  • During all episodes of major global ice loss, sea level rise has reached rates of at least 1.2 metres per century (equivalent to 12 mm per year). This is 4 times the current rate of sea level rise.

Figure 1 - Sea level reconstruction from 150,000 years ago to the present. Relative sea level (RSL) in grey-shaded area, with RSL data in blue crosses. The downward-pointing red arrows indicates peaks in sea level rise exceeding 1.2 metres per century (12mm per year). The break in the record is due to the absence of foraminifera (upon which the reconstruction is based) as a result of excessively salty seawater during the last ice age. Adapted from Grant (2012).    



Global Dimming in the Hottest Decade

Posted on 25 October 2012 by Rob Painting

Key points



Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years

Posted on 11 October 2012 by Rob Painting

Jerry Mitrovica is a Professor of Geophysics at Harvard University in the USA. He is one of a group of scientists who have, in the last few decades, dramatically increased our understanding of sea level rise from the last ice age to present-day. As his lengthy list of peer-reviewed scientific publications will attest, he is one of the world's foremost experts on this topic.

The video below is a Washington DC talk he gave in 2011, which covers an excellent overview of sea level rise since the last ice age. In the lecture he takes contrarian talking points and uses them as teachable moments, demonstrating the following key points:

  • 2mm of sea level rise per year, which is roughly the rate during the 20th Century, was anomalous, and is something the Earth has not seen for about 10,000 years - when it was in the midst of the last ice age deglaciation.
  • The current rate of sea level rise varies from place to place, however this is to be expected due to the location and presence of land-based ice sheets, and gravitational changes brought about by the disintegration of these present-day glaciers and ice sheets.
  • The rate of sea level rise has increased from the 20th century average of 2-2.5mm per year to over 3mm per year during the record of satellite-based observations (1993-present).
  • The future sea level rise projections of the 2007 IPCC report were too low. Current sea level rates are already at the uppermost range of projections, which reinforces this view. 

For any reader interested in sea level change, it is well worth the half-hour investment of time. 




Sea Level Isn't Level: Ocean Siphoning, Levered Continents and the Holocene Sea Level Highstand

Posted on 29 September 2012 by Rob Painting

Continued from: Sea Level Isn't Level: This Elastic Earth

Key Points
  • Melting of the massive land-based ice sheets that formed during the peak of the last ice age (approx 20,000 years ago) is still affecting sea level today.
  • As ice mass drained into the global oceans in the form of glacial meltwater, this exchange of mass created collapsing areas of ocean floor into which the ocean water was slowly siphoned. This deepening of the ocean basins was effectively disguised until such time glacial meltwater was no longer being added to the oceans. The reason for this is that the rate of glacial meltwater-driven global sea level rise was much greater than the rate of ocean basin deepening and therefore obscured this process.
  • Once the natural orbitally-driven warming had ceased, eventually so too did the addition of meltwater to the global oceans.
  • Because the ocean volume was no longer increasing, the siphoning of seawater into the collapsing seafloor regions became the dominant signal, and "relative" sea level (for much of the Earth) actually declined for most of the last 4-5000 years. This "relative" sea level fall exposed the "three metre beaches" which are common throughout the equatorial ocean.
  • With human-caused climate change now underway, the seas are rising and this ocean basin-deepening effect is once again disguised because the rate of current sea level rise is outpacing the rate of ocean basin collapse and siphoning. Satellites that measure global sea level height add 0.3mm per year to their observations to compensate for this.
  • The supposition of warm periods in human history (Roman, Minoan or Medieval) approaching anything like the global warmth of modern-day is contradicted by paleo sea level research.
  • Current sea level rise and globally-synchronous ice melt is anomalous. The Earth has not seen its like for at least 7-8000 years, and probably longer.

The Holocene sea level highstand

When deglaciation ended around 4-5 thousand years ago there was less water in the oceans than today. Now this may at first seem hard to fathom but, for a broad swathe of ocean centered on the equator, sea level height back then was several meters higher than now. The evidence for this sea level highstand is obvious throughout the equatorial oceans in the form of "3 metre beaches" - chemically-dated wave marker notches, sediment, and coral remnants stranded well above current sea level (see Pirazzoli & Montaggioni [1986]Woodroffe & Horton [2004]). Indeed, coral atolls were formed by this sea level highstand - coral growing up to the then higher sea level and later becoming exposed as sea level fell.



Will the Wet Get Wetter and the Dry Drier?

Posted on 30 August 2012 by Rob Painting

"The wet get wetter and the dry drier", or "The rich get richer and the poor poorer",  these are phrases that pop up from time to time when discussion focuses on future rainfall or drought. But what does it actually mean?

The animation below, from the NOAA Geophysical Fluid Dynamics Laboratory, explains the basic scientific premise behind this turn of expression and features a nifty climate model simulation to boot. And yes, this process appears to be well under way.




Sea Level Isn't Level: This Elastic Earth

Posted on 18 August 2012 by Rob Painting

Continued from: North Carolina Lawmakers Turning a Blind Eye to Sea Level Reality? 

Although sea level rise might, at first glance, seem to be a relatively easy subject to grasp, much of the misunderstanding that exists in the blogosphere (and elsewhere) can be put down to the flawed notion that the sea behaves like water in a swimming pool, or bathtub. In reality the Earth's surface (lithosphere) is elastic and deformable which contributes to a complicated picture where  local sea level might be somewhat different than the global sea level trend. In order to make sense of this it's necessary to cover some of the fundamentals of sea level rise - starting with Glacial Isostatic Adjustment (GIA).

What is Glacial Isostatic Adjustment?

The term describes the deformation of Earth's surface from the growth and decay of giant ice sheets over time, or more specifically, from the exchange of mass, in the form of water or ice, between the continents and ocean during the ice age cycles. The planet-wide changes which result  from this loading and unloading are due to the Earth's lithosphere wanting to reach equilibrium (isostasy). 

