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Fourth Assessment Report of the Intergovernmental
The Intergovernmental Panel on Climate Change (IPCC) was established by WMO and the United Nations Environment Programme to assess scientific, technical and socio-economic information relevant for the understanding of climate change, its potential impacts and options for adaptation and mitigation.
The report confirms that global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750. It goes on to say that continued greenhouse-gas emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century.
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.
The second volume Climate Change Impacts, Adaptation and Vulnerability was released in Brussels on 6 April. It concludes that the world’s rivers, lakes, wildlife, glaciers, permafrost, coastal zones, disease carriers and many other elements of the natural and physical environment are already responding to the effects of humanity’s greenhouse-gas emissions.
Scientists are increasingly confident that, as global warming continues, certain weather events and extremes will become more frequent, widespread or intense. Some events, in particular sea-level rise, have the potential for significant impacts on natural ecosystems, water resources and agricultural production in certain regions, especially after the 21st century.The IPCC also finds, however, that early action to improve seasonal climate forecasts, food security, freshwater supplies, disaster and emergency response, famine early-warning systems and insurance coverage, can minimize the damage from future climate change, while generating many immediate practical benefits.
The next volume—Mitigation of Climate Change—will be issued by Working Group III at its ninth session in Bangkok, Thailand, in May.
The Synthesis Report integrates the information around six topic areas. It will be issued at the 27th session of the IPCC in November 2007 in Valencia, Spain.
Progress in observations and measurements of the weather and climate are key to improved climate research, with National Meteorological and Hydrological Services playing a crucial role.