Climate scientists agree that the global average surface temperature has risen over the last century. Within this general agreement, some individual scientists disagree with the scientific consensus that most of this warming is attributable to human activities. The scientific consensus was summarized in the 2001 Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) as follows:
1. The global average surface temperature has risen 0.6 ± 0.2 °C since the late 19th century, and 0.17 °C per decade in the last 30 years.
2. "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities", in particular emissions of the greenhouse gases carbon dioxide and methane.
3. If greenhouse gas emissions continue the warming will also continue, with temperatures projected to increase by 1.4 °C to 5.8 °C between 1990 and 2100. Accompanying this temperature increase will be increases in some types of extreme weather and a projected sea level rise of 9 cm to 88 cm, excluding "uncertainty relating to ice dynamical changes in the West Antarctic ice sheet". On balance the impacts of global warming will be significantly negative, especially for larger values of warming.
Those listed here have, since the Third Assessment Report of the IPCC, opposed at least one of these principal conclusions. Inclusion is based on specific, attributable statements in the individual's own words, and not on listings in petitions or surveys. In February 2007, the IPCC released a summary of a Fourth Assessment Report, which contains similar conclusions. In judging opposition to the consensus, each scientist's statements are compared to the most recently released IPCC report at the time of the statement.
For the purpose of this list a "scientist" is an individual who has published at least one peer-reviewed article during their lifetime in the broadly-construed area of natural sciences, though not necessarily in recent years nor in a field relevant to climate.
Believe global warming is not occurring or has ceased
* Timothy F. Ball, former Professor of Geography, University of Winnipeg: " warmed from 1680 up to 1940, but since 1940 it's been cooling down. The evidence for warming is because of distorted records. The satellite data, for example, shows cooling." (November 2004) "There's been warming, no question. I've never debated that; never disputed that. The dispute is, what is the cause. And of course the argument that human CO2 being added to the atmosphere is the cause just simply doesn't hold up..." (May 18, 2006; at 15:30 into recording of interview)"The temperature hasn't gone up. ... But the mood of the world has changed: It has heated up to this belief in global warming." (August 2006) "Temperatures declined from 1940 to 1980 and in the early 1970's global cooling became the consensus. ... By the 1990's temperatures appeared to have reversed and Global Warming became the consensus. It appears I'll witness another cycle before retiring, as the major mechanisms and the global temperature trends now indicate a cooling." (Feb. 5, 2007)
* Robert M. Carter, geologist, researcher at the Marine Geophysical Laboratory at James Cook University in Australia: "the accepted global average temperature statistics used by the Intergovernmental Panel on Climate Change show that no ground-based warming has occurred since 1998 ... there is every doubt whether any global warming at all is occurring at the moment, let alone human-caused warming."
* Vincent R. Gray, coal chemist, founder of the New Zealand Climate Science Coalition: "The two main 'scientific' claims of the IPCC are the claim that 'the globe is warming' and 'Increases in carbon dioxide emissions are responsible'. Evidence for both of these claims is fatally flawed."
Believe accuracy of IPCC climate projections is questionable
Individuals in this section conclude that it is not possible to project global climate accurately enough to justify the ranges projected for temperature and sea-level rise over the next century. They do not conclude specifically that the current IPCC projections are either too high or too low, but that the projections are likely to be inaccurate due to inadequacies of current global climate modeling.
* Hendrik Tennekes, retired Director of Research, Royal Netherlands Meteorological Institute: "The blind adherence to the harebrained idea that climate models can generate 'realistic' simulations of climate is the principal reason why I remain a climate skeptic. From my background in turbulence I look forward with grim anticipation to the day that climate models will run with a horizontal resolution of less than a kilometer. The horrible predictability problems of turbulent flows then will descend on climate science with a vengeance."
* Antonino Zichichi, emeritus professor of nuclear physics at the University of Bologna and president of the World Federation of Scientists : "models used by the Intergovernmental Panel on Climate Change (IPCC) are incoherent and invalid from a scientific point of view".
Believe global warming is primarily caused by natural processes
Individuals in this section conclude that the observed warming is more likely attributable to natural causes than to human activities.
