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.