Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


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.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Bluesky Facebook LinkedIn Mastodon MeWe

Twitter YouTube RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


State of the climate: Heat across Earth’s surface and oceans mark early 2019

Posted on 8 May 2019 by Zeke Hausfather

This is a re-post from Carbon Brief

Global surface temperatures in 2019 are on track to be either the second or third warmest since records began in the mid-1800s, behind only 2016 and possibly 2017.

On top of the long-term  warming trend, temperatures in 2019 have been buoyed by a moderate El Niño event that is likely to persist through the rest of the year.

That’s one of the key findings from Carbon Brief’s latest “state of the climate” report, a quarterly series on global climate data that now includes temperatures, ocean heat, sea levels, greenhouse gas concentrations, climate model performance and polar ice.

Ocean heat content (OHC) set a new record in early 2019, with more warmth in the oceans than at any time since OHC records began in 1940.

The latest data shows that the level of the world’s oceans continued to rise in 2019, with sea levels around 8.5 centimetres (cm) higher than in the early 1990s.

Atmospheric methane concentrations have increased at an accelerating rate, reaching record highs in recent months, though scientists are divided on the cause of this trend.

Arctic sea ice is currently at a record low for this time of year. Antarctic sea ice set new record lows in January, and is currently at the low end of the historical range.

Third warmest start to a year

Global surface temperatures are recorded and reported by a number of different international groups, including NASANOAAMet Office Hadley Centre/UEABerkeley Earth and Cowtan and WayCopernicus/ECMWF also produces a surface temperature estimate based on a combination of measurements and a weather model – an approach known as “reanalysis”.

The chart below compares the annual global surface temperatures from these different groups since 1970 – or 1979 in the case of Copernicus/ECMWF. The coloured lines show the temperature for each year, while the dots on the right-hand side show the year-to-date estimate for January through March 2019. Values are shown relative to a common baseline period, the 1981-2010 average temperature for each series. Surface temperature records have shown around 0.86C warming since the year 1970, a warming rate of about 0.19C per decade.

Year-to-date values are only shown for NASA, NOAA, and Copernicus as data for March is not yet available from the UK Hadley Centre, which also prevents the Berkeley Earth and Cowtan and Way records from being released. The year-to-date values in this chart will be updated when that data becomes available.

Annual global mean surface temperatures from NASA GISTEMPNOAA GlobalTempHadley/UEA HadCRUT4Berkeley EarthCowtan and Way and Copernicus/ECMWF (lines), along with 2019 temperatures to-date (January-March, coloured dots). Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief using Highcharts.

Based on temperatures in the first quarter, 2019 is likely to be the second or third warmest year on record for all of the surface temperature series. However, with only three months of 2019 available so far it is not out of the question that it could be the warmest year – or as cool as the fourth warmest on record.

The figure below shows how temperatures to-date compare to prior years in the NASA GISTEMP dataset (using its new version 4). It shows the temperature of the year-to-date for each month of the year, from January through the full annual average.

Year-to-date temperatures for each month from 2012 to 2019 from NASA GISTemp. Anomalies plotted with respect to a 1981-2010 baseline. Chart by Carbon Brief using Highcharts.

In the NASA dataset, 2019 has had the third warmest January-March average on record, after the record warm years of 2016 and 2017. However, while both of those years had cooler temperatures in the summer and autumn, this year may see a weak El Niño help current warmth persist. As a result, it is likely that 2019 will end up as the second warmest on record in the NASA dataset.

The first three months of 2019 have already been modestly warmed by a weak El Niño event. The majority of forecast models expect weak El Niño conditions to persist for the remainder of 2019, with sea surface temperatures in the tropical Pacific around between 0.5C and 1C above the recent average.

El Niño and La Niña events – collectively referred to as the El Niño Southern Oscillation, or ENSO – are the main driver of year-to-year variation on top of the long-term surface warming trend. ENSO events are characterised by fluctuations in temperature between the ocean and atmosphere in the tropical Pacific, which help to make some years warmer and some cooler.

