|
The United Nations Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment, released in 2007, concludes that it is “unequivocal” that the climate is warming and that there is “very high confidence” (i.e., at least 90% certainty) that human activities have caused “most of the observed increase in globally averaged temperatures since the mid-twentieth century." The findings include the following:
- 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 determined from ice cores spanning many thousands of years.
- The IPCC expresses very high confidence that the global average net effect of human activities since 1750 has been one of warming.
- Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and since, and rising global average sea level.
- Numerous long-term changes in climate have been observed. These include changes in arctic temperatures and ice, widespread changes in precipitation amount, ocean salinity, wind patterns and aspects of extreme weather including droughts, heavy precipitation, heat waves and the intensity of tropical cyclones.
- Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.
- Anthropogenic warming and sea level rise would continue for centuries due to the time scales associated with climate processes and feedbacks, even if greenhouse gas concentrations were to be stabilised.
The Fourth Assessment reports include: "The Physical Science Basis" (Working Group 1), "Impacts, Adaptation, and Vulnerability" (Working Group II), and "Mitigation of Climate Change" (Working Group III). The IPCC Fourth Assessment "Synthesis Report" will be released in November 2007. These reports are the result of the work of over 2,500 scientific expert reviewers and over 800 contributing authors and 450 lead authors from more than 130 lead countries. Click here for IPCC report updates.
The United Nations Environment Programme established the Intergovernmental Panel on Climate Change in 1988. The IPCC's role is to "assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. "
In October, 2007, the Nobel Peace Prize was awarded to the Intergovernmental Panel on Climate Change and Albert Arnold Gore Jr. "for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change."
|
