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IPCC Report Devastating

Page history last edited by PBworks 13 years ago

1. http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf


Summary for Policymakers of the Synthesis Report of the IPCC Fourth Assessment Report



This Synthesis Report is based on the assessment carried out by the three Working Groups of the IPCC. It provides an integrated view of climate change as the final part of the IPCC’s Fourth Assessment Report.


A complete elaboration of the topics covered in this summary can be found in this Synthesis Report and in the underlying reports of the three Working Groups.


1. Observed changes in climate and their effects

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 ice, and rising global average sea level (Figure SPM.1). {1.1}


Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850). The 100-year linear trend (1906-2005) of 0.74 [0.56 to 0.92]°C 1 is larger than the corresponding trend of 0.6 [0.4 to 0.8]◦C (1901-2000) given in the Third Assessment Report (TAR) (Figure SPM.1). The temperature increase is widespread over the globe, and is greater at higher northern latitudes. Land regions have warmed faster than the oceans (Figures SPM.2, SPM.4). {1.1, 1.2}


Rising sea level is consistent with warming (Figure SPM.1). Global average sea level has risen since 1961 at an average rate of 1.8 [1.3 to 2.3]mm/yr and since 1993 at 3.1 [2.4 to 3.8]mm/yr, with contributions from thermal expansion, melting glaciers and ice caps, and the polar ice sheets. Whether the faster rate for 1993 to 2003 reflects decadal variation or an increase in the longer-term trend is unclear. {1.1}


Observed decreases in snow and ice extent are also consistent with warming (Figure SPM.1). Satellite data since 1978 show that annual average Arctic sea ice extent has shrunk by 2.7 [2.1 to 3.3]% per decade, with larger decreases in summer of 7.4 [5.0 to 9.8]% per decade. Mountain glaciers and snow cover on average have declined in both hemispheres. {1.1}


From 1900 to 2005, precipitation increased significantly in eastern parts of North and South America, northern Europe and northern and central Asia but declined in the Sahel, the Mediterranean, southern Africa and parts of southern Asia. Globally, the area affected by drought has likely to have increased since the 1970s. {1.1}


It is very likely that over the past 50 years: cold days, cold nights and frosts have become less frequent over most land areas, and hot days and hot nights have become more frequent. It is likely that: heat waves have become more frequent over most land areas, the frequency of heavy precipitation events has increased over most areas, and since 1975 the incidence of extreme high sea level3 has increased worldwide. {1.1}


There is observational evidence of an increase in intense tropical cyclone activity in the North Atlantic since about 1970, with limited evidence of increases elsewhere. There is no clear trend in the annual numbers of tropical cyclones. It is difficult to ascertain longer term trends in cyclone activity, particularly prior to 1970.

Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1300 years. (For full document see http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf)


2. http://www.time.com/time/health/article/0,8599,1685199,00.html



A Last Warning on Global Warming

The language of science, like that of the United Nations, is by nature cautious and measured. That makes the dire tone of the just-released final report from the fourth assessment of the U.N.'s Intergovernmental Panel on Climate Change (IPCC), a network of thousands of international scientists, all the more striking. Global warming is "unequivocal." Climate change will bring "abrupt and irreversible changes." The report, a synthesis for politicians culled from three other IPCC panels convened throughout the year, read like what it is: a final warning to humanity. "Today the world's scientists have spoken clearly, and with one voice," said U.N. Secretary-General Ban Ki Moon, who attended the publication of the report in Valencia, Spain. Climate change "is the defining challenge of our age."


posted to ClimateConcern

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