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Saturday, November 17, 2007

IPCC publishes its fourth assessment report

Human readable IPCC report without the media hype, politics or scientific gobbledygook:
  1. Earth has warmed 0.74°C in the last 100 years

  2. Sea level has risen on average between 1.8mm and 3.8mm per year since 1961

  3. Snow and ice cover has been shrinking by 0.27% every year since 1978

  4. In the last 100 years, rains increased in some parts of the world and decreased in others. It is unclear however if drought has increased overall.
  5. It is likely that cold days have become less frequent and warm days more frequent in the last 50 years

  6. It is difficult to tell if intense tropical cyclone activity has increased since 1970



Observed changes in (a) average temperature; (b) average sea level and (c) Northern Hemisphere snow cover for March-April. All differences are relative to 1961-1990 averages. The shaded areas mark the uncertainty in the data.

  1. Atmospheric concentrations of greenhouse gasses in 2005 far exceed the natural range over the last 650,000 years. These increases are due primarily to fossil fuel.

  2. Most of the observed increase in temperatures in the last 50 years is very likely due to the observed increase in greenhouse gasses.



Global annual emissions of human-caused greenhouse gasses from 1970 to 2004.5

  1. Current governmental policies are highly likely to allow greenhouse gas emissions to grow over the next few decades.

  2. Continued greenhouse gas emissions at or above current rates would cause further warming effects larger than those observed during the last 100 years



The solid lines are averages of surface warming for various possible scenarios from worst-case (red) to best case (blue). The uncertainty is shown in the shaded areas. The bars at the end show the likely range of temperature increases in the 100 year period after 2100. All temperatures are relative to today.

Conclusions


  • In the next 100 years temperature will rise between 1.8°C and 4.0°C over today.


  • The sea level will rise between 0.2m and 0.6m (between 0.6 and 1.9 feet) in the next 100 years


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