The figure below shows a range of ENSO forecast models produced by different scientific groups, with the average for each type of models shown by thick red, blue and green lines. Positive values above 0.5C reflect El Niño conditions, while negative values below -0.5 reflect La Niña conditions.

El Niño Southern Oscillation (ENSO) forecast models for three-month periods in the Niño3.4 region (February, March, April – FMA – and so on), taken from the CPC/IRI ENSO forecast.

El Niño Southern Oscillation (ENSO) forecast models for three-month periods in the Niño3.4 region (February, March, April – FMA – and so on), taken from the CPC/IRI ENSO forecast.

In general, El Niño periods tend to be warmer than other months, with the large warm patch in the tropical east Pacific transferring extra heat to the atmosphere. Similarly, La Niña events cool global temperatures. In both cases the effects tend to have a bit of a lag: the effect on global temperatures is small at the beginning of the event, and larger by the end – or slightly after.

Comparing climate models with observations

Climate models provide physics-based estimates of future warming given different assumptions about future emissions, greenhouse gas concentrations and other climate-influencing factors.

Model estimates of temperatures prior to 2005 are a “hindcast” using known past climate influences, while temperatures projected after 2005 are a “forecast” based on an estimate of how things might change.

The figure below shows the range of individual models forecasts featured in the IPCC fifth assessment report – known collectively as the CMIP5 models – between 1970 and 2020 with grey shading and the average projection across all the models shown in black. Individual observational temperature records are represented by coloured lines.

Annual global average surface temperatures from CMIP5 models and observations between 1970 and 2020. Models use RCP4.5 forcings after 2005. They include sea surface temperatures over oceans and surface air temperatures over land to match what is measured by observations. Anomalies plotted with respect to a 1970-2000 baseline. Chart by Carbon Brief using Highcharts.

While global temperatures were running a bit below the pace of warming projected by climate models between 2005 and 2014, the last few years have been pretty close to the model average. This is particularly true for globally-complete temperature records such as NASA, Berkeley Earth and the Copernicus reanalysis that include temperature estimates for the full arctic. Temperatures were warmer than the multimodel average during the 2015-16 super-El Niño event and were a bit cooler during the 2018 La Niña. In recent months, temperatures have been ticking back upward.

Ocean heat content at a record high

Human-emitted greenhouse gases trap extra heat in the atmosphere. While some of this warms the Earth’s surface, the vast majority – upwards of 90% – goes into the oceans. Most of this accumulates in the top 700 metres, but some is also mixed into the deep oceans.

Ocean heat content (OHC) estimates between 1940 and the present day for both the upper 700m (light blue shading) and 700m-2000m (dark blue) depths of the ocean are shown in the chart below.

Monthly global ocean heat content (in zettajoules – billion trillion joules, or 10^21 joules) for the 0-700 metre and 700-2000 metre layers. Data from Cheng et al 2017, updated through March 2019. Chart by Carbon Brief using Highcharts.

The first few months of 2019 have set new records for OHC, with a particularly pronounced jump in February and March 2019. Dr Lijing Cheng, an associate professor at the Institute of Atmospheric Physics in China and the lead researcher on the OHC dataset, tells Carbon Brief that the unusual jump was concentrated “below 300m at around 40N in the Atlantic Ocean”. He cautions against drawing conclusions from the last two months until researchers have had time to investigate and make sure the data is accurate.

In many ways, OHC represents a much better measure of climate change than global average surface temperatures. It is where most of the extra heat ends up and is much less variable on a year-to-year basis than surface temperatures. Most years set a new record for OHC and 2019 has been no exception so far, with the first three months showing the warmest OHC since records began.

Changes in the amount or rate of warming are much easier to detect in the OHC record than on the surface. For example, OHC shows little evidence of the slowdown in warming in the mid-2000s, seen in surface temperature records. It also shows a distinct acceleration after 1991, matching the increased rate of greenhouse gas emissions over the past few decades.

Sea level rise continues

Modern-day sea levels rose to a new high in 2019 to-date, due to a combination of melting land ice – glaciers and ice sheets – and the thermal expansion of water as it warms.

The figure below shows the increase in global sea level since it was first measured by satellites in the early 1990s. The different coloured lines indicate different satellite missions over the years. Earlier sea level data from tide gauges is also available, with data going back to the late 1800s.

