The importance of the topic of this article is undeniable. We continue to read about it every day in the newspapers, in an unceasing stream of books pouring from the presses, and not least of all, online. Climate change (or, as some insist on saying, global warming) is one of the most prominent scientific, political, and even — as many would claim — moral issues of our time.
But if the choice of topic is self-evident, the selection of individuals we have made for this list, and especially the way we have gone about it, certainly require explanation.
The criteria we have set for this article are quite strict. They had to be, because there are many thousands of climate scientists in the world today, a large number of whom have been involved in the debate over global warming/climate change and would have a legitimate claim to appear on a list like this. To boil all these scientists down to 15 names, we had to be extremely selective.
Here are the criteria we applied to make our selection:
- Scientific prestige. Note that in this category, we did not limit ourselves to card-carrying climatologists. Many sciences legitimately impinge upon the climate debate, from the earth sciences to biology to physics, especially thermodynamics and fluid dynamics. That is one reason why the subject is so highly fraught: it is just so complex, with so many different kinds of information that must be taken into account. Since no one can claim to be an expert in all of these fields, we require that all the scientists who appear on this list have demonstrated a very high degree of expertise in one or more such relevant sciences. Note that for the purposes of this list, we are excluding economists. While their expertise may be highly relevant to the question of what we ought to do about global warming/climate change, it is clearly downstream from the scientific debate about the nature and extent of the threat itself.
- Prominence in the debate. This criterion does not necessarily mean that the individual in question will be a household name. Rather, it means that his or her work must known to many, if not most, of the other scientists participating in the climate-change discussion (whether they agree or disagree with it is a different matter). In many cases, of course, such individuals will be household names — at least to those who have been following this issue closely in the media.
- Representation of both sides. We are well aware that those who support the mainstream position that anthropogenic climate change represents a grave threat to the future of humanity will deplore our decision to represent both side of the debate (or even to characterize the ongoing discussion as a “debate” at all). They have convinced themselves that only cranks and paid stooges could possibly disagree with them. We see things differently.
Simply stated, we maintain that appeals to authority and scurrilous ad hominem attacks are no substitute for rational argument. We also hold that what is sauce for the goose is sauce for the gander. This means, among other things, that mainstream climate scientists who roundly condemn climate skeptics for seeking support from private industry ought to be a bit more circumspect, seeing that they themselves receive millions in financial backing from government agencies. The tacit assumption behind their indignation — that only private actors have material interests, while public actors are by definition impartial seekers after truth — simply won’t wash. We strongly suspect that in, say, 100 years' time, when (we hope!) scholars will be in a position to investigate this whole disgraceful episode in the history of science more objectively, they will find plenty of blame to go around.
Our position is simple. It is the classical liberal one. Drumroll. Cue the shade of Voltaire (channeled by Evelyn Beatrice Hall): “I disagree with what you say, but I will defend to the death your right to say it.” Why should I defend someone else’s freedom to say what I myself believe to be wrong? Because the truth is one thing, my knowledge of it is something else. And because this means that the essence of rational inquiry is intellectual humility. And also because the slow and painful advance towards truth is best served by the open and honest airing of disagreement. For all of these reasons, we deplore all attempts to use political muscle to shut down academic debate. Perhaps our liberal take on the ethics of inquiry has become unfashionable in this postmodern age. To which we respond: So much the worse for intellectual fashion.
That said, we do not feel under any obligation to give “equal time” to both sides. In the end, we came up with the following formula: the mainstream position will be represented by 10 scientists; the skeptical position by five.
Please note that the two sub-lists are alphabetical.
The Top 10 Consensus Climate-Change Scientists
1. Wallace S. Broecker
Broecker was born in Chicago, Illinois, in 1931. He holds a Ph.D. (1958) in geology from Columbia University. He is currently Newberry Professor of Geology in the Department of Earth and Environmental Sciences and the Earth Institute at Columbia University, as well as a research scientist with Columbia’s Lamont-Doherty Earth Observatory.
Often called the “Grandfather of Climate Science,” Broecker pioneered the study of the history of the earth’s oceans since the Pleistocene epoch by means of radiocarbon and other isotope-based dating systems. This work enabled him to reconstruct the biogeochemical carbon cycle, as well as the influence of climate change on polar ice and ocean sediments, among other important results. Moreover, Broecker is the discoverer of the global ocean conveyor belt, a deep-ocean circulation system driven by temperature and salinity, which connects all three of the world’s major oceans. The great ocean conveyor, as it is also known (it was Broecker who hit upon the conveyor belt image to describe this system), is a prime causal factor determining the earth’s climate. Its discovery has been hailed as one of the most significant in the history of oceanography. More recently, Broecker has been involved in work on carbon sequestration.
Broecker is the author, co-author, or editor of more than 20 books, pamphlets, and technical reports, as well as the author or co-author of over 900 peer-reviewed journal articles and book chapters. He has won numerous awards, prizes, and other honors, including the National Medal of Science in 1997 and the Crafoord Prize in Geosciences in 2006.
