Despite the common perception amongst the general public that the scientists are divided about climate this is far from the case.  In fact, there is hardly an area of science where they are more united in opinion than they now are on this topic.  In 2004 Naomi Oreskes surveyed abstracts of every scientific paper she could find written on the subject of anthropogenic climate between 1993 and 2003.[1]  Of 928 papers not a single one took the position that global warming is not man-made.  In 2013 a review by Cook et al in Skeptical Science,  a periodical devoted to picking holes in scientific theories in order to disprove them (an important part of the methodology of science) found over 97% of the papers written between 1991 and 2011 that they had surveyed agreed with the consensus position that humans are causing global warming.[2] Almost without exception every official scientific body in the world agrees with the consensus position.


In America NASA, often in the person of the redoubtable James Hansen who is often regarded as the world’s foremost authority on climate, is unequivocal in its support of the consensus position.  But in fact this stance  has been taken up, now without exception, by every scientific  body in America.  Even the Association of Petroleum Scientists, who were understandably reluctant to concur, did so in 2007.


Here is a list of statements by these bodies


Statement on climate change from 18 American scientific associations. ?“Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver.” (2009)??


American Association for the Advancement of Science.  ?“The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society.” (2006)


American Chemical Society?.  “Comprehensive scientific assessments of our current and potential future climates clearly indicate that climate change is real, largely attributable to emissions from human activities, and potentially a very serious problem.” (2004)??


American Geophysical Union?.  “Human?induced climate change requires urgent action. Humanity is the major influence on the global climate change observed over the past 50 years. Rapid societal responses can significantly lessen negative outcomes.” (Adopted 2003, revised and reaffirmed 2007, 2012, 2013)


American Medical Association  ?“Our AMA … supports the findings of the Intergovernmental Panel on Climate Change’s fourth assessment report and concurs with the scientific consensus that the Earth is undergoing adverse global climate change and that anthropogenic contributions are significant.” (2013)??



American Meteorological Society?.  “It is clear from extensive scientific evidence that the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases, including carbon dioxide (CO2), chlorofluorocarbons, methane, and nitrous oxide.” (2012)??


American Physical Society?  “The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.” (2007)



The Geological Society of America?.  “The Geological Society of America (GSA) concurs with assessments by the National Academies of Science (2005), the National Research Council (2006), and the Intergovernmental Panel on Climate Change (IPCC, 2007) that global climate has warmed and that human activities (mainly greenhouse?gas emissions) account for most of the warming since the middle 1900s.” (2006; revised 2010)??





    ?International academies: Joint statement ?“Climate change is real. There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001).” (2005, 11 international science academies)??


    U.S. National Academy of Sciences?.  “The scientific understanding of climate change is now sufficiently clear to justify taking steps to reduce the amount of greenhouse gases in the atmosphere.” (2005)??






?U.S. Global Change Research Program.  ?“The global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases. Human ‘fingerprints’ also have been identified in many other aspects of the climate system, including changes in ocean heat content, precipitation, atmospheric moisture, and Arctic sea ice.” (2009, 13 U.S. government departments and agencies).



How is it, then, that, in the face of this overwhelming unanimity amongst the scientists, the sceptics have been so successful  in persuading the public that there is a scientific division of opinion on the issue?   Much of the confusion has arisen from the scientific process itself.  Scientists are trained sceptics.  They greatly value what they call falsifiability.  Any theory must be capable of being falsified if contrary data is discovered, and must survive every attempt to falsify it before it can be declared robust.  Their whole methodology, with its precise process of data gathering, hypothesis, experiment, proof and peer review, is designed to test any theory to destruction before it is accepted.  One or two experiments are never enough.  But as more and more confirmation of a thesis arises more and more scientists come to accept it.  But even then there are always diehards.  Thus Priestley’s experiments were crucial in enabling Lavoisier to discover oxygen, but Priestley remained a devout believer in phlogiston to the end of his life.  Quantum physics would never have even begun without Einstein’s discoveries.  But Einstein himself remained a bitter opponent of quantum physics’ most basic proposition, that position and momentum can never both be measured at the same time because of the inherent uncertainty of phenomena at the quantum level, until his dying breath.                                    


But the progress of science fells even these giants.  You would not find a single scientist today who thinks that Einstein was right.   In the end, there is so much evidence scientists accept a new thesis as true universally.  Anthropogenic climate change has now achieved that status, even though it is peculiarly resistant to scientific method.  Because it is in the future experiments cannot be performed on it. The best scientists can do is to run computer models of possible scenarios.  But the subject is so complicated, and future developments so uncertain, no-one can ever be sure that even the most powerful computers can give reliable information.  Even the IPCC (unlike Christopher Booker and The Daily Mail one can’t help thinking) claims to be only 95% sure about man-made climate change.  It is this aspect that has made many scientists cautious and has allowed the sceptics to make such play about scientific uncertainty.   

[1] Oreskes Naomi (Dec 2004): Beyond the Ivory Tower:  the Scientific Consensus on Climate Change. Science 306 (5702) 1686

[2] J. Cook et al. ‘Quanitfying the Consensus on Anthropogenic Global Warming.’  Environmental Research Letters vol8/2 April 2013


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