
Researchers at Purdue University researcher projects a 200 percent to 500 percent increase in the number of dangerously hot days in the Mediterranean by the end of the 21st century if the current rate of greenhouse gas emissions continues, with France projected to have the most increase in high-temp extremes.
The study also showed a reduction in greenhouse gas emissions could reduce projected dangerous hot days by up to 50 percent.
"Rare events today, like the 2003 heat wave in Europe, will become much more common as greenhouse gas concentrations increase," said Noah Diffenbaugh, the Purdue assistant professor of earth and atmospheric sciences who led the study. "The frequency at which that scale of event occurs at high greenhouse gas concentrations is staggering. Rare events become the norm, and the extreme events of the future are unprecedented in their severity."
A 2003 heat wave led to 15,000 deaths in France and almost 3,000 in Italy. The researchers found that global warming causes summer temperatures to dramatically exceed the range that was correlated with the increased number of deaths.
"The thresholds of the 2003 event are substantially exceeded in the future in both of our research scenarios," said Diffenbaugh. "This research is about understanding the response to different emissions levels. We find that decreases in greenhouse gas emissions greatly reduce the impact, but we see negative effects even with reduced emissions. Technological and behavioral changes that are made now will have a big influence on what actually happens in the future."
Extremely high temperatures could also affect the region’s economy, including metropolitan areas such as Rome, Paris and Barcelona. The study covered the entire Mediterranean area, which includes 21 countries in Europe, Africa and Asia. Major cities covered in the study include: Prague, Zurich, Bucharest, Athens, Istanbul, Tel Aviv, Cairo, Algiers and Casablanca.
The researchers found that this warming and reduced precipitation contribute to a preferential warming of the hottest days of the year. "We found that the hottest days of the year, or the 'hot tail,' warm more than the typical summer days warm," Diffenbaugh said.
"One might expect that an average warming of four degrees would equate to each day warming by four degrees, but in fact the hottest days warm quite a bit more."
This is due, in large part, to a surface moisture feedback. The surface gets dryer as it gets hotter and the dry soil leads to less moisture in the area and less evaporative cooling. The locations of intensified warming on hottest days of the year matched the locations where surface drying occurred, Diffenbaugh said.
"The hottest temperatures we are used to experiencing will become the normal temperatures of the summer, and the hot periods will be magnified," Diffenbaugh said. "Take Paris: If we look at the temperatures that occurred there during the heat wave in 2003, when 15,000 people died, those temperatures are exceeded a couple dozen times every year in the future projection. That means that severe heat waves, such as those rare events that have occurred in the past couple of years, are likely to become far more common."
Related Web sites:
Purdue Climate Change Research Center:
http://www.purdue.edu/climateDiffenbaugh Research Group:
http://www.purdue.edu/eas/earthsystem/See the Source:
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global-warmingLabels: climate change, environment, global warming, recent environmental studies, recent studies