2. James E. Hansen
Hansen was born in Denison, Iowa, in 1941. He holds a master’s degree (1965) in astronomy and a Ph.D. (1967) in physics, both from the University of Iowa, where he trained with famed astrophysicist James Van Allen. Having retired in 2013 as Director of the NASA Goddard Institute for Space Studies, where he spent a career spanning some four and a half decades, Hansen is currently Adjunct Professor at Columbia University and Director of the Program on Climate Science, Awareness and Solutions in Columbia’s Earth Institute.
Hansen is one of the two or three people on this list most visible to the general public. In 1988, he catapulted into the national limelight as a result of testimony he gave before the US Senate Energy and Natural Resources Committee that is widely considered a turning point in the history of climate change as a public policy issue. In this testimony, he emphasized the trend toward warming over the past century or more and the correlation of this trend with increased CO2 emissions worldwide. Hansen told the Senate Committee that global warming is anthropogenic and will, if allowed to continue unabated, pose a grave threat to the future of humanity. Hansen’s own research on these questions began with his studies of Venus, culminating in his now widely accepted theory that that planet’s extremely high surface temperatures are due to a runaway greenhouse effect. Beginning in 1981 and continuing throughout most of the '80s, he worked on global temperature analysis, co-authoring a landmark paper 1987 that demonstrated the feasibility of combining meteorological data from widely separated stations to explain long-term patterns in weather variability. After that, Hansen and his team studied how sooty aerosol particles (“black carbon”), produced by the incomplete burning of coal, impact cloud formation, hence atmospheric and ground temperatures.
Hansen is the author or co-author of more than 180 peer-reviewed journal articles and book chapters, as well as one book for a popular audience. He has received numerous awards, prizes, and other honors, including the American Physical Society’s Leo Szilard Award for Outstanding Promotion and Use of Physics for the Benefit of Society (2007) and NASA’s Distinguished Service Medal (2013).
3. Phil D. Jones
Jones was born in Redhill, England, in 1952. He holds a Ph.D. in hydrology (1977) from the Department of Civil Engineering at the University of Newcastle upon Tyne. Most of his career has been spent with the University of East Anglia’s Climatic Research Unit (CRU), which he served as Director from 1998 until 2016. Jones is currently Professorial Fellow in the School of Environmental Sciences at the University of East Anglia.
Jones is without doubt best known to the general public on account of his involvement in the so-called “Climategate” affair. In late 2009, someone hacked the CRU’s Internet server and downloaded emails that had been exchanged among Jones, Michael E. Mann (see below), Tom Wigley (see below), and several other prominent scientists. These emails were subsequently made public and found to contain passages that climate-change skeptics considered incriminating. Critics claimed these passages showed (1) the contempt in which mainstream scientists held those who disagreed with them; (2) behind-the-scenes efforts they were making to pull political strings with the UN-sponsored Intergovernmental Panel on Climate Change (IPCC) and certain academic journals to ensure that skeptical viewpoints would be excluded; and, above all, collusion in downplaying or even falsifying data that did not support the mainstream view. Jones, Mann, Wigley, and the others stoutly defended their innocence, insisting that the cited passages were being taken out of context. Responding to a firestorm of negative publicity, the House of Commons’s Science and Technology Committee spearheaded an official investigation into the allegations. In the spring of 2010, this group released a report exonorating Jones and all the other scientists involved. Several other similar investigations were launched in the UK, in the US, and internationally, none of which found sufficient evidence to support the critics' most-damning charges.
The scientific work for which Jones is best known among his peers is probably his construction of time series of the instrumental temperature record. Other areas of his research include work on palaeoclimatology, the temperature record of the past 1000 years, and means of detection of climate change (including proxy climate reconstructions). He has also published papers on the study of climate extremes (especially heavy precipitation and drought) and riverflow reconstructions for the British Isles.
Jones is the author or co-author of more than 500 peer-reviewed journal articles or book chapters. He ranks among the top one-half of one percent of highly cited researchers in geosciences, as calculated by the Institute for Scientific Information (ISI). In 2009, Jones was appointed a Fellow of the American Geophysical Union.
4. Syukuro Manabe
Manabe was born in Ehime Prefecture on the island of Shikoku in Japan, in 1931. He received his Ph.D. in geophysics from the University of Tokyo in 1958. That same year, he joined the US Weather Bureau, working in the General Circulation Research Section — now known as the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration (NOAA) — until 1997. That year, he returned to Japan, where he was appointed Director of the Global Warming Research Division of the Frontier Research System for Global Change — now known as the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) Research Institute for Global Change — a position he held until 2001. In 2002, he returned to the US as a Visiting Researcher with Princeton University’s program in Atmospheric and Oceanic Sciences. Manabe is currently Senior Meteorologist at Princeton University.
Manabe is best known for his pioneering work on empirically adequate models of the circulatory dynamics of the earth’s atmosphere. In a highly important series of papers beginning in the mid-1960s, Manabe and his collaborators applied the principles of fluid dynamics, along with massive amounts of meteorological data, to develop first of all a one-dimensional, single-column model of the atmosphere in radiative-convective equilibrium, together with positive feedback effects deriving from water vapor. He then gradually expanded this model to two and then three dimensions. This work turned out to be critically important for the development a comprehensive, general, and realistic circulation model of the earth’s atmosphere. In a 1969 paper (see below), Manabe published the first general-circulation simulations of the atmosphere coupled with the ocean. Then, in a 1975 paper, he used his model to simulate the response of temperature and the hydrologic cycle to increased atmospheric carbon dioxide levels, thus demonstrating for the first time the feasibility of relatively accurate, long-term predictions of climate response to changes in atmospheric CO2, and simultaneously signalling the potential seriousness of the anthropogenic global warming problem — a problem that Manabe and his team have continued to investigate during the past four decades.