In the last several million years the Earth's climate has been dominated by the ice age cycles - alternating cold and warm periods driven by small changes in Earth's orbit and tilt as it circles the sun. During the much longer cool periods (glacials) global temperature dropped sufficiently for gigantic ice sheets to grow upon Antarctica and the Northern Hemsiphere land masses. As water was evaporated off the ocean and dumped upon the colder land masses (at, or near the poles) in the form of snow, this in turn lowered global sea level.

Figure 1 - Ice sheet coverage (white) at the last ice age maximum. Image adapted from Peltier & Fairbanks (2006)



An American Heatwave: The United States Glimpses its Hot Future

Posted on 18 July 2012 by Rob Painting

All-time heat records are tumbling like dominoes in the United States this year, and summer in the Northern Hemisphere hasn't even reached the halfway point (at the time of writing). These record-breaking warm temperatures have  stepped up a notch with the United States very recently enduring a widespread, and rather extreme, summer heatwave.

Figure 1 - temperatures over the contiguous United States on 29th June 2012. Image from Capital Climate. Sadly the temperatures are in the archaic Fahrenheit scale, but for comparison the lightest pink areas (105°) = 40.55°C   

That the world will endure more extreme, and more frequent, heatwaves is a rather obvious outcome as the Earth continues to warm from the continued increase in greenhouse gas emissions. The Intergovernmental Panel on Climate Change (IPCC) reported as much in its very first assessment of the peer-reviewed scientific literature back in 1990.

This timely reminder of one of the harmful impacts of global warming has predictably led to climate science contrarians to churn out misinformation in an attempt to put the blame down to natural variability but, as will be explained below, an increase in record-breaking warm extremes is simply a logical consequence of a warming climate, because it raises the odds of weather fluctuations breaking heat records.



North Carolina Lawmakers Turning a Blind Eye to Sea Level Reality?

Posted on 28 June 2012 by Rob Painting

Ruler of England, Sweden, and Norway at one time, the accomplishments of King Canute (985-1035AD) were many and it seemed to some of his followers that he was all-powerful. In order to dispel such a notion, and to demonstrate the limitations of human power and influence, King Canute had his throne set by the sea side and commanded the incoming sea to turn back. When the sea paid him no heed his point was made.

The moral of that tale seems to have eluded lawmakers in North Carolina, USA who recently attempted to make it illegal to consider accelerated rates of sea level rise in future planning assessments. Sadly, as with Canute, the sea won't pay any attention to the North Carolina legislature, whether they are successful in turning a blind eye to reality, or not. Professor John Bruno, being a North Carolina resident, has taken a keen interest in these shennanigans, and lays out much of the background story at his blog SeaMonster here, here, here and here.    

Quite ironically, the East Coast of the United States is one of the regions on Earth that are likely to see much greater-than-average rates of sea level rise throughout the 21st Century and beyond. It just so happens that the US East Coast is sinking (more on this in later posts) as a consequence of the loss of the giant Laurentide Ice Sheet, which once covered the upper North American continent at the height of the last Ice Age (Glacial Maximum).  

For some perspective, current rates of North Carolina sea level rise within the conext of the last 2000 years is shown below. A rapid acceleration of sea level rise at North Carolina in the 20th Century is very hard to miss. 

Figure 1 - Sea level reconstruction by Kemp (2011) using sediment from salt marshes in North Carolina. 



David Evans: All at Sea about Ocean Warming and Sea Level Rise

Posted on 19 May 2012 by Rob Painting

Sea levels around Australia are currently rising at a rate much greater than the global average, which is probably why there appears to be a surge in Australian skeptic activity strenuously resisting the implications of these observations. One of these said skeptics is Dr.David Evans, a self-described carbon cycle modeler.

In a recent video (starting at 6 mins 55 seconds), David Evans makes a number misleading comments on the continued warming of the oceans, and the rising sea level trend. Indeed many of his erroneous claims were also recently propagated by Cliff Ollier, a retired Australian geology professor. As ever, we'll discuss how and why Evans is wrong, but perhaps the most notable feature of his video clip is that David Evans utilizes key chararcteristics of scientific denialism to reach his ill-founded conclusions.

Before that though, a recap of some relevant background is in order. Informed climate blog regulars can skip the next three headings, as it'll be covering topics you're probably familiar with.



Cliff Ollier: Swimming In A Sea of Misinformation

Posted on 17 April 2012 by Rob Painting

One of the benefits, it seems, of being a 'skeptic' scientist is never having to bother with the time-consuming chore of actually researching the subject you're writing about. One might also expect some degree of reason, logic, and coherency from someone with a background in science, but all too often these rather fundamental requirements are sadly lacking when these 'skeptic' scientists comment publicly.

A recent example of this is an op-ed written in The Australian by Cliff Ollier, a retired Australian geology professor, where he makes numerous erroneous claims about sea level rise. It seems Ollier's comments were prompted by the Port Macquarie Hastings Council's recent proposals, an acknowledgement of the threat of future sea level rise to low-lying coastal properties. 

If some of the territory I'm about to cover seems awfully familiar to long-time SkS readers, that's because we've covered the same topics many times before.  But, as always, it's necessary to cover some background to fully appreciate the scientific basis for concern over future sea level rise. 

Acceleration of sea level rise is a historical fact

Figure 1 - acceleration of sea level rise  from the late 19th century to 21st  century. From Church (2008).



Falling Cloud Height In the Last Decade: Is It Just ENSO?

Posted on 30 March 2012 by Rob Painting

In the old fable of the same name, Chicken Licken (aka Chicken Little, aka Henny Penny) has an acorn fall on her head and mistakenly believes the sky is falling. Unable to contain herself, she begins to inform all she comes into contact with that the sky is falling. Depending on which version of the fable you may have read, things don't always end so well for Chicken Licken.

