Worse
to Come From Global Warming
By Richard A. Kerr
ScienceNOW Daily News
6 April 2007
The U.N.-sponsored Intergovernmental Panel on Climate Change
(IPCC) report released today in Brussels has a familiar ring.
As the climate disasters headlined recently--intense hurricanes,
drought in the American West, Arctic thawing--become commonplace
in a greenhouse world, plants, animals, and people will suffer.
That has been the presumption, but the latest report from
the IPCC projecting greenhouse impacts calculates mounting
costs that will fall the heaviest on the world's poor.
February's IPCC report on the physical science of climate
(ScienceNOW, 2 February) firmly links most of the recent warming
of the world to human activity. Scientists authoring the second
report had a tougher challenge: figuring out the likely consequences.
To do that, they considered 29,000 datasets from 75 studies.
Of those data series, 89% showed changes--receding glaciers
or earlier blooming, for example--consistent with a response
to warming. Because those responses usually occurred where
the warming has been greatest, the scientists concluded that
it's "very unlikely" the changes were due to natural
variability of climate or of the system involved. "For
the first time, we concluded anthropogenic warming has had
an influence on many physical and biological systems,"
says Cynthia Rosenzweig of NASA's Goddard Institute for Space
Studies in New York City, a coordinating lead author on the
report.
The IPCC scientists also projected the effects of future warming.
Assuming that nothing's done to slow greenhouse emissions,
the February report predicted a temperature increase of roughly
3°C toward the end of the century, drying at lower latitudes,
more precipitation at higher latitudes, and rising sea levels.
This report finds that such a warming will bleach most coral
reefs by mid-century, drying will begin decreasing crop yields
at lower latitudes within a few decades, and sea level rise
and tropical cyclone intensification will increase the likelihood
of millions of people being flooded out each year on river
mega-deltas such as that of the Ganges-Brahmaputra in southern
Asia.
Bottom line? "You don't want to be poor and living on
a river delta or the Florida coast," says climate scientist
Stephen Schneider of Stanford University, a coordinating lead
author. The poor--especially subsistence farmers--tend to
be more vulnerable to climate change, notes the report. And
they are least able to adapt, say by building levees against
storms or dams for irrigation. Schneider's other advice: "Try
not to go over 2°C or 3°C because that triggers the
really nasty stuff." With that much warming, the bad
effects of this century only get worse, and the rare benefits,
such as higher crop yields in wetter areas, fade. To avoid
that disaster, see next month's IPCC report on how to reduce
greenhouse gas emissions.
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