Wednesday, July 14, 2010
why the situation in Greenland is so serious...
While for every Greenlander there are nearly 120,000 other people in the world, what happens along these remote and barely populated shores of the world’s largest island affects people everywhere. The bottom line for the work that I do studying the climate of Greenland is the ice sheet’s contribution to global sea level rise. Scientists like me expect global sea level to be 1-2 m (3.3-6.6 feet) above its year 2000 stage by year 2100. Imagine if you're the mayor of a major coastal city and your nation's top scientists inform you that in the next century, your city better be well on it's way building ramparts against the sea. That's going to be downright costly and not just to managers of coastal infrastructure but to society well inland because of the economic ripple effects of coastal impacts and migration. I'll talk more in detail about this during our upcoming cruise. Suffice it to say for now that Greenland is currently a top source of global sea level rise.
I should not be so astonished that year 2010 so far, according to NASA, is the warmest on record for the globe, but also for Greenland. I'm preparing my 7th annual State of the Climate report already now and I accept the science of climate change. Note that I say accept, not believe. Scientists accept or reject hypotheses. A body of evidence that has withstood a reasonable amount of skeptical inquiry becomes theory. So far in nearly 150 years of now mature science, global warming theory has not been rejected. Anyway, winter 2009/2010 air temperatures, were a whopping 8.8 degrees C (15.8 degrees F) above normal*. Think about that, a 3 month average, setting a new record! If you're a dog sledder living above the mid point of Greenland’s west coast, like my good friend Ole-Jurgen Hammeken, that means NO DOG SLEDDING ALL WINTER. His sled dogs were going crazy chained up all winter. There was NO SEA ICE in his memory. As far as the glaciers are concerned (they are not, existentially-speaking), it's off to the races! Glaciers have reacted to climate warming.
It's not just air temperature. Actually, ocean temperature increases that are most important for glacier stability. Sea surface temperatures around Greenland have increased, on average, in all seasons since reliable satellite observations began in 1982. The DOUBLING IN SPEED OF ESSENTIALLY ALL SOUTHERN GREENLAND GLACIERS during the past decade have been attributed to the incursion of a warm ocean waters**. Water has a much much higher heat capacity than air. Globally, the amount of additional heat the oceans have absorbed, if re-released into the atmosphere would increase by you don't want to know how much, but I will mention this figure during one of my talks on board the Fram on the cruise 26 September - 10 October.
There's a lot more in store for us in the record setting warm year of 2010. Myself, my students, and colleagues are scrutinizing daily updates to satellite images. We're already finding this year retreats to new minima for the modern age for Greenland glaciers.
On our cruise, we're re-tracing the migration of the Norse. When south Greenland was settled MORE THAN 1000 YEARS AGO, temperatures were warm like today. The primary cause of the warming then was due to earth’s orbit. Unfortunately for the human guilt factor, the situation is very different today, the heat content of the climate system has increased while orbital changes and solar output has decreased. Humans have become, by far, the most important climate forcing agent these days, unlike in the time of the Norse. So, while it will be interesting to consider the similarities with Greenlanders 1000 years ago and now growing bumper crops of potatoes, broccoli, the situation today is so very different.
* The World Meteorological Organization defines a "climate normal" as the most recent 30-year period beginning at the first year of the most recent complete decade, that is, 1971-2000.
** Holland, D.M., R.H. Thomas, B. de Young, M.H. Ribergaard and B. Lyberth. 2008. Acceleration of Jakobshavn Isbræ triggered by warm subsurface ocean waters, Nature Geoscience, 1, 659–664, (10.1038/ngeo316.)