Climate models for the layman

The Global Warming Policy Foundation, a British think tank, has just published an excellent review of climate models, their problems and uncertainties, all of which show that they are inadequate for policy formulation. The paper is written by Dr. Judith Curry, the author of over 180 scientific papers on weather and climate. She recently retired from the Georgia Institute of Technology, where she held the positions of Professor and Chair of the School of Earth and Atmospheric Sciences. She is currently President of Climate Forecast Applications Network.

You can read the 30-page paper here:

Here is the executive summary:

There is considerable debate over the fidelity and utility of global climate models (GCMs). This debate occurs within the community of climate scientists, who disagree about the amount of weight to give to climate models relative to observational analyses. GCM outputs are also used by economists, regulatory agencies and policy makers, so GCMs have received considerable scrutiny from a broader community of scientists, engineers, software experts, and philosophers of science. This report attempts to describe the debate surrounding GCMs to an educated but nontechnical audience.

Key summary points

• GCMs have not been subject to the rigorous verification and validation that is the norm for engineering and regulatory science.

• There are valid concerns about a fundamental lack of predictability in the complex nonlinear climate system.

• There are numerous arguments supporting the conclusion that climate models are not fit for the purpose of identifying with high confidence the proportion of the 20th century warming that was human-caused as opposed to natural.

• There is growing evidence that climate models predict too much warming from increased atmospheric carbon dioxide.

• The climate model simulation results for the 21st century reported by the Intergovernmental Panel on Climate Change (IPCC) do not include key elements of climate variability, and hence are not useful as projections for how the 21st century climate will actually evolve.

Climate models are useful tools for conducting scientific research to understand the climate system. However, the above points support the conclusion that current GCMs are not fit for the purpose of attributing the causes of 20th century warming or for predicting global or regional climate change on timescales of decades to centuries, with any high level of confidence. By extension, GCMs are not fit for the purpose of justifying political policies to fundamentally alter world social, economic and energy systems. It is this application of climate model results that fuels the vociferousness of the debate surrounding climate models.

The Stadium Wave Hypothesis – how the climate cycles between warm and cool

All climate models used by the IPCC failed to predict the “pause” in global warming since 1998. Two Georgia Tech researchers, Dr. Marcia Glaze Wyatt and Dr. Judith A. Curry, hypothesize that multi-decadal oscillations in atmospheric and oceanic circulation regimes, such as the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) can amplify or diminish longer term atmospheric warming or cooling.

Their hypothesis is likened to a “stadium-wave signal that propagates like the cheer at sporting events whereby sections of sports fans seated in a stadium stand and sit as a ‘wave’ propagates through the audience.  In like manner, the ‘stadium wave’ climate signal propagates across the Northern Hemisphere through a network of ocean, ice, and atmospheric circulation regimes that self-organize into a collective tempo.”

This study analyzed data from the atmosphere, ocean, and sea ice since 1900.  “The study provides an explanation for seemingly incongruous climate trends, such as how sea ice can continue to decline during this period of stalled warming, and when the sea ice decline might reverse.  After temperatures peaked in the late 1990s, hemispheric surface temperatures began to decrease, while the high latitudes of the North Atlantic Ocean continued to warm and Arctic sea ice extent continued to decline. According to the ‘stadium wave’ hypothesis, these trends mark a transition period whereby the future decades will see the North Atlantic Ocean begin to cool and sea ice in the Eurasian Arctic region begin to rebound.”

The Stadium Wave hypothesis predicts that the current “pause” in warming will continue well into the 2030s.

Near the end of their paper, the researchers provide this caveat: “While evidence strongly supports our hypothesis of a secularly varying climate signal propagating through a hemispheric network of synchronized ocean, atmosphere, and ice indices during the 20th century, we cannot know if this variability, tempo, and sequential chronology will continue into the future. How changes in external forcing might affect the Eurasian Arctic sea ice in context of an apparent quasi-oscillatory ocean-ice-atmosphere system is a burning question.”

They do note that study of 300 year proxy data suggests changes in tempo and amplitude of the “Stadium Wave” did occur prior to the 1800s.

The bottom line is that this hypothesis explains the behavior of global temperature while the carbon dioxide hypothesis does not.

The research is published in the September issue of Climate Dynamics.

See more detail at Dr. Judith Curry’s blog here. You can download the full manuscript (in pre-publication form) here.