The mainstream media, and 'skeptic' climate scientist Pat Michaels have jointly assumed the role of Chicken Licken and have likewise grossly misinterpreted a recent paper by two Auckland University researchers, Davies and Molloy (2012) , which shows cloud height decreased between 2000-2010. This trend is also seen in other papers, Loeb (2012), Laken (2012)(not yet published) and Erlykin and Wolfendale (2010). The most likely explanation is that these cloud changes are simply a response to the ENSO (La Niña/El Niño) trend over the decade, and may have nothing whatsoever to do with a feedback to global warming. Indeed, Laken (2012) state:

"We observe a net increase in cloud detected by MODIS over the past decade of ~0.58 %, arising from a combination of a reduction in high – middle level cloud (-0.31 %) and an increase in low level cloud (of 0.89%); these long term changes may be largely attributed to ENSO induced cloud variability"

The figure below, from Davies & Molloy (2012), also shows a very strong relationship (correlation) between cloud height and the Southern Oscillation Index (a measurement of ENSO) over the decade. The increase of cloud height over Indonesia/Australia/New Zealand (blue), and decrease over the central and eastern Pacific (red), indicates a substantial La Niña influence over the decade. See Figure 1.

Figure 1 - Correlation of cloud height distribution anomaly with the Southern Oscillation Index (ENSO) over 2000-2010. From Davies & Molloy (2012).



Search For 'Missing Heat' Confirms More Global Warming 'In The Pipeline'

Posted on 19 February 2012 by Rob Painting

Increased concentrations of greenhouse gases, from the burning of fossil fuels, slows the loss of heat from Earth's atmosphere to space. This creates an imbalance between incoming solar energy and outgoing heat. The Earth will continue to warm until the balance is restored. 

Because this planetary heat imbalance is tiny compared to the energy coming in from the sun, and the heat being radiated back out to space, it is too small to be measured directly by satellites. Earlier attempts to quantify this planetary heat imbalance were made in Hansen (2005) and Trenberth (2009) using earlier climate model-based estimates. Hansen (2005) had this planetary imbalance at 0.85 (±0.15) watts per square meter, and Trenberth 0.9 (±0.5) W/m2, in the earlier part of this century.

An apparent mismatch between the modeled estimate and the heat that could be accounted for on Earth, led to well-known climate scientist, Kevin Trenberth to lament that it was a travesty. Trenberth was, of course, referring to the inadequate state of global observations, such as the sparsely sampled deep ocean among other things, but his comment was predictably distorted by misinformers and spawned a fake-skeptic climate myth of its own.

Loeb (2012) takes an updated look at the issue and finds that, using observations rather than modeled estimates, the Earth's energy imbalance is consistent with heat building up with the Earth system. They have this imbalance at 0.5 (±0.43) W/m2, much smaller than previous estimates, but the error margins are huge. Not unexpectedly the authors confirmed that heat is continuing to build up in the sub-surface ocean, which agrees with other recent studies on ocean heat. The persistent energy imbalance measured by this study is essentially future global warming, or "warming in the pipeline". It puts paid to wishful thinking-based claims that global warming has halted.


Figure 1 - typical dive cycle of the ARGO submersible float system - the most detailed set of ocean heat observations yet obtained. Image from UK Met Office.



Global Sea Level Rise: Pothole To Speed Bump?

Posted on 7 February 2012 by Rob Painting

As indicated in a press release from the NASA Jet Propulsion Lab last year, short-term trends in global sea level rise are greatly affected by temporary exchanges of water mass between the land surface and ocean - creating 'potholes' and 'speed bumps' in the sea level record. This a consequence of changes in precipitation (rainfall & snow) resulting from the El Niño-Southern Oscillation (ENSO).

During La Niña the sea surface is cooler-than-normal and rainfall is concentrated over land, which leads to a temporary fall in global sea level. With El Niño the surface of the tropical Pacific Ocean becomes warmer-than-normal, and rainfall gets concentrated over the ocean. This, combined with the drainage of water from land, causes a temporary spike in global sea level.

ENSO is principally responsible for the large year-to-year fluctuations evident in the global sea level record, but neither of these two phenomena (El Niño/La Niña) alter the long-term sea level rise which results from the melting of land-based ice, and the thermal expansion of the oceans as they warm. They do, however, cause sufficient 'noise' to obscure the long-term sea level rise when viewed at short intervals.

In the last two years two back-to-back La Niña have temporarily lowered sea level, but La Niña appears to have weakened in recent months and accordingly we would expect an uptick in sea level rise as conditions move closer to neutral. A quick look at AVISO confirms this, see Figure 1.

Figure 1 - The reference mean sea level since January 1993 (left) is calculated after removing the annual and semi-annual signals. A 2-month filter is applied to the blue points, while a 6-month filter is used on the red curve. By applying the postglacial rebound correction (-0.3 mm/year), the rise in mean sea level has thus been estimated as 3.18 mm/year. Image from AVISO.



NASA scientists expect more rapid global warming in the very near future (part 2)

Posted on 5 February 2012 by Rob Painting

In part 1 we saw that NASA scientists James Hansen, Reto Ruedy, Makiko Sato and Kwok-Wai Ken Lo from the Goddard Institute for Space Studies (GISS) have released an analysis of global temperature in 2011, and looked at future prospects. Reviewing the evidence, the authors concluded that rapid global warming is likely in the next few years. This is not a new phenomenon, but simply a reflection of natural variability, cool (La Niña) and warm (El Niño) phases which still exert a temporary cooling/warming influence on global surface temperatures even in the presence of a persistent global warming trend. 

