Thursday, February 9, 2012

Study of Melting Land Ice

A new study is out that utilized global GRACE satellite gravimetric data to estimate land ice changes. In brief, this means a pair of satellites (in space) took measurements of the earth's gravitational field, and that was used to computed fluctuations over time in the amount of ice over land. Not a routine as sticking a thermometer into something, but it is not magic. Geodesy is a real science.

Let us start by taking some key points from the overview. The data analyzed were from 2003-2010, which is not a long time especially through the prism of climate change. Over that time frame sea level is known to have increased about one inch in total. About half of that is from thermal expansion of the warming oceans. The study concludes that about 4 to 5 tenths of the inch is due to melting of land ice. That number does not seems as small when you consider it is 4.3 trillion tons of ice, and that amount of water would cover the US with about 1.5 feet or North Dakota by about 80 feet. Of that amount from land ice, about 72% was from the major ice sheets on Antarctica and the remaining 28% was from other glaciers and ice.

So of course there are vast numbers of online headlines about this saying something to the effect of 'Himalayas have lost no ice in the past 10 years'. Shocking, eh?

It is an interesting result that this study determined less ice loss there than previous work that had to extrapolate from limited ground-based and generally low elevation surveying. However an 8 year snapshot there or any location does not necessarily say much about the long-term trend there, especially looking down the road a few decades. The plateau in the Himalayas may be at high enough elevation such that warming has not affected it much so far, but that need not continue. And precipitation changes have not even been mentioned.

Somehow though this research showing "ice is being lost from around the globe, with just a few areas in precarious balance" is getting sold as something rolling back global warming because of the Himalaya aspect and that the global total rate amount is on the lower side of previous estimates. Pointing out that this is science at work draws the usual septic armchair commentors... That this supposedly is counter to previous info is considered more proof of a conspiracy to suppress, no question at all of the results or how they were obtained or if they are the final word on the subject (as long as they seem to dispute there is climate change), and so many of the pet arguments the conspiracy-mongers fail to understand are long debunked.