Another paper relating the AMO and PDO cycles to conditions in the Southwestern US concludes: “If the AMO continues its quasi-cyclic behavior the US SW temperature should remain stable and the precipitation should significantly increase during the next few decades.”  That bodes well for our future water supply.  For that story see here.

See also:

The significance of the 17-year pause in global warming

Critique of the IPCC’s Summary for Policymakers

IPCC downplays abrupt climate change danger

Why climate science is fallible

IPCC AR5 climate report may be dead on arrival

IPCC 95% Certain – hold on to your wallets

The new IPCC climate report is already in trouble

More evidence that climate models are wrong

On consensus in science

“Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the result will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory.” –Stephen Hawking

“It does not matter who you are, or how smart you are, or what title you have, or how many of you there are, and certainly not how many papers your side has published, if your prediction is wrong then your hypothesis is wrong. Period.” –Richard Feynman

“Who would dare assert that we know all there is to be known?” –Galileo Galilei

On many of my posts about climate change, I get comments from believers in catastrophic anthropogenic global warming that take issue with what I have written.  That’s fine.  But, instead of presenting facts to support their case, many of these commenters resort to invoking the myth alleging that about 98% of climate scientists say human carbon dioxide emissions are the major cause of recent warming. This alleged consensus, they say, must mean it’s true and should end all argument.  Some of these commenters also seem to be confused about cause and effect, and so conflate the perceived incidence of warming or cooling with attribution of cause.

So let’s look first at where these consensus numbers came from and then I will comment more generally on consensus in science.

One source was from a study by Peter Doran and Maggie Zimmerman at the University of Illinois. (See here and here.) They emailed 10,257 scientists and asked two questions:

Question 1: “When compared with pre-1800s levels, do you think that mean global temperatures have generally risen, fallen, or remained relatively constant?” I would answer that temperatures have risen because in the 20th Century the planet warmed from the depths of the “Little Ice Age.” The answer to this question is verifiable by observation of physical evidence.

Question 2 (the controversial question): “Do you think human activity is a significant contributing factor in changing mean global temperatures? The researchers didn’t define “significant.” This question solicits an opinion. The basic premise of the question has not been verified by physical evidence.

Of the original 10,257 scientists queried, 3,146 responded. Of those, Doran and Zimmerman whittled the number down to 77 who had been successful in getting more than half of their papers recently accepted by peer-reviewed climate science journals. Of the 77, 75 answered “yes” to question 2,that’s 97.4%. So, in that study the whole 98% claim is based on 75 positive answers out of 3,146 respondents.

The other possible source for the consensus myth is a paper by Anderegg et al, in PNAS. In that study, the researchers didn’t bother to poll scientists, rather they scanned the literature and constructed a “database of 1,372 climate researchers based on authorship of scientific assessment reports and membership on multi-signatory statements about ACC [anthropogenic climate change]” as outlined by the Intergovernmental Panel on Climate Change. The researchers then arbitrarily assigned “expert” status to those who had published at least 20 papers. That cut the number of “experts” to 908. In the supporting material at the end of the paper we find that of the original 1,372 researchers, 619 were contributors to the IPCC’s Fourth Assessment report, and 212 were signatories to the UN’s Bali declaration. After culling duplicate names, the paper’s authors wound up with 472 “experts” out of tens of thousands of practicing researchers.

We see from the two studies, therefore, that this claim of a 98% consensus comes from carefully culled researchers, most of whom worked on the IPCC reports, are said to believe that humans are the principal cause of climate change. The 98% consensus consists of researchers who have a vested interest in continuing the myth of significant global warming caused by human carbon dioxide emissions. Follow the money. The 98% consensus is just another manipulated number pulled out of the air.

Now, let’s turn to a more general discussion of consensus.

Dr. Judith Curry, Chair of the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology, has a long paper on consensus in climate science. She begins by saying: “The manufactured consensus of the IPCC has had the unintended consequences of distorting the science, elevating the voices of scientists that dispute the consensus, and motivating actions by the consensus scientists and their supporters that have diminished the public’s trust in the IPCC.”

She goes on the write: “With genuinely well-established scientific theories, ‘consensus’ is not discussed and the concept of consensus is arguably irrelevant… While a consensus may arise surrounding a specific scientific hypothesis or theory, the existence of a consensus is not itself the evidence.” And she notes: “If the objective of scientific research is to obtain truth and avoid error, how might a consensus seeking process introduce bias into the science and increase the chances for error? ‘Confirmation bias’ is a well-known psychological principle that connotes the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or an existing hypothesis. Confirmation bias usually refers to unwitting selectivity in the acquisition and interpretation of evidence.”

