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Global cooling - Is global warming still happening?
What the science says...
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All the indicators show that global warming is still happening. |
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Climate Myth...
It's cooling
"In fact global warming has stopped and a cooling is beginning. No climate model has predicted a cooling of the Earth – quite the contrary. And this means that the projections of future climate are unreliable." (source: Henrik Svensmark)
At a glance
Earth's surface, oceans and atmosphere are all warming due to our greenhouse gas emissions, but at different rates. Some places are also warming much faster than others: parts of the Arctic for example. That variability is partly because other phenomena act to offset or enhance warming at times. A good example are the effects of La Nina and El Nino, an irregular variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean that can influence temperatures and rainfall patterns right around the world.
El Nino causes even warmer years whereas La Nina tends to peg temperatures back to an extent. Thus 2023 – an El Nino year - was the warmest year on record, according to the USA-based National Oceanic and Atmospheric Administration, but other recent years have not been far behind – 2016 and 2019 are in second and third place respectively. The worrying thing is that 2019 only saw a mild El Nino. And even with a La Nina featuring, 2021 and 2022 were, respectively, still the seventh and sixth hottest years on record.
The year 1998 featured a massive El Nino and consequent temperature spike that was a strong outlier, well above the steady upward trend. That spike and the subsequent return to a more “normal” warming pattern led to claims in the popular media that global warming had “paused” or had even stopped. This was a typical misinformation tactic that, as usual, time has proved wrong. As things currently stand, the top ten warmest years have all been since 2010 and 1998 is nowhere to be seen any more. By modern standards, it simply wasn't warm enough.
Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!
Further details
In the years following 1998, at the time the hottest year on record, there was a concerted misinformation campaign to convince the public that global warming had variously slowed down, stopped or even that we were entering a period of cooling. Of course, we now know that such claims were nowhere near correct. In today's top ten ranking of warmest years, the year 1998 is nowhere to be seen. It simply wasn't warm enough. So let's take a look at how the claims came about, because they reveal insights into the methodology of those who design and spread misinformation.
The entire planet continues to accumulate heat due to the energy imbalance created through our greenhouse gas emissions. Earth's atmosphere is warming. Oceans are accumulating energy. Land absorbs energy and ice absorbs heat to melt. Year to year ups and downs in these things are simply noise, reflecting variations in how that heat is moved around the planet and what other influences are at work, such as the irregular El Nino Southern Oscillation (ENSO) that can nudge the global temperature one way or another by up to 0.3C. That's why 1998 was such a warm outlier: it coincided with a very strong El Nino. El Nino conditions always warm things up whereas La Nina conditions cool things down (figure 1).
Figure 1: GISTEMP anomalies to end-2023 (with respect to late 19th Century), coded for ENSO state in the early spring - red is El Nino, blue La Nina. 2023 is in grey because that El Nino did not develop until later in the year. Graphic courtesy of Realclimate.
Climatologists routinely use multi-decadal blocks of time when presenting temperature trends for a very good reason. Such blocks allow you to stand back and look at the bigger picture. Due to the noise, taking a much shorter time-span – say just five or ten years – allows you to say anything you like about trends, depending on the particular block you pick.
For example, if you picked a short run of 5-10 years ending in 1998, you could have – if you were so inclined – said, “look how fast it's warming!” Likewise, taking a number of years starting with 1998, you could have made the equally invalid claim that global warming had stopped. And of course, that claim was made, vociferously, in the early-mid 2000s. It was a classic example of cherry-picking: the manifestly unscientific practice of choosing the data that supports the argument one is paid to make on behalf of those who sponsor misinformation campaigns. Once you know about such tricks, you can challenge them yourself. You can ask someone why they showed such a short temperature record when showing a much longer one is the normal practice.
It is difficult but technically possible to filter out the noise described above from temperature datasets. In the paper Foster and Rahmstorf (2011) the authors used the statistical technique of multiple linear regression to filter out the effects of ENSO, solar and volcanic activity (Figure 2). They found that the underlying global surface and lower atmosphere warming trends have in fact remained steady in recent years. There's still noise in there but nowhere near as much. We were still warming all along.