Manabe is the author or co-author of a great many peer-reviewed journal articles and book chapters, some of the best-known and/or most important of which are listed below. He is a Member of the US National Academy of Sciences (NAS), the Japan Academy, the European Academy, and the Royal Society of Canada. In 2015, Manabe was awarded the Benjamin Franklin Medal by the Franklin Institute of Philadelphia, and in 2018, he shared the prestigious Crafoord Prize in Geosciences with Susan Solomon (see below).
5. Michael E. Mann
Mann was born in Amherst, Massachusetts, in 1965. After undergraduate and graduate work in physics and geology, he obtained his Ph.D. in geophysics in 1998 from Yale University. Mann is currently Distinguished Professor of Atmospheric Science with a joint appointment in the Department of Meteorology and Atmospheric Science and the Department of Geosciences at Pennsylvania State University. He is also Director of Penn State’s Earth System Science Center.
The scientific focus of Mann’s career has been the improvement of methodologies for finding patterns in high-resolution paleoclimate reconstructions. In part, this has meant developing new and refining old “proxies” correlated with climate change, such as tree-ring patterns (which vary in width from year to year as a function of temperature and other factors). In part, it has meant research on climate signal detection and the improvement of coupled ocean-atmosphere modeling. And partly, it has meant the assessment and refinement of statistical methods such as time-series data analysis, and the comparison of modelling results against data. Perhaps Mann’s single most famous scientific contribution has been his famous “hockey stick” graph. This was an illustration in a 1999 paper of Mann’s (with two co-authors) showing mean surface temperature anomaly (departures from an reference value, or “calibration period”) in C° for the Northern Hemisphere during the past millennium.
The graph clearly shows two phases: a mostly flat phase (the hockey stick “handle”) during roughly nine-tenths of the period since 1000 AD, followed by a sharply increasing phase (the hockey stick “blade”) beginning around 1900 and continuing until 1998, the year before the paper was published. This graph was made famous by former US Vice President Al Gore, who featured it prominently in his 2006 film, An Inconvenient Truth.
The hockey stick graph has been the subject of some controversy, with critics claiming a methodological bias in the way different kinds of data representing the two phases — before 1900: tree ring, ice core, and other proxy data (in blue in the figure below); and after 1900: thermometer readings (in red) — were handled.
However, Mann has been stalwart in defending the integrity of his methodology and the fundamental correctness of the graph, and many other climate scientists from around the world have sprung to his and the graph’s defense, as well.
Mann has authored or co-authored more than 200 peer-reviewed journal articles and book chapters, as well as delivering countless invited lectures and presentations. He is also the author of three books aimed at a popular audience (see below). He has been extraordinarily active professionally, serving on numerous academic, editorial, and governmental advisory committees and panels. He has also been one of the most tireless defenders of the mainstream view on climate change in the popular and political arena; to this end, he has given government testimony, co-founded the RealClimate.org website, and written a great many essays, book reviews, op-ed pieces, and other articles aimed at a broad public. The recipient of many grants, fellowships, and honorary degrees, in 2015, Mann was elected a Fellow of the American Association for the Advancement of Science (AAAS).
6. John Francis Brake Mitchell
Mitchell was born in 1948 in the United Kingdom. He holds a Ph.D. in theoretical physics (1973) from Queen’s University Belfast. He is currently Principal Research Fellow, advising the British government’s meteorological division (Met Office) on climate change, and is Visiting Professor at the University of Reading.
In 1978, Mitchell became Head of what later became the Met Office’s Hadley Centre for Climate Prediction and Research. From 2002 until 2008, he was the Hadley Centre’s Chief Scientist, and from 2008 until 2010, he was its Director of Climate Science. Mitchell was a convening lead author for the first and third reports of Working Group I: The Physical Science Basis (WGI) of the Intergovernmental Panel on Climate Change (IPCC), and lead author for WGI’s second report. Mitchell’s current work for the Met Office includes keeping a watching brief on climate science internationally, handling concerns of those skeptical about climate change, and working with other Research Fellows to ensure they make an effective contribution to the Met Office research program.
Mitchell’s own published research — consisting of several hundred peer-reviewed journal articles and book chapters over his 40-year career, as author or co-author, primarily in the area of palaeoclimate and climate sensitivity — has been extraordinarily influential, to the point that he is regularly mentioned as the “most-cited scientist” in the world on the topic of climate change/global warming. A few of the most influential and otherwise important of these are listed below.
Mitchell is the recipient of numerous awards and other honors, including, in 2004, the Hans Oeschger Medal bestowed by the European Geosciences Union (EGU), in recognition of his “[p]ioneer research in using atmosphere-ocean general circulation models to understand natural and anthropogenic influences on climatic changes,” and, in 2010, the Symons Gold Medal bestowed every other year by the Royal Meteorological Society. In 2002, Mitchell was appointed an Officer of the Order of the British Empire (OBE), and in 2004, he was elected a Fellow of the Royal Society of London (FRS).