There are some famous failures of consensus in history. The pre-eminent one was the belief that the Earth was the center of the universe. That was the prevailing consensus 500 years ago. That consensus was shown to be in error, first by Nicolaus Copernicus and later by Galileo, Kepler, and Newton.

In 1912, Alfred Wegener, building on earlier work by Frank Bursley Taylor, proposed that the continents did not have a permanent spacial relationship to each other, i.e., there was continental drift. Wegener could not, however, provide a reasonable mechanism for his hypothesis, therefore the consensus, for 50 years, was that he was wrong. By the 1960s, geological research did provide the mechanism and Wegener’s continental drift became part of the larger theory of plate tectonics.

Those who credulously invoke the “ 98% consensus” as an argument are displaying an ignorance of the facts and of how science works.  I refer you to Michael Crichton who said:

“I regard consensus science as an extremely pernicious development that ought to be stopped cold in its tracks. Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled. Whenever you hear the consensus of scientists agrees on something or other, reach for your wallet, because you’re being had.”

“Let’s be clear: The work of science has nothing whatever to do with consensus. Consensus is the business of politics. Science, on the contrary, requires only one investigator who happens to be right, which means that he or she has results that are verifiable by reference to the real world. In science consensus is irrelevant. What is relevant is reproducible results. The greatest scientists in history are great precisely because they broke with the consensus.”

Berkeley temperature study update: colleague says claim was huge mistake

Last week I wrote about Dr. Richard Muller’s BEST (Berkeley Earth Surface Temperature) program and its depiction by the press in the post Press punked by Berkeley temperature study.

Now, another voice has come forward.  The British paper Mail Online says that “Prof Judith Curry, who chairs the Department of Earth and Atmospheric Sciences at America’s prestigious Georgia Institute of Technology, said that Prof Muller’s claim that he has proven global warming sceptics wrong was also a ‘huge mistake’, with no  scientific basis.”  (See article here.)  Dr. Curry is a member of the BEST team and co-author of the four papers Dr. Muller released.

The Mail article goes on:

“In fact, Prof Curry said, the project’s research data show there has been no increase in world temperatures since the end of the Nineties – a fact confirmed by a new analysis that The Mail on Sunday has obtained.”

‘There is no scientific basis for saying that warming hasn’t stopped,’ she said. ‘To say that there is detracts from the credibility of the data, which is very unfortunate.’

However, Prof Muller denied warming was at a standstill.

‘We see no evidence of it [global warming] having slowed down,’ he told BBC Radio 4’s Today programme. There was, he added, ‘no leveling off’.

See Dr. Curry’s version of the Mail interview on her blog here.

The Mail Online article included the graph below.  The top panel shows the temperature data, which stopped in 2006, as published by Dr. Muller.  The bottom panel shows the last ten years of BEST data including 2011 so far.  The bottom panel shows a graph with level temperatures in spite of continuing increase in atmospheric carbon dioxide.


Dr. Curry, on her blog, says of the graph, “I agreed that the way the data is presented in the graph ‘hides the decline.’”

The phrase “hide the decline” refers to a now infamous part of the Climategate emails where we learned that in the construction of the Michael Mann’s “hockey stick” graph, tree ring proxy temperature data that had been used for most of the graph started to decline. It  was therefore truncated and surface temperature data was substituted in order to hide the decline and make it appear that warming was accelerating.

Dr. Curry adds in her criticism of the BEST graph, “There is NO comparison of this situation to Climategate.  Muller et al. have been very transparent in their methods and in making their data publicly available, which is highly commendable.”

Meteorologist Anthony Watts says on his blog, referring to the flatness of the temperature during the last ten years versus what was depicted on the BEST graph:

Indeed Best seems to have worked hard to obscure it. They present data covering .. almost 200 years… with a short x-axis and a stretched y-axis to accentuate the increase. The data is then smoothed using a ten year average which is ideally suited to removing the past five years of the past decade and mix the earlier standstill years with years when there was an increase. This is an ideal formula for suppressing the past decade’s data.

Watts also comments on how Muller handled the press and peer-review in the post: The BEST whopper ever.

To get the full story to date, read my last post, the Mail article, and Dr. Curry’s article, all linked above.  There are additional links of interest within Dr. Curry’s post.

I will reiterate that the BEST study dealt with only (rather unreliable) surface temperature data and does not attribute causes to temperature change.

For my perspective on climate change see:

A Perspective on Climate Change a tutorial