* Khabibullo Abdusamatov, mathematician and astronomer at Pulkovo Observatory of the Russian Academy of Sciences: "Global warming results not from the emission of greenhouse gases into the atmosphere, but from an unusually high level of solar radiation and a lengthy - almost throughout the last century - growth in its intensity...Ascribing 'greenhouse' effect properties to the Earth's atmosphere is not scientifically substantiated...Heated greenhouse gases, which become lighter as a result of expansion, ascend to the atmosphere only to give the absorbed heat away."
* Sallie Baliunas, astronomer, Harvard-Smithsonian Center for Astrophysics: "The recent warming trend in the surface temperature record cannot be caused by the increase of human-made greenhouse gases in the air."
* George V. Chilingar, Professor of Civil and Petroleum Engineering at the University of Southern California: "The authors identify and describe the following global forces of nature driving the Earth’s climate: (1) solar radiation ..., (2) outgassing as a major supplier of gases to the World Ocean and the atmosphere, and, possibly, (3) microbial activities ... . The writers provide quantitative estimates of the scope and extent of their corresponding effects on the Earth’s climate show that the human-induced climatic changes are negligible."
* Ian Clark, hydrogeologist, professor, Department of Earth Sciences, University of Ottawa: "That portion of the scientific community that attributes climate warming to CO2 relies on the hypothesis that increasing CO2, which is in fact a minor greenhouse gas, triggers a much larger water vapour response to warm the atmosphere. This mechanism has never been tested scientifically beyond the mathematical models that predict extensive warming, and are confounded by the complexity of cloud formation - which has a cooling effect. ... We know that the sun was responsible for climate change in the past, and so is clearly going to play the lead role in present and future climate change. And interestingly... solar activity has recently begun a downward cycle."
* David Douglass, solid-state physicist, professor, Department of Physics and Astronomy, University of Rochester: "The observed pattern of warming, comparing surface and atmospheric temperature trends, does not show the characteristic fingerprint associated with greenhouse warming. The inescapable conclusion is that the human contribution is not significant and that observed increases in carbon dioxide and other greenhouse gases make only a negligible contribution to climate warming."
* Don Easterbrook, emeritus professor of geology, Western Washington University: "global warming since 1900 could well have happened without any effect of CO2. If the cycles continue as in the past, the current warm cycle should end soon and global temperatures should cool slightly until about 2035"
* William M. Gray, Professor Emeritus and head of The Tropical Meteorology Project, Department of Atmospheric Science, Colorado State University: "This small warming is likely a result of the natural alterations in global ocean currents which are driven by ocean salinity variations. Ocean circulation variations are as yet little understood. Human kind has little or nothing to do with the recent temperature changes. We are not that influential." "I am of the opinion that global warming is one of the greatest hoaxes ever perpetrated on the American people." "So many people have a vested interest in this global-warming thing—all these big labs and research and stuff. The idea is to frighten the public, to get money to study it more."
* William Kininmonth, meteorologist, former Australian delegate to World Meteorological Organization Commission for Climatology: "There has been a real climate change over the late nineteenth and twentieth centuries that can be attributed to natural phenomena. Natural variability of the climate system has been underestimated by IPCC and has, to now, dominated human influences."
* George Kukla, retired Professor of Climatology at Columbia University and Lamont-Doherty Earth Observatory, said in an interview: "What I think is this: Man is responsible for a PART of global warming. MOST of it is still natural."
* David Legates, associate professor of geography and director of the Center for Climatic Research, University of Delaware: "About half of the warming during the 20th century occurred prior to the 1940s, and natural variability accounts for all or nearly all of the warming."
* Tad Murty, oceanographer; adjunct professor, Departments of Civil Engineering and Earth Sciences, University of Ottawa: global warming "is the biggest scientific hoax being perpetrated on humanity. There is no global warming due to human anthropogenic activities. The atmosphere hasn’t changed much in 280 million years, and there have always been cycles of warming and cooling. The Cretaceous period was the warmest on earth. You could have grown tomatoes at the North Pole"
* Tim Patterson, paleoclimatologist and Professor of Geology at Carleton University in Canada: "There is no meaningful correlation between CO2 levels and Earth's temperature over this geologic time frame. In fact, when CO2 levels were over ten times higher than they are now, about 450 million years ago, the planet was in the depths of the absolute coldest period in the last half billion years. On the basis of this evidence, how could anyone still believe that the recent relatively small increase in CO2 levels would be the major cause of the past century's modest warming?"
* Ian Plimer, Professor emeritus of Mining Geology, The University of Adelaide: "We only have to have one volcano burping and we have changed the whole planetary climate... It looks as if carbon dioxide actually follows climate change rather than drives it".
