These scientists have said that the observed warming is more likely to be attributable to natural causes than to human activities. Their views on climate change are usually described in more detail in their biographical articles.
Khabibullo Abdusamatov, astrophysicist at Pulkovo Observatory of the Russian Academy of Sciences[74][75]
Sallie Baliunas, retired astrophysicist, Harvard-Smithsonian Center for Astrophysics[76][77][78]
Timothy Ball, historical climatologist, and retired professor of geography at the University of Winnipeg[79][80][81]
Ian Clark, hydrogeologist, professor, Department of Earth Sciences, University of Ottawa[82][83]
Chris de Freitas, associate professor, School of Geography, Geology and Environmental Science, University of Auckland[84][85]
David Douglass, solid-state physicist, professor, Department of Physics and Astronomy, University of Rochester[86][87]
Don Easterbrook, emeritus professor of geology, Western Washington University[88][89]
William Happer, physicist specializing in optics and spectroscopy; emeritus professor, Princeton University[90][91]
Ole Humlum, professor of geology at the University of Oslo[92][93]
Wibjörn Karlén, professor emeritus of geography and geology at the University of Stockholm.[94][95]
William Kininmonth, meteorologist, former Australian delegate to World Meteorological Organization Commission for Climatology[96][97]
David Legates, associate professor of geography and director of the Center for Climatic Research, University of Delaware[98][99]
Anthony Lupo, professor of atmospheric science at the University of Missouri[100][101]
Tad Murty, oceanographer; adjunct professor, Departments of Civil Engineering and Earth Sciences, University of Ottawa[102][103]
Tim Patterson, paleoclimatologist and professor of geology at Carleton University in Canada.[104][105]
Ian Plimer, professor emeritus of mining geology, the University of Adelaide.[106][107]
Arthur B. Robinson, American politician, biochemist and former faculty member at the University of California, San Diego[108][109]
Murry Salby, atmospheric scientist, former professor at Macquarie University and University of Colorado[110][111]
Nicola Scafetta, research scientist in the physics department at Duke University[112][113][114]
Tom Segalstad, geologist; associate professor at University of Oslo[115][116]
Nir Shaviv, professor of physics focusing on astrophysics and climate science at the Hebrew University of Jerusalem[117][118]
Fred Singer, professor emeritus of environmental sciences at the University of Virginia[119][120][121][122]
Willie Soon, astrophysicist, Harvard-Smithsonian Center for Astrophysics[123][124]
Roy Spencer, meteorologist; principal research scientist, University of Alabama in Huntsville[125][126]
Henrik Svensmark, physicist, Danish National Space Center[127][128]
George H. Taylor, retired director of the Oregon Climate Service at Oregon State University[129][130]
Jan Veizer, environmental geochemist, professor emeritus from University of Ottawa[131][132]
Scientists arguing that the cause of global warming is unknown
These scientists have said that no principal cause can be ascribed to the observed rising temperatures, whether 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.[133][134]
Claude Allègre, French politician; geochemist, emeritus professor at Institute of Geophysics (Paris).[135][136]
Robert Balling, a professor of geography at Arizona State University.[137][138]
Pål Brekke, solar astrophycisist, senior advisor Norwegian Space Centre.[139][140]
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.[141][142][143]
Petr Chylek, space and remote sensing sciences researcher, Los Alamos National Laboratory.[144][145]
David Deming, geology professor at the University of Oklahoma.[146][147]
Stanley B. Goldenberg a meteorologist with NOAA/AOML's Hurricane Research Division [148] [149]
Vincent R. Gray, New Zealand physical chemist with expertise in coal ashes[150][151]
Keith E. Idso, botanist, former adjunct professor of biology at Maricopa County Community College District and the vice president of the Center for the Study of Carbon Dioxide and Global Change[152][153]
Antonino Zichichi, emeritus professor of nuclear physics at the University of Bologna and president of the World Federation of Scientists.[154][155]
Kary Mullis, 1993 Nobel Laureate in Chemistry