In part 2 we'll see that seasonal extreme warm anomalies in 2009-2011 are well above the 1951-1980 base period typically used in GISTEMP analyses - indicative of global warming's role in heatwaves. That measuring of manmade aerosols (pollution particles that reflect sunlight) is still highly problematic, and significantly, that the current warming phase of the 11-year solar cycle is likely to have a noticable warming effect on the climate over the next 3-5 years. 

Figure 1 -Solar irradiance from composite satellite-based time series. Data sources: For 1976/01/05 to 2011/02/02 Physikalisch Meteorologisches Observatorium Davos, World Radiation Center and for 2011/02/03 to 2012/01/11 University of Colorado Solar Radiation & Climate Experiment. The circled area is (roughly) the solar energy already absorbed by the ocean and yet to manifest itself in global temperatures i.e - warming already committed. 



NASA scientists expect more rapid global warming in the very near future (part 1)

Posted on 26 January 2012 by Rob Painting

As a recent SkS post by Dana Nuccitelli has pointed out global warming hasn't stopped, despite a recent lull in global surface temperatures. The oceans, which are the main heat sink for global warming, have scarcely skipped a beat in soaking up heat. The hiatus in global surface temperatures appears to simply be a reflection of natural variability, principally the exchange of heat between the ocean surface and the atmosphere. But we shouldn't expect this to last much longer. Eventually that ocean heat buried in deeper layers will come back to the surface, and we'll experience the warm phase of this natural cool/warm (La Niña/El Niño-based) cycle.

As if to reinforce this very point, a group of scientists at the NASA Goddard Institute for Space Studies (NASA GISS), have released an analysis of global temperatures in 2011, and near-future prospects. They find that 2011 was the 9th-hottest year on record (9 out of the 10 hottest years on record since 1880, have occurred in the 21st century), and that this cool-ish year (by 21st century standards, but hot by 20th century standards) was largely due to the cooling influence of a quiet phase of the 11 year-long solar cycle (small changes in the intensity of sunlight reaching Earth), and La Niña which has been dominant over the last 3 years (See figure 1). They conclude that the lull is an illusion, and that rapid warming of global surface temperatures is likely to resume in the next few years.

Figure 1 - Global monthly and 12-month running mean (average) surface temperature anomalies relative to the 1951-1980 base period (GISTEMP), and the 12-month running mean of the Nino 3.4 index of sea surface temperatures (an index of La Niña/El Niño intensity and duration). Image adapted from NASA GISS.



Puget Sound, Under Threat From Ocean Acidification, Put on "Waters of Concern" List

Posted on 16 January 2012 by Rob Painting

This is a re-post of a press release from the Center For Biological Diversity

OLYMPIA, Wash.— In its water-quality report to the Environmental Protection Agency, the state of Washington classified the entire Puget Sound as “waters of concern” because of ocean acidification’s threat to local shellfish and fish resources. This means the data show that ocean acidification is threatening the region’s ability to support fish and shellfish. It also makes the area a priority for more monitoring and assessment.



Ocean Acidification Is Fatal To Fish

Posted on 22 December 2011 by Rob Painting

Fossil fuel-burning is acidifying the oceans and, up until recently, it has generally been thought that the greatest risk posed by ocean acidification was the change to seawater carbon chemistry. This is because rising levels of atmospheric carbon dioxide reduce the concentration of seawater carbonate ions, a vital building-block in the shells and skeletons of many marine life. Fish were not thought to be at direct risk from acidification, because they clearly don't build shells, and were considered to have well-developed physical mechanisms to tolerate falling pH (acidification). 

Several studies published in the journal Nature Climate Change, Baumann (2011) and Frommel (2011), indicate that this might not be the case. Fish may, in fact, be seriously threatened by ocean acidification. Although adult fish seem well-equipped to deal with low pH waters, or higher levels of CO2 in seawater, their egg and larval life stages, a typically vulnerable time for all marine life, may not be so fortunate.

Baumann (2011) show that larvae survival in one fish species drops with increased levels of CO2 (figure 1). Survival rates plummeting some 75% under a scenario with 1000ppm (parts per million) of atmospheric CO2. And Frommel (2011) discovered considerable tissue damage and necrosis (dead tissue) in fish larvae of another species exposed to higher levels of CO2 than the present day. In the high CO2 experiments, this damage to internal organs was so extensive it lead to the death of afflicted larvae. Each of these studies are discussed in detail below.

Figure 1 -Survival rates of larvae with increasing CO2. Thin grey lines=error bars (95% confidence intervals). Experiment 1, red squares; experiment 2, blue down triangles; experiment 3, green diamonds; experiment 4, yellow circles; experiment 5, black up triangles. Points represent means±1 standard deviation (a spread of measurements deviating from the average).



Ocean Acidification: Corrosive waters arrive in the Bering Sea

Posted on 14 December 2011 by Rob Painting

You've probably read it before, some aspect of global warming is happening much faster, or sooner than anticipated by the scientific community. Well, this is one of three blog posts that continue in that vein. This time the bad news is corrosive seawater brought about by global warming's evil twin - ocean acidification. Something once considered to be some decades away is already here, and may be killing marine life.

A number of recently published scientific papers (Feeley [2010], Pfister [2011], Mathis [2011a], and Mathis [2011b]) have revealed that, rather than being some far-off future threat, corrosive seawater (from ocean acidification) is making its presence felt, both in the coastal waters of the US/Canadian North Pacific, and the eastern Bering Sea. As well as putting the finishing touches on the struggling oyster farming industry in the US states of Oregon and Washington, ocean acidification is likely to seriously impact the valuable US fishing catch, almost 50% of which (by weight) comes from the Bering Sea. See figure 1.

