Arctic defrosting faster than ever
With the world expecting to celebrate world records at the London Olympics from today, the weather in recent weeks has delivered many high scores we should be less happy with: Record breaking high temperatures in the USA, droughts in Canada or deadly floods in Russia are just the most prominent examples.
Now there’s more. This summer, ice in arctic regions has been melting more extensively than ever seen before.
NASA scientists reported that in mid-July a whopping 97 percent of Greenland’s ice surface was melting. While the amount of surface melting can change extensively and in a matter of days (depending on the temperature of the air above), it’s never been observed to cover that large an area in more than 30 years of satellite observations.
Is this just a freak event or global warming in action? Scientists are careful not to draw a direct link between extreme weather events and climate change. For good reason: Some phenomena may not have been observed before, but scientists are not surprised to see them regardless of a global warming. Cores drilled out the Greenland ice sheets can help recover the temperature history for the place and indicate that extreme melting regularly occured every 150 years or so. This summer’s thawing episode is “right on time”, says one NASA glaciologist.
But the accumulation of extreme weather events is something you would plausibly expect under conditions of global warming, says Global Ideas climate expert Anders Levermann of the Potsdam Institute of Climate Impact Research. Even then, “we can’t say what the further impacts will be,” he cautions. In the case of Greenland “we don’t know what a period of extreme melting actually means except that in this moment more water is being lost and the water level is rising.”
Taking a long hard look at individual regions, however, can help establish more direct links between regional trends and global warming. At least 70 percent of the reduction of Arctic sea ice over the last 30 years may be man made suggests a study by a British-Japanese team of scientists. Here’s how the lead author puts it:
DateJuly 27, 2012