Friday, July 22, 2016

Antarctic Peninsula Has Cooled, but Warming Will Win

A gentoo penguin colony on the Antarctic Peninsula. (Credit: David Stanley/flickr) Click to Enlarge.
For most of the latter half of the 20th century, the Antarctic Peninsula was one of the fastest-warming places on the planet, with serious repercussions for the local environment, including the spectacular disintegration of a millennia-old ice shelf, and global sea level rise.

But a new study detailed Thursday in the journal Nature suggests temperatures on the peninsula have dropped slightly since the late 1990s.  This relative cooling is partly driven by the recovery of the ozone hole, and is, along with the warming that preceded it, within the realm of the wild shifts in climate the region has naturally experienced in the past, they found.

The cooling is relatively minor — less than 2°F (1°C) since the 1990s — and it doesn’t negate the background warming that is happening because of the steady rise of heat-trapping greenhouse gases in the Earth’s atmosphere, the researchers said.  It is simply masking it for the time being.  Eventually, human-driven warming will overwhelm the influence of the ozone hole recovery and natural climate drivers, and temperatures will once again rise.

“We’re talking about a tiny little downturn in temperatures.  Temperatures are still high” compared to the early 20th century, study leader John Turner, a meteorologist with the British Antarctic Survey, said.

Up and Down
The Antarctic Peninsula is the arm of land that juts up from the continent.  Between 1951 and 2000, the temperature at one weather station on its west coast rose by about 5°F (2.8°C), compared to a little more than 1°F (0.5°C) globally.

That warming was accompanied by significant decreases in sea ice, changes to plant and animal communities, and the melt of land-bound glaciers and the floating ice shelves that buttress them.

In 2002, the Larsen B ice shelf spectacularly collapsed, stunning Antarctic researchers.  A 2014 study pointed to the warm air that bathed the peninsula in the preceding summers as the precipitating cause of the ice shelf’s demise.

But since the 1990s, the average temperature of the peninsula has declined by 0.9°F (0.5°C) per decade, Turner and his colleagues found when they looked at weather station data.  That is about the same rate that it had warmed in the previous five decades.

Read more at Antarctic Peninsula Has Cooled, but Warming Will Win

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