Climate Change
Sunday, 16. December 2007, 05:06:49
IPCC Fourth Assessment Report: Climate Change 2007
Main article: IPCC Fourth Assessment Report
The Fourth Assessment Report (AR4) was completed in early 2007[11]. Like previous assessment reports, it consists of four reports, three of them from its working groups.
Working Group I dealt with the "Physical Science Basis of Climate Change." The Working Group I Summary for Policymakers (SPM) was published on 2 February 2007[12] and revised on 5 February 2007[13]. There was also a 2 February 2007 press release[14]. The full WGI report[15] was published in March. The key conclusions of the SPM were that[16]:
-Warming of the climate system is unequivocal.
-Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (human) greenhouse gas concentrations.
-Anthropogenic warming and sea level rise would continue for centuries due to the timescales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized, although the likely amount of temperature and sea level rise varies greatly depending on the fossil intensity of human activity during the next century (pages 13 and 18)[13].
-The probability that this is caused by natural climatic processes alone is less than 5%.
-World temperatures could rise by between 1.1 and 6.4 °C (2.0 and 11.5 °F) during the 21st century and that:
-Sea levels will probably rise by 18 to 59 cm (7.08 to 23.22 in) [table 3].
-There is a confidence level >90% that there will be more frequent warm spells, heat waves and heavy rainfall.
-There is a confidence level >66% that there will be an increase in droughts, tropical cyclones and extreme high tides.
-Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium.
-Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values over the past 650,000 years
In IPCC statements "most" means greater than 50%, "likely" means at least a 66% likelihood, and "very likely" means at least a 90% likelihood.
An outline of chapters in the WGI report (as of November 3, 2005)[17] and a list of the report's authors (as of March 10, 2005)[18] were made available before publication of the SPM.
The Summary for Policymakers for the Working Group II [1] report was released on April 6, 2007[19]. The Summary for Policymakers for the Working Group III report [20] was released on May 4, 2007. The AR4 Synthesis Report (SYR) was released on November 17, 2007.
Main article: IPCC Fourth Assessment Report
The Fourth Assessment Report (AR4) was completed in early 2007[11]. Like previous assessment reports, it consists of four reports, three of them from its working groups.
Working Group I dealt with the "Physical Science Basis of Climate Change." The Working Group I Summary for Policymakers (SPM) was published on 2 February 2007[12] and revised on 5 February 2007[13]. There was also a 2 February 2007 press release[14]. The full WGI report[15] was published in March. The key conclusions of the SPM were that[16]:
-Warming of the climate system is unequivocal.
-Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic (human) greenhouse gas concentrations.
-Anthropogenic warming and sea level rise would continue for centuries due to the timescales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilized, although the likely amount of temperature and sea level rise varies greatly depending on the fossil intensity of human activity during the next century (pages 13 and 18)[13].
-The probability that this is caused by natural climatic processes alone is less than 5%.
-World temperatures could rise by between 1.1 and 6.4 °C (2.0 and 11.5 °F) during the 21st century and that:
-Sea levels will probably rise by 18 to 59 cm (7.08 to 23.22 in) [table 3].
-There is a confidence level >90% that there will be more frequent warm spells, heat waves and heavy rainfall.
-There is a confidence level >66% that there will be an increase in droughts, tropical cyclones and extreme high tides.
-Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium.
-Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values over the past 650,000 years
In IPCC statements "most" means greater than 50%, "likely" means at least a 66% likelihood, and "very likely" means at least a 90% likelihood.
An outline of chapters in the WGI report (as of November 3, 2005)[17] and a list of the report's authors (as of March 10, 2005)[18] were made available before publication of the SPM.
The Summary for Policymakers for the Working Group II [1] report was released on April 6, 2007[19]. The Summary for Policymakers for the Working Group III report [20] was released on May 4, 2007. The AR4 Synthesis Report (SYR) was released on November 17, 2007.
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