GLOBAL WARMING
The State of Scientific Knowledge
History
“Most of the observed increase in global average temperatures since the mid-20th century is very likely ( >90%) due to the observed increase in anthropogenic (human emission caused) greenhouse gas concentrations.”- 2007 Report of the Intergovernmental Panel on ClimateChange (IPCC)
The anticipated increase in the temperature due to the greenhouse effect was predicted long before it was detectable in the atmosphere, indeed long before it was known that atmospheric CO2 was really increasing; it was first predicted by Arrhenius in 1896, using extremely simple radiation balance ideas, and was reproduced using modern radiation physics by Manabe and co-workers in the 1960's. Neither of these predictions rests on general circulation models, which came in during subsequent decades and made more detailed forecasts possible. Read the Arrhenius paper here.
Before the IPCC (source)
In 1979, the first “World Climate Conference” organized by the World Meteorological Organization (WMO) expressed concern that “continued expansion of man’s activities on earth may cause significant extended regional and even global changes of climate”. It called for “global cooperation to explore the possible future course of global climate and to take this new understanding into account in planning for the future development of human society.”
In 1985, a joint Conference was convened in Villach (Austria) on the “Assessment of the Role of Carbon Dioxide and of Other Greenhouse Gases in Climate Variations and Associated Impacts.” The conference concluded that “as a result of the increasing greenhouse gases, it is now believed that in the first half of the next century (21st century) a rise of global mean temperature could occur which is greater than any in man’s history.” It also noted that past climate data may no longer be a reliable guide for long term projects because of expected increase in the global temperature; that climate change and sea level rises are closely linked with other major environmental issues; that some warming appears inevitable because of past activities; and that the future rate and degree of warming could be profoundly affected by policies on emissions of greenhouse gases.
In 1987, the 10th Congress of the WMO recognized the need for objective, balanced, and internationally coordinated scientific assessment of the understanding of the effects of increasing concentrations of greenhouse gases on the earth’s climate and on ways in which these changes may impact socio-economic patterns.
At its 40th Session in 1988, the WMO Executive Council decided on the establishment of the Intergovernmental Panel on Climate Change (IPCC). The UNEP Governing Council authorized UNEP’s support for IPCC. It was suggested that the Panel should consider the need for:
(a) Identification of uncertainties and gaps in our present knowledge with regard to climate changes and its potential impacts, and preparation of a plan of action over the short- term in filling these gaps;
(b) Identification of information needed to evaluate policy implications of climate change and response strategies;
(c) Review of current and planned national/international policies related to the greenhouse gas issue;
(d) Scientific and environmental assessments of all aspects of the greenhouse gas issue and the transfer of these assessments and other relevant information to governments and intergovernmental organizations to be taken into account in their policies on social and economic development and environmental programs.
In 1989, the 44th session of the UNGA requested the report by the IPCC to be submitted to its 45th Session and it agreed to take, after the adoption of the IPCC report, a decision on ways, means and modalities for pursuing negotiations of a framework convention. Such negotiations would be coordinated with the preparations for the UN Conference on Environment and Development (UNCED) in Rio de Janeiro in 1992.
1990 - First IPCC Assessment Report
Responding to this request, the IPCC adopted its first assessment report on 30 August 1990 in Sundsvall, Sweden.
The experts concluded that they are certain that emissions from human activities are substantially increasing the atmospheric concentrations of greenhouse gases and that this will enhance the greenhouse effect and result in an additional warming of the Earth’s surface.
The UNGA at its 45th session in 1990 noted the findings of the IPCC and decided to initiate negotiations of an effective framework convention on climate change, which should be completed prior to the UN Conference on Environment and Development in June 1992.
In November of 1990 at the World Climate Conference in Geneva, over 700 scientists from around the world reviewed the IPCC First Assessment technical report. Following that review, they released the Scientists’ Declaration. Within this document, they said, ‘‘A clear scientific consensus has emerged on estimates of the range of global warming that can be expected during the 21st century…Countries are urged to take immediate actions to control the risks of climate change’’ (quoted in Leggett, 2001, p. 21).
1992 - Adoption of the United Nations Framework Convention on Climate Change
(UNFCCC) http://unfccc.int/
160 countries, including the U.S. signed the UNFCCC. It says, in part: “Each of these Parties (developed countries) shall adopt national policies and take corresponding measures on the mitigation of climate change, by limiting its anthropogenic emissions of greenhouse gases and protecting and enhancing its greenhouse gas sinks and reservoirs.”
1995 - Second IPCC Assessment Report
“The balance of evidence suggests a discernible human influence on global climate.”
1997 - Adoption of the Kyoto Protocol
In which every industrialized nation except the U.S. and Australia agreed to reduce CO2 emissions. As the UNFCCC describes it, “while the Convention encouraged developed countries to stabilize GHG emissions, the Protocol commits them to do so.”
2001 - Third IPCC Assessment Report
“Most of the warming of the past 50 years is likely (>66%) to be attributable to human activities.”
2007 – Fourth IPCC Assessment Report
“Warming of the climate system is unequivocal (unequivocal: absolute; unqualified; not subject to conditions or exceptions), as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”
“Most of the observed increase in global average temperatures since the mid-20th century is very likely (>90%) due to the observed increase in anthropogenic (human emission caused) greenhouse gas concentrations.”
Here is the UNFCC’s description of the fourth assessment: “Compelling scientific evidence - Some scientists have doubted the scientific basis of the Kyoto Protocol, claiming that there is not a clear connection between increases in GHG emissions and climate change. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), launched in the course of 2007, put an end to that discussion. Prepared by scientists from all over the world, it placed the reality of human-induced climate change beyond any doubt. It is politically significant that governments endorsed the IPCC’s Fourth Assessment Report by consensus, making it a solid foundation for sound political decision-making.”
IPCC
The IPCC: Who Are They and Why Do Their Climate Reports Matter?
Find an excellent summary of the 2007 4th assessment by the Intergovernmental Panel on Climate Change (IPCC) here.
The Summary for Policy Makers is available here.
More Science
The Architecture 2030 website has an excellent, succinct, and well documented explanation of Global Warming, Coal Plants, and potential solutions.
A study showing the number of authors publishing articles on “Global Climate Change” in peer reviewed journals who disagree with the “consensus” that warming is happening and human caused greenhouse gas emissions are a significant contributor. Findings – of 928 abstracts, published in refereed scientific journals between 1993 and 2003, none of the papers disagreed with the consensus position. Article on the report Here.
A good, if somewhat complex, description of how Jim Hansen’s models of global warming due, in part, to human CO2 emissions, presented in 1988 appear to have done a good job of predicting the temperatures between then and now. In 1988 Hansen said he could state "with 99% confidence" that a long-term warming trend was underway, and he strongly suspected that the greenhouse effect was to blame. Here.
Skeptics and Deniers
As noted in the “Selling Uncertainty” section, major corporations, in particular Exxon Mobil, have funneled millions into think tanks and advocacy groups which support and promote a small number of climate change deniers and skeptics. The following sites address the skeptic’s claims from a scientific perspective. If any of the alternative explanations for climate change - natural variation, water vapor, sun spots, and such - make sense to you, please consult these sites.
http://www.skepticalscience.com/argument.php
http://www.realclimate.org/index.php/archives/2004/12/index/#Responses
http://www.metoffice.gov.uk/corporate/pressoffice/myths/index.html
http://www.nerc.ac.uk/about/consult/debate/climatechange/summary.asp
http://gristmill.grist.org/skeptics
http://www.logicalscience.com/skeptic_arguments/skeptic-arguments.html