Hivers glacés et global warming

Hivers glacés et global warming

L’hiver exceptionnellement rigoureux et enneigé que connaît l’Europe met pour certains en question les constats du global warming, selon la technique de plus en plus courante de traiter cette affaire avec le simplisme extrémiste d’une polémique politique et idéologique. (Voir par exemple le commentaire du Washington Times du 24 décembre 2010 : «Global warming goes gaga».)

The Independent, quotidien particulièrement actif sur les questions de l’environnement, publie un article (le 24 décembre 2010), où il entend montrer que cet hiver rigoureux (le second de suite), qui devrait devenir un modèle courant en Europe, est effectivement la conséquence indirecte du global warming et de la crise climatique en général).

«Scientists have established a link between the cold, snowy winters in Britain and melting sea ice in the Arctic and have warned that long periods of freezing weather are likely to become more frequent in years to come.

»An analysis of the ice-free regions of the Arctic Ocean has found that the higher temperatures there caused by global warming, which have melted the sea ice in the summer months, have paradoxically increased the chances of colder winters in Britain and the rest of northern Europe.

»The findings are being assessed by British climate scientists, who have been asked by ministers for advice on whether the past two cold winters are part of a wider pattern of climate change that will cause further damaging disruption to the nation's creaking transport infrastructure.

»Some climate scientists believe that the dramatic retreat of the Arctic sea ice over the past 30 years has begun to change the wind patterns over much of the northern hemisphere, causing cold, Arctic air to be funnelled over Britain during winter, replacing the mild westerly airstream that normally dominates the UK's weather.

»The study was carried out in 2009, before last year's harsh winter started to bite, and is all the more prescient because of its prediction that cold, snowy winters will be about three times more frequent in the coming years compared to previous decades.

»The researchers used computer models to assess the impact of the disappearing Arctic sea ice, particularly in the area of the Barents and Kara seas north of Scandinavia and Russia, which have experienced unprecedented losses of sea ice during summer.

»Their models found that, as the ice cap over the ocean disappeared, this allowed the heat of the relatively warm seawater to escape into the much colder atmosphere above, creating an area of high pressure surrounded by clockwise-moving winds that sweep down from the polar region over Europe and the British Isles. Vladimir Petoukhov, who carried out the study at the Potsdam Institute for Climate Impact Research in Germany, said the computer simulations showed that the disappearing sea ice is likely to have widespread and unpredictable impacts on the climate of the northern hemisphere.»

dedefensa.org