Figure 2: Five datasets of global surface temperature and lower troposphere temperature are shown before and after removing the short-term effects of the El Niño Southern Oscillation (ENSO), solar variability, and volcanic aerosols. A 12-month running average was applied to each dataset.
Last updated on 4 June 2024 by John Mason. View Archives
scliu94 wrote: "What do you guys make of this?"
I can make...
scliu94 - Fun word for the day: the proper term for that particular article, and its author, is mumpsimus. "A view stubbornly held in spite of clear evidence that it's wrong; a person who holds such a view."
It seems to me that sea level gives the clearest evidence of continued heating of the earth’s surface. It is possible to estimate the rate of increase of ocean heat content from the rate of rise in sea level. My estimate below is about double the rate determined from ocean temperature measurements in the top two kilometers of the oceans. I haven’t seen a similar computation elsewhere. If someone else has done this before, please let me know.
The largest contributors to changes in global sea level are heating of the oceans and decrease of Greenland glaciers and Antarctic glaciers and ice shelves. Storage of liquid water on land decreases sea level and extraction of groundwater increases sea level. Storage can have significant short-term effects; but the long term combination of storage and groundwater extraction is modest (See IPCC WG1 Report Chapter 3 p. 318, 2007). Gravity measurements tell us the contribution from Greenland and Antarctic ice. Once we correct the rate of rise of sea level for polar ice, we can compute the rate of ocean heating required to cause the thermal increase in sea level.
The complication is that ocean heating varies with location and depth and that the thermal expansion coefficient varies with seawater temperature and pressure. See this for the computation of seawater thermal properties. The variation of thermal expansion is greatest for temperatures above 15 Centigrade and very little seawater exceeds 15 C for depths greater than 100 meters. Thermal expansion is small below 10 Centigrade at low pressures, but it increases with either increasing pressure or temperature. We can set an upper limit for thermal expansion at a particular temperature by using the high-pressure value. Nearly all the volume of the Atlantic Ocean is 15 C or colder. With these considerations, we can select the high-pressure thermal expansion coefficient for 12 C as an upper limit to a representative value for the entire ocean. That value is 0.00022 / Centigrade. For comparison, the effective coefficient in Schuckmann 2009 (pre-publication copy) is 0.00017.
Here are details of the computation:
The net rate of sea level rise is
Rn = Rt – G / (So * Dw) = 3.2 mm/yr – 213 Gtonne/yr /(
Rt = 3.2 mm/yr over the last 20 years
G = 213 Gtonne/yr over the last 20 years Shepherd et al. (2012)
So = ocean surface area = 3.6 E+14 m^2
Dw = mean density of fresh water = 1000 kg/m^3
Rn = 2.6 mm/yr
dV = rate of increase of seawater volume = Rn * So
dV/V = a * dT
V = total seawater volume
a = effective thermal expansion coefficient for seawater = 0.00022/C
dT = mean rate of increase of seawater temperature
dT = dE/(V * Ds *Cp)
dE = rate of increase of ocean heat content
Ds = mean density of seawater = 1030 kg/m^3
Cp = mean heat capacity of seawater = 4000 Joules/kg/C
Combining the last two equations, we can eliminate the ocean volume and obtain
dE = Ds * C * dV / a = Ds * C * Rn * So / a = 1.76 E+22 J/yr = 5.6 E+14 Watts
The heating rate averaged over the ocean surface area is dE / So = 1.55 W/m^2, twice what Schuckmann gets from temperature measurements. Averaged over the earth’s entire surface the rate is 1.09 W/m^2, which is consistent with the IPCC estimate of net radiative forcing (Climate Change 2007: Synthesis Report, p. 39).
The greatest uncertainty in this computation is in the effective thermal expansion coefficient. If anything, the value I've used is too large. A smaller value would result in a larger computed rate of heating.
Another one from the guy:
"I agree that D-O events may not be global events. On the other hand, if you look at the temperature profiles I posted in the forums previously, you see that the equater is cooling, as is the antarctic.