Figure 1 - Observations of aragonite (shown in colour) and calcite (shown in black with contour lines) saturation states along the transect lines of two oceanographic voyages in the summer and fall of 2009. Pink indicates regions corrosive to aragonite shells/skeletons, and the dashed contour line indicates an area corrosive to calcite shells (a less easily dissolved shell-building material). From Mathis (2011b) 



What's Happening To Tuvalu Sea Level?

Posted on 26 November 2011 by Rob Painting

Because the coral atoll of Funafati, Tuvalu is densely populated and generally less than 3 metres above sea level, this small island nation in the Pacific is often the subject of intense media speculation about the impact of rising seas. The atoll is likely to begin to be overtopped by the sea sometime between mid to late 21st century, however Tuvaluans have often featured in the mainstream media claiming to be already experiencing the detrimental effects of sea level rise. Scientific studies to support these claims has been have been hard to find, but now a recently published study vindicates what many Tuvaluans have insisted all along - sea level has risen rapidly around Tuvalu.

Becker (2011) has examined sea level rise in the western tropical Pacific Ocean using a combination of tide gauges, satellite-based measurements, ocean modelling and GPS, and found that the region is experiencing sea level rise much larger than the global average. At Funafati Island, the study authors found that between 1950-2009 'total' sea level, which also accounts for the rate of island subsidence or sinking, rose at 5.1 (±0.7) mm per year, almost 3 times larger than the global average over the same period.  

Figure 1- Sea level curves at tide gauge sites since 1950. Time series of reconstructed sea level (black), tide-gauge (red) and altimetry satellite in blue continue and in dash line (when tide gauge records were supplemented using altimetry data). From Becker (2011). Image cropped from original.



Arctic Sea Ice Hockey Stick: Melt Unprecedented in Last 1,450 years

Posted on 24 November 2011 by Rob Painting

Many climate change "skeptics" obsess over the 'hockey stick', and their discussion inevitably leads back to 1998, when climate scientist Michael Mann first published his paper indicating that current global warming was anomalous in the last 1000 years or so. In plain language, Mann's work suggested that current warming was likely due to mankind's carbon dioxide pollution, not any as-yet-unidentified, or yet-to-be-discovered or observed natural phenomenon.

Despite the "skeptics" cherry-picked focus on a  peer-reviewed paper more than a decade old, the science has moved on considerably since then. Paper after paper has basically affirmed that current warming is outside the bounds of natural variation, and therefore likely due to human activities. For example we have seen a sea level hockey stick, an underwater hockey stick, a South American hockey stick, an Arctic summer temperature hockey stick, a tropical glacier hockey stick, a North American mountain snowpack hockey stick, a glacier length hockey stick, and warming of Atlantic water into the Arctic hockey stick

Into this league of hockey sticks, we have a just published scientific paper, (Kinnard [2011]), which shows that the Arctic sea ice retreat is also a hockey stick, and that the present rate of melt in the Arctic summer is unprecedented in the last 1,450 years. See figure 1. (Note that the hockey stick blade is facing down in this reconstruction).



Climategate 2.0: Denialists Serve Up Two-Year-Old Turkey

Posted on 23 November 2011 by Rob Painting

Not satisfied with the fake scandal that was Climategate 1.0, climate denialists have returned with another collection of quote-mined excerpts from the same batch of e-mails hacked from the University of East Anglia's Climate Research Unit (CRU) two years ago.

The original release of quote-mined stolen e-mails coincided with the lead-up to Denmark's Copenhagen Climate Conference in 2009, where world leaders met to discuss and agree on actions to address man-made climate change (so much for that). Once again, this new batch of e-mails just so happen to surface before the gathering of world leaders for the climate conference in Durban, South Africa, which is to start next week.

Given that the quote-mined excerpts from the stolen e-mails contain nothing that challenges the robustness and validity of the veritable mountain of scientific evidence that underpins man-made global warming, its timing and content (or more accurately, lack thereof) strongly suggest this is yet another desperate attempt to influence public opinion and distract the policymakers attending the Durban conference. This is, no doubt, why prominent climate modeler Gavin Schmidt labels the new e-mail release "Two-year old turkey."



Increase Of Extreme Events With Global Warming (Basic Version)

Posted on 11 November 2011 by Rob Painting

For a more technical version of this post, see here

It seems common sense  that as the Earth warms we will see more record-breaking warm extremes, and less cold ones.  What the authors of a recent study, Rahmstorf & Coumou (2011), sought to find out is how much of these extreme events can we put down to the slowly evolving change in climate, and how much is due to random variations in weather.

The authors developed a statistical approach to evaluate record-breaking events. They found that long-term warming increased the odds of record warm events in global temperature, and when applied to the 2010 monster summer heatwave in Moscow, Russia, they calculated an 80% probability the record-breaking heatwave would not have happened without climate warming.  

Analogy time - if it floats your boat

Before going any further, a useful analogy here is to consider a boat moored in a marina. The incoming tide is our slowly changing component (warming climate), and waves are our rapidly fluctuating short-term component (weather). Over a period of time we measure the height of the boats mast, from the top of the jetty to which it is tied. Was the incoming tide responsible for the greatest recorded height?, or was it because of random wave action alone?  



Extreme Events Increase With Global Warming

Posted on 11 November 2011 by Rob Painting

For a more basic version of this post, see here

That continued warming of the Earth will cause more frequent and intense heatwaves is hardly surprising, and has long been an anticipated outcome of global warming. Indeed the 1990 Intergovernmental Panel on Climate Change (IPCC) Policymakers Summary stated that: 

"with an increase in the mean temperature, episodes of high temperatures will most likely become more frequent in the future, and cold episodes less frequent."

One such "high temperature episode" was the monster summer heatwave centred near Moscow, Russia in 2010, where temperatures rocketed well above their normal summertime maximum and were so record-shattering they may have been the warmest in almost 1000 years.

