|The Scientific Consensus|
Historian of science, Naomi Oreskes of UC San Diego, states: "Scientific knowledge is the intellectual and social consensus of affiliated experts based on the weight of available empirical evidence, and evaluated according to accepted methodologies. If we feel that a policy question deserves to be informed by scientific knowledge, then we have no choice but to ask, what is the consensus of experts on this matter."
Climate change has been extensively researched and the overwhelming majority of climate scientists agree that the observed modern day global warming is unprecedented and is very likely caused by humans. The 2007 IPCC reports detail this widespread consensus. Although there is little serious debate between climate experts, many in the general public still think that these scientists are unsure about climate change and the role that humans have played in modern day global warming (Doran & Zimmerman, 2009). There are some reasons why the general public may be confused and they are not accidental.
So whom do you trust? The statement below from Prof. Stephen Schneider answers the question quite well and can be considered a litmus test for the veracity of climate change claims:
Examining the Scientific Consensus on Climate Change:
48% of Americans think most climate scientists do not agree that the Earth has been warming in recent years, and 53% think climate scientists do not agree that human activities are a major cause of that warming (Doran and Zimmerman, 2009). A poll performed by Peter Doran and Maggie Kendall Zimmerman at Earth and Environmental Sciences, University of Illinois at Chicago of 3,146 Earth scientists showed 96.2% of climatologists who are active in climate research agree that mean global temperatures have risen compared to pre-1800s levels, and 97.4% agree that human activity is a significant factor in changing mean global temperatures. Among all respondents, 90% agreed that temperatures have risen compared to pre-1800 levels, and 80% agreed that humans significantly influence the global temperature. Petroleum geologists were among the biggest doubters, with only 47 percent believing in human involvement.
Doran and Zimmerman conclude:
Anderegg et al. (2010) in their PNAS paper, Expert credibility in climate change, used an extensive dataset of 1,372 climate researchers and their publication and citation data to show that:
“A vocal minority of researchers and other critics contest the conclusions of the mainstream scientific assessment, frequently citing large numbers of scientists whom they believe support their claims…This group, often termed climate change skeptics, contrarians, or deniers, has received large amounts of media attention and wields significant influence in the societal debate about climate change impacts and policy."
“Despite media tendencies to present ‘both sides’ in ACC debates [anthropogenic climate change], which can contribute to continued public misunderstanding regarding ACC, not all climate researchers are equal in scientific credibility and expertise in the climate system. This extensive analysis of the mainstream versus skeptical/contrarian researchers suggests a strong role for considering expert credibility in the relative weight of and attention to these groups of researchers in future discussions in media, policy, and public forums regarding anthropogenic climate change.”
In another smaller survey via email, Brown, Pielke, and Anaan (2007) contacted 1807 climate scientists and received responses from 140 of those scientists. In the poll scientists were asked to discuss their opinion about the role of human-caused radiative forcing of CO2 in climate change and how climate science was represented in the IPCC's WG1 Report. The response is summarized below:
Intergovernmental Panel on Climate Change, IPCC:
The IPCC is a scientific intergovernmental body set up by the World Meteorological Organization (WMO) and by the United Nations Environment Programme (UNEP). Its constituency is made of :
The governments: the IPCC is open to all member countries of WMO and UNEP. Governments participate in plenary sessions of the IPCC where main decisions about the IPCC work program are taken and reports are accepted, adopted and approved. They also participate in the review of IPCC reports.
The scientists: hundreds of scientists all over the world contribute to the work of the IPCC as authors, contributors and reviewers.
Its role is to assess on a comprehensive, objective, open and transparent basis the latest scientific, technical and socio-economic literature produced worldwide relevant to the understanding of the risk of human-induced climate change, its observed and projected impacts and options for adaptation and mitigation.
The IPCC 4th Assessment Report (2007) is the result of 2500+ scientific expert reviewers, 800+ contributing authors, and 450+ lead authors from 130+ countries.
Below are some excerpts from the IPCC WGI 4th Assessment Report (IPCC, 2007) which leaves little doubt that the present climate is experiencing an unprecedented global warming rate which is primarily due to human (anthropogenic) activities:
For more information please see: IPCC Website
Climate Change: Global Risks, Challenges and Decisions:
Since the IPCC 2007 reports, new research has been reviewed by the International Alliance of Research Universities (IARU). IARU organized an international scientific congress on climate change, Climate Change: Global Risks, Challenges and Decisions, which was held in Copenhagen from 10-12 March 2009. Participation in the Congress was open to all. Most of the approximately 2500 people attending the Congress were researchers, many of whom have also been contributors to the IPCC reports. Participants came from nearly 80 different countries and contributed with more than 1400 scientific presentations. The Synthesis Report (Richardson, et al., 2009) contains six key messages:
No Scientific Body of National or International Standing Holds a Dissenting Opinion:
A strong, credible body of scientific evidence shows that climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems…. Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities. (U.S. National Academy of Sciences, 2010)
"Decades of scientific research have shown that climate can change from both natural and anthropogenic causes. 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. If current trends continue, the projected increase in global temperature by the end of the twentyfirst century will result in large impacts on humans and other species. Addressing the challenges posed by climate change will require a combination of adaptation to the changes that are likely to occur and global reductions of CO2 emissions from anthropogenic sources." (The Geological Society of America [GSA], 2010)
"The Earth's climate is now clearly out of balance and is warming. Many components of the climate system-including the temperatures of the atmosphere, land and ocean, the extent of sea ice and mountain glaciers, the sea level, the distribution of precipitation, and the length of seasons-are now changing at rates and in patterns that are not natural and are best explained by the increased atmospheric abundances of greenhouse gases and aerosols generated by human activity during the 20th century." (American Geophysical Union, 2007)
"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." (Union of Concerned Scientists, 2009)
"Observations show that warming of the climate is unequivocal. The global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities." (U.S. Global Change Research Program, 2009)
"Human activity is most likely responsible for climate warming. Most of the climatic warming over the last 50 years is likely to have been caused by increased concentrations of greenhouse gases in the atmosphere." (European Academy of Sciences and Arts, 2007)
"Scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society....The pace of change and the evidence of harm have increased markedly over the last five years. The time to control greenhouse gas emissions is now." (American Association for the Advancement of Science, 2006)
More official statements can be viewed at: Wiki: Scientific Opinion on Climate Change.
These two quotes also show the consensus:
"Consensus as strong as the one that has developed around global warming is rare in science."
--- Donald Kennedy, editor of Science
Most-Cited Authors on Climate Science:
Jim Prall, from the University of Toronto, has compiled a list of homepages and some citation stats for all the authors from Working Group 1 of the 2007 Fourth Assessment Report (AR4) from the Intergovernmental Panel on Climate Change (IPCC), as well as a longer list including other active climate science researchers. Please see his Most-Cited Authors on Climate Science table for an excellent representation of those that agree there is AGW and those that are skeptical.
|Climate Consensus: A Cautionary Tale, Part 1/2
Prof. Barry Bickmore examines the following questions. 1) What does it mean to have a scientific consensus? 2) Is there a strong scientific consensus about whether humans are significantly affecting the climate? 3) How do people convince themselves to go against the consensus?
What About Scientists and Papers That Challenge the Consensus?
Some claim that there are 31,000 U.S. scientists and over 850 peer-reviewed papers that challenge the consensus that humans are causing climate change. Skeptical Science gave these claims the greatest benefit of the doubt and came up with this interesting factoid:
It is quite foolish to hang one's hat on those statistics!
Next: Determining the Climate Record
Last updated: 02/13/11