Since we are predominantly seeing global warming in the arctic and northern temperate zones, how do you know the data isn't a more regional warming event - as opposed to global warming."
I was wondering if evidence could be supplied to help me prove this guy wrong?
Another one from the peanut gallery.
"if you look at the temperature profiles I posted in the forums previously, you see that the equater is cooling, as is the antarctic.
Since we are predominantly seeing global warming in the arctic and northern temperate zones, how do you know the data isn't a more regional warming event - as opposed to global warming.”
tkman0 - It's global. Here's a video demonstrating that. And here's Marcott et al 2013, who show that recent climate changes are unprecedented in the Holocene despite any possible Bond events.
I would suggest giving him a link to the Most Used Myths, and having him tell you what doesn't answer his questions and hypotheses. If he has to keep changing his argument he didn't have a solid one to start with.
tkman0 - Where is this discussion occurring?
tkman0 @204, looks pretty global to me:
The graphs of the trend in warming from 1880-2013. The upper graph shows the data by zone, while the lower shows the average for each latitude band. As you can see, the equator shows a trend of around 0.8 C over that period, or 0.06 C per decade. The band with lowest warming is at 60 degres South (0.02 C per decade). That is low relative to the average (0.07 C per decade) but it is still warming - not cooling.
I suspect your interlocuter's data only shows ocean temperature anomalies relative to some recent period, where the recent La Nina's have draged the equatorial trend down. They are, however, short term fluctuations, and if that is what they have done, they are cherry picking.
The data comes from the GISS website, and is very usefull for debunking denier claims. You absolutely should bookmark it if you are interested in the debate.
tkman0, there are a variety of tools available to look at such things. Here's GIS Land-Ocean Temperature Index (GIS L-OTI) for the last decade, and here's the main page for the tool.
Here's graphed data for three latitudinal bands.
@KR, they're private messages back and forth between us because we were causing a rucus on the forums. As to the website...you probably dont wana know, not really your typical website for every day use.
Out of interest, the difference between the video linked to by KR and the data in the graph I showed above is that the data above is pure thermometer based data. Because there were no meteorological stations in Antarctica in 1880 (and indeed, not till the 1950s), it is unable to show temperatures for that period and hence no trend from that period either. In contrast, KR's video appears to be a reanalysis product. With reanalysis, they feed actual observations into a climate computer so that the computer's output is constrained to match observations where they are available. They then allow the computer to fill in the missing data. The process is accurate to a fairly high standard, but not perfect (nothing in science is). I would trust it as as good a representation of the actual temperature trends in those areas we are likely to get. You should, however, be aware of the difference so you can answer sensible questions (how did they measure Antarctic temperatures in 1880) and stupid ones ("I did not know we had satellites in orbit in 1884"). For the last, check the Youtube comments, or alternatively keep a hold of your braincells, and don't.
tkman0: Suggest that you invite your friend to post his/her concerns here on SkS. there really is no need for you to play the role of middleman.
[TD] But please inform your "friend" to keep each of his/her comments narrowly on one topic, to post each comment on an appropriately narrow thread, and to read the original post to which that thread is attached before writing the comment. I strongly suggest your friend not write any comments until after reading The Big Picture followed by The New Abridged Skeptical Science Reference Guide.
Global cooling - Is global warming still happening?
My first post: Antarctic ice is above 1981-2010 mean. March 20, 2014 Arctic ice is 3-5% below that same mean. There have been 3 consecutive recovery winters at the Arctic.Arctic sea ice area is 800,000 sq. km. below mean amount of >15% sea ice coverage. This is a lot, but this past winter added 800 cubic miles (3200 GTonnes) to the Arctic ice mass, to reach a peak of 2200 cubic miles of sea ice. This has to poke a hole in the "Polar Vortex" story. With normal ice volume, near normal ice area, how could it be so warm that the polar vortex was caused. This polar vortex narrative is getting harder to justify as each day goes by.
[JH] Pelease cite the sources for your data and for your assertions.
BTW, your subesequent comment was pure unadulterated, off-topic, concern trolling. It therefore was deleted.
