June 11, 2011

No More Cool Summers?

According to a new study on climate change, researchers project that, by 2050, the coolest summers in the tropics and parts of the northern hemisphere will still be hotter than the hottest summers seen since the 1950s if global warming continues its rapid upswing.

"The permanent emergence of unprecedented summer heat" could be felt in tropical regions in Africa, Asia and South America within the coming decades, according to the study, being published in the journal Climate Change Letters later this month.

"Large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years," said lead author Noah Diffenbaugh, a professor at Stanford University's Woods Institute for the Environment.

Such rapid changes in temperature would have a significant impact on human health, food resources and biodiversity, warn researchers.

For years, Scientists have predicted that climate change driven by greenhouse gas emissions would cause more frequent heat waves, such as those that struck Europe in 2003, Russia last summer, and the US just this week.

"That got us to thinking -- at what point can we expect the coolest seasonal temperatures to always be hotter than the historically highest temperatures for that season?" Diffenbaugh told AFP in a statement.

Diffenbaugh chose an assortment of 50 climate models that accurately matched past increases and projected them into the future. The analysis assumed a scenario of a "moderate" increase in heat-trapping carbon dioxide emissions as forecast by the UN's panel of climate scientists.

The researchers found that many areas of the world can anticipate a "new normal" of summers that today would be classified a heatwave within a matter of decades. They also analyzed historical data from weather stations around the world to see if the projected increase in temperatures had already started.

"This extreme heat emergence is occurring now, and climate models represent the historical pattern remarkably well," Diffenbaugh said.

Their results differed from region to region, with the tropics being hit earliest and hardest.

The team's model showed up to 70 percent of summer seasons from 2010 to 2039 exceeded the late-20th century maximum in the zones around the Equator. But also wide areas of North America, China and Mediterranean Europe would also likely enter a "new normal" by 2070.

Recent heat waves and the consequences that often follow provides a taste of what hotter summers will do to disrupt human lives, the researchers noted. The likelihood of out-of-control fires increases dramatically with higher temperatures. Heat waves can also cost lives: the 2003 heatwave in Europe killed 40,000 people.

Projected heat increase could also devastate staple food crops in tropical regions, according to a recent report by a grouping of agriculture experts. The increase in loss of species is also projected to coincide with persistently hotter climates.


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