Global average sea level based on satellite data from January 1993 to present from NOAA. A correction for global average isostatic rebound of 0.3mm/yr is added.

Sea level rise is sensitive to global surface temperatures; El Niño years where temperatures are a bit warmer tend to have more rapid sea level rise than La Niña years. For example, sea level increased rapidly from 2014 to 2016. However, these are relatively small fluctuations around the consistent long-term trend. Overall sea levels have risen around 8.5cm since the early 1990s, and around 22cm since the 1880s.

Sea level data is corrected for glacial isostatic adjustment –  the rebound of the Earth from the several kilometre-thick ice sheets that covered much of North America and Europe around 20,000 years ago. This adjustment is relatively small, only adding around 0.3mm/yr to sea level rise rates, or around 10% of the current rate of sea level rise.

Rapid rise in atmospheric methane

While CO2 is by far the largest factor in rising global temperatures – accounting for roughly 50% of the increase in “radiative forcing” since the year 1750 – methane is the second most important, accounting for for 29% of the increase in forcing.

Atmospheric methane concentration increased rapidly from the mid-1980s through to the early 1990s, before slowing down and ultimately pausing in the late 1990s and 2000s. However, starting in 2008, levels of atmospheric methane began growing again and have seen a notable acceleration over the past four years. The chart below shows concentrations of methane – in parts per billion (ppb) – from the early 1980s when global measurements were first available through to the present.

Global concentrations of methane based on data from NOAA’s Earth Systems Research Laboratory. Chart by Carbon Brief using Highcharts.

The cause of the increase in methane concentrations over the last decade is still a subject of scientific debate. Some studies have suggested that wetlands and rice cultivation in the tropics are the primary culprit and that the expansion of unconventional oil and gas extraction plays a limited role. Others argue that fossil fuels have had just as important a role in the increase as agriculture.

Unlike CO2, methane has a relatively short lifetime in the atmosphere, only lasting about nine years on average before breaking down into its component parts. This means that while CO2 keeps accumulating even if emissions remain flat, the amount of methane in the atmosphere is directly related to the rate of emissions. This means that increases in atmospheric concentrations in recent years reflect increases in methane emissions.

Arctic sea ice at record low

Arctic sea ice spent much of early 2019 at the low end of the historical range and has fallen to record lows for this time of year during the past month. Antarctic sea ice hit record lows in early January, though it has since recovered a bit. Both the Arctic sea ice winter maximum and Antarctic summer minimum in 2019 were the seventh smallest in their respective satellite records.

The figure below shows both Arctic and Antarctic sea ice extent in 2019 (solid red and blue lines), the historical range in the record between 1979 and 2010 (shaded areas) and the record lows (dotted black line). Unlike global temperature records, sea ice data is collected and updated on a daily basis, allowing sea ice extent to be viewed through to the present.

Arctic and Antarctic daily sea ice extent from the US National Snow and Ice Data Center. The bold lines show daily 2019 values, the shaded area indicates the two standard deviation range in historical values between 1979 and 2010. The dotted black lines show the record lows for each pole. Chart by Carbon Brief using Highcharts.

The chart below shows the average Arctic sea ice extent for each week of the year for every year between 1978 and 2019. (Prior to 1978, satellite measurements of sea ice extent are not available and the data is much less reliable.)

Arctic and Antarctic weekly sea ice extent from the US National Snow and Ice Data Center from 1979 through April 2019.

The figure shows a clear and steady decline in Arctic sea ice since the late 1970s, with darker colours (earlier years) at the top and lighter colors (more recent years) much lower. A typical summer now has nearly half as much sea ice in the Arctic as it had in the 1970s and 1980s, though 2012 still holds the record for the lowest summer minimum sea ice extent.

1 0

Printable Version  |  Link to this page


Comments 1 to 4:

  1. Also remarkable is the rapid rise in atmospheric Methane since the fracking boom took off in the USA.

    Fossil methane is 87 times as potent as CO2 on a 20-year time scale.