Jetfuel @213 writes, "There have been 3 consecutive recovery winters at the Arctic." Those would have to be the winters of (in reverse order) 2013/14, 2012/13, and 2011/12. It is amazing how the summer record low Arctic sea ice extent in 2012, with a minimum sea ice extent nearly half (55%) of the 1981-2010 mean, and around 1/5th lower than the prior record in 2007 (82%). That the winter of 2011/12 could be a "recovery winter" clearly shows that what ever that undefined term means, it is irrelevant to Arctic sea ice analysis.
Even worse, the Arctic sea ice extent as of May 5th was 13.07 million km^2, only 0.657 million km^2 (4.8%) less than the 1982-2010 record, but still the third lowest on record - and lower than any year since 2007. So not only are "recovery winters" no indication of summer sea ice extent, they are no indication of spring sea ice extent either.
Jet Fuel, in other words, is feeding us irrelevant (and dated) data, not to mention completely failing to indicate how the facts he adduces are relevant to either the OP, or the claims he makes about polar vortexes.
Just to add to Tom's comment on the three recovery winters, thisimage from the NSIDC puts those winters into context very nicely:
The annual maximum sea ice extent usually takes place in March each year, and as you can see the last three winters have basically followed the long term declining trend in March sea ice.
My recommendation to jetfuel is to look at the long term trends because measurements for individual years or a few years are too susceptible to cherry picking. As Tom says, the winter sea ice extent maximum is not a good predictor of the summer minimum, as it depends a lot on Arctic weather during the summer (which causes a lot of variability around the long term trend). Also we should expect a larger *increase* in sea ice following a decreasing summer minima, simply because it leaves more open water to freeze (which gives a good opportunity for a misleading report of the "recovery", indeed SkS rebutted such arguments made by WUWT and Steve Goddard last year).
Yesterday PIOMAS came out with Arctic Sea Ice Volume measurements (h/t Neven). Their site says:
"The 2014 ice volume reached its annual maximum in April with 22,900 km3 which is just slightly below the long term trend and is the second lowest on record; just 400 km3 above the previous April minimum which occurred in 2011. However, variations over the last 4-years are well within the error bars of the volume estimates so that inter-annual variability over this period maybe due to errors in the sea ice reanalysis."
This is the second lowest annual maximum on record. Within the error measurements it is equal to the record low. Where did Jetfuel come up with a recovery???
Another set up for an interesting summer in the Arctic.
jetfuel wrote: "This has to poke a hole in the "Polar Vortex" story"
Umm... why exactly? Even if we pretended that Arctic sea ice really was 'recovering'... how would that call in to question the long term common Arctic air flow pattern?
nsidc data shows late March peaks of 15.22 million sq km for 2012, 15.1 million for 2013 and 14.9 million for 2014. The 1981 to 2010 avg is 15.4. The avg of 2012-2014 March peaks is 2.13% below the 1981-2010 avg peak of 15.4 million. 2.13% less ice area is the reason the Polar Vortex fell apart? The other 14.9 million sq km of ice couldn't save the vortex? Then, why hasn't this Vortex disintegration happened nearly every other year? Area with at least 15% ice is a rough indicator. the tremendous increase in ice volume in 2013 and 2014 also needs consideration. 2014 saw an 800 cubic mile seasonal increase in sea ice volume. That's the source of the 'recovery' I spoke of. For me to believe the 'polar vortexfell apart' line, I'd expect 10% less ice volume compared to last year, not 1.3% less ice area (14.9M vs 15.1M sq km) and a volume increase.
[JH] What is the basis of your "10% less ice voume" metric? Is it merely your personal opinion, or is it based on sound scientific research?
In case you have not noticed, personal opnions about science carry very little weight with the users of this website.
jetfuel:
Do you think that Arctic maximum extent is the only factor determining the behaviour of the polar vortex? Yes or no?
If yes, can you justify this position?
As far as your comment on the ice volume goes, PIOMAS anomaly data show ice volume has dropped by approximately 10,000 km³ since 1979. An 800 km³ increase in one year (and there are plenty of upward jolts in the data even as it follows the downwards trend) is much too short a time period to start speaking of a "recovery".
