From NCAR:
Future warming likely to be on high side of climate projections, analysis finds
November 08, 2012
BOULDER—Climate model projections showing a greater rise in global temperature are likely to prove more accurate than those showing a lesser rise, according to a new analysis by scientists at the National Center for Atmospheric Research (NCAR). The findings, published in this week’s issue of Science, could provide a breakthrough in the longstanding quest to narrow the range of global warming expected in coming decades and beyond.
NCAR scientists John Fasullo and Kevin Trenberth, who co-authored the study, reached their conclusions by analyzing how well sophisticated climate models reproduce observed relative humidity in the tropics and subtropics.
The climate models that most accurately captured these complex moisture processes and associated clouds, which have a major influence on global climate, were also the ones that showed the greatest amounts of warming as society emits more greenhouse gas into the atmosphere.
“There is a striking relationship between how well climate models simulate relative humidity in key areas and how much warming they show in response to increasing carbon dioxide,” Fasullo says. “Given how fundamental these processes are to clouds and the overall global climate, our findings indicate that warming is likely to be on the high side of current projections.”
The research was funded by NASA.
Moisture, clouds, and heat
The world’s major global climate models, numbering more than two dozen, are all based on long-established physical laws known to guide the atmosphere. However, because these relationships are challenging to translate into software, each model differs slightly in its portrayal of global climate. In particular, some processes, such as those associated with clouds, are too small to be represented properly.
The most common benchmark for comparing model projections is equilibrium climate sensitivity (ECS), or the amount of warming that eventually occurs in a model when carbon dioxide is doubled over preindustrial values. At current rates of global emission, that doubling will occur well before 2100.
For more than 30 years, ECS in the leading models has averaged around 5 degrees Fahrenheit (3 degrees Celsius). This provides the best estimate of global temperature increase expected by the late 21st century compared to late 19th century values, assuming that society continues to emit significant amounts of carbon dioxide. However, the ECS within individual models is as low as 3 degrees F and as high as 8 degrees F (, leaving a wide range of uncertainty that has proven difficult to narrow over the past three decades.
The difference is important to reconcile, as a higher temperature rise would produce greater impacts on society in terms of sea level rise, heat waves, droughts, and other threats.
Clouds are one of the main sticking points, say the NCAR authors. Although satellites observe many types of clouds, satellite failure, observing errors, and other inconsistencies make it challenging to build a comprehensive global cloud census that is consistent over many years.
However, satellites perform better in measuring water vapor, and estimates of the global distribution of relative humidity have become more reliable. Relative humidity is also incorporated in climate models to generate and dissipate clouds.
Fasullo and Trenberth checked the distribution of relative humidity in 16 leading climate models to see how accurately they portray the present climate. In particular, they focused on the subtropics, where sinking air from the tropics produce very dry zones where most of the world’s major deserts are located. The researchers drew on observations from two NASA satellite instruments — the Atmospheric Infrared Sounder (AIRS) and Clouds and Earth’s Radiant Energy System (CERES) – and used a NASA data analysis, the Modern-Era Retrospective Analysis for Research and Applications (MERRA).
The seasonal drying in the subtropics and the associated decrease in clouds, especially during May through August, serve as a good analog for patterns projected by climate models.
“The dry subtropics are a critical element in our future climate,” Fasullo says. “If we can better represent these regions in models, we can improve our predictions and provide society with a better sense of the impacts to expect in a warming world.”
Accurate humidity yields higher future temperatures
Estimates based on observations show that the relative humidity in the dry zones averages between about 15 and 25 percent, whereas many of the models depicted humidities of 30 percent or higher for the same period. The models that better capture the actual dryness were among those with the highest ECS, projecting a global temperature rise for doubled carbon dioxide of more than 7 degrees F. The three models with the lowest ECS were also the least accurate in depicting relative humidity in these zones.
“Because we have more reliable observations for humidity than for clouds, we can use the humidity patterns that change seasonally to evaluate climate models,” says Trenberth. “When examining the impact of future increases in heat-trapping gases, we find that the simulations with the best fidelity come from models that produce more warming.”
