NASA study suggests extreme summer warming in the future
http://www.eurekalert.org/pub_releases/2007-05/nsfc-nss050907.php

A new study by NASA scientists suggests that greenhouse-gas warming
may raise average summer temperatures in the eastern United States
nearly 10 degrees Fahrenheit by the 2080s.

NASA study suggests extreme summer warming in the future
http://www.eurekalert.org/pub_releases/2007-05/nsfc-nss050907.php

A new study by NASA scientists suggests that greenhouse-gas warming
may raise average summer temperatures in the eastern United States
nearly 10 degrees Fahrenheit by the 2080s.

"There is the potential for extremely hot summertime temperatures in
the future, especially during summers with less-than-average frequent
rainfall," said lead author Barry Lynn of NASA's Goddard Institute for
Space Studies and Columbia University, New York.

The research found that eastern U.S. summer daily high temperatures
that currently average in the low-to-mid-80s (degrees Fahrenheit) will
most likely soar into the low-to-mid-90s during typical summers by the
2080s. In extreme seasons - when precipitation falls infrequently -
July and August daily high temperatures could average between 100 and
110 degrees Fahrenheit in cities such as Chicago, Washington, and
Atlanta.

To reach their conclusions, the researchers analyzed nearly 30 years
of observational temperature and precipitation data and also used
computer model simulations that considered soil, atmospheric, and
oceanic conditions and projected changes in greenhouse gases. The
simulations were produced using a widely-used weather prediction model
coupled to a global model developed by NASA's Goddard Institute for
Space Studies.

The global model, one of the models used in the recently issued
climate report by the Intergovernmental Panel on Climate Change
(IPCC), was utilized in this study to identify future changes in
large-scale atmospheric circulation patterns due to the build up of
greenhouse gases. This information was then fed into the weather
prediction model to forecast summer-to-summer temperature variability
in the eastern United States during the 2080s.

The weather model showed that extreme summertime surface temperatures
developed when carbon dioxide emissions were assumed to continue to
increase about two percent a year, the "business as usual" scenario.
These findings are too recent to be included in the latest IPCC
report.

The weather prediction model used in this research is advantageous
because it assesses details about future climate at a smaller
geographic scale than global models, providing reliable simulations
not only on the amounts of summer precipitation, but also on its
frequency and timing. This is an important capability for predicting
summer temperatures because observed daily temperatures are usually
higher on rainless days and when precipitation falls less frequently
than normal.

Observational climate data also showed that sea surface temperatures
in the Pacific Ocean have a significant influence on summer air
temperatures in the eastern U.S.

"Relatively cool waters in the eastern Pacific often result in
stubborn summer high-pressure systems over the eastern states that
block storms, reducing the frequency of precipitation below normal,"
noted study co-author Richard Healy of the Woods Hole Oceanographic
Institution, Woods Hole, Mass. "Less frequent storms result in higher
surface and atmospheric temperatures that then feedback on the
atmospheric circulation to further reduce storm frequency and raise
surface temperatures even more."

The global model simulated rainfall too frequently, so that its
surface temperatures were not appropriately sensitive to interannual
changes in Pacific sea surface temperatures. "Since the weather
prediction model simulated the frequency and timing of summer
precipitation more reliably than the global model, its daily high
temperature predictions for the future are also believed to be more
accurate," added co-author Leonard Druyan, NASA Goddard Institute for
Space Studies and Columbia University.

In comparison, the researchers say that a number of the global models
used in previous studies of future climate change predict too frequent
precipitation that often falls too early in the day. As a result, they
tend to underestimate the amount of future warming by reflecting solar
radiation back to space before it can warm the surface and by
simulating excessive evaporation from the wet ground.

To the authors' knowledge, this is the first study that has documented
the impact of precipitation simulation imperfections on model
predictions of surface air temperature. "Using high-resolution weather
prediction models, we were able to show how greenhouse gases enhance
feedbacks between precipitation, radiation, and atmospheric
circulations that will likely lead to extreme temperatures in our not
so distant future," said Lynn.


--
There may come a time when the CO2 police will wander the earth telling
the poor and the dispossed how many dung chips they can put on their
cook fires. -- Captain Compassion.

Wherever I go it will be well with me, for it was well with me here, not
on account of the place, but of my judgments which I shall carry away
with me, for no one can deprive me of these; on the contrary, they alone
are my property, and cannot be taken away, and to possess them suffices
me wherever I am or whatever I do. -- EPICTETUS

"Civilization is the interval between Ice Ages." -- Will Durant.


"Progress is the increasing control of the environment by life.
--Will Durant

Joseph R. Darancette
daranc@NOSPAMcharter.net