Yonatan Zunger (zunger) wrote,
Yonatan Zunger
zunger

The ice models are wrong.

Polar ice retreating much faster than climate models predict.

Something I've been saying for a while: The ice modeling in the current gold-standard models (like GISS-E) is Just Plain Wrong: it doesn't adequately account for positive feedback in ice-melting, such as the way meltwater changes the ambient environment for ice, or the way that ice melt affects ambient atmospheric properties. A calculation like that is pretty much guaranteed to predict that ice melts only very slowly and adiabatically, instead of quickly and with marked "tipping points".

Conclusion: We're going to have a seasonally navigable North Polar Sea a lot sooner than many people anticipate.
Tags: science
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  • 9 comments

troglodyteking

April 30 2007, 20:21:55 UTC 8 years ago

Well, at least that's good for shipping, right? Maybe?

zunger

April 30 2007, 20:28:16 UTC 8 years ago

Good for shipping, interesting question for geopolitics (the borders up there aren't really well-defined...), really damned alarming for the rest of the world as it's a symptom of potentially widespread climactic mayhem.

On a completely unrelated note, you would probably appreciate this...

evelio

April 30 2007, 20:56:23 UTC 8 years ago

Shouldn't you have an icon with an unhappy face for these types of posts? :)

gaaneden

April 30 2007, 21:37:12 UTC 8 years ago

What will that mean for the rest of the world?

zunger

April 30 2007, 21:59:13 UTC 8 years ago

It's not quite clear; we'd have to really fix the models to be sure. Ice melting does a few things. It decreases the salinity of the water, which changes fluid flow; that could change water evaporation rates and so on, and have a lot of effects on the regional (e.g. European) climate, but I'm not sure in which direction. At an extreme it could shut off the North Atlantic thermohaline cycle, which would seriously mess with climates all over the place and change the pattern of warm/cold coastal areas.

It changes the reflectivity of the ground, so more sunlight is absorbed by the surface beneath it. (Whether that be ice or water) That tends to mean more heating. Also, ice sheets cool air that's passing overhead, so eliminating those again heats things up more.

I think the only way to really get a good picture of the impact is to fix the ice sheet modelling in a comprehensive model like GISS-E, and run it again to see what happens. I'd expect that it leads to increased worldwide warming to some extent, but it's not clear how much and what the regional distribution would be.

(There's also the sea level question -- melting of floating ice doesn't change the sea level, but melting of ice that's currently sitting on land does. And that brings up whole new categories of trouble that are possible)

covenantscave

May 1 2007, 02:19:03 UTC 8 years ago

Did you see An Inconvenient Truth? They covered a number of the issues related to this in that.

At some point, you sort of move out of the "is this happening?" phase and into the Dr. Strangelove phase.

BTW, I just finished Twilight in the Desert as another in the list of world-changing tectonic shifts...

zunger

May 1 2007, 02:26:26 UTC 8 years ago

Yup. Heard his talk in person, too.

covenantscave

May 1 2007, 02:38:38 UTC 8 years ago

So what did you think?

zunger

May 1 2007, 02:50:04 UTC 8 years ago

Good summary, and very well-spoken. He emphasized a lot of the right things -- things like the correlation between CO2 levels and ambient temperatures, the positive-feedback loop in ice melting, and so on. And apparently he got people's attention, which is the most important part. :)