The authors focused on climate models used for the 2007–08 assessment by the Intergovernmental Panel on Climate Change. The next-generation models being used for the upcoming 2013–14 IPCC assessment were found to behave in a similar fashion, as described in a preliminary analysis by the authors in a supplement to their paper.
“In addition to providing a path forward and focus for improving models, results strongly suggest that the more sensitive models perform better, and indeed the less sensitive models are not adequate in replicating vital aspects of today’s climate,” write the authors in the paper.
About the article
Title: A Less Cloudy Future: The Role of Subtropical Subsidence in Climate Sensitivity
Authors: John Fasullo and Kevin Trenberth
Journal: Science
Joachim Seifert says:
November 9, 2012 at 4:02 am
I think DGH was being sarcastic…
Climastrology 101:
1. Write two dozen climate model programs.
2. Run 100,000 simulations with each.
3. Find the handful that almost approximate reality.
4. Trumpet the accuracy of the models!
Climate models are like physicist Arthur Eddington’s version of the infinite monkey theorem:
Given enough time, an army of monkeys strumming on typewriters could write all the books in the British Museum.
Bob says:
November 9, 2012 at 4:02 am
You forgot the /sarc. Be careful about that, or you will have the nutters thinking you support their lunacy.
“The worlds major global climate models, numbering more than two dozen, are all based on long-established physical laws known to guide the atmosphere.”
“Based upon…physical laws” is pretty much all you can say about the climate model formulations. They do NOT actually solve the instantaneous equations which govern the conservation of fluid mass, momentum, energy, and species/phase. And, of course, they will say NOTHING about how they are “solved” numerically…(nobody seems very interested in that).
As someone who doesn’t enjoy sweaty summers, I was thrilled to see they are apparently promising us rh levels that all fall comfortably below 50%, in exchange for a paltry couple of dry bulb degrees. Guys, give me that and I will be your friend for life!
I think an interesting complementary study would be to take the models that have done the best job of modeling global temperature and see how well they do at modeling humidity at subtropical and tropical latitudes.
Lance Wallace noted:
Perhaps there should be two study periods, 2002-2007 (six years?) and 2002-2011. It seems to me that cause and effect doesn’t really matter in this sort of study unless you’re trying to describe the processes involved.
robert barclay says:
November 9, 2012 at 12:32 am
> You can’t heat water from above.
I’m not sure why you posted that here, perhaps I missed the relevant reference.
I’m quite confident I can heat water from above with air whose dew point is warmer than the water. I’ll likely make fog too.
Remarkable that what is nothing more than an exercise in proxy parameter tweaking should warrant publication in Science.
Quote:
“Clouds are one of the main sticking points, say the NCAR authors. Although satellites observe many types of clouds, satellite failure, observing errors, and other inconsistencies make it challenging to build a comprehensive global cloud census that is consistent over many years.”
Top of the atmosphere measurement of radiation does not support Trenberth’s hypothesis. Planetary clouds in the tropics increase or decrease in the tropics to reflective more or less sunlight off into space, thereby resisting forcing changes.
http://www-eaps.mit.edu/faculty/lindzen/236-Lindzen-Choi-2011.pdf
Quote:
“On the Observational Determination of Climate Sensitivity and Its Implications
We estimate climate sensitivity from observations, using the deseasonalized fluctuations in sea surface temperatures (SSTs) and the concurrent fluctuations in the top-of-atmosphere (TOA) outgoing radiation from the ERBE (1985-1999) and CERES (2000-2008) satellite instruments. Distinct periods of warming and cooling in the SSTs were used to evaluate feedbacks. An earlier study (Lindzen and Choi, 2009) was subject to significant criticisms. The present paper is an expansion of the earlier paper where the various criticisms are taken into account. ….
….we show that simple regression methods used by several existing papers generally exaggerate positive feedbacks and even show positive feedbacks when actual feedbacks are negative. We argue that feedbacks are largely concentrated in the tropics, and the tropical feedbacks can be adjusted to account for their impact on the globe as a whole. Indeed, we show that including all CERES data (not just from the tropics) leads to results similar to what are obtained for the tropics alone – though with more noise.