* Harrison Schmitt, former Astronaut, chair of the NASA Advisory Council, Adjunct Professor of engineering physics at the University of Wisconsin-Madison:"I don't think the human effect is significant compared to the natural effect".
* Tom Segalstad, head of the Geology Museum at the University of Oslo: "The IPCC's temperature curve (the so-called 'hockey stick' curve) must be in error...human influence on the 'Greenhouse Effect' is minimal (maximum 4%). Anthropogenic CO2 amounts to 4% of the ~2% of the "Greenhouse Effect", hence an influence of less than 1 permil of the Earth's total natural 'Greenhouse Effect' (some 0.03°C of the total ~33°C)."
* Nir Shaviv, astrophysicist at the Hebrew University of Jerusalem: "The truth is probably somewhere in between the common view and that of skeptics, with natural causes probably being more important over the past century, whereas anthropogenic causes will probably be more dominant over the next century. ... About 2/3's (give or take a third or so) of the warming over the past century should be attributed to increased solar activity and the remaining to anthropogenic causes." His opinion is based on some proxies of solar activity over the past few centuries.
* Fred Singer, Professor emeritus of Environmental Sciences at the University of Virginia: "The greenhouse effect is real. However, the effect is minute, insignificant, and very difficult to detect." “It’s not automatically true that warming is bad, I happen to believe that warming is good, and so do many economists.”
* Willie Soon, astrophysicist, Harvard-Smithsonian Center for Astrophysics: "There's increasingly strong evidence that previous research conclusions, including those of the United Nations and the United States government concerning 20th century warming, may have been biased by underestimation of natural climate variations. The bottom line is that if these variations are indeed proven true, then, yes, natural climate fluctuations could be a dominant factor in the recent warming. In other words, natural factors could be more important than previously assumed."
* Roy Spencer, principal research scientist, University of Alabama in Huntsville: "I predict that in the coming years, there will be a growing realization among the global warming research community that most of the climate change we have observed is natural, and that mankind’s role is relatively minor"
* Philip Stott, professor emeritus of biogeography at the University of London: "...the myth is starting to implode. ... Serious new research at The Max Planck Society has indicated that the sun is a far more significant factor..."
* Henrik Svensmark, Danish National Space Center: "Our team ... has discovered that the relatively few cosmic rays that reach sea-level play a big part in the everyday weather. They help to make low-level clouds, which largely regulate the Earth’s surface temperature. During the 20th Century the influx of cosmic rays decreased and the resulting reduction of cloudiness allowed the world to warm up. ... most of the warming during the 20th Century can be explained by a reduction in low cloud cover."
* Jan Veizer, environmental geochemist, Professor Emeritus from University of Ottawa: "At this stage, two scenarios of potential human impact on climate appear feasible: (1) the standard IPCC model ..., and (2) the alternative model that argues for celestial phenomena as the principal climate driver. ... Models and empirical observations are both indispensable tools of science, yet when discrepancies arise, observations should carry greater weight than theory. If so, the multitude of empirical observations favours celestial phenomena as the most important driver of terrestrial climate on most time scales, but time will be the final judge."
Believe cause of global warming is unknown
Scientists in this section conclude it is too early to ascribe any principal cause to the observed rising temperatures, man-made or natural.
* Syun-Ichi Akasofu, retired professor of geophysics and Founding Director of the International Arctic Research Center of the University of Alaska Fairbanks: "The method of study adopted by the International Panel of Climate Change (IPCC) is fundamentally flawed, resulting in a baseless conclusion: Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations. Contrary to this statement ..., there is so far no definitive evidence that 'most' of the present warming is due to the greenhouse effect. ... The IPCC should have recognized that the range of observed natural changes should not be ignored, and thus their conclusion should be very tentative. The term 'most' in their conclusion is baseless."
* Claude Allègre, geochemist, Institute of Geophysics (Paris): "The increase in the CO2 content of the atmosphere is an observed fact and mankind is most certainly responsible. In the long term, this increase will without doubt become harmful, but its exact role in the climate is less clear. Various parameters appear more important than CO2. Consider the water cycle and formation of various types of clouds, and the complex effects of industrial or agricultural dust. Or fluctuations of the intensity of the solar radiation on annual and century scale, which seem better correlated with heating effects than the variations of CO2 content."