Rahmstorf and Coumou (2011) developed a statistical model and found that record-breaking extremes depend on the ratio of trend (warming or cooling) to the year-to-year variability in the record of observations. They tested this model by analysing global temperatures and found that warming increased the odds of record-breaking. When applied to the July 2010 temperatures in Moscow, they estimated a 80% probability that the heat record would not have occurred without climate warming.

Figure 1 - Probability of July average temperature anomalies in Moscow, Russia since 1950. This image shows that the average temperature in Moscow for July 2010 was significantly hotter than in any year since 1950. Credit: Claudia Tebaldi and Remik Ziemlinski. From



Amazon Drought: Heat Stress Linked To Mass Tree Die Off In 2005 and 2010

Posted on 27 October 2011 by Rob Painting

In 2005 & 2010 the Amazon rainforest experienced two "once-in-a-century" droughts, adding to concerns that the rainforest may undergo massive die-back in the 21st century under global warming

When discussing the potential for die-back of the Amazon rainforest, attention is often focused on reductions in rainfall, for obvious reasons; however, rising temperatures may also be a threat to the future prospects of the Amazon, as some research suggests that tropical rainforests exist near a high temperature threshold.

As if to underscore this potential threat, a recent peer-reviewed paper (Toomey 2011) finds that, aside from reduced rainfall, greater-than-normal surface temperatures in the 2005 and 2010 extreme droughts very likely contributed to a mass die-off of trees.

Figure 1 - 2010 drought in the Amazon, illustrating the severity of reduced rainfall experienced in parts of the basin. Picture from Greenpeace International.



How Increasing Carbon Dioxide Heats The Ocean

Posted on 18 October 2011 by Rob Painting

Much like a heated kettle of water takes some time before it comes to the boil, it seems intuitive that the world's oceans will also take some time to fully respond to global warming. Unlike a kettle, however, it's not obvious how the oceans warm.

Adding further greenhouse gases to the atmosphere warms the ocean cool skin layer, which in turn reduces the amount of heat flowing out of the ocean. Reducing the heat lost to the atmosphere allows the oceans to steadily warm over time - as has been observed over the last half century.

Warming on sunshine

Sunlight penetrating the surface of the oceans is responsible for warming of the surface layers. Once heated, the ocean surface becomes warmer than the atmosphere above, and because of this heat flows from the warm ocean to the cool atmosphere above. This process is represented in the graphic below:

Figure 1 - simplified steps of ocean heating 



Ocean Heat Poised To Come Back And Haunt Us?

Posted on 15 October 2011 by Rob Painting

Comments about a recent post on Meehl (2011), a climate model-based study, indicated that a number of issues had not been made very clear. For instance, what was meant by natural variability, and what were the mechanisms in the climate model which allowed heat to be distributed to the deep ocean? Hopefully I can clarify a few things with this additional post. 

The natural variability referred to in the climate model is simply the exchange of heat in the surface and subsurface layers of the ocean, as is apparent in real world observations of La Niña and El Niño. La Niña-like patterns cause cooler-than-average surface temperatures because large areas of cool subsurface oceanic waters are brought to the surface.

And no, this isn't some new, as-yet-unexplained phenomena. The climate model suggests that La Niña and the (La Niña-like) negative phase of the Interdecadal Pacific Oscillation, well-observed ocean patterns, are when large amounts of heat are pumped down into the deep ocean.



The Deep Ocean Warms When Global Surface Temperatures Stall

Posted on 2 October 2011 by Rob Painting

Despite being the warmest decade on record, the last decade has seen a slowdown in the rate of global warming in some temperature datasets. The factors responsible for this slowdown have been discussed at SkS, most recently in the SkS post Ocean Heat Content And The Importance Of The Deep Ocean, which looked at three Hadley Centre climate models. 

Meehl (2011) is also climate modeling-based study, which finds that decade-long periods of little or no warming are relatively common in the model simulations. This helps to explain why global warming is not a steadily rising, or monotonic trend, consistent with the temperature observations to date (Figure 1).

Figure 1 - Ocean heat content (0-700 mtrs) for the period 1955 to 2008. Adapted from Levitus (2009). Two periods of ocean warming hiatus highlighted in blue. Both periods exceed 10 years in length.



Ocean Heat Content And The Importance Of The Deep Ocean

Posted on 24 September 2011 by Rob Painting

Most of the heat from global warming is going into the oceans. Covering some 70% of the Earth's surface and having a heat capacity a thousand times more than the atmosphere, it's easy to understand why the oceans are the main heat sink.

Multiple studies measuring from the ocean surface down to 700 metres show very little warming, or even cooling, over multiple years in the last decade. This is surprising given that some studies estimate that the imbalance at the-top-of-the-atmosphere (TOA), the difference between energy entering and leaving Earth's atmosphere over that time, has actually grown. So we might have expected the 700 metre sea surface layer to show increased warming. However the average depth of the ocean is around 4300 metres, and in a recent SkS post, we saw that when measurements were extended down to 1500 metres, the oceans were found to still be warming, indicating that heat is somehow finding a way down to the deep ocean.



Dessler Demolishes Three Crucial 'Skeptic' Myths

Posted on 8 September 2011 by dana1981

Andrew Dessler's new paper, which we first examined in a post yesterday, has some very far-reaching implications in terms of refuting climate "skeptic" myths.  In fact, its results are relevant to three seperate myths in the Skeptical Science databaseAs a result, we have incorporated the findings of Dessler (2011) into the three myth rebuttals as follows.



