As the USA swelters through its hottest year on record - and the
Earth sees yet another top-10 year for heat - a study published today
in the journal Science says we'd better get used to it.
study finds that future temperature rises due to global warming will
probably be on the high end of projections, as much as a potentially
catastrophic 8 degrees warmer than now by the end of the century.
Most predictions of upcoming temperature rises are roughly 3.6 degrees to 8.1 degrees.
co-authors John Fasullo and Kevin Trenberth of the National Center for
Atmospheric Research in Boulder, Colo., reached their conclusions by
looking at how well 16 top climate computer models reproduced actual
relative humidity in the tropics and subtropics, as measured by
Higher levels of humidity tend to produce clouds,
which remain one of the most vexing aspects of predicting future
climate. Though additional clouds can cause temperatures to cool as
less heat reaches the ground, they can also act to increase the heat
that's trapped below them. In their study, the scientists used humidity
as a substitute for clouds, since models cannot accurately forecast
"There is a striking relationship between how well
climate models simulate relative humidity in key areas and how much
warming they show in response to increasing carbon dioxide," Fasullo
says. "Given how fundamental these processes are to clouds and the
overall global climate, our findings indicate that warming is likely to
be on the high side of current projections."
would bring greater impacts on society, they say, in terms of a rise in
sea level, heat waves, droughts and other threats.
1900, the average temperature of the Earth's surface has risen by
roughly 1.4 degrees, and close to two-thirds of the increase has
occurred since 1980, according to a National Academy of Sciences report.
NASA funded the new study.