* Robert C. Balling, Jr., a professor of geography at Arizona State University: "It is very likely that the recent upward trend in global surface temperature is very real and that the upward signal is greater than any noise introduced from uncertainties in the record. However, the general error is most likely to be in the warming direction, with a maximum possible (though unlikely) value of 0.3 °C. ... At this moment in time we know only that: (1) Global surface temperatures have risen in recent decades. (2) Mid-tropospheric temperatures have warmed little over the same period. (3) This difference is not consistent with predictions from numerical climate models."
* John Christy, professor of atmospheric science and director of the Earth System Science Center at the University of Alabama in Huntsville, contributor to several IPCC reports: "I'm sure the majority (but not all) of my IPCC colleagues cringe when I say this, but I see neither the developing catastrophe nor the smoking gun proving that human activity is to blame for most of the warming we see. Rather, I see a reliance on climate models (useful but never "proof") and the coincidence that changes in carbon dioxide and global temperatures have loose similarity over time."
* Petr Chylek, Space and Remote Sensing Sciences researcher, Los Alamos National Laboratory: "carbon dioxide should not be considered as a dominant force behind the current warming...how much of the temperature increase can be ascribed to CO2, to changes in solar activity, or to the natural variability of climate is uncertain"
* William R. Cotton, Professor of Atmospheric Sciences at Colorado State University said in a presentation, "It is an open question if human produced changes in climate are large enough to be detected from the noise of the natural variability of the climate system."
* David Deming, geology professor at the University of Oklahoma: "The amount of climatic warming that has taken place in the past 150 years is poorly constrained, and its cause – human or natural – is unknown. There is no sound scientific basis for predicting future climate change with any degree of certainty. If the climate does warm, it is likely to be beneficial to humanity rather than harmful. In my opinion, it would be foolish to establish national energy policy on the basis of misinformation and irrational hysteria."
* Chris de Freitas, Associate Professor, School of Geography, Geology and Environmental Science, University of Auckland: "There is evidence of global warming. ... But warming does not confirm that carbon dioxide is causing it. Climate is always warming or cooling. There are natural variability theories of warming. To support the argument that carbon dioxide is causing it, the evidence would have to distinguish between human-caused and natural warming. This has not been done."50
* Richard Lindzen, Alfred P. Sloan Professor of Atmospheric Science at the Massachusetts Institute of Technology and member of the National Academy of Sciences: "We are quite confident (1) that global mean temperature is about 0.5 °C higher than it was a century ago; (2) that atmospheric levels of CO2 have risen over the past two centuries; and (3) that CO2 is a greenhouse gas whose increase is likely to warm the earth (one of many, the most important being water vapor and clouds). But – and I cannot stress this enough – we are not in a position to confidently attribute past climate change to CO2 or to forecast what the climate will be in the future." "There has been no question whatsoever that CO2 is an infrared absorber (i.e., a greenhouse gas – albeit a minor one), and its increase should theoretically contribute to warming. Indeed, if all else were kept equal, the increase in CO2 should have led to somewhat more warming than has been observed."
Believe global warming will not be significantly negative
Scientists in this section conclude that projected rising temperatures will be of little impact or a net positive for human society and/or the earth's environment.
* Craig D. Idso, faculty researcher, Office of Climatology, Arizona State University and founder of the Center for the Study of Carbon Dioxide and Global Change: "the rising CO2 content of the air should boost global plant productivity dramatically, enabling humanity to increase food, fiber and timber production and thereby continue to feed, clothe, and provide shelter for their still-increasing numbers ... this atmospheric CO2-derived blessing is as sure as death and taxes."
* Sherwood Idso, former research physicist, USDA Water Conservation Laboratory, and adjunct professor, Arizona State University: "Warming has been shown to positively impact human health, while atmospheric CO2 enrichment has been shown to enhance the health-promoting properties of the food we eat, as well as stimulate the production of more of it. ... We have nothing to fear from increasing concentrations of atmospheric CO2 and global warming."54
* Patrick Michaels, part-time research professor of Environmental Sciences at the University of Virginia: "scientists know quite precisely how much the planet will warm in the foreseeable future, a modest three-quarters of a degree (Celsius), plus or minus a mere quarter-degree ... a modest warming is a likely benefit... human warming will be strongest and most obvious in very cold and dry air, such as in Siberia and northwestern North America in the dead of winter."
From http://en.wikipedia.org/
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