Differences

source: Agence France-Presse, Washington

February 25, 2013

translation doxa-louise

DISTURBANCES IN ATMOSPHERIC COURANTS THE LIKELY CULPRITS FOR CRAZY WEATHER

Climate researchers have identified the mechanism behind extreme weather events such as droughts, heat or cold spells, which come from disturbances in atmospheric circulation provoqued by global warming.

The United States went through an extreme heat spell in 2011, on the heels of Russia in 2010 while Pakistan experienced, that same year, unheard of levels of flooding.

According to the works of climate reserchers published Monday, these devastating phenomena can all be attribured to the same disturbance of atmospheric currents around the globe in the Northern hemisphere, which are affected by heating resulting from the release of  greenhouse gases due to human activity.

‘An important part of air circulation in the mid latitudes of earth normally takes the shape of waves circling the globe, oscillating between tropical and artic regions’ explains Vladimir Petoukhov, from the Potsdam Institute for Climate Impact Research (PIK) in Germany, principal author of this study.

‘When these waves oscillate upward they pull up hot air from the tropics toward Europe and Russia or the United States, and when they oscillate downward they produce the same phenomenon, but with cold air masses from the Artic’, continues the scientist, whose study is being published in the Annals of the American Academy of Science (PNAS).

‘We have discovered that, in the cousre of these recent extreme weather events, those waves were stalled in their mouvement for many weeks’, he adds.

Global warming is not uniform on the planet. In the Antartic the rise in temperatures is more amplified by the melting of ice and snow, the climatologist makes more precise.

This reduces differences in temperature between the Artic region et say Europe, which affects the circulation of air around the globe whose principal motor is differences in temperature, he explains.

Further continents heat up and cool down more quickly than oceans, contributing as well to stagnation of air mases.

‘These two factors are crucial to the mechanism which we have detected, which provoques long periods of hot or cold’, adds Vladimir Petoukhov.

Two or three days with a temperature of 30 degrees Celsius is not a problem, but twenty days or more create an important level of stress for many ecosystems and urban areas not adapted to this kind of prolonged heat wave, he opines, citing greater mortality, forest fires and loss of crops.