The real story on glaciers

2010-03-02

in Geek stuff, Politics, Rants, Science, The environment

There has been a huge amount of talk about the claim in the IPCC’s most recent report that Himalayan glaciers would be gone by 2035. That figure is wrong, and came from a dubious source. That said, the state of the world’s glaciers is not encouraging. Germans are putting a reflective cover on their last glacier, to slow down its melting. The global glacier index shows a clear trend of decline. This graph shows the data on all glaciers, 30 reference glaciers of special importance, and a subset of North American glaciers. Not only is the decline clear, but it is clearly accelerating.

Perhaps the biggest news is from Greenland, as described in Alun Anderson’s excellent After the Ice:

If you take into account the rapid collapse of the glaciers, how much water is Greenland adding to the world’s oceans? In 2008, [Caltech glaciologist Eric] Rignot teamed up with scientists from around the world and estimated that the ice sheet had been losing 30 gigatons of ice a year from the 1970s through the 1980s, 97 gigatons in 1996, and between 239 and 305 gigatons in 2007… A gigaton is a billion metric tons, or the weight of a cubic kilometer of water. Add the latest annual figure of 305 gigatons to the oceans and the sea level rises by close to a millimeter. Keep going faster for a century on top of the natural thermal expansion of the oceans as they warm and ice melting elsewhere and that is enough for governments around the world to have to add billions to the cost of coastal defences. The acceleration is deeply worrying. Its cause appears to be those rapidly moving glaciers: the paper shows that they account for between 40 and 80 percent of the ice loss.

I called up Eric Rignot in his laboratory and asked if he was surprised too. He laughed. “Even just a couple of years ago, to state that the ice sheet was losing as much mass as it is, would make me considered a wild man. I think if you had told people in 1990 that I would make a prediction in 2008 that we were going to lose three hundred gigatons per year of ice in Greenland, everybody would have laughed. He is not serious, they would have said. There is no way you can get anything like that.” So what will happen next? “We see acceleration. It’s not a linear trend; it’s more rapid than that. I don’t know where it’s going to go. Ten years ago we thought we knew everything. Now we know we don’t.” (p.233 hardcover)

Once this ice is lost, it won’t be coming back. When bright shiny snow gets replaced with dark ground, the Arctic absorbs even more energy from the sun. Furthermore, the shrubs that replace tundra (and the forests that replace them) are progressively more absorptive of sunlight. Partly, this is because the new vegetation extends above the snow.

It is really hard to see how anybody looking at the data can conclude that glaciers provide support for the contention that climate change is not happening, or not likely to be a problem for human beings.

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{ 4 comments… read them below or add one }

R.K. March 3, 2010 at 10:25 am

When all you need to do is spread confusion, you just need a few little nuggets to point to. The less awareness people have of the big picture, the easier a delayer’s job becomes.

Those Greenland figures are dramatic BTW. The large number of cases where scientists find themselves surprised by the case of climate changes makes me fear that we have underestimated how quickly and savagely the real problems may arise.

. March 3, 2010 at 11:58 am

“The glaciers of the West Antarctic ice cap have also “unplugged.” We’ve got twenty years of observation in West Antarctica, explained Shepherd. “In the first ten years, we lost one hundred cubic kilometers [one hundred gigatons] of ice per year. In the second ten years, we lost two hundred cubic kilometers of ice per year. Keep doubling that to four hundred, eight hundred, and you get a very, very large sea level rise in a very short time. There is no theory to support that, but there is also no evidence that this is slowing down. We just see it getting bigger and bigger.””

-Anderson, Alun. After the Ice. p.236 hardcover

Milan March 3, 2010 at 12:28 pm

Just think how much energy melting hundreds of cubic kilometres of ice removes from the climate system. If the ice sheets ever get massively depleted in size, that energy will go towards warming the air and oceans instead.

Melting ice requires 80 calories (not kilocalories) per gram. A cubic kilometre of water weighs a billion tonnes…

. March 4, 2010 at 1:14 pm

Glacier melting a key clue to tracking climate change

SINGAPORE/ANCHORAGE (Reuters) – The world has become far too hot for the aptly named Exit Glacier in Alaska.

Like many low-altitude glaciers, it’s steadily melting, shrinking two miles over the past 200 years as it tries to strike a new balance with rising temperatures.

At the Kenai Fjords National Park south of Anchorage, managers have learned to follow the Exit and other glaciers, moving signs and paths to accommodate the ephemeral rivers of blue and white ice as they retreat up deeply carved valleys.

“Some of the stuff is changing fast enough that we now have signs on moving pedestals,” said Fritz Klasner, natural resource specialist at Kenai Fjords.

The vast amounts of water stored in glaciers play crucial roles in river flows, hydropower generation and agricultural production, contributing to steady run-off for Ganges, Yangtze, Mekong and Indus rivers in Asia and elsewhere.

But many are melting rapidly, with the pace picking up over the past decade, giving glaciers a central role in the debate over causes and impacts of climate change.

That role has come even more sharply into focus after recent attacks on the U.N.’s climate panel, which included a wrong estimate for the pace of melting for Himalayan glaciers in a major 2007 report.

The report said Himalayan glaciers could all melt by 2035, an apparent typographical error that stemmed from using literature not published in a scientific journal. Climate skeptics seized on the error and used it to question the panel’s findings on climate change.

The evidence for rapid glacial melting, though, is overwhelming.

The problem is no one knows exactly what’s occurring in the more remote Himalayas and parts of the Andes. Far better measurements are crucial to really understand the threat to millions of people downstream.

“There is no serious information on the state of the melting of the glaciers in the Himalayan-Tibetan complex,” Kurt Lambeck, President of the Australian Academy of Science, told a climate science media briefing in late February.

The high altitude and remoteness of many glaciers in the Himalayas and Andes is the main reason.

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