Andrew Dessler's New Paper Debunks Both Roy Spencer And Richard Lindzen

Posted on 6 September 2011 by Rob Painting

Andrew Dessler, a climate scientist at Texas A&M University, has released a scientific paper (Dessler 2011) that looks at the claims made by two of a small group of "skeptic" climate scientists who regular SkS readers will be familiar with: Roy Spencer and Richard Lindzen.  Both were co-authors on peer-reviewed papers released this year (Spencer & Braswell [2011] & Lindzen & Choi [2011]) which, once again, sought to overturn the orthodox view of climate.  Dessler (2011) finds that the conclusions of these two papers are unsupported by observational data. 



Extreme Flooding In 2010-2011 Lowers Global Sea Level

Posted on 5 September 2011 by Rob Painting

The last 18 months has seen some epic deluges throughout the world, countries such as Pakistan, Sri Lanka, Australia, the Philippines, Brazil, Colombia and the United States have been hammered with extreme flooding. It will take some time for studies about these episodes to appear in the scientific literature, so how the recent spate of massive floods stack up in a historical context is as yet unknown. 

A recent news release over at the NASA Jet Propulsion Lab, which was re-posted here at SkS, helps in putting the extreme flooding into perspective - so much rain and snow has fallen over land in the period from March 2010-March 2011 that it has contributed to a large fall in global sea level. But this is only a temporary effect, as water is swapped back-and-forth between the continents and ocean, and does not alter the long-term rise in sea level which results from warming oceans and the melting of the polar icesheets and glaciers worldwide.

         Color Bar

Figure 1 - sea level rise 1993-2011 from satellite altimetry. Image from NASA JPL



NASA Satellites Detect Pothole on Road to Higher Seas

Posted on 4 September 2011 by Rob Painting

The following is a re-posted article from the NASA Jet Propulsion Lab

Like mercury in a thermometer, ocean waters expand as they warm. This, along with melting glaciers and ice sheets in Greenland and Antarctica, drives sea levels higher over the long term. For the past 18 years, the U.S./French Jason-1, Jason-2 and Topex/Poseidon spacecraft have been monitoring the gradual rise of the world's ocean in response to global warming.

While the rise of the global ocean has been remarkably steady for most of this time, every once in a while, sea level rise hits a speed bump. This past year, it's been more like a pothole: between last summer and this one, global sea level actually fell by about a quarter of an inch, or half a centimeter.

           Color Bar

Figure 1 - sea level rise 1993-2011 from satellite altimetry.



Murry Salby - Confused About The Carbon Cycle

Posted on 13 August 2011 by Rob Painting

Every year humans release about 30 billion tons of carbon dioxide (CO2) into the atmosphere through the burning of fossil fuels, such as coal and oil. This is causing the Earth to warm by disrupting the biological (fast) carbon cycle, and is therefore increasing the Greenhouse Effect. Although there are large annual fluctuations in carbon dioxide, as it is exchanged back-and-forth between the atmosphere, oceans, soils, and forests, just under half of human emissions (the airborne fraction) remain in the air because the oceans, soils and forests are unable to absorb all of it. As a result, carbon dioxide has been steadily accumulating in the atmosphere.

Figure 1 - Fraction of the total human emissions (fossil fuel burning & land use change) that remain in the: a) atmosphere, b) land vegetation and soil, c) the oceans. From Canadell (2007)



Ocean Cooling Corrected, Again

Posted on 28 July 2011 by Rob Painting

The ongoing difficulty of accurately measuring the Earth's ocean heat content has led to premature "skeptic" claims about ocean cooling. A recent paper Von Schuckmann & Le Traon (2011) put the kibosh on ocean cooling claims. They find that from 2005 to 2010 the global oceans (10 to 1500 metres down) have continued to warm, although they caution that their result is based on the assumption that there are no more systematic errors in the data gathered from ARGO floats which measure ocean heat.

Figure 1 -Revised estimate of global ocean heat content (10-1500 mtrs deep) for 2005-2010 derived from Argo measurements. The 6-yr trend accounts for 0.55±0.10Wm−2. Error bars and trend uncertainties exclude errors induced by remaining systematic errors in the global observing system. See Von Schuckmann & Le Traon (2011)



Why Wasn't The Hottest Decade Hotter?

Posted on 15 July 2011 by Rob Painting

After a rapid rise in global surface air temperatures during the late 1970s to 1990s, the rate of global warming in the last decade or so has slowed. A recent scientific paper, Kaufmann (2011), suggests that once relevant factors are taken into consideration, the observed slow-down from 1998-2008 is in line with scientific understanding of the climate. 

Rapid industrialization in East Asia, particularly China, led to a big jump in sunlight-reflecting sulfate aerosol pollution, mainly through coal burning. This additional reflective aerosol pollution sheilded the Earth from greater warming, but is only a temporary reprieve. Sulfates have a short lifetime in the atmsophere, and when East Asia stops burning so much coal, the Earth is going to get an extra nudge in warming. 

20th to 21st Century global warming

Figure 1 - Hadley Centre temperature record (HADCRUT3).The red bars show the global annual average near-surface temperature anomalies from 1850 to 2009. The error bars show the 95% uncertainty range on the annual averages. The thick blue line shows the annual values smoothed. Vertical banded column indicates the 'slow-down' period.



The Medieval Warm(ish) Period In Pictures

Posted on 10 July 2011 by Rob Painting

The Medieval Warm Period (MWP) is a subject of "skeptic" focus, primarily because it was a time of natural warming. It took place from about 950-1250 AD, and, as opposed to today's warming which is global in extent and due to human activities, the MWP was mainly a northern hemisphere phenomenon and smaller in scale. Indeed, the advance of North American glaciers during the MWP is in stark contrast to what is happening in North America today. 

The MWP in global maps 

Mann (2009) was an analysis of a large set of climate/temperature proxies (ice cores, tree rings, cave mineral deposits, sediments, etc.) covering the MWP. See below:



Climate Solutions by Rob Painting

Posted on 9 July 2011 by Rob Painting

After writing the blog post Throwing Down the Gauntlet, 'Actually Thoughtful' suggested SkS authors/contributors write about what personal measures they've taken in regard to climate change, and what steps readers could take. This is my response.

