Richard Muller: Climate Change Skeptic

August 13, 2019

In other posts within this blog series, we have profiled several science deniers who, adhering to Neil deGrasse Tyson’s pithy definition, “reject the evidence” when it invalidates their predetermined conclusions. In order to illustrate the contrast with Tyson’s “skeptics” who “embrace the evidence,” it is useful to compare the cases of Richard Muller of the University of California, Berkeley and Will Happer of Princeton University, the latter of whom is profiled elsewhere in this series.

Figure 1.  Richard Muller

Muller and Happer have somewhat analogous biographies. Both have enjoyed well-regarded research careers as inventive experimental physicists at prestigious universities. Muller received one of the MacArthur Foundation “genius” awards in 1982. He did important early work on developing the technique of accelerator mass spectrometry and on measuring the anisotropy of the cosmic microwave background relic radiation from an early stage in the universe’s evolution. He made a major contribution to cosmological research by co-founding the Berkeley Real-Time Supernova Search, which later morphed into the Supernova Cosmology Project and led to Muller’s student Saul Perlmutter sharing the 2011 Nobel Prize in Physics for the discovery of the accelerating expansion of the universe.

Both Happer and Muller accepted invitations to join the exclusive and somewhat secretive JASON scientific group, which advised the Department of Defense and other government agencies, at early stages of their careers: Happer when he was still a post-doctoral assistant at Columbia University in 1973, and Muller when he was a junior faculty member at Berkeley in the early 1980s. Both made important contributions to the Jason project to improve the correction for atmospheric distortions of surveillance or astronomical images obtained with terrestrial telescopes. Both share the arrogant self-confidence of most Jason physicists that they can find the best solutions to any scientific problem, and that few solutions are validated before they have weighed in to evaluate the evidence themselves. That self-confidence can fuel brilliant scientific breakthroughs, but at the same time, the arrogance can sometimes be manifested as a dismissive attitude toward the work of others. Muller has referred to Happer as “my friend.”

Unlike Happer, who has done no original climate-related research himself, Muller’s eclectic interests have included work on earth sciences, specifically on the causes of periodic ice ages and deglaciation periods in the planet’s history. Both Happer (in his early 1990s position as Director of Energy Research in the Department of Energy) and Muller (as a researcher) first became skeptical of studies establishing the record of global warming when they received what they perceived as inadequate responses from researchers regarding the rigor of their measurements and methods. But Happer’s and Muller’s paths have diverged during the current century as they have taken quite different approaches to addressing their initial skepticism.

Muller’s Initial Skepticism

Muller first waded publicly into the debate over climate science in the early years of this century, addressing the infamous “hockey stick” plot in Fig. 2. The graph represents an attempt, first reported in peer-reviewed papers by Michael Mann, Raymond Bradley and Malcolm Hughes, to reconstruct systematically northern hemisphere mean surface temperatures across the past millennium. The graph appears to show that the rapid warming trend of the past century or so is historically anomalous. A version of it was featured prominently in the 2001 Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) and became a focus of critical attention from skeptics, deniers and Congressional opponents.

Figure 2. The original 1999 “hockey stick” graph of Mann, Bradley and Hughes, compiling information on mean northern hemisphere temperatures over a 1000-year period. The red curve represents global temperature measurements, available from 1850 onward. The blue curve represents an average over several proxies sensitive to northern hemisphere temperatures, with uncertainties represented by the light blue band. The green dots represent 30-year global averages reconstructed in 2013 (Nature Geoscience 6, 339) by the PAGES 2k Consortium.