… We again find that the outgoing radiation resulting from SST fluctuations exceeds the zerofeedback response thus implying negative feedback. In contrast to this, the calculated TOA outgoing radiation fluxes from 11 atmospheric models forced by the observed SST are less than the zerofeedback response, consistent with the positive feedbacks that characterize these models. The results imply that the models are exaggerating climate sensitivity.”
Observed warming also does not support Trenberth.
http://www.spiegel.de/international/world/0,1518,662092,00.html
Quote:
Even though the temperature standstill probably has no effect on the long-term warming trend, it does raise doubts about the predictive value of climate models, and it is also a political issue. For months, climate change skeptics have been gloating over the findings on their Internet forums. This has prompted many a climatologist to treat the temperature data in public with a sense of shame, thereby damaging their own credibility.
Quote:
“It cannot be denied that this is one of the hottest issues in the scientific community,” says Jochem Marotzke, director of the Max Planck Institute for Meteorology in Hamburg. “We don’t really know why this stagnation is taking place at this point.”
Quote:
Just a few weeks ago, Britain’s Hadley Centre for Climate Prediction and Research added more fuel to the fire with its latest calculations of global average temperatures. According to the Hadley figures, the world grew warmer by 0.07 degrees Celsius from 1999 to 2008 and not by the 0.2 degrees Celsius assumed by the United Nations Intergovernmental Panel on Climate Change. And, say the British experts, when their figure is adjusted for two naturally occurring climate phenomena, El Niño and La Niña, the resulting temperature trend is reduced to 0.0 degrees Celsius — in other words, a standstill.
Quote:
But a few scientists simply refuse to believe the British calculations. “Warming has continued in the last few years,” says Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (PIK). However, Rahmstorf is more or less alone in his view. Hamburg Max Planck Institute scientist Jochem Marotzke, on the other hand, says: “I hardly know any colleagues who would deny that it hasn’t gotten warmer in recent years.”
FFS….
The graph above in the article shows two things
1) That almost all models lie well outside the observations, and thus are not likely to be accurate
2) That the VERY FEW models that lie inside the observations are ON ODDS likely to simply be there by chance, given that almost all model got it wrong.
What Trenberth is proposing is that we take the results of these models, which he has now shown to be wrong, and use their wrong answer to predict the right answer.
However, this is faulty reasoning. You cannot take demonstratably wrong answers and from this predict the right answer. That is nonsense logic. There are an infinte number of wrong answers and only one right answer.
The only conclusion to be drawn from this work is that almost all models got it wrong and thus models are not reliable. Wrong answers cannot be used to predict the right answer. All that wrong answers tell you is that the source of the answers is likely to give more wrong answers.
We just reelected Obama. The earth is really going to start cooling and the oceans stop rising now. Trenberth can relax and declare victory.
So first the humidity of upper atmosphere was expected to go up, thus increasing the recycled IR flow back to the surface. Then it was measured, that exact opposite is happening. However, it was found out to be worse than we thought, because in drying atmosphere, CO2 increase will even more increase the IR back flow.
IMO the back radiation causing 33K warming is nonsense by itself, but let them boys play.
In effect, Trenberth is using a version of the “selection bias” that created the hockey stick. He is “calibrating” the climate models using relative humidity, to tell him which climate models make “good thermometers”.
What Trenberth has assumed is that even though the models got the humidity wrong, they got the temperature right, thus the near straight line relationship between temperature and humidity shown in the graph can be used to predict where the correct answer lies.
However, the graph shows clearly that the model have the humidity wrong, and thus their prediction of temperature is not reliable. As a result, none of the data points that lie outside the observation can be trusted to draw any sort of a trend.
What the large number of models that lie outside the observations are telling you is that a large number of models got it wrong. Since all the models are based on the same basic science, it is telling you that climate models in general are not reliable.
How this nonsense analysis got past peer review says mountains about the state of peer review in climate science. But then, many other forms of “selection bias” are accepted as gospel in climate science. What Trenberth has discovered is yet another way to draw the hockey stick.