I have reproduced the graph below:
jetfuel:
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jetfuel, I demonstrated that the "recovery" was actually just a continuation of the downward trend in March maximum sea ice extent, and that an increase in the winter gain is what is expected simply because March sea ice extent is declining a bit more slowly than the September minimum extent.
There is nothing special about the recovery in the last three years. If you disregard the evidence and cherry pick in this manner, don't be surprised if your assertions are viewed with skepticism.
jetfuel's numbers for ASIV make no sense whatever unless it is about the state of the Arctic back in early November 2013 & the numbers are not meant to be exact.
@218 jetfuel states "This is a lot, but this past winter added 800 cubic miles (3200 GTonnes) to the Arctic ice mass, to reach a peak of 2200 cubic miles of sea ice." Since the summer 2013 minimum, PIOMAS has never shown numbers higher than 2,620 cu km (ie GTonnes) above the previous year. That was back at the beginning of November 2013, more Autumn than Winter. That difference has been shrinking since then & since the beginnng of March 2014, ASIV has been lower than the 2013 equivalent. This '2200 cubic miles' figure is ~9,000 cu km. That was the value of ASIV back at the beginning of November 2013.
As for the relevance of these numbers - pass.
JH, from your response to my 10% number. I'm trying to find support for the polar vortex line I've been told. Does the scientific expert concensus say 2% or more under March 2013 mean total ice area easily triggered this winter's polar vortex disintegration? I'm looking for an anomoly where it is much warmer in the Arctic in the winter so as to cause a once in decades event. I'm not seeing such an anomoly is total late March 2014 sea ice. Not seeing it in Antarctic sea ice coverage over last 2 years. Not seeing it in 2014 ice volume at the Arctic (up 800 cubic miles). What I do see is a dramatic improvement from 2012 to 2013 Sept Arctic sea ice area, revovering 49% of the gap to 1981-2010 mean sea ice coverage (nsidc). From the 3.45M sq km of sea ice on Sept 13, 2012 to 5.1M sq km on same day of 2013 is a 49% recovery of the 3.37M sq km gap from the 3.45 of 2012 to the 1981-2010 mean of 6.82 M sq km. Why just focus on the .8M sq km or so gap in max ice area (~2-3%) in March and ignore the 11+M sq km seasonal 2013 increase? In questioning my use of 'recovery'? 11+M is a whole lot more new added ice for it to be coinciding with the Polar Vortex falling apart. On the contrary, with 11+M sq km of new ice added, it makes sense to me that this winter was like it was. It was ranked 53rd coldest in Indiana in the last 100 years. Pretty average for the last 100 years. 2nd consecutive winter wher it is colder than the previous one. If the '14-'15 winter makes another similar jump, we might break the 1979 Great Lakes frozen area % record that we came within 1% of this past winter.
jetfuel.
It is probably too simplistic to try and relate the splitting of the polar vortex to just ice extent. There were major influxes of warm air into the Arctic along 2 corridors - the east pacific and US West coast, and east of Greenland over Svalbard. These incursions of warm air split the vortex and in effect partly pushed it out of the Arctic. Given the time of year this occurred at I think it was more likely directly caused by weather patterns further south. However that doesn't rule in or out other relationships between the polar regions and lower latitudes. For example changes in NH snow cover, changes to the Polar Jet Stream, warming of ocean currents affecting Sea Surface Temperatures etc. Things are changing up there, global warming is a very big part of that, but the exact dynamics and trajectory of everything that will happen isn't clear. One thing that is pretty clear is that the cause-and-effect chain for any changes won't have just two links in it.
From nsidc: Preliminary measurements from CryoSat show that the volume of Arctic sea ice in autumn 2013 was about 50% higher than in the autumn of 2012. In October 2013, CryoSat measured approximately 9,000 cubic kilometers (approximately 2,200 cubic miles) of sea ice compared to 6,000 cubic kilometers (approximately 1,400 cubic miles) in October 2012. About 90% of the increase in volume between the two years is due to the retention of thick, multiyear ice around Northern Greenland and the Canadian Archipelago.
This didn't have anything at all to do with this last very cold winter?