7. Veerabhadran Ramanathan
Ramanathan was born in Chennai (then Madras) in the state of Tamil Nadu in India, in 1944. He holds a Ph.D. (1974) in planetary atmospheres from the State University of New York at Stony Brook. He is currently Victor C. Alderson Professor of Applied Ocean Sciences and Professor of Atmospheric Sciences at the University of California San Diego, as well as Director of the Center for Atmospheric Sciences at the Scripps Institution of Oceanography there.
Ramanathan is primarily known for his development of general circulation models (GCMs) of the atmosphere, as well as more-focused research on problems involving atmospheric chemistry and radiative transfer. One of his most influential discoveries came relatively early in his career, in 1975, when he published a groundbreaking paper reporting his findings on the impact of chlorofluorcarbons (CFCs) as a greenhouse gas relative to carbon dioxide — by a factor of more than 10,000 to 1! Other climate-related phenomena he has studied intensively include anthropogenic “brown clouds,” consisting of soot (or black carbon), which are plentiful over the Indian Ocean. He was co-leader of the team, known as the Indian Ocean Experiment, that was assembled during the 1990s to study this issue, which he believes has contributed to changes in the pattern of the monsoon phenomenon characteristic of the Indian subcontinent.
While by no means downplaying the threat of global warming, Ramanathan is more optimistic than some of his confreres about the possibility of mitigating its worst effects without the enormous economic and social dislocations that strict curtailment of carbon emissions would entail. In a 2014 paper published with several collaborators, Ramanathan suggested that reducing methane, carbonaceous aerosol particles (soot), ozone, and hydrofluorocarbons in the atmosphere — even leaving carbon dioxide to one side — could still significantly slow the expected rise in sea level due to global warming. In the late 2000s, Ramanathan proposed another creative idea he calls Project Surya (after the Sanskrit word for the sun), which is an effort to introduce cheap, solar-powered cookers throughout rural India, to help cut both soot and CO2 emissions.
Ramanathan is the author or co-author of nearly 300 peer-reviewed journal articles and book chapters. He has also written upon occasion for a broad, educated audience on the policy implications of his work. The recipient of numerous grants, awards, and other honors, he is a Fellow of the American Association for the Advancement of Science (AAAS), the American Meteorological Society (AMS), the American Geophysical Union, and the American Academy of Arts and Sciences. In 2002, Ramanathan was elected a Fellow of the US National Academy of Sciences (NAS).
- Clouds, Chemistry, and Climate (Springer, 1995)
8. William F. Ruddiman
Ruddiman was born in Washington, DC, in 1943. He holds a Ph.D. (1969) in marine geology from Columbia University. After working first for the US Naval Oceanographic Office and then Columbia’s Lamont–Doherty Earth Observatory, in 1991 he moved to the University of Virginia where he has spent the remainder of his career, retiring in 2001. Ruddiman is currently Professor Emeritus in the Department of Environmental Sciences at the University of Virginia.
Ruddiman’s field of specialization is in paleoclimatology. He is particularly known for two hypotheses, one advanced relatively early in his career, the other considerably later. First, in work done during the 1980s with his student Maureen Raymo and others, he conjectured that the tectonic uplift of the Himalaya Mountains and the Tibetan Plateau during the late Cenozoic era (roughly three million years ago) caused a reduction in atmospheric CO2 due to an increase in chemical weathering. If correct, this would mean that the creation of the Himalayas was a major causal factor in the Cenozoic Cooling phenomenon, a previously known climatic event which led to our most recent series of Ice Ages.
More recently, Ruddiman has gained additional renown for his “early-Anthropocene hypothesis,” the idea that in the early Holocene epoch (~12,000 years BP) human activity had already begun to have a major impact on global climate. If correct, this idea would explain the apparent cessation of a well-established climatic pattern consisting of a periodic rising and falling of atmospheric CO2 concentrations, which, in turn, is correlated with features of the earth’s solar orbit (the Milankovitch cycle). The pattern is also believed to be linked to periodic cooling (glacial) and warming (interglacial) trends over the past three million years, which would have been expected to lead to a new glaciation about 8000 years ago, but did not (the “overdue-glaciation” phenomenon). If Ruddiman is right, anthropogenic global warming is anything but a recent phenomenon; rather, it has deep roots in human prehistory.
Ruddiman is the author or co-author of some 140 peer-reviewed journal articles and book chapters, as well as the author, co-author, or editor of some dozen books, journal special issues, and technical reports. A Fellow of both the Geological Society of America and the American Geophysical Union, in 2010, he was awarded the Lyell Medal by the Geological Society of London, and in 2012, he received the Distinguished Career Award bestowed by the American Quaternary Association. In 2006, Ruddiman’s book, Plows, Plagues, and Petroleum (see below), won the Phi Beta Kappa award for the best book in general science.
