By Dr. David Whitehouse The GWPF (video follows)
Warming Interruptus
What is the reason for the lack of warming observed at the surface of the Earth since about 1997? Many causes have been proposed, and with increasing frequency, but most only rep- resent partial explanations. There are clearly more putative causes than can possibly be the case.
The pause has given climate science several things. It has provided a reassessment of the importance of natural climatic variability and its relationship to human influences on the climate. It has also shed light on the role of so-called sceptics as well as the successes and failures of climate communication.
Here are the current explanations for what has been called the biggest problem in climate science.
There is no pause
Some argue that the pause does not exist and that the warming trend seen to commence around 1980 has continued linearly with predictable variance around the mean. Of course it is possible to draw a straight line through most sets of data and attempt to justify it. However the length of the pause – 17 years – means that it cannot reasonably be regarded as part of a linear trend since 1980, so this explanation no longer works.¹
Low solar activity
Placing the role of solar activity in recent climate has been problematical. It is obvious that that periods of low solar activity in the past have coincided with cooler climatic conditions. Examples include the Dalton solar minimum around 1800 and the Maunder minimum in the 17th century (now shown to undoubtedly be a global event). Prior to about 1960 solar ac- tivity played a major role in the Earth’s climate, but in recent decades the IPCC has declared that it plays only a minor part, being dwarfed by human influences on the climate. So what is to be made of the recent decline in solar activity from the relatively high levels in the late 20th century? Some believe that the sun is entering a lengthy period of low activity as it has done in the past. Curiously, the commencement of that low activity coincides with the pause in global surface temperature. There are indications that almost all climate models underplay the effect of solar activity. Some have asked how, if the slight increase in total solar irradiance over the past 30 years cannot cause the warming, it can have contributed to the pause. This effect is likely to be relatively short lived. ²
As one paper on the subject put it:
The purpose of this communication is to demonstrate that the reduced rate in the global temperature rise complies with expectations related to the decaying level of solar activ- ity according to the relation published in an earlier analysis Without the reduction in the solar activity-related contributions the global temperatures would have increased steadily from 1980 to present.
The IPCC Fifth Assessment report estimates that despite the decline in solar output since 2000, total warming influences have increased faster since 1998 than over 1951–1998 or 1971–1998.
The heat is in the oceans
The most cited explanation for the pause is that the warming has gone into the oceans, and indeed the oceans are expected to absorb far more energy from the greenhouse effect than the land. But while the oceans have warmed in the past few decades, the extent to which this is due to mankind is debateable and the ocean heat content data is not behaving as some expected.
The best data we have is from the ARGO project. It goes back ten years and shows no warming in the uppermost layers of the oceans, and only modest warming down to 1800 m. If more heat is there it must be at deeper levels, where it is far harder to detect, and where it may well be locked out of the way for a thousand years. ³
Pacific decadal oscillation/Atlantic multidecadal oscillation
The Pacific decadal oscillation (PDO) switches from warm to cool every 30 years or so. It went positive in 1976–98 and has been mostly negative since about 2000. Given the Pacific’s pos- tulated influence on global climate this might indicate that the pause will continue until the PDO changes again, which will be in 15–20 years. A similar effect has also been suggested for the 60–70-year Atlantic multidecadal oscillation. (4)
Stratospheric water vapour
A very interesting paper suggests that natural variations in stratospheric water vapour could be responsible for about a third of the 1980–98 warming phase. Lead author Susan Solomon, of the US National Oceanic and Atmospheric Administration, said:
Current climate models do a remarkable job on water vapour near the surface. But this is different – it’s a thin wedge of the upper atmosphere that packs a wallop from one decade to the next in a way we didn’t expect.
Solomon and her co-authors concluded that decreases in stratospheric water vapor concentrations acted to slow the rate of increase in global surface temperature over 2000–9 by about 25% compared to the warming that would have occurred due only to carbon dioxide and other greenhouse gases.
More limited data suggest that stratospheric water vapour probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% compared to estimates neglecting this change. (5) However, the IPCC Fifth Assessment report shows very little warming from stratospheric water vapour over 1980– 2000 and no cooling from it over 2000–2010.