    More on this specific subject:

    => Global spike in methane emissions over last decade likely due to US shale
    => Research shows that natural gas no better than coal for mitigating climate change
    => US oil and gas methane emissions equivalent to 14 coal-fired power plants
    => Oil and gas is sector top source of US methane emissions, ahead of agriculture

    A gas well remains a gas well, even when production is long ceased, the well is just being plugged. As shale gas exploration needs an ever growing amount of wells being drilled just to keep production flat, we will see an ever growing amount of gas wells. 5% of gas wells leak from day one. After 14 years, 50% of the wells are leaking. So it’s only a matter of time when methane will be released into the atmosphere.
    => Why gas wells leak

    Robert Howarth, PhD, concludes that the global increase in methane over the last 10 years is largely driven by the oil/gas industry. His updated estimate for average, full-cycle methane leakage rate from natural gas operations is 4.1%. Leakage rates above 2% means natural gas is worse than coal for the climate!

    The same applies to the methane called "by-product" at shale oil fields.

    => Methane emissions from oil production up to twice as high as estimated
    => Methane from gas and oil wells found to travel farther than expected underground
    => Studies reveal extent of methane emissions from Canadian oil and gas operations

    There are some 1.7 milion active oil and gas wells in the US. One well per 200 capita. Doesn't that sound insane?

    1 0
  2. Just to give you a clue what modern fracking means. George Mitchell pioneered the technology used today known as high volume slickwater horizontal hydraulic fracturing (fracking) in the late 1990's in the Barnett Shale play of North Texas, just outside Fort Worth. That technology was not perfected and used on a commercial scale until around 2005, give or take a year. Prior to around 2005, the technique the industry referred to as "hydraulic fracturing" consisted of drilling a vertical well bore, perf'ing the production casing, then injecting about 50,000 gallons of fresh water with sand or Pearlite as a proppant using about 3,000 psi to fracture the well and perform "enhanced recovery." This was usually used to try to stimulate existing wells that were producing lower than in the past and the attempt is being made to bring them back to life.

    Flash forward to today. In the Barnett Shale wells averaged about 5 MILLION gallons of fresh water plus about 50,000 gallons of toxic, neurotoxic and carcinogenic chemicals that include endocrine disruptors, BTEX chain chemicals and many other injected hazards in addition to those unearthed by the very process of drilling the well! Barnett wells capped around 9-10 million gallons per well for a single frac job. The Eagle Ford averaged 9 million gallons per well and ranged up to 13 million gallons per well. Some wells in Michigan required up to 35 MILLION gallons of fresh water for EACH frac job! That is water which is permanently destroyed and disposed of by deep injection to "permanently" remove it from our hydrologic cycle, and THAT cost is not even being considered at all. NOTHING living on this planet survives without the abundance of clean, fresh water!

    There is NO similarity, other than name, between "hydraulic fracturing" from 1950's until 2005, and what has taken place since Mitchell's process has been implemented.

    1 0
  3. In addition to shale oil and gases negative environmental impacts, the methane problem and tendency to cause small earthquakes, it is still not a very profitable industry. Some references here and here.

    Briefly fracking is an expensive operation "scraping the bottom of the barel", and so needs oil at about $100 barrel to be truly profitable and is marginal at oil around $50 barrel and of course global prices fluctuate a lot. The industry still isn't very profitable, and is very sensitive to global oil prices (so much for energy independence!).

    Imho it looks like fracking is surviving almost like a ponzi scheme, by increasing production and pulling in investors, while barely breaking even. Its all based on promises of future profits. This has been going on too long, and cannot continue forever and makes it susceptible to a crash like bitcoin.

    The whole fracking issue is also driven by geopolitics and energy independence more than economics. But if America truly wants energy independence that is sustainable on all levels, build solar, hydro and wind. While some materials may have to be imported, it's not on a scale comparable to importing oil and doesn't cause the problems of oil and gas.

    0 0
  4. The legend on the last graph incorrectly states "Arctic and Antarctic" sea ice extent.

    0 0

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

The Consensus Project Website


(free to republish)

© Copyright 2024 John Cook
Home | Translations | About Us | Privacy | Contact Us