Nobody likes a hypocrite    

From time to time we get the odd comment here, suggesting that we (SkS contributors) are hypocrites; that we're using electricity and consumer goods that generate greenhouse gases and that we should be living in caves. These silly comments always give me a laugh, how do they know I'm not living in a cave running my recycled computer off a homemade exercycle Gilligan's Island-style?

More seriously though, it does raise an issue about perceptions of hypocrisy. It's only natural to scoff when watching a TV segment about obesity and type 2 diabetes, only for the camera to switch to an interview with the health spokesperson doling out healthy eating and exercise advice, but who happens to be obese themselves! Well I can assure you that while no 'eco-saint', I don't dig hypocrisy either. Here's a sample of the measures my wife and I have taken; some simple, some not so :



New Zealand Snow No Show = No Jobs

Posted on 28 June 2011 by Rob Painting

An unusually warm autumn and early winter in New Zealand 2011 has meant skifields up and down the country are without snow.



CO2 Currently Rising Faster Than The PETM Extinction Event

Posted on 17 June 2011 by Rob Painting

The Paleocene-Eocene Thermal Maximum (PETM) was a period of natural global warming that took place almost 56 million years ago.  It came at a time when the atmospheric concentration of CO2 was already higher than today, and global temperatures also much warmer. The PETM warming was a roughly 200,000-year long event where global temperatures rose by a further 6–8°C, and is thought to have been caused by a massive injection of CO2 into the atmosphere.



Ocean acidification: Some Winners, Many Losers

Posted on 10 June 2011 by Rob Painting

Numerous lab experiments have shown that ocean acidification is harmful to marine life. Creatures that build chalk-like shells (or skeletons) fare poorly under conditions which mimic the low ocean pH levels expected later this century. This isn't a universal response however; some starfish, brittle stars and sea urchins, seem relatively unaffected by ocean acidification, so it's likely there will be winners and losers as the world's oceans become less alkaline. 



Amazon drought: A death spiral? (Part 3: 2005 & 2010 droughts)

Posted on 2 June 2011 by Rob Painting

Continued from Part 2



Amazon drought: A death spiral? (part 2:climate models)

Posted on 1 June 2011 by Rob Painting

This post continues from Part 1 



Coral atolls and rising sea levels: That sinking feeling

Posted on 20 May 2011 by Rob Painting

People living on coral atolls have long been the 'poster child' of global warming, and the threat posed by rising sea levels. Some emotive reporting in the media (and rightly so) tend to give the impression that the atolls should have been under water by now. Clearly this isn't the case, as Webb & Kench (2010) show, the sea level rises experienced in the South Pacific so far (2mm per year) have had little effect on the loss of land area on the atolls. Despite some people being confused regarding the timescale involved, the threat is still very real.  



Drought in the Amazon: A death spiral? (part 1:seasons)

Posted on 15 May 2011 by Rob Painting

By and large, the mainstream media has a pretty dismal record in reporting about climate change, and a recent op-ed in the National Post, written by Lawrence Solomon, continues in this vein. In the piece, Solomon makes light of the dire threat global warming poses to the continued existence of the Amazon rainforest. After the IPCC Amazon non-controversy, it's probably time to look at the issue in a bit more depth, and debunk Solomon at the same time. 



Acidification: Oceans past, present & yet to come

Posted on 31 March 2011 by Rob Painting

Through the burning of fossil fuels, humans are rapidly altering the chemistry of the global oceans, making seawater increasingly more acidic. Most attention to date has focused on what we might expect in the years to come, and rightly so, many studies have shown that the seas of the future are likely to be corrosive to shell-building marine life. Some areas, such as the Arctic, might even reach a corrosive state within a decade. But, knowing that ocean acidity has increased by almost 30% since the beginning of the industrial civilization, has the change so far already had an effect on marine life?



Maize harvest to shrink under Global Warming

Posted on 16 March 2011 by Rob Painting

With global food prices at an all-time high, out comes a new study demonstrating once again, that global warming will generally have a very negative impact on food production. The study shows that warming of 1°C will lead to smaller maize (corn) harvests throughout Africa.



Monckton Myth #8: Rising sea levels

Posted on 27 January 2011 by Rob Painting

Regular readers will know the drill by now, this is one of a series of posts responding to a number of claims recently put forth by British climate skeptic Chris Monckton, in response to an article in the Australian by Mike Steketee. So let's begin.



Coral: life's a bleach... and then you die

Posted on 13 January 2011 by Rob Painting

Despite what you may read or see in the mainstream media, out in the real world, massive and rapid changes are taking place in many ecological systems as a result of global warming. The Earth seems to be already convinced of global warming and is responding quickly.

Perhaps the most significant, and likely most enduring, are the shifts taking place in the Earth's oceans. Whilst many readers may have read or heard about Ocean Acidification, there are numerous other changes taking place in the oceans which should be equally as concerning. One such phenomena to appear in the last few decades is mass coral bleaching, a consequence of the continued warming of the oceans. Once vast stretches of colourful reefs teeming with marine life are being reduced to lifeless rubble covered in seaweed or slime. Many areas are not recovering, and the scale and frequency of bleaching worldwide is getting worse. In fact, early reports suggest 2010 may have witnessed the largest single bleaching event ever recorded.



The Grumble in the Jungle

Posted on 29 October 2010 by Rob Painting

An article in a British newspaper claimed that the Intergovernmental Panel on Climate Change (IPCC) published wrong information about the Amazon Rainforest in their 2007 report. The issue centred on the statement that about 40% of the Amazon was susceptible to the effects of drought, or more specifically "slight reductions in rainfall".



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