"A
World of Change: Climate Yesterday, Today, and Tomorrow"
The first part of this talk summarizes key evidence from the 2007
report of the Intergovernmental Panel on Climate Change for changes in
the Earth's climate, and the causes of those changes.
Understanding how temperatures are increasing around the world, how ice
is melting at the poles, and how rain is decreasing in key regions, are
among the issues that will be addressed. Observations of
the greenhouse gases and aerosols that are the main reasons for current
climate change will also be discussed. The
second part of the talk reviews findings that were not detailed in IPCC
on the subject of the time scales of climate changes due to carbon
dioxide increases. It is not generally appreciated that man-made
warming that takes place due to increases in carbon dioxide
concentration is nearly irreversible for more than 1000 years after
emissions stop. This is due to physical linkages between
transport of heat and of carbon dioxide to the deep ocean, rendering
the cumulative effects of every year's carbon dioxide emissions and
resulting climate changes unique among major anthropogenic greenhouse
gases. Illustrative impacts that should be expected if
atmospheric carbon dioxide concentrations increase from current levels
near 385 ppmv to a peak of 450-600 ppmv over the coming century are
irreversible dry-season rainfall reductions in several regions
comparable to those of the 'dust bowl' era, as well as a lower limit to
slow but inexorable sea level rise that could eventually exceed 1 meter.