Objections to the hockey stick graph were raised about both the proxy reconstructions during the medieval period and possible biases in the data and statistical analyses used for the industrial era. The proxies rely on such indirect temperature-sensitive measurements as the width and density of tree rings, the ratio of different oxygen isotopes in glacial ice core samples, and variations in the species of microscopic organisms trapped in ocean sediment. Muller weighed into the controversy with a 2003 column and a 2004 article published in the MIT Technology Review. He supported an analysis by McIntyre and McKitrick that pointed to quality control errors in the use of medieval reconstructions and flaws in the statistical treatment of more modern data by Mann, et al. Muller was particularly struck by the McIntyre-McKitrick claim that when they subjected randomly generated fake proxy data to the Mann analysis procedure, the resulting “fit” still produced a hockey-stick shape. Muller’s take:

That discovery hit me like a bombshell, and I suspect it is having the same effect on many others. Suddenly the hockey stick, the poster-child of the global warming community, turns out to be an artifact of poor mathematics. How could it happen?… If you are concerned about global warming (as I am) and think that human-created carbon dioxide may contribute (as I do), then you still should agree that we are much better off having broken the hockey stick. Misinformation can do real harm, because it distorts predictions.”

It later turned out that McIntyre and McKitrick had carried out 10,000 independent simulations of their randomly generated data, but then made their point by preselecting for consideration only the 1% of those whose results gave the highest “hockey stick index.”

Rather than calming the scientific discussion, Muller’s comments contributed to the political uproar that ensued, including Senator James Inhofe’s 2003 claimthat man-made global warming is the greatest hoax ever perpetrated on the American people.” Competing investigations were launched by Congressmen, one by the National Research Council (NRC) and one by a selected small team of statisticians with no particular climate expertise. The rigorously reviewed NRC report included, in addition to a summary and overview, 11 chapters detailing instrumental and proxy temperature records, statistical analysis procedures, paleoclimate models, the synthesis of large-scale temperature reconstructions, and prospects for future technical improvements. It broadly agreed with the basic Mann, Bradley, Hughes findings, while allowing that the non-optimal analysis methodology they used was slightly biased, though with little influence on the final reconstructions. That conclusion was further supported by other reconstructions, proxy records and analysis approaches that came after the initial papers of Mann, et al. The independent Congressional investigation report supported the idea of statistical shortcomings in Mann’s work, but without attempting to quantify the effect of those shortcomings.

Muller was further exercised by Al Gore’s 2006 documentary An Inconvenient Truth and by the 2009 hack of e-mails and other documents from the Climatic Research Unit of the University of East Anglia, producing the controversy popularly known as Climategate. In a 2011 lecture at U.C. Berkeley, Muller made the exaggerated claim that “80 percent or 90 percent of what’s in Inconvenient Truth is wrong or exaggerated or cherry-picked.” (More about his dismissal of Al Gore later in this post.) He argued in a Congressional hearing that the Climategate e-mails revealed that the involved scientists “were not showing the discordant data…as a scientist I was trained that you always have to show the negative data, the data that disagrees with you, and then make the case that your case is stronger. And they were hiding the data, and a whole discussion of suppressing publications, I thought, was really unfortunate.” The “discordant data” that were excluded from a number of global temperature analyses are tree-ring data from high-latitude northern locations, which have diverged from instrumental measurements of temperature and from other proxies since 1960 or so, for reasons that are not well understood. But this omission was in no way “hidden” – it has been widely discussed in the peer-reviewed climate research literature since at least 1995, and in the Third and Fourth IPCC Assessment Reports.

Muller’s “Conversion”

The concerns about An Inconvenient Truth and Climategate are standard issue for climate change skeptics and deniers. But in response to his concerns, Muller took the approach of a serious skeptic, rather than digging in on his doubts and ignoring subsequent evidence, as Happer and other deniers appear to have done. He decided to do his best to improve the quality of the evidence and to delay his own conclusions until he had. Together with his daughter Elizabeth Muller, he launched the Berkeley Earth project in 2010, with the aim of reanalyzing the Earth’s surface temperature record with more inclusive data and simplified analysis procedures. According to their website: “Berkeley Earth systematically addressed the five major concerns that global warming skeptics had identified, and did so in a systematic and objective manner. The first four were potential biases from data selection, data adjustment, poor station quality, and the urban heat island effect…The fifth concern related to the over reliance on large and complex global climate models by the Intergovernmental Panel on Climate Change (IPCC) in the attribution of the recent temperature increase to anthropogenic forcings.” Their non-profit efforts have been supported by a series of mostly unrestricted educational grants from foundations (including the Charles G. Koch Charitable Foundation, among many others), listed on their website.

