Climate Change

IPCC Reaffirms Dangerous Climate Change

What leaked IPCC report really says on climate change.

A draft of a major report on climate change, due to be published next year, has been leaked online. Climate skeptics immediately claimed it contains an admission that much of global warming is a result of the sun's variability, not greenhouse gas emissions. In fact, the report says nothing of the sort. It does, however, show that our understanding of the climate is shifting. And while some future threats now seem less likely, others loom larger. The report is the latest from the Intergovernmental Panel on Climate Change (IPCC), which releases detailed assessments of climate science every few years. Its last major report came out in 2007, and the next is scheduled to be published, section by section, from September 2013 onwards. The IPCC is predicting greater sea level rise than it did in 2007, as it now includes models of ice sheet movements. And we now have a gloomier picture of the extent to which smog and other human-made aerosols in the atmosphere shade us from the worst of global warming.

This is still a big uncertainty in temperature forecasting. The draft says their cooling effect is 40 per cent less than thought in 2007, suggesting this positive side effect of air pollution has been overstated. The report says that we could see almost 9 °C of warming by 2300; and that "a large fraction of climate change is largely irreversible on human timescales." Changes in the sun's brightness do have an important effect on the climate, but not in the way climate sceptics would like to think. The sun's brightness changes very little on human timescales, so the amount of heat Earth receives does not change much. But the type of radiation the sun puts out changes more significantly, and this has complex effects on atmospheric circulation patterns like the jet streams. As a result, the sun has a significant effect on regional climates.


Climatologists anxious to figure out how global warming will affect specific places, particularly Europe, must pay close attention to the sun.

Kemo D. 7


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