Chinese coal
Kaufman et al. (2012) suggest that the increased burning of coal in China is producing aerosols that are cooling the world. Others suggest this conclusion uses computer model data that has been cherrypicked to give the required result. It also does not include the latest solar data. (6,7) Moreover, the IPCC Fifth Assessment report does not support this finding.
The Pacific and the La Niñas
Some scientists suggest that recent cooling in the eastern equatorial Pacific reconciles cli- mate simulations and observations. Although they consider only 8.2% of the global surface they maintain that their computer model reproduces the annual-mean global temperature remarkably well for 1970–2012, a period that includes the current hiatus and a period of ac- celerated global warming. They postulate that the pause is part of natural climate variability, tied to a La-Niña-like decadal cooling. Although similar decadal hiatus events may occur in the future, they say, the multidecadal warming trend is very likely to continue due to man’s influence on the climate. (8)
Stadium waves
In this idea the extent of sea ice in the Eurasian Arctic enhances or dampens the long-term trend in rising temperature. Such changes introduce a low-frequency climate signal, which propagates across the Northern Hemisphere through a network of synchronised climate in- dices. The tempo of its propagation is rationalised in terms of the multidecadal component of Atlantic Ocean variability – the Atlantic multidecadal oscillation. The authors of the stadium wave paper say, ‘the Eurasian Arctic Shelf-Sea Region, where sea ice is uniquely exposed to open ocean in the Northern Hemisphere, emerges as a strong contender for generating and sustaining propagation of the hemispheric signal’. This explanation suggests that the pause should end in the 2030s. (9)
Arctic stations
Could it be that the pause is an artefact of poor spatial sampling? This is the suggestion from Cowtan and Way (2013). They compare different ways of accounting for the lack of weather- station data in various regions of the globe, principally the Arctic. They maintain that when the data are infilled the pause goes away and that the warming rate is similar to that seen in the 1990s.
The problem with this approach is that it involves creating a hybrid dataset using different infilling techniques for different regions, leaving it open to suggestions of cherrypicking. (10,11)
Pacific trade winds
According to some scientists a key component of the pause has been identified as the cool eastern-Pacific sea-surface temperature, even though it is not clear how this ocean has re- mained cool despite the long-term warming effect on the climate due to human activity. It is contended that there has been a strengthening in Pacific trade winds over the past two decades that has not been factored into climate models and that when these changes are made the effect is sufficient to account for the cooling of the tropical Pacific and a substan- tial slowdown in surface warming through increased subsurface ocean heat uptake. The sci- entists who suggest this have used model-based ocean temperature ‘reanalyses’, not mea- surements, and the mechanism involved implies the heat uptake in the top few hundred metres of the ocean should have increased during the pause, but measurements suggest otherwise. (12)
Note also that a few years ago other scientists were suggesting the opposite: that weak trade winds were responsible for the pause. (13)
Volcanoes
Since Mt Pinatubo in 1991 there have been no volcanic eruptions sufficiently large to obvi- ously reduce global temperatures. However, it has been argued that there has been a num- ber of smaller eruptions, the cumulative effect of which might partly account for the pause. This is the argument of Santer et al. (2014). However, these authors estimate this is likely to have caused only a 15% reduction in the temperature trend since 1998, only a fraction of the actual reduction. (14,15)
A coincidence!
