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A meter of sea level rise by 2100?

Popular Science has published a terrific article, “Konrad Steffen: The Global Warming Prophet,” about one of the world’s leading climatologists. Steffen has spent “18 consecutive springs on the Greenland ice cap, personally building and installing the weather stations that help the world’s scientists understand what’s happening up there.” The article notes:

Water from the melting ice sheet is gushing into the North Atlantic much faster than scientists had previously thought possible. The upshot of the news out of Swiss Camp is that sea levels may rise much higher and much sooner than even the most pessimistic climate forecasts predicted.

What is going on in Greenland? Steffen explains what he and NASA glaciologist Jay Zwally figured out from their study of fissures in the ice sheet (called moulins — see figures above and below):

What happens is that the melting accelerates as meltwater funnels down to the bedrock. At the bottom, the water acts as a lubricant, flowing under the outlet glaciers and allowing the ice to slip into the sea more quickly. We hadn’t expected that ice sheets could react to warming so quickly. But that is the kind of feedback we are coming to understand in the Arctic; it’s a very sensitive environment.

This dynamic response of the ice sheet has not yet been incorporated into the climate models. So the IPCC’s recent Fourth Assessment Report estimates sea levels will rise by 7 to 23 inches — but acknowledges that dynamic ice-flow processes “not included in current models but suggested by recent observations could increase the vulnerability of the ice sheets to warming.” Duh.

What does Steffen predict for 2100 based on his experience and expertise:

Unfortunately, I think we are looking at more like a meter.

And this prediction matches recent work based on the temperature/sea-level-rise trend over the past few decades, which assumes that trend continues as the Earth warms. And it isn’t just a one-time sea level rise — seas would keep rising up to 6 inches a decade, making adaptation difficult and expensive.

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Is a meter of sea level rise by 2100 our certain future? No. But it is looking more and more like our probable future — and certainly the future that we should be planning for (and do damage projections for) if we don’t reverse emissions trends soon.