Atmospheric Warming and Amplification of Precipitation Extremes

——————————————————–
“…the observed amplification of rainfall extremes
is found to be larger than predicted by models,
implying that projections of future changes in
rainfall extremes due to anthropogenic global
warming may be underestimated.”
—————————————————-

Science
August 7, 2008

Atmospheric Warming and the Amplification of Precipitation Extremes
Richard P. Allan 1* and Brian J. Soden 2

1 Environmental Systems Science Centre, University of Reading,
Berkshire, RG6 6AL, UK.
2 Rosenstiel School of Marine and Atmospheric Sciences, University of
Miami, FL 33149, USA.

* To whom correspondence should be addressed.
Richard P. Allan , E-mail: r.p.allan@reading.ac.uk

ABSTRACT: Climate models suggest that extreme precipitation events
will become more common in an anthropogenically warmed climate.
However, observational limitations have hindered a direct evaluation
of model projected changes in extreme precipitation. Here, we use
satellite observations and model simulations to examine the response
of tropical precipitation events to naturally driven changes in
surface temperature and atmospheric moisture content. These
observations reveal a distinct link between rainfall extremes and
temperature, with heavy rain events increasing during warm periods
and decreasing during cold periods. Furthermore, the observed
amplification of rainfall extremes is found to be larger than
predicted by models, implying that projections of future changes in
rainfall extremes due to anthropogenic global warming may be
underestimated.

————————————————————————————

Scientists: Tropical Downpours Intensifying

Tropical downpours worsening, say scientists
Thu Aug 7, 2008 2:02pm EDT   By Alister Doyle, Environment Correspondent

OSLO (Reuters) – Tropical downpours are becoming more frequent and the
trend seems worse than expected, bringing greater risks of flash floods,
scientists said on Thursday.

“As the tropics warm are seeing an increased frequency in the heaviest
rainfall,” said Richard Allan of the University of Reading in England, who
co-authored a study of tropical rains with Brian Soden of the University
of Miami.

Continue reading

Forecasters Increase Atlantic Basin Hurricane Outlook

Forecasters increase Atlantic hurricane outlook
Could be up to 18 named storms

JENNIFER KAY Published: 08.08.2008

MIAMI – Federal forecasters on Thursday upgraded their outlook for this Atlantic hurricane season to include two more named storms than previously predicted.
The National Oceanic and Atmospheric Administration projects an 85 percent probability of an above-normal season — up from 65 percent in May.

In its August update, NOAA said there was a better than average chance of 14 to 18 named storms, seven to 10 hurricanes and three to six hurricanes of at least Category 3 strength, which would be top sustained winds of at least 111 mph.

Continue reading

Grasslands to Replace Most U.S. Forests?

National Geographic News: NATIONALGEOGRAPHIC.COM/NEWS
August 6, 2008

Will Grasslands Overtake U.S. Forests Due to Warming?
William Cocke for National Geographic News

Climate change may cause grasslands to spread to
parts of the United States that are currently
covered in forest, a new study says.

If local climates become more extreme due to
global warming, then entire ecotones – boundaries
between ecosystems – could shift, the study says,
highlighting the central United States, where
prairie gives way to forests of the east.

Continue reading