Muller described the results of this study in a 2012 New York Times op-ed entitled “The Conversion of a Climate-Change Skeptic”:

Our Berkeley Earth approach used sophisticated statistical methods developed largely by our lead scientist, Robert Rohde, which allowed us to determine earth land temperature much further back in time. We carefully studied issues raised by skeptics: biases from urban heating (we duplicated our results using rural data alone), from data selection (prior groups selected fewer than 20 percent of the available temperature stations; we used virtually 100 percent), from poor station quality (we separately analyzed good stations and poor ones) and from human intervention and data adjustment (our work is completely automated and hands-off). In our papers we demonstrate that none of these potentially troublesome effects unduly biased our conclusions.”

And what were Muller’s conclusions?

“I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.”

Those conclusions are supported by results shown in Figs. 3-5. Figure 3 compares the historical global mean temperature record from 1850 established by Muller’s team to results from other research groups. The results from different analyses indeed track each other very closely, with deviations (especially during the 19th century) typically on the order of only a tenth of a degree Celsius. The other groups, who have been involved in the tracking for far longer than Muller, would claim that the skeptical questions raised about their methodologies were never likely to cause significant systematic errors in their results. Muller himself has claimed that he has now confirmed for himself that the results of other groups were largely correct, even though they were unable when he queried them to justify their assumptions to his own satisfaction.

Berkeley Earth ComparisonFigure_2018-1024x582
Figure 3. Comparison of 1850-2018 global mean temperature reconstructions from instrumental measurements, by Berkeley Earth (black line) and other research groups (colored lines).

The Berkeley Earth results in Fig. 4 show that Muller’s team has been able to extend the instrumental global temperature record about a hundred years further back in time than other groups, albeit with sizable uncertainties in the late 18th and early 19th centuries. To alleviate his concerns about over-reliance on complex global climate models, Muller has compared the global temperature record in Fig. 4 with an exceedingly simple model that treats temperature as proportional to measured atmospheric carbon dioxide concentrations, coupled only with occasional few-year cooling episodes attributable to known major volcanic eruptions (named explicitly in Fig. 4). It is this comparison that convinces him that “humans are almost entirely the cause” of the observed warming. From his 2012 op-ed:

How definite is the attribution to humans? The carbon dioxide curve gives a better match than anything else we’ve tried. Its magnitude is consistent with the calculated greenhouse effect — extra warming from trapped heat radiation. These facts don’t prove causality and they shouldn’t end skepticism, but they raise the bar: to be considered seriously, an alternative explanation must match the data at least as well as carbon dioxide does. Adding methane, a second greenhouse gas, to our analysis doesn’t change the results. Moreover, our analysis does not depend on large, complex global climate models, the huge computer programs that are notorious for their hidden assumptions and adjustable parameters. Our result is based simply on the close agreement between the shape of the observed temperature rise and the known greenhouse gas increase… Just as important, our record is long enough that we could search for the fingerprint of solar variability, based on the historical record of sunspots. That fingerprint is absent.”

Berkeley Earth results-plot-volcanoes
Figure 4. Berkeley Earth comparison of the historical record of measured annual global land surface temperatures with a simple model based on measured carbon dioxide concentrations in ice cores and the atmosphere and known major volcanic eruptions.

Muller’s analysis of the measurements made him skeptical of climate change denier claims that the data for a decade spanning the start of the 21st century signaled the end of the warming trend. Already in his 2012 op-ed, he stated: “There are small, rapid variations attributable to El Niño and other ocean currents such as the Gulf Stream; because of such oscillations, the ‘flattening’ of the recent temperature rise that some people claim is not, in our view, statistically significant.” He made the same basic point a year later in a follow-up New York Times op-ed contribution entitled “A Pause, Not an End, to Warming.”

