Tropical regions to get even hotter summers within 20 years

Today I've got a interesting article by Daily Mail Reporter (7th June 2011) for you.

Tropical regions in Africa, Asia and South America could see 'the permanent emergence of unprecedented summer heat' in the next 20 years, scientists have warned.

The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures if greenhouse gas emissions continue at their present rate, a study claims.

Researchers at Stanford University said North America - including the U.S. - southern Europe and China are likely to undergo extreme summer temperature shifts within 60 years.

Red dunes in Namibia. Much of Africa, Asia and South America could see 'the permanent emergence of unprecedented summer heat' in the next 20 years

This dramatic change could have severe consequences for human health, agricultural production and ecosystem productivity.

Lead author Noah Diffenbaugh said: 'According to our projections, 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.'

He added: 'When scientists talk about global warming causing more heat waves, people often ask if that means that the hottest temperatures will become "the new normal".

'That got us thinking - at what point can we expect the coolest seasonal temperatures to always be hotter than the historically highest temperatures for that season?'

To determine the seasonal impact of global warming during the coming decades, Dr Diffenbaugh and co-author Martin Scherer analysed more than 50 climate model experiments.

Among these were computer simulations of the 21st century when global greenhouse gas concentrations are expected to increase, and simulations of the 20th century that accurately 'predicted' Earth's climate during the last 50 years.
Their analysis revealed that many parts of the planet could experience a permanent spike in seasonal temperatures within 60 years.

Death Valley in California. North America, southern Europe and China are likely to undergo 'extreme' summer temperature shifts within 60 years

Dr Diffenbaugh said: 'We also analysed historical data from weather stations around the world to see if the projected emergence of unprecedented heat had already begun.

'It turns out that when we look back in time using temperature records, we find that this extreme heat emergence is occurring now, and that climate models represent the historical patterns remarkably well.'

According to both the climate model analysis and the historical weather data, the tropics are heating up the fastest.

The scientists found that the most immediate increase in extreme seasonal heat occurs in the tropics, with up to 70 per cent of seasons from 2010 to 2039 exceeding the late-20th century maximum.

Tropical regions may see the most dramatic changes first, but wide swathes of North America, China and Mediterranean Europe are also likely to enter into a new heat regime by 2070, according to the study.

As an example of the severe consequences of such a drastic change, Dr Diffenbaugh pointed to record heat waves in Europe in 2003 that killed 40,000 people.

He also cited studies showing that projected increases in summer temperatures in the Midwestern U.S. could reduce the harvest of staples, such as corn and soy beans, by more than 30 per cent.

Dr Diffenbaugh was surprised to see how quickly the new, potentially destructive heat regimes are likely to emerge, given that the study was based on a relatively moderate forecast of greenhouse gas emissions in the 21st century.

The results will be published in the journal Climatic Change