An Exchange With Andrew Revkin
January 8, 2008
Melting Ice = Rising Seas? Easy. How Fast? Hard.
By Andrew C. Revkin
Most forecasting is easier and more reliable in the short run than over the long haul. Think of weather prediction. (And history is full of failed long-term forecasts of everything from oil prices to human population trends.)
But for scientists studying the fate of the vast ice sheets of Greenland and West Antarctica, the situation seems reversed. Their views of sea trends through this century still vary widely, while they agree, almost to a person, that centuries of eroding ice and rising seas are nearly a sure thing in a warming world... I wrote about some of that work for Science Times this week. This post offers a bit more depth than could fit on the printed page.
• FULL TEXT OF ARTICLE
• 9. [ Seitz to Revkin] January 8th,2008 6:47 am
Don’t they teach isostasy in journalism school?
It seems a considerable failure of candor to discuss Greenland’s ice at such length without noting that the base of most of it lies far below sea level, the weight of it having pressed the underlying crust of the Earth into the mantle by roughly the ratio of the ice’s thickness to the density of the underlying rock- Though the glaciated surface flows down to the sea, much of the miles thick ice fills a vast central basin, the land beneath sloping downhill towards Greenland’s center, much of which is over a kilometer below the elevation of the coast.
The icebergs calving at the fringe are like dandruff compared to the massive skull of ice stuck in the central basin. Ignoring the consequences- and the time scale– of isostasy and isostatic rebound does more that condone cartoon visions of meltwater sending the icecap tobogganing uphill. It obscures the role of post-glacial isostatic rebound elsewhere, as in Hudson’s Bay and the Baltic, both in forcing more water into the ocean and in some locales raising land faster than the measured rate of sea level rise
[ANDY REVKIN notes: Hi Russell. Isostasy is fine, but the overall calculations for Greenland’s sea level potential are — of course — only for the ice that’s above sea level. When you fly there and land on the summit, 10,500 feet above sea level, all that ice below you is what has the potential to add to sea heights. The whole point of today’s print story and post was to clarify how much ice is at stake, how soon. The IPCC was clear that total loss of the Greenland ice sheet (above sea level) could only happen on a time scale of millennia. Not sure where you come off thinking I’ve shirked my journalistic responsibilities here.]
— Posted by Russell Seitz
Hi Andy:..You ask where I come off thinking you’ve shirked your journalistic responsibilities here ?
Silence gives consent. Oz Elliot was of the opinion that journalists have a constructive duty to correct popular misconceptions, and the Climate Wars have seen politicians amplify some a thousandfold by juggling real pictures and stills taken from computer animated sci fi flicks.
So it’s up to you to take the point–especially if it makes David Guggenheim unhappy– in explaining things like the isostatic difference between shore and shelf ice, and how post-glacial rebound is locally tipping the Bering seashore into the drink. If somebody doesn’t,the credibility of geophysics will disappear like meltwater down a moulin, and as surely as the number of polar bears on TV is rising, the arctic may go down as a locus classicus of bad science journalism driving the good out of circulation.
— Posted by Russell Seitz