Tuesday, August 14, 2012

A pair of glacier retreat more slowly than expected does not change the irrefutable fact that most are melting fast

Glaciers are one of the most widely used natural environments to illustrate the effects of climate change. It is quite undeniable that in a warming world, glaciers are melting faster. However, two recent studies published in scientific journals (more here and here) suggest that, in the Himalayas, the rate of mass loss was small and too expensive, and further west, in the Karakoram, glaciers are actually a little weight gain.

Is there a conflict between these studies and the entire body of research indicating that in the world, glaciers are retreating for decades?

To answer this question, we must look a little closer than the studies show, and its place in the context of global changes in land and sea ice Both studies refer to a relatively short period of time: between eight and nine years, more or less the last decade. The Himalayas, vary widely in snowfall from year to year depending on the strength of the monsoon. However, atmospheric science, climate trends is usually determined from records covering at least 30.

For comments on these longer time scales is a difficult task for glaciologists. There are over 160,000 glaciers on the planet, less than 120 that are continuous and long term measures. These ground measurements were supplemented by data from satellite and airborne sensors. The combined records indicate that most but not all, systems of glaciers lost mass at least for the past four decades, and that the rate of loss has accelerated since mid-1990 for key regions such as Patagonia, the Canadian Arctic, Alaska and, most important of all for rising sea levels, large ice sheets covering Antarctica and Greenland.

The impacts of these changes have on water resources, rising sea levels and climate feedback are already observable and significant. Some recent predictions of rising sea level in 2100 over a meter. The loss of Arctic sea ice in the Arctic Ocean has increased warming due to a strong positive feedback.

Most glaciologists believe we are witnessing unprecedented changes in land and sea ice The big question is not whether, but how fast the ice on earth and the sea will disappear, and what we can do to mitigate and adapt to these changes.

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