Title:Extreme heat rising worldwide: temperature records reveal
increased odds of swelter
Author(s):Janet Raloff
Source:Science News. 182.5 (Sept. 8, 2012): p10. From Science In
Context.
Document Type:Article
Full Text:
It's not your imagination. Not only are extremely hot temperatures
occurring more frequently across the globe, but those heat waves are
getting more severe.
Back in the 1950s, temperatures on any given summer day were just
as likely to be near average as they were to be unseasonably high or
low. Climatologist James Hansen of NASA's Goddard Institute for
Space Studies in New York City likens that scenario to rolling a die
with two sides each corresponding to low, average and above-normal
temperature.
Since the 1980s, that metaphorical die has increasingly become
weighted toward delivering a warm day, Hansen and his coworkers
report online August 6 in the Proceedings of the National Academy of
Sciences. In fact, Hansen says, since 2000 it's as though on any roll
four sides will draw hotter than average summer heat.
Hansen says the study also suggests that a new level of extreme
heat is emerging "that almost never occurred 50 years ago." Formerly
striking about 0.2 percent of the Northern Hemisphere's land in any
given summer, this degree of anomalous warmth now strikes about
10 percent of that area. Within a decade, his data suggest, these hot
spells could reach 16.7 percent of the hemisphere's land mass.
"We're not showing that this is a consequence of an increase in
carbon dioxide and other greenhouse gases," Hansen says. In fact,
his team's analysis makes no attempt to attribute the underlying
source of warming to any particular cause. He does volunteer,
however, that there is "a strong consensus within the scientific
community that the warming we're seeing is primarily a response to
an increase in greenhouse gases."
John M. Wallace of the University of Washington in Seattle says he is
not surprised to see this shift toward more extremely warm days--and
hotter extremes within those periods. "Just as a rising tide lifts all
ships," he says, there is good reason to believe that growing global
warming should elevate extremes. Computer projections of Earth's
changing climate call for such a pattern. "If a trend in that direction is
detectable already," Wallace says, "that would constitute an important
finding."
The focus on temperature changes in recent decades--as opposed to
all types of weather extremes, including floods, storms, droughts and
more--constitutes "picking a relatively easy target," says Thomas
Knutson of the National Oceanic and Atmospheric Administration's
Geophysical Fluid Dynamics Laboratory in Princeton, N.J. Still, he
says, the new data are interesting and "underscore the substantial
changes already underway in terms of surface temperatures and their
extremes."
Raloff, Janet
Source Citation (MLA 7th Edition)
Raloff, Janet. "Extreme heat rising worldwide: temperature records
reveal increased odds of swelter." Science News 8 Sept. 2012: 10.
Science In Context. Web. 11 Nov. 2012.
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