Wednesday, May 15, 2013

Two Views on Sea Level Rise

Two different views on the seriousness of sea level rise caused by global warming climate change came out today with drastically different conclusions.  First, a re-evaluation from Norway which tends to minimize, if not completely eliminate the impact of sea level rise:
A melt of ice on Greenland and Antarctica is likely to be less severe than expected this century, limiting sea level rise to a maximum of 69 cm (27 inches), an international study said on Tuesday. Even so, such a rise could dramatically change coastal environments in the lifetimes of people born today with ever more severe storm surges and erosion, according to the ice2sea project by 24, mostly European, scientific institutions.

Some scientific studies have projected sea level rise of up to 2 metres by 2100, a figure that U.N. Secretary-General Ban Ki-moon has called a worst case that would swamp large tracts of land from Bangladesh to Florida.

Ice2sea, a four-year project to narrow down uncertainties of how melting ice will pour water into the oceans, found that sea levels would rise by between 16.5 and 69 cm under a scenario of moderate global warming this century.

"This is good news" for those who have feared sharper rises, David Vaughan, of the British Antarctic Survey who led the ice2sea project, told Reuters in a telephone interview. "But 69 cm is a very real impact ... it changes the frequency of floods significantly," he said. And seas would keep rising for centuries beyond 2100, in a threat to coastal cities and low-lying islands such as the Maldives or Tuvalu.

Ice2sea said a thaw of Antarctica, Greenland and glaciers from the Alps to the Andes would contribute between 3.5 and 36.8 cm to sea level rise this century. The fact that water expands as it warms would add another 13 to 32 cm, Vaughan said.
Note that the lower bound of the prediction , 16.5 cm rise by 2100 does not differ much from the current (and long standing) rate of sea level rise of about 2 mm per year (0.2 cm year X 88 years = 17.6 cm), so it's unlikely they'll underestimate it by much.

In contrast, Scientific American  put out a report with a much higher prediction, and presented it as a near doom scenario: Sea Level Could Rise Five Feet in New York City by 2100
By 2100 devastating flooding of the sort that Superstorm Sandy unleashed on New York City could happen every two years all along the valuable and densely populated U.S. east coast—anywhere from Boston to Miami.

And unless extreme protection measures are implemented, people could again die.

Hyperbole? Hardly. Even though Sandy’s storm surge was exceptionally high, if sea level rises as much as scientists agree is likely, even routine storms could cause similar destruction. Old, conservative estimates put the increase at two feet (0.6 meter) higher than the 2000 level by 2100. That number did not include any increase in ice melting from Greenland or Antarctica—yet in December new data showed that temperatures in Antarctica are rising three times faster than the rate used in the conservative models. Accelerated melting has also been reported in Greenland. Under what scientists call the rapid ice-melt scenario, global sea level would rise four feet (1.2 meters by the 2080s, according to Klaus Jacob, a research scientist at Columbia University’s Lamont–Doherty Earth Observatory. In New York City by 2100 “it will be five feet, plus or minus one foot,” Jacob says.
To be fair, they probably wrote this piece a few days ago, without any knowledge of the Norwegian study, but this seems like a rather dramatic difference.

I guess it's fair to say the science is not settled.

1 comment:

  1. there is lots of good data out there but the "chicken littles" are only using cherry picked data to sell fear...