This is desperate stuff – even for Trenberth.
This Fasullo et al paper sounds very much like Spencer and Braswell 2011, wherein they looked at how models tracked radiative imbalance and temperatures, and compared climate sensitivities in those models to observations. S&P 2011 seemed to be very celebrated in the skeptic community.
Except, of course, that S&B 2011 examined 14 models, only showed six of those results – omitting those that directly contradicted their _low sensitivity_ conclusions. S&B 2011 were widely and directly rebutted in the literature; that work simply didn’t hold up under examination.
Fasullo and Trenberth 2012 (http://phys.org/news/2012-11-future-high-side-climate.html), http://www.sciencemag.org/content/338/6108/792.short) appears to include _all_ of the models that they examined, which (IMO) in itself is a considerable improvement over S&B 2011. And humidity, the basis of their comparison, is indeed better observed than cloud cover and cloud types. It will be interesting to see how their conclusions (which reject low climate sensitivity models as failing to match observations) hold up under detailed examination and future observations.
[snip – policy violation to link bomb your own site]
Are we still pretending that Trenberth is an actual scientist? I saw a talk from him at my university a few years ago…he wouldn’t answer ANY skeptical questions whatsoever….he would literally reply that he would not answer skeptical questions that denied climate change…even when the questions did nothing of the sort.
NCAR scientists John Fasullo and Kevin Trenberth, who co-authored the study, reached their conclusions after realizing that the Obama climate scam gravy train was pulling back into the station and tickets were still free.
Ummmmmm. We have 2 feet of “white globull warming” here in Edmoton,and -18C.Man.I am some happy it’s warming! Oh. And it is all unprecented(sp?)! Good thing we are getting a drought.
Are these people really serious?
So Trenberth finds that the models don’t get temperature and humidity correct at the same time. If I was him I would say:
“Hmmm. There must be something wrong with the physics in our models that we can’t get both right. Let’s study that and figure out what’s wrong with the models.”
However, Trenberth says:
“Hmmm…. We know the physics in our models is correct therefore it’s time to look at that pairwise algorithm we use and see if we can falisify (adjust) the historical record of temperatures and make the data match the models then we have models that match all the data.”
Well he didnt say that at least not publicly. Publicly he just ignored the fact that the models that get humidity right are the models that get temperature the most wrong. As someone else asked: How is this worthy of being published? Since none of the models got anything right it seems that publishing a single amusing conundrum of the models is a pointless valueless exercise considering the models have hundreds of amusing conundrums and inaccuracies.
From http://motls.blogspot.com/2012/10/climate-sensitivities-in-various-papers.html
Year Authors Med. Interval C.L.
2010 Pagani et al. [8] 7-9
2012 Dowsett [6] 4-8
2012 Hansen, Sato with slow feedbacks 6 4-8 66%
2004 Lea 5.2 4.4-6.0 95%
2012 Rohling et al. 3.1 1.7-5 66%
2007 IPCC AR4 3 2-4.5 66%
2011 Annan, Hargreaves [3] 2-4 95%
2012 Hansen, Sato w/o slow feedbacks 3 2-4 66%
2006 Forest et al. 2.9 2.1-8.9 90%
2010 Kohler et al. 2.4 1.4-5.2
2011 Schmittner et al. 2.3 1.7-2.6 66%
2008 Chýlek, Lohmann [1.8] 1.3-2.3 95%
2012 Gillett [1.55] 1.3-1.8
2012 Lewis 1.3 0.8-2.1 90%
2009 Douglas, Christy 1.1
2012 Asten 1.1 0.7-1.5 66%
2011 Lindzen, Choi 0.7 0.5-1.3 95%
Doesn’t appear that Trenberth has much company in his projections…
A correction:
The research was funded by
NASAthe American taxpayers (who are now going to be taxed even more to pay for this garbage).The opening post appears to be an uncredited copy of the article in http://phys.org/news/2012-11-future-high-side-climate.html – directly reproducing someone else’s article, in entirety, without attribution, is both a copyright and intellectual property violation.