If we plan to cope with a 5 meter rise over the next 100 years, then the worst that would happen is that we would be marginally premature. Perhaps we should have contingency plans to cope with a 10 m rise.

Where new infrastructure has an expected life over 100 years then we really do need to look at the higher levels.

There are so many unknowns that we are only guessing and the models are so conservative that we are almost certainly guessing low. I am glad that I live 60 meters above sea level.

The UNEP Year Book 2009, Ch 3 says:

“From the Greenland ice sheet, most of the water would initially stay in the Atlantic. Fifty years after release, sea level rise would be thirty times greater in parts of the North Atlantic, including the gulf of Mexico, than in the Pacific. Similarly, the study found that water from a collapsed Antarctic ice sheet would swamp coastlines in the southern hemisphere, while being barely measurable in the northern hemisphere for at least 50 years (Stammer 2008).”

The Stammer study is behind the pay wall, but there is a blog post here that does quite nicely.

The map there shows that the water piles up along the US coastline. bad news for New York, as well as Florida, but the upside is that if New York is threatened the world will act.

http://www.newsy.com/videos/antarctic_anxiety/

The estimate in the Pollard paper of WAIS collapse after 5C rise in nearby ocean T relies on a modelled estimate by Beckham and Goosse that explicitly excludes ice shelf breakup.

As the various shelf collapses show, breakup is manifest. So I would not take comfort with the 5C number or the 1000 year timescale. The measured rise of ocean T under the iceshelves now is 0.2 C and they collapse.

I think Bindschadler is absolutely correct when he says that 1000 yr is an upper limit.

Given the history of climatology, we tend to look down on ice, when in fact the source of heat threatening the WAIS is the ocean at the base of the ice which is hard to see from above. Consider http://www.osdpd.noaa.gov/ PSB/ EPS/ SST/ data/ anomnight.4.6.2009.gif and go back and look at the April sea surface temperature anomalies along the west coast of the Antarctic Peninsula for the last 10 years. What I see is that for the last 10 years that patch of water has been warmer than it was in the previous climate regimes, and this worries me because the difference between salt water that keeps fresh water ice intact; and, salt water that melts fresh water ice is only a fraction of a degree. The WAIS is sitting in thousands of feet of salt water. Despite the support from the water, that ice is highly stressed. If the surrounding salt water warms a fraction of a degree, then the ice is not likely to maintain structural strength, and is likely to collapse.

I am going out on a limb here and suggest that current models of WAIS overestimate its stability in the same way that models of Arctic sea ice over predicted Arctic sea ice stability just 5 years ago. Those Arctic ice models were off by an order of magnitude. Any risk management model for sea level rise that does not frankly acknowledge that the forecasts of sea level rise may be off by an order of magnitude is merely wishful thinking.

“WASHINGTON – The Arctic is treading on thinner ice than ever before.

“U.S researchers say that as spring arrives, more than 90 percent of the sea ice in the Arctic is only one or two years old. That makes it thinner and more vulnerable than ever before, according to researchers with NASA and the National Snow and Ice Data Center in Colorado. That is the type of ice that is more likely to melt in the summer.”

I agree Nova’s Extreme Ice is a must see.

Thanks Joe, I shouldn’t post comments so late at night

I was on the board of a group that produced a 4 day interfaith environmental festival in Seattle last year.

It inspired one of the leaders of the Episcopal Church in America to declare his commitment to halving greenhouse emissions in the church in a decade. 500 people stood and cheered.

If the commitment is profound, or appropriate for the challenge, people will respond.

Don’t worry if your membership is declining. The moment you assume a prophetic task your ranks will swell. Just make it grand.