The limitation of Muller’s simple model is that its reliance on historical CO2 data renders it incapable of making all but the most straightforward projections of future climate behavior. The most straightforward projection is that shown in Fig. 5, a simple linear extrapolation of the essentially linear rise in global mean temperatures since 1970. Such a continuing increase would lead to a globe in 2060 that is warmer by 1.6°C than it was in 1970, or by 2.0°C than it was in 1900, on average. The more sophisticated, but complex, global models of which Muller remains suspicious predict some acceleration in the temperature increase trend if global greenhouse gas emissions continue on their current trajectory.

Berkeley Earth TemperatureProjection_2018-1024x582
Figure 5. A linear extrapolation of current global mean temperature trends established by the Berkeley Earth analysis of worldwide data.

The Continuing Cloak of Skepticism

Muller’s Berkeley Earth team has made a significant and valuable addition to the research literature establishing global warming. The team’s website makes publicly available an impressive amount of raw data, graphs and details about methodology and error estimation. However, their results merely confirm trends that were already well established by the time they began their work, and one can forgive the apparent resentment voiced by some long-time climate scientists regarding Muller’s attitude that he has finally put the issue on a sound scientific footing.

Although he has now convinced himself that the global warming trend is real and attributable to human burning of fossil fuels, Muller retains the cloak of scientific skepticism with regard to the work of others, the impacts of climate change, and the potential mitigating strategies to be pursued. This skeptical attitude is reasonably and succinctly presented in a pamphlet available on the Berkeley Earth website, entitled “Know the Facts: A Skeptic’s Guide to Climate Change.” In his lectures, public statements and interviews, however, Muller’s skepticism is expressed often with a veneer of arrogance, and occasionally with a looseness of facts that undermines his claimed devotion to care and accuracy.

Muller is especially dismissive of people he considers “extremists,” who express concern that the impacts of climate change may be at the high end of projections by the IPCC. Among these, he reserves particular disdain for Al Gore, whom he claims pays no attention at all to the science. Gore is not a scientist, but among politicians he has devoted more interest and care in understanding the science than most others. Gore’s documentary An Inconvenient Truth is widely vilified by climate change deniers, but we agree with the judgment rendered in a (failed) civil suit brought in the United Kingdom to prevent the film’s distribution to schools: “It is substantially founded upon scientific research and fact, albeit that the science is used, in the hands of a talented politician and communicator, to make a political statement and to support a political programme.” As we detail below, Muller has gone so far as inventing (or repeating) false anecdotes to emphasize some among what Muller considers to be many errors in An Inconvenient Truth.

In contrast, Muller deals quite gently with his colleague Will Happer, sidestepping Happer’s rejection of evidence:

My friend Will Happer believes that humans do affect the climate, particularly in cities where concrete and energy use cause what is called the ‘urban heat island effect.’ So he would be included in the 97% who believe that humans affect climate, even though he is usually included among the more intense skeptics of the IPCC. He also feels that humans cause a small amount of global warming (he isn’t convinced it is as large as 1 degree), but he does not think it is heading towards a disaster; he has concluded that the increase in carbon dioxide is good for food production, and has helped mitigate global hunger.”

Muller’s much more critical attitude toward Gore (with whom Happer often clashed) is illustrated by this excerpt from a 2011 lecture Muller gave in Berkeley:

Al Gore, when he talks about the polar bears being killed by the receding glaciers, no basis for that. In fact, let me jump ahead and tell a little story. Ralph Cicerone, head of the National Academy, said there are lots of things wrong in his movie, and Al Gore asked him to come and explain this to him, and he did come. And he said, ‘Well, what’s wrong with my movie?’

Well, lots of things, like the polar bears. We track polar bears. Not a single polar bear has died because of retreating ice.’

And Al Gore turned to his movie producer and said, ‘So, why did we put that in?’ The movie producer said, ‘Well, it really gets people emotionally involved.’

See, this is what politicians do. They put in things that they consider a real danger that represents what they consider to be reality. Doesn’t matter if it’s technically true or not. So, there’s so much misinformation on this field. Global warming is real. I am deeply concerned about it. I am leading a major study on global warming. But most of what made the newspaper headlines is either wrong, or backward, or simply exaggerated.”

