This is from today’s L.A. Times:
Much of the world, including the drought-plagued American West, will
face more deadly heat waves, intense rainstorms and prolonged dry spells before the end of the century, according to a new climate change study released Thursday.
Focusing not on averages but on extremes, the new research draws on
nine climate models to predict what will happen if worldwide greenhouse gases
Longer periods of high heat and heavy rainfall are predicted for nearly
all areas by 2080 to 2099. In addition, dry periods will last longer in the
Southwestern United States, southern Europe and several other areas, the
"In the future, rising frequency, intensity and duration of
temperature extremes … are likely to have adverse effects on human mortality and
morbidity," says the scientists' report, "Going to Extremes," which will be
published in the December issue of the journal Climatic Change. "Changes in
precipitation-related extremes such as heavy rainfall and associated flooding
also have the potential to [cause] significant economic losses and
The federally funded analysis is among the first to use supercomputer
simulations developed in the U.S., Japan, France and Russia for an international
committee of scientists, the Intergovernmental Panel on Climate
The scenarios were based on three projections in volumes of greenhouse
gas emissions, which come largely from the burning of gasoline, coal and other
Even under the lowest-emissions scenario, more extreme events were
predicted, although the trend was significantly weaker. That means reducing
greenhouse gas emissions will lower the risk of severe heat waves and heavy
Wetter weather was one of the most significant and consistent patterns
that showed up in the modeling, the study shows.
"Depictions of a wetter world and greater precipitation intensity
emerge unequivocally," the report says.
Extra precipitation is tied to global warming because warm oceans
evaporate more and warm air holds more moisture.
The higher latitudes, above 40 degrees north — in the United States,
north of Reno, Denver and Philadelphia — are expected to feel the most effects
of more extreme precipitation.
"We see increases in precipitation intensity almost everywhere, but
particularly at higher latitudes," said co-author Gerald Meehl, a scientist in
the National Center for Atmospheric Research's climate and global dynamics
Along with more precipitation, more days will pass between rain events
in the Southwest, he said.
"The reason these can both happen simultaneously is that you can have
longer dry spells between rainfall events, but when it does rain, it rains
harder," Meehl said.
In the Southwest, the more frequent heat waves would be caused by
changes in atmospheric circulation created by greenhouse gases.
Other changes that were called pronounced in the models include a
longer growing season and fewer frost days in the Northwestern U.S. and Eastern
Europe, and more heat waves in Northern Australia.
The scientists looked at 10 indicators of extremes: heat wave duration,
the difference between a year's high and low temperatures, growing season
length, frost days, warm nights and five factors involving
Other recent studies have predicted more widespread wildfires,
droughts, and die-offs of plants and wildlife.
Although scientists say global temperatures have already increased, the
report says the rate will be magnified.
Generally, the more greenhouse gases that are emitted, "the more
extreme things get," Meehl said. He warned, however, that "it's not a simple
linear relationship"; if gases decline 20% that doesn't mean there is an
equivalent decline in the effect, because localized phenomena guide climate
extremes. Still, even small declines, he said, mean fewer