9. Susan Solomon
Solomon was born in Chicago, Illinois, in 1956. She holds a Ph.D. (1981) in chemistry from the University of California, Berkeley. She spent most of her career working for the National Oceanic and Atmospheric Administration (NOAA), first with the Chemistry and Climate Processes Group, and later with the Earth System Research Laboratory. In 2011, she moved to MIT, where she is currently Lee and Geraldine Martin Professor of Environmental Studies in the Department of Earth, Atmospheric and Planetary Sciences (with a joint appointment in the Chemistry Department).
Solomon’s field of specialization is atmospheric chemistry. She is best known for her hypothesis that the hole in the ozone layer of the stratosphere that had opened up above the polar regions sometime during the 1970s was the result of interaction with man-made chemicals, especially chlorofluorocarbons (CFCs), widely used at that time in refrigerants. The ozone hole was a serious matter, as the ozone layer protects all living things from otherwise lethal levels of ultraviolet radiation from the sun. In 1986 — 1987, Solomon led a team to Antarctica to make measurements and take samples to test her hypothesis — which was confirmed. As a direct result of her work, an international agreement was reached in 1989 to ban CFCs for commercial uses. Since then, the ozone hole has stopped growing and begun to shrink. Complete recovery to pre-1970 levels is projected for late in the twenty-first century. Solomon has also served on the Intergovernmental Panel on Climate Change (IPCC). She was a contributing author for the Third Assessment Report, and Co-Chair of Working Group I for the Fourth Assessment Report.
Solomon was the third-most-highly cited geoscientist in the world during the decade of the 1990s according to Science Watch newsletter. She is the author or co-author of nearly 200 peer-reviewed journal articles and book chapters, as well as the author or editor of three books (see below). The recipient of many honorary degrees and other prizes and honors, she is a Member of the US National Academy of Sciences (NAS), the European Academy of Sciences, and the French Academy of Sciences. In 1999, she was awarded the National Medal of Science, and in 2008, she was elected a Fellow of the Royal Society of London (FRS). In 2018, Solomon shared the prestigious Crafoord Prize in Geosciences with Syukoro Manabe (see above). The Solomon Glacier in Antarctica is named in her honor.
10. Tom M.L. Wigley
Wigley was born in Adelaide, Australia, in 1940. He holds a Ph.D. (1967) in mathematical physics from the University of Adelaide. In a long and productive career, he has held posts with Australia’s Commonwealth Bureau of Meteorology, the University of Waterloo in Canada, the University of East Anglia’s Climatic Research Unit (CRU) in the UK, and the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, in the US. He is currently Professor of Climatology in the Department of Ecology and Environmental Science at the University of Adelaide.
Wigley is one of the most highly cited climate researchers in the world. He is perhaps best known for developing the Model for the Assessment of Greenhouse Gas Induced Climate Change (MAGICC), which is one of the most widely used and highly respected climate simulation models in existence. Wigley, working with colleague Sarah Raper, developed MAGICC largely during his tenure with the Climatic Research Unit (CRU) at the University of East Anglia, where he served as Director from 1979 until 1993. He continued to refine and update the model for many years after his move to NCAR in Colorado. Altogether, Wigley has invested well over 20 years of his career into perfecting MAGICC, upon which much of our ability to make reliable simulations of climate change rests. In addition to his work on MAGICC, Wigley has published groundbreaking research on atmospheric aerosols, on statistical analyses of data to isolate the “signal” of human-induced warming, and on aqueous geochemistry, including the now-standard method for the carbon dating of groundwater, among many other discoveries.
Wigley has encountered criticism from some of his erstwhile environmentalist allies for backing increased reliance on nuclear power to help reduce carbon emissions — a position he came to after realizing that greenhouse gas reductions projected by the IPCC were far too optimistic and were essentially unachievable. Along with two American colleagues, Wigley articulated this critique in a highly controversial, widely discussed Nature Commentary piece published in 2008.
Wigley is the author or co-author of more than 150 peer-reviewed journal articles and book chapters, as well as the author or editor of two books (see below). He is a Fellow of the American Association for the Advancement of Science (AAAS).
The Top Five Skeptical Climate-Change Scientists
1. Lennart O. Bengtsson
Bengtsson was born in Trollhättan, Sweden, in 1935. He holds a Ph.D. (1964) in meteorology from the University of Stockholm. His long and productive career included positions as Head of Research and later Director at the European Centre for Medium-Range Weather Forecasts in Reading in the UK (1976 — 1990), and as Director of the Max Planck Institute for Meteorology in Hamburg (1991 — 2000). Bengtsson is currently Senior Research Fellow with the Environmental Systems Science Centre at the University of Reading, as well as Director Emeritus of the Max Planck Institute for Meteorology.
Bengtsson’s scientific work has been wide-ranging, including everything from climate modelling and numerical weather prediction to climate data and data assimilation studies. Most recently, he has been involved in studies and modeling of the water cycle and extreme events. From his twin home bases in the UK and Germany, he has cooperated closely over the years with scientists in the US, Sweden, Norway, and other European countries.
