Stifling summers forecast by Nasa for US east coast

http://news.independent.co.uk/world/americas/article2530788.ece

By David Usborne in New York

Published: 11 May 2007

Researchers at Nasa have warned that unless growth in greenhouse gas emissions can be successfully curbed, large areas of the eastern United States, from Washington DC to Florida, can expect to suffer through catastrophically hotter summers within just a couple of generations.

A study released by Nasa's Goddard Institute for Space Studies at Columbia University finds that by 2080 average summer high temperatures in parts of the east will be about 10F higher than now, pushing them from the low to mid-80s to the low to mid-90s.

Moreover, in particularly dry years with only limited rainfall to cool conditions, average high temperatures in cities as far apart as Atlanta, Washington DC and even Chicago to the north could peak at a baking 110F roughly the kinds of readings seen today only in the desert south-west.

The institute made its projections after studying data from the past 30 years and using computer models to predict future trends. The study is unusual because it attempts to draw conclusions for a limited geographical area including individual metropolitan areas.

"Our analysis shows that there is the potential for extremely hot summertime temperatures, especially during summers with less-than-average rainfall," confirmed the Nasa researcher Barry Lynn, who is also a lead author of the new report. "Using high resolution weather prediction models, we showed how greenhouse gases enhance feedbacks between precipitation, radiation, and atmospheric circulation that will likely lead to extreme temperatures in our not-so-distant future," he added.

Such a dramatic jump in thermometer readings could have a devastating impact on health in America's largest cities as well as on agriculture and general economic conditions. It would also put significant extra demand on electricity producers for air-conditioning, raising emissions further.

The study is based on the "business-as-usual" premise which assumes that carbon dioxide emissions will continue to increase in the US at a rate of 2 per cent a year. But the scorching of the eastern US would intensify if those emissions grow.

Highlighted in the study is the role played by the eastern Pacific Ocean in determining summer conditions on the eastern seaboard of the continent. "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," said the study's co-author Richard Healy of the Woods Hole Oceanographic Institution in Massachusetts. "Less frequent storms result in higher surface and atmospheric temperatures that then feed back on the atmospheric circulation to further reduce storm frequency and raise surface temperatures even more."

The report was published too late to be included in the findings of the Intergovernmental Panel on Climate Change recently submitted to the United Nations. But it will be seized upon by those pressing governments to take more urgent steps to curb emissions.

It also comes days before the opening on Monday of the Large Cities Climate Summit in New York, a forum at which mayors from 30 of the largest metropolises, including London, Paris, Tokyo and Istanbul, will discuss plans for combating global warming.

Ken Livingstone, the Mayor of London, is also due to tour New York's emergency response centre which was built after 9/11 to co-ordinate the handling not just of terror-related incidents but also of climate-induced events such as hurricanes and flooding.