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Heat waves set to become 'brutal'
August 12, 2004

Heat waves are set to intensify with increasing greenhouse emissions
Heat waves in the 21st Century will be more intense, more frequent and longer lasting, US experts report in the journal Science.
Scientists from the National Center for Atmospheric Research (NCAR) used climate modelling to predict geographic patterns of future heat waves.

Future heat waves in some areas of Europe and North America will become more common and extreme in the second half of the 21st Century.

The research shows greenhouse emissions are likely to exacerbate the problem.

It's the extreme weather and climate events that will have some of the most severe impacts on human society as the climate changes

Jerry Meehl, NCAR
This is suggested by data that shows present-day heat waves coincide with an atmospheric circulation pattern that is intensified by ongoing increases in greenhouse gases.

As the pattern becomes more pronounced, severe heat waves will hit the Mediterranean and southern and western US.

"It's the extreme weather and climate events that will have some of the most severe impacts on human society as the climate changes," said Jerry Meehl of NCAR, who co-authored the research with his colleague Claudia Tebaldi.

Other parts of France, Germany and the Balkans are expected to become more susceptible to heat waves.

Maximum intensity

The researchers chose to model the climates of Europe and North America because the Chicago heat wave of 1995 and the Paris heat wave of 2003 had particularly severe impacts.

An estimated 15,000 people died as a result of the heatwave in France last August. Chicago's heatwave of July 1995 killed about 739.

Meehl and Tebaldi chose grid points near these two cities to illustrate heat wave characteristics and generate future predictions using their model.

Over the coming century, the number of heat waves in Paris was expected to increase by 31% and in Chicago by 25%. In both cities, they would also become more intense.

Forest fires are common events during heat waves in southern Europe
The researchers used a computer model called the Parallel Climate Model to examine future heat wave behaviour for the period 2080 to 2099.

This generated predictions of so called "worst" three-day heat-waves.

These three-day heat waves showed a rise of more than 3C in minimum night-time temperatures in the Mediterranean region and western and southern US.

The model was also able to show that they would increase in duration. Parisian heat waves were expected to stretch from the present day range of 8.33 - 12.69 days to between 11.39 - 17.04 days in the coming decades.

For Chicago, heat waves would expand from 5.39 - 8.85 to between 8.5 - 9.24 days


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