It doesn’t seem to matter to Muller whether his anecdote is “technically true or not.” Spokespeople for both Gore and Cicerone deny that there was ever any such meeting or conversation between the two regarding either An Inconvenient Truth or the situation for polar bears. What Gore actually says in his documentary is the following:

Right now, the Arctic ice cap acts like a giant mirror, all the sun’s rays bounce off, more than 90%. It keeps the Earth cooler, but as it melts, and the open ocean receives that sun’s energy instead, more than 90% is absorbed, so there is a faster buildup of heat here, at the North Pole, in the Arctic Ocean, and the Arctic generally than anywhere else on the planet. That’s not good for creatures like polar bears, who depend on the ice. They’re now, actually, looking for other ecological niches. A new scientific study shows that for the first time they’re finding polar bears that have actually drowned, swimming long distances up to 60 miles to find the ice. They didn’t find that before. What does it mean to us to look at vast expanse of open water at the top of our world that used to be covered by ice? We ought to care a lot because it has planetary effects.”

Gore’s reference to drowning polar bears may have been based on a controversial 2004 scientific report and the observation that Hudson Bay polar bear population had declined by 22% between 1980 and 2004. But the claim was soon enough validated by the scientific tracking of a polar bear that swam 426 miles in search of sea ice and lost a cub during the journey. The latter report would have been available to Muller before he attributed to Cicerone a statement he never made: “Not a single polar bear has died because of retreating ice.” In fact, Cicerone had testified on the subject to the U.S. Senate in 2005 in a manner consistent with Gore’s presentation:

The Arctic has warmed at a faster rate than the Northern Hemisphere over the past century. A Vision for the International Polar Year 2007-2008 (2004) reports that this warming is associated with a number of impacts including: melting of sea ice, which has important impacts on biological systems such as polar bears, ice-dependent seals and local people for whom these animals are a source of food; increased rain and snow, leading to changes in river discharge and tundra vegetation; and degradation of the permafrost.”

This brings us to some of Muller’s other skeptical claims about climate change impacts. In his 2012 New York Times op-ed, he states: “The number of hurricanes hitting the United States has been going down, not up; likewise for intense tornadoes. Polar bears aren’t dying from receding ice, and the Himalayan glaciers aren’t going to melt by 2035. And it’s possible that we are currently no warmer than we were a thousand years ago, during the ‘Medieval Warm Period’ or ‘Medieval Optimum,’ an interval of warm conditions known from historical records and indirect evidence like tree rings.” There is by now substantial evidence indicating that several of these claims are, at best, misleading.

Munich Re statistics on worldwide natural disasters 1980-2018
Figure 6. Actuarial data recorded by the world’s largest reinsurance company Munich RE since 1980 on the annual number of severe natural loss events, which cause fatalities and/or substantial monetary loss, of various types. The statistics are updated annually at Munich RE’s NatCatService site.

The issue with respect to extreme weather is not confined to “hurricanes hitting the United States,” but rather to the frequency of severe storms, floods, droughts, forest fires and heat waves recorded worldwide. We reproduce in Fig. 6 the actuarial data demonstrating that this frequency has, in fact, more than tripled since 1980, while the frequency of earthquakes, tsunamis and volcanoes – disasters not attributed to climate change – has remained essentially constant. But in a 2012 interview, Muller has cast doubt on such data from insurance companies, because the insurance industry is likely to benefit from instilling the “perception” of danger from climate change. Where, then, does he get his statistics to back up a claim of decreasing frequency?

On the question of receding ice, measurements show the rate of sea ice melt in both Arctic and Antarctic regions now exceeding that of the 1970s by a factor of 6 or so, beyond even the most dire IPCC projections. There is extensive evidence of the substantial receding of the vast majority of glaciers in such high latitude locations as Alaska and Iceland. From even the earliest detailed studies of global warming, climate models predicted that Arctic regions would warm faster than the global mean by a factor of 2–3. Despite the fact that the temperature record (see Fig. 7) validates that prediction, Muller has insisted that “the widely reported warming of Alaska (‘the canary in the mine’) doesn’t match the pattern of carbon dioxide increase–it may have an explanation in terms of changes in the northern Pacific and Atlantic currents.” Of course, the global climate models Muller denigrates attempt to include ocean current changes, ice melt and reductions in sunlight reflection that result as secondary effects from warming oceans, while his own simplistic model assumes that all changes are directly proportional to the primary blanketing effect of CO2 in the atmosphere. That attitude allows him to claim: “No human can sense global warming.” Many citizens of Alaska and Iceland, as well as inhabitants of low-lying Pacific coral atolls (e.g., the Marshall Islands) at the mercy of rising sea levels, beg to disagree.