Bengtsson is best known to the general public due to a dispute which arose in 2014 over a paper he and his colleagues had submitted to Environmental Research Letters, but which was rejected for publication for what Bengtsson believed to be “activist” reasons. The paper disputed the uncertainties surrounding climate sensitivity to increased greenhouse gas concentrations contained in the Intergovernmental Panel on Climate Change (IPCC) Fourth and Fifth Assessment Reports. Bengtsson and his co-authors maintained that the uncertainties are greater than the IPCC Assessment Reports claim. The affair was complicated by the fact that Bengtsson had recently agreed to serve on the board of the Global Warming Policy Foundation (GWPF), a climate skeptic organization. When Bengtsson voiced his displeasure over the rejection of his paper, and mainstream scientists noticed his new affiliation with the GWPF, intense pressure was brought to bear, both in public and behind the scenes, to force Bengtsson to recant his criticism of the journal in question and to resign from the GWPF. He finally did both of these things, but not without noting bitterly in his letter of resignation:
I have been put under such an enormous group pressure in recent days from all over the world that has become virtually unbearable to me. If this is going to continue I will be unable to conduct my normal work and will even start to worry about my health and safety. I see therefore no other way out therefore than resigning from GWPF. I had not expecting [sic] such an enormous world-wide pressure put at me from a community that I have been close to all my active life. Colleagues are withdrawing their support, other colleagues are withdrawing from joint authorship etc.
I see no limit and end to what will happen. It is a situation that reminds me about the time of McCarthy. I would never have expecting [sic] anything similar in such an original peaceful community as meteorology. Apparently it has been transformed in recent years.
Bengtsson is the author or co-author of over 180 peer-reviewed journal articles and book chapters, as well as co-editor of several books (see below). In addition to numerous grants, commission and board memberships, honorary degrees, and other forms of professional recognition, he has received the Milutin Milanković Medal (1996) bestowed by the European Geophysical Society, the Descartes Prize (2005) bestowed by the European Union, the International Meteorological Organization Prize (2006), and the Rossby Prize (2007) bestowed by the Swedish Geophysical Society. Bengtsson is an Honorary Member of the American Meteorological Society (AMS), a Member of the New York Academy of Sciences and the Gesellschaft Deutscher Naturforscher und Ärzte, an Honorary Fellow of the Royal Meteorological Society (UK), and a Fellow of the Swedish Academy of Science, the Finnish Academy of Science, and the European Academy.
2. John R. Christy
Christy was born in Fresno, California, in 1951. He holds a Ph.D. (1987) in atmospheric science from the University of Illinois. He is currently Distinguished Professor of Atmospheric Science and Director of the Earth System Science Center at the University of Alabama in Huntsville.
Christy is best known for work he did with Roy W. Spencer beginning in 1979 on establishing reliable global temperature data sets derived from microwave radiation probes collected by satellites. Theirs was the first successful attempt to use such satellite data collection for the purpose of establishing long-term temperature records. Although the data they collected were initially controversial, and some corrections to the interpretation of the raw data had to be made, the work — which is coming up on its fortieth anniversary — remains uniquely valuable for its longevity, and is still ongoing. Christy has long been heavily involved in the climate change/global warming discussion, having been a Contributor or Lead Author to five Intergovernmental Panel on Climate Change (IPCC) reports relating to satellite temperature records. He was a signatory of the 2003 American Geophysical Union’s (AGU) statement on climate change, although he has stated that he was “very upset” by the AGU’s more extreme 2007 statement.
Christy began voicing doubts about the growing climate-change consensus in the 2000s. In an interview with the BBC from 2007, he accused the IPCC process of gross politicization and scientists of succumbing to “group-think” and “herd instinct.”; In 2009, he made the following statement in testimony to the House Ways and Means Committee (altogether, he has testified before Congress some 20 times):
From my analysis, the actions being considered to “stop global warming” will have an imperceptible impact on whatever the climate will do, while making energy more expensive, and thus have a negative impact on the economy as a whole. We have found that climate models and popular surface temperature data sets overstate the changes in the real atmosphere and that actual changes are not alarming. And, if the Congress deems it necessary to reduce CO2 emissions, the single most effective way to do so by a small, but at least detectable, amount is through the massive implementation of a nuclear power program.
Christy has not been shy about publicizing his views, making many of the same points in an op-ed piece he published with a colleague in 2014 in the Wall Street Journal. In an interview with the New York Times published that same year, he explains the price he has had to pay professionally for his skeptical stance toward the climate-change consensus. However, Christy stands his ground, refusing to give in to ad hominem attacks or the exercise of naked political power, insisting the issues must be discussed on the scientific merits alone.
Christy is the author or co-author of numerous peer-reviewed journal articles and book chapters (for a selection of a few of his best-known articles, see below). In 1991, Christy was awarded the Medal for Exceptional Scientific Achievement bestowed by the National Aeronautics and Space Administration (NASA) for his groundbreaking work with Spencer. A Fellow of the American Meteorological Society (AMS), since 2000 Christy has been Alabama’s official State Climatologist.
3. Judith A. Curry
Curry was born in 1953. She holds a Ph.D. (1982) in geophysical sciences from the University of Chicago. She has taught at the University of Wisconsin, Purdue University, Pennsylvania State University, the University of Colorado at Boulder, and Georgia Institute of Technology (Georgia Tech). In 2017, under a torrent of criticism from her colleagues and negative stories in the media, she was forced to take early retirement from her position as Professor in the School of Earth and Atmospheric Sciences at Georgia Tech, a position she had held for 15 years (during 11 of those years, she had been Chair of the School). Curry is currently Professor Emerita at Georgia Tech, as well as President of Climate Forecast Applications Network, or CFAN (see below), an organization she founded in 2006.
