Fourth Assessment Report of the Intergovernmental Panel
 on Climate Change (IPCC) 

The evidence for human-caused global warming is now “unequivocal”

The first major global assessment of climate change science in six years was released on 2 February 2007. It concludes that changes in the atmosphere, the oceans and glaciers and ice caps show unequivocally that the world is warming. 

The reports 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. 

The 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. 

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 the Antarctic 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, the Secretary-General of 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.” 

For WMO/UNEP press release: http://www.wmo.int/pages/mediacentre/press_releases/pr_IPCC_en.html