NASA global warming visualization
Figure 7. NASA maps of annual mean surface temperatures, with respect to the average temperatures recorded during the 1951-1980 period, for 1970, 1986, 2002 and 2017, illustrating rapid global warming trends. In 2017, the global mean temperature was about 1.8 degrees F (1.0 degrees C) higher than in 1970, but many places in the northern hemisphere saw temperature changes twice the global mean.

The issue of the so-called Medieval Warm Period has been addressed in very recent detailed analyses by Neukom, et al. of the 2000-year-long (Common Era) global mean temperature record reconstructed from the PAGES 2k proxy temperature database, using seven different statistical methods. These analyses have revealed that “even when we push our perspective back to the earliest days of the Roman Empire, we cannot discern any event that is remotely equivalent — either in degree or extent — to the warming over the past few decades. Today’s climate stands apart in its torrid global synchrony.” In particular, “even at the height of the Medieval Climate Anomaly, only 40% of Earth’s surface reached peak temperatures at the same time. Using the same metrics, global warming today is unparalleled: for 98% of the planet’s surface, the warmest period of the Common Era occurred in the late twentieth century — the authors’ analysis does not encompass the continued warming in the early twenty-first century, because many of their proxy records were collected more than two decades ago.”

On the issue of mitigation strategies for the human-caused global warming he now validates, Muller has on occasion appeared to minimize the importance of the U.S. role. He argues that the most important global strategy is to give China the technology to efficiently convert from coal to natural gas-fired power plants. And he has unfairly and incorrectly accused both Al Gore and Bill McKibben of promoting insufficient mitigation that focuses exclusively on the role of the West, ignoring China and other emerging large populations. Muller is certainly correct to note that as populations and GDP grow rapidly in China and India, those countries may come to dominate future greenhouse gas emissions (China already leads the world in this regard). But he seriously underestimates the crucial leadership role the U.S. must play if the countries of the world are to take the Paris Climate Accord and any subsequent global agreements to curb greenhouse gas emissions seriously. And he also underestimates the seriousness of the problem if he honestly believes that conversion from coal to a lower-carbon natural gas fuel will, by itself, adequately address the global problem.

Muller has summarized his stance in the Berkeley Earth Skeptics’ Guide to Climate Change: “global warming is real, and caused by human greenhouse gas emissions. But much of what you hear about ‘climate change’ is exaggerated and/or highly uncertain.” He has demonstrated his ability to be persuaded by evidence, even if only by his own research, and must therefore be considered an honest skeptic, in contrast to his friend Will Happer. But still, there is a potential hazard associated with his intense skepticism, a hazard that has been described by George Marshall in a 2012 blog post entitled “The Irresistible Story of Richard Muller:”

Professor Muller’s greatest contribution is not his actual findings, but the role model he provides for other climate change skeptics to change camp. My concern is that Muller may actually be a new species of climate change denier who has identified an unfilled niche in the pundit ecosystem… there is surely an opportunity for Muller to brand himself as a ‘real skeptic’ who sees everything as up for challenge. Whatever his intentions, people will not listen to the detail of what he concludes is right and will only hear that climate science is still unreliable and untrustworthy.”

And the political exploitation of that doubt can lead to dangerous policy, such as Donald Trump’s proposed U.S. withdrawal from the 2015 Paris Climate Accord. On issues such as climate change at the interface between science and public policy, it is challenging, but crucial, for scientists to strike the correct balance between professional skepticism and the sowing of unprofessional doubt.