Curry is an atmospheric scientist and climatologist with broad research interests, including atmospheric modeling, the polar regions, atmosphere-ocean interactions, remote sensing, the use of unmanned aerial vehicles for atmospheric research, and hurricanes, especially their relationship to tornadoes. Before retiring, she was actively researching the evidence for a link between global warming and hurricane frequency and severity.
Curry was drummed out of academia for expressing in public her reservations about some of the more extreme claims being made by mainstream climate scientists. For example, in 2011, she published (with a collaborator) an article stressing the uncertainties involved in climate science and urging caution on her colleagues. After having posted comments along these lines on other people’s blogs for several years, in 2010, she created her own climate-related blog, Climate Etc. (see below), to foster a more open and skeptical discussion of the whole gamut of issues involving climate change/global warming. She also gave testimony some half dozen times between 2006 and 2015 to Senate and House subcommittees, expressing in several of them her concerns about the politicization of the usual scientific process in the area of climate change. Writing on her blog in 2015 about her most-recent Congressional testimony, Curry summarized her position as follows:
The wickedness of the climate change problem provides much scope for disagreement among reasonable and intelligent people. Effectively responding to the possible threats from a warmer climate is made very difficult by the deep uncertainties surrounding the risks both from the problem and the proposed solutions.
The articulation of a preferred policy option in the early 1990’s by the United Nations has marginalized research on broader issues surrounding climate variability and change and has stifled the development of a broader range of policy options.
We need to push the reset button in our deliberations about how we should respond to climate change.
Finding herself denounced as a “climate change denier” and under intense pressure to recant her views, in 2017 Curry instead took early retirement from her job at Georgia Tech and left academia, citing the “craziness” of the present politicization of climate science. She continues to be active in the field of climatology through her two blogs and her many public lectures.
Curry is the author or co-author of more than 180 peer-reviewed journal articles and book chapters, as well as the co-author or editor of three books (see below). She has received many research grants, been invited to give numerous public lectures, and participated in many workshops, discussion panels, and committees, both in the US and abroad. In 2007, Curry was elected a Fellow of the American Association for the Advancement of Science (AAAS).
4. Richard S. Lindzen
Lindzen was born in Webster, Massachusetts, in 1940. He holds a Ph.D. (1964) in applied mathematics from Harvard University. He is currently Professor Emeritus in the Department of Earth, Atmospheric and Planetary Sciences at MIT.
Already in his Ph.D. dissertation, Lindzen made his first significant contribution to science, laying the groundwork for our understanding of the physics of the ozone layer of the atmosphere. After that, he solved a problem that had been discussed for over 100 years by some of the best minds in physics, including Lord Kelvin, namely, the physics of atmospheric tides (daily variations in global air pressure). Next, he discovered the quasi-biennial oscillation (QBO), a cyclical reversal in the prevailing winds in the stratosphere above the tropical zone. Then, Lindzen and a colleague proposed an explanation for the “superrotation” of the highest layer of Venus’s atmosphere (some 50 times faster than the planet itself), a model that is still being debated.
The idea for which Lindzen is best known, though, is undoubtedly the “adaptive infrared iris” conjecture. According to this model, the observed inverse correlation between surface temperature and cirrus cloud formation may operate as a negative feedback on infrared radiation (heat) build-up near the earth’s surface. According to this proposal, decreasing cirrus cloud formation when surface temperatures rise leads to increased heat radiation into space, while increasing cirrus cloud formation when surface temperatures decline leads to increased heat retention — much as the iris of the human eye adapts to ambient light by widening and narrowing. If correct, this phenomenon would be reason for optimism that global warming might be to some extent self-limiting. Lindzen’s hypothesis has been highly controversial, but it is still being discussed as a serious proposal, even by his many critics.
Lindzen was a Contributor to Chapter 4 of the 1995 Intergovernmental Panel on Climate Change (IPCC) Second Assessment, and to Chapter 7 of the 2001 IPCC Working Group 1 (WG1). Nevertheless, in the 1990s, Lindzen began to express his concern about the reliability of the computer models upon which official IPCC and other extreme climate projections are based. He has been especially critical of the notion that the “science is settled.” In a 2009 Wall Street Journal op-ed, he maintained that the science is far from settled and that “[c]onfident predictions of catastrophe are unwarranted.” For his trouble, Lindzen has suffered the usual brutal, ad hominem attacks from the climate-change establishment.
Lindzen is author or co-author of nearly 250 peer-reviewed journal articles and book chapters, as well as author, co-author, or editor of several books, pamphlets, and technical reports (see below). He is a Member of the US National Academy of Sciences (NAS) and the Norwegian Academy of Science and Letters, and a Fellow of the American Academy of Arts and Sciences, the American Association for the Advancement of Science (AAAS), the American Geophysical Union (AGU), and the American Meteorological Society (AMS).