It has been suggested that the computer climate predictions are running too warm because they are not properly accounting for volcanic aerosols, aerosols in general, solar activity and the effects of El Niños. In a recent Nature commentary, Schmidt et al. suggest that, taking these climatic influences together, they can completely explain the pause. The problem with this approach is that other influences are ignored and a non-unique combination of factors has been cherrypicked to provide the explanation. (16)
Notes
1 http://www.lse.ac.uk/GranthamInstitute/Media/Commentary/2012/october/myth-that-global-warming-stopped-in-mid-1990s.aspx
2 http://www.scirp.org/journal/PaperInformation.aspx?PaperID=41752
3 http://onlinelibrary.wiley.com/store/10.1002/2013EF000165/asset/eft24.pdf
4 http://www.pnas.org/content/110/6/2058.full.pdf
5 http://www.thegwpf.org/water-vapour-and-the-recent-global-temperature-hiatus/
6 http://wattsupwiththat.files.wordpress.com/2011/07/pnas-201102467.pdf
7 http://www.cawcr.gov.au/staff/jma/Decadal.trends.Meehl.JClim.2013.pdf
8 http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12534.html
9 http://judithcurry.com/2013/10/10/the-stadium-wave/
10 http://www.thegwpf.org/pause/. 11http://onlinelibrary.wiley.com/doi/10.1002/qj.2297/abstract. 12http://www.thegwpf.org/pacific-pause/
13 http://www.nature.com/nature/journal/v441/n7089/abs/nature04744.html
14 http://www.thegwpf.org/volcanoes-20-year-pause/
15 http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2098.html.
16 http://www.nature.com/ngeo/journal/v7/n3/full/ngeo2105.html
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These explanations are a distraction. The real answer is obvious.
THE MODELS ARE WRONG !
Did the oceans eat the 1910 to 1940 warming? Long live the pause.
You mean it’s not settled science that the missing atmospheric heat is hiding in the deep oceans, where it can’t be measured & for how it got there a good physical explanation not in violation of the laws of thermodynamics is lacking?
John: We know the models are wrong. The goal is to find out why and fix them or at least make them better.
Science marches on.
kenw says:
March 26, 2014 at 2:11 pm. If we know the models are wrong, why are climatologists still claiming they can be used to explain the climate? Experimenting with CGMs is one thing, though it seems to be about as successful as was seeking the Philosopher’s Stone by the pseudo-scientists of yore. Claiming wholly false skills for models is quite another.
Fake a chart showing temp and CO2 as a hockey stick…
…fake and lie about past and current temp records
lie about functions of CO2, etc etc
base computer games on fake temperature records, etc
Debate and discuss this “science” as if it wasn’t lies..
…and then wonder why no one can explain or predict anything
There is no cause for the pause or the trivial ups and downs in the last century. This is all just average weather and everyone is making a huge deal out of nothing. What do you expect that each date every year must have the exact same high and low temperature and precipitation; every year the same first and last frost date, same number of tornados and hurricanes, and if not there must be billions in research money to find the cause? What you are looking it is a stable climate, and it will remain so until it slides into the next ice age. But looking at it that way can’t justify requests for government grants.
typo, One r too many in the title. 😛
Prima facie, it would seem to be PDO, wouldn’t it? Same pattern as 1950-1975: Mild AGW counteracted by negative PDO, followed by positive PDO amplified by mild AGW. The latter of which led to the gross exaggeration of AGW, before the PDO was described by science (in 1996).
That even supports the so-called “97%” meme that “at least half the warming” from 1950-date is AGW of one variety or other.
This is entirely consistent with the lukewarmer position (i.e., Monckton, Spencer, Christie, Lindzen, both Pielkes, Curry, McIntyre, etc., etc.). It’s also the simplest, easiest solution.
If the Chinese burning coal causes cooling, shouldn’t the alarmists be rejoicing in this very clever (inscrutable!?) Chinese solution 🙂
There will be many more panicked excuses and much frantic hand flapping to come. What the fellow travelers are desperate for now is a “sciencey” sounding excuse to hide the fist-biting mistake at the foundation of every warming claim.
The problem is that adding radiative gases to the atmosphere cannot reduce the atmosphere’s radiative cooling ability. Our oceans can accumulate a huge amount of solar energy were it not for atmospheric cooling. And how does our atmosphere cool? Radiative gases.
The problem for the fellow travelers is the Internet means that the foundation claim that our oceans would be frozen solid without atmospheric cooling or DWLWIR can never be erased. Every one can see that the maths at core of the false claims can’t cope with SW accumulation in transparent materials.
There is no warming since 1980. Just plot the data on a time scale that shows the “big picture” instead of with a microscope.
http://www.woodfortrees.org/plot/best/scale:3/from:1880/plot/rss-land
Some have theorized that there are two primary climate trends 1) the first is a long term warming trend since circa 1750 which has maintained the virtually the same slope from circa 1750 through today. 2) The second trend is a 60-70 year cycle of warming and cooler (approx 23-35 years of alternating warming and cooling. (The Pacific decadal oscillation (PDO) switches from warm to cool every 30 years or so.)
