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The evidence for human-caused global warming is now “unequivocal”, says IPC
Paris, 2 February 2007 – The first major global assessment of climate change science in six years has concluded that changes in the atmosphere, the oceans and glaciers and ice caps show unequivocally that the world is warming.
The Intergovernmental Panel on Climate Change (IPCC) concludes that major advances in climate modelling and the collection and analysis of data now give scientists “very high confidence” (at least a 9 out of 10 chance of being correct) in their understanding of how human activities are causing the world to warm. This level of confidence is much greater than what could be achieved in 2001 when the IPCC issued its last major report.
Today’s report, the first of four volumes to be released this year by the IPCC, also confirms that the marked increase in atmospheric concentrations of greenhouse gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) since 1750 is the result of human activities.
An even greater degree of warming would likely have occurred if emissions of pollution particles and other aerosols had not offset some of the impact of greenhouse gases, mainly by reflecting sunlight back out to space.
Three years in the making, the report is based on a thorough review of the most-up-to-date, peer-reviewed scientific literature available worldwide. It describes an accelerating transition to a warmer world marked by more extreme temperatures including heat waves, new wind patterns, worsening drought in some regions, heavier precipitation in others, melting glaciers and Arctic ice and rising global average sea levels. For the first time, the report provides evidence that the ice sheets of Antarctica and Greenland are slowly losing mass and contributing to sea level rise.
“This report by the IPCC represents the most rigorous and comprehensive assessment possible of the current state of climate science and has considerably narrowed the uncertainties of the 2001 report,” said Michel Jarraud, Secretary General of the World Meteorological Organization (WMO). “Progress in observations and measurements of the weather and climate are keys to improved climate research, with National Meteorological and Hydrological Services playing a crucial role.”
“While the conclusions are disturbing, decision makers are now armed with the latest facts and will be better able to respond to these realities. The speed with which melting ice sheets are raising sea levels is uncertain, but the report makes clear that sea levels will rise inexorably over the coming centuries. It is a question of when and how much, and not if,” he said.
“In our daily lives we all respond urgently to dangers that are much less likely than climate change to affect the future of our children,” said Achim Steiner, Executive Director of the United Nations Environment Programme (UNEP), which, together with WMO, established the IPCC in 1988.
“The implications of global warming over the coming decades for our industrial economy, water supplies, agriculture, biological diversity and even geopolitics are massive. Momentum for action is building; this new report should spur policymakers to get off the fence and put strong and effective policies in place to tackle greenhouse gas emissions,” he said.
The report also concludes that:
The Summary for Policymakers for IPCC Working Group I, which was finalized line-by-line by governments during the course of this week, has now been posted in English at www.ipcc.ch. The full underlying report – “Climate Change 2007: The Physical Science Basis” – will be published by Cambridge University Press.
The report was produced by some 600 authors from 40 countries. Over 620 expert reviewers and a large number of government reviewers also participated. Representatives from 113 governments reviewed and revised the Summary line-by-line during the course of this week before adopting it and accepting the underlying report.
The Working Group II report on climate impacts and adaptation will be launched in Brussels on 6 April. The Working Group III report on mitigation will be launched in Bangkok on 4 May. The Synthesis Report will be adopted in Valencia, Spain on 16 November. Together, the four volumes will make up the IPCC’s fourth assessment report; previous reports were published in 1990, 1995 and 2001.
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