Glacier Melt Is Worse Than Expected

by Patrick Appel

Andrea Thompson summarizes the bad news:

Greenland’s glaciers are more vulnerable to melting by warm ocean waters than previously thought, a new study of the topography of the bedrock under the ice finds. This clearer picture of the underpinnings of the miles-thick ice sheet, along with other recent studies that suggest parts of Earth’s polar regions are not as stable as once thought, could mean that current projections of future sea level rise are too low.

The new Greenland findings, detailed online May 18 in the journal Nature Geoscience, come on the heels of an announcement by the same group of researchers at the University of California, Irvine, that some of the largest and fastest-moving glaciers of the West Antarctic Ice Sheet have entered a phase of “unstoppable” collapse.

What this means:

The West Antarctic Ice Sheet alone contains enough ice to add another 10 to 13 feet of sea level rise, and the Greenland Ice Sheet contains enough to contribute another 20 feet.

Ryan Avent uses the new findings to discuss how “to calculate the present value of future benefits from reduced emissions today”:

Unfortunately, peeling apart how people actually discount benefits centuries or more in the future is very hard. But a fascinating new NBER working paper uses a clever approach to take a crack at it.

The authors exploit an oddity in British real estate: Britons buying a home may either purchase what is known as a freehold (which means they own the land outright) or a leasehold (which means they “own” it for the duration of the leasehold). But leaseholds aren’t like your standard rental contract; they often grant ownership for periods between 80 and 999 years. The authors reckon that by finding the premium paid for freeholds relative to super-long-dated leaseholds on otherwise identical properties, they can come up with an estimate of how distant benefits are actually valued in the market.

Remarkably, they find that people pay a premium of 10%-15% less for 100-year leaseholds and 5%-8% less for leaseholds of between 125-150 years. Only for leaseholds of 700 years or more do they detect no difference in price. On the whole, they reckon, a discount rate of about 2.6% appears to apply out well beyond a century. Oddly enough, people are willing to part with real money now in exchange for benefit flows accruing well beyond any reasonable expected lifespan.

That won’t make it any easier to generate the political support for meaningful action to slow climate change. But it does make it harder to justify delay based on the fact that people simply don’t care much about the distant future.