Tuesday, July 28, 2015

Uncertain meters

Catastrophic Sea Level Rise: More and sooner – Greg Laden's Blog

Greg Laden talks generally about the new James Hansen paper that warns that sea level rise may be more rapid than most scientists think:
Let me rephrase that to make it clear. We have already caused
something like 14 meters of sea level rise. Like the horrifically sad
words uttered by a movie or TV character who has received a fatal wound
and turns to the killer, uttering “You’ve killed me” (then they die),
we’ve done this. It is just going to take some time to play out. But it
will play out.

A conservative estimate is that likely sea levels will rise 8 meters
or more, quite possibly considerably more. But generally, people who
talk about sea level tend to suggest that this will take centuries. Part
of the reason for that is that it takes a long(ish) time for the added
CO2 to heat up the surface, then it takes a while for that heat to melt
the ice sheets. However, there is no firm reason to put a time frame on
this melting.

A new paper that is making a great deal of news, and that is still in
peer review, suggests that the time frame may be shorter than man have
suggested. We may see several meters of sea level rise during the
lifetime of most people living today.

We don’t really how long this will take. Looking at the paleo record,
we are lucky to get two data points showing different ancient sea
levels that are less than a thousand years apart. There are a few
moments during the end of the last glaciation where we have data points
several centuries apart during which sea levels went up several meters.
We don’t have a good estimate for the maximum rate at which polar ice
caps and other ice can melt.

The current situation is, notably, very different from those periods
of rapid sea level rise. The amount of CO2 in the atmosphere is
approximately double the Pleistocene average, and the rate at which CO2
levels and temperatures have gone up has not been seen in tens of
millions of years. Whatever rate of sea level rise over the last several
tens of thousands of years must be regarded as a minimum, perhaps a
very low minimum.
Australian Libertarians, meanwhile, are fretting about not being able to get a drink at Kings Cross at 3.30 am after a day of riding their mountain bike without a helmet with their repeat action shotgun slung over their shoulder for killing feral cats with which to make a fur coat for their gay friend's wedding.

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