5. Nir J. Shaviv
Shaviv was born in Ithaca, New York, in 1972, but was raised in Israel. He holds a doctorate (1996) in physics from the Israel Institute of Technology in Haifa. He spent a year as an IBM Einstein Fellow at the highly prestigious Institute for Advanced Study in Princeton, New Jersey (2014 — 2015). He is currently Professor and Chair of the Racah Institute of Physics at the Hebrew University of Jerusalem.
Shaviv first made a name for himself (see his 1998 and 2001 papers, below) with his research on the relationship between inhomogeneities in stellar atmospheres and the Eddington limit (the equilibrium point at which the centrifugal force of stellar radiation production equals the centripetal force of gravitation). This theoretical work led to a concrete prediction that was later confirmed telescopically (see the 2013 Nature paper listed below).
Of more direct relevance to the climate-change debate was a series of papers Shaviv wrote, beginning in 2002 (see below), detailing a bold theory linking earth’s ice ages with successive passages of the planet through the various spiral arms of the Milky Way galaxy, and with cosmic radiation more generally. He has also expressed his conviction that variations in solar radiation have played an equal, if not greater, role in the observed rise in mean global temperature over the course of the twentieth century than has human activity (see his 2012 paper, below). He maintains, not only that anthropogenic greenhouse gases have played a smaller role in global warming than is usually believed, but also that the earth’s climate system is not nearly so sensitive as is usually assumed.
In recent years, Shaviv has become an active critic of the results and predictions of the Intergovernmental Panel on Climate Change (IPCC) and other organizations supporting the consensus view. In particular, he rejects the often-heard claim that “97% of climate scientists” agree that anthropogenic climate change is certain and highly dangerous. Shaviv emphasizes (see the video clip, below) that “science is not a democracy” and all that matters is the evidence for these claims — which he finds deficient.
Shaviv is the author or co-author of more than 100 peer-reviewed journal articles or book chapters, of which some of the most important are listed below.
1. “Statement of Dr. James Hansen, Director, NASA Goddard Institute for Space Studies” (Congressional Record, June 23, 1988).
2. James E. Hansen and Satoshi Matsushima, “The Atmosphere and Surface Temperature of Venus: A Dust Insulation Model,” Astrophysical Journal, 1967, 150: 1139 — 1157.
3. James Hansen and Sergei Lebedeff, “Global Trends of Measured Surface Air Temperature,” Journal of Geophysical Research, 1987, 92(D11): 13345 — 13372.
4. Surabi Menon, James Hansen, Larissa Nazarenko, and Yunfeng Luo, “Climate Effects of Black Carbon Aerosols in China and India,” Science, 2002, 297(5590): 2250 — 2253.
5. Michael E. Mann, Raymond S. Bradley, and Malcolm K. Hughes, “Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations,” Geophysical Research Letters, 1999, 26: 759 — 762; the original hockey stick graph is Fig. 3 on p. 761.
8. V. Ramanathan, “Greenhouse effect due to chlorofluorocarbons — climatic implications," Science, 1975, 190: 50 — 51.
9. Aixue Hu, et al., “Mitigation of short-lived climate pollutants slows sea-level rise," Nature Climate Change, 2014, 3: 730 — 734.
10. For example: David G. Victor, Charles F. Kennel, and Veerabhadran Ramanathan, “The Climate Threat We Can Beat: What It Is and How to Deal With It,” Foreign Affairs, May/June 2012, 91(3): 112 — 121.
11. Maureen E. Raymo, William F. Ruddiman, and Philip N. Froelich, “Influence of late Cenozoic mountain building on ocean geochemical cycles," Geology, 1988, 16: 649 — 653.
12. William F. Ruddiman, “The early anthropogenic hypothesis: challenges and responses,” Reviews of Geophysics, 2007, 45: RG4001; see, also, W.F. Ruddiman, M.C. Crucifix, and F.A. Oldfield, eds., “The early-Anthropocene hypothesis,” The Holocene (Special Issue), 2011, 21(5): 713 — 879.
13. Roger Pielke, Jr., Tom Wigley, and Christopher Green, “Dangerous assumptions,” Nature, 2008, 452: 531 — 532; see, also, T.M.L. Wigley, “A combined mitigation/geoengineering approach to climate stabilization," Science, 2006, 314: 452 — 454.
14. Global Warming Policy Foundation (GWPF), “Lennart Bengtsson resigns: GWPF voices shock and concern at the extent of intolerance within the climate science community” (GWPF website, Press Releases, May 14, 2014).
19. Michael Wines, “Though Scorned by Colleagues, a Climate-Change Skeptic Is Unbowed” (New York Times website, July 15, 2014).
22. Richard Lindzen and Richard Goody, “Radiative and photochemical processes in mesospheric dynamics: Part I. Models for radiative and photochemical processes,” Journal of the Atmospheric Sciences, 1965, 22: 341 — 48.
24. Lindzen tells the story of his discovery of the QBO in the following semi-autobiographical paper: Richard S. Lindzen, “On the development of the theory of the QBO,” Bulletin of the American Meteorologcal Society, 1987, 68: 329 — 37.
25. Stephen B. Fels and Richard S. Lindzen, “The interaction of thermally excited gravity waves with mean flows,” Geophysical Fluid Dynamics, 1874, 6: 149 — 191.
27. Richard S. Lindzen, “The climate science isn’t settled” (Wall Street Journal website, November 30, 2009).