Mesh these two trends together and it matches the warming, cooling and the current pauses of warming going all the way back to circa 1750.
There appear to be numerous shorter term trends, el nino, la nino, volcanic activity, etc. which seem to be only minor players.
Scientists, meteorologists, etc have known about the Pacific decadal oscillation/Atlantic multidecadal oscillation for more than a century and is common knowledge among meteorologists.
Why then – did our esteemed climate scientists – who are obviously smarter that the rest of us – not factor this into the models.
They should be trying to understand the ramp up in warming 1980-1998 rather than the “pause.”
To my mind, the advent of computer controlled gas engines with fuel injection explains the warm up – the skies clear as the auto population gradually changes over to clean engines, followed by the Chinese smog beginning near the end of that period and growing. Carbon was given credit for
much too large a portion of the warming trend. Warmists are all-too prolific in their speculations but very deficient in producing evidence.
17 years in which atmospheric levels of CO2 have risen from 364.09ppm (Feb 1997) to 398.03ppm (Feb 2014). That’s a 9% rise without any statistically-significant rise in global air surface temperatures.
ftp://aftp.cmdl.noaa.gov/products/trends/co2/co2_mm_mlo.txt
The obvious cause for the pause is the one the warmists dare not utter……
Tgasloli, quite so! Just natural variations … which cannot be admitted to by the natural climate change deniers
Perhaps data follow Hooke’s Law. The more you bend them the harder they resist?
FWIW, I think that measuring the length of the pause in terms of CO2 rise (33.96ppm by my measure) would be a really simple and effective way of getting the skeptics message across.
The most absurd aspect of the pause/hiatus is the contention that it is:
“the biggest problem in climate science”
It ceases to be a problem — great or small — the instant climate scientists concede that the extra CO2 is in no way responsible for dangerous runaway global warming.
It always was an implausible hypothesis And, regarding this hypothersis as flawed, obviates any need for an explanation. So why not simply draw the obvious cloncluion that the demonization of CO2 is entirely misplaced.
.
-The heat is in the oceans
The most cited explanation for the pause is that the warming has gone into the oceans, and indeed the oceans are expected to absorb far more energy from the greenhouse effect than the land. But while the oceans have warmed in the past few decades, the extent to which this is due to mankind is debateable and the ocean heat content data is not behaving as some expected.-
Ocean certainly absorb more sunlight than land.
But I don’t see how oceans absorb more energy from greenhouse effect, as the ocean is transparent to sunlight and is not transparent to IR of greenhouse gases.
So more 90% of energy of sunlight warms beneath the surface of the ocean, whereas no IR reaches below the surface of the ocean.
It seems sunlight has most effect upon temperature of ocean and greenhouse effect has least effect upon ocean.
Some comments seem indicated and their authors think that alarmist climate “scientists” are trying to make the models better. Nothing could be further from the truth. The models exist to create alarm and panic so as to justify draconian government action. No more, no less.
A working climate model would be destroyed as heresy.
All are aware of the ever growing pauses in the cause
David Whitehouse’ brief elaboration of “the plateau” (as Nature dubbed it), will figure quite prominently this spring.
I give an annual global warming talk to Denver, Colorado, area “skeptics” – those who mostly lean gullibly Warmist, yet still harbor pretensions of being critical thinkers about scientific matters. This brilliantly summarizes the quandary that certain, settled global warming science has become – a lacunae for out time to Believers.
Real skeptics, of course, have long thought their pretensions of knowledge and claims of “science” were bunk. Just because something is fashionably labeled “science” doesn’t mean it is. And now the most pretentious chickens of all have come home to roost, because a re-think is so painfully called for.
Cynics of authority – now is out time to delight in our Schadenfreude.
Amen Lattitude amen.
Like it. It’s cheeky.
In fact very tongue in cheeky. 🙂
Brit humour. 🙂