"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Monday, December 17, 2007

World Doesn't End in 2100

Or so most of us hope, anyway.

There is plenty more to geophysics than climate, so there were three very accessible climate change talks in huge rooms at the AGU meeting in San Francisco last week. Of the plenary climate change talks, Hansen's got most of the press attention and perhaps Lonnie Thompson's got the most attention from the attendees, but I thought Richard Alley's was the most interesting and compelling.

Here's a slide of Alley's that I think presented nothing new to climate scientists, but that the public seems not to understand. The climate disruptions we are seeing now are very small compared to the ones we are worrying about. The importance of the past record is in confirming our understanding, but our expectation in business-as-usual scenarios is very much worse than a linear extrapolation.

Please also note that so far, we have been exceeding the steepest of the standard scenarios. Also note that as Dr Alley points out, the fact that the graphs traditionally end in 2100 doesn't mean the temperatures don't keep going up after that.

So what does a warming of 6 C portend? There's a book out about that called Six Degrees that you might want to have a look at. To give you an idea of the scale, warming over land is typically double the global average, and 12 C is about 20 degrees F.


William M. Connolley said...

I wrote this reply on my blog, but I'll paste it in here:

Its a fair point, and one that is often forgotten. However... its one that I have come to increasingly downweight as time goes by. For two reasons. One is practical: it simply won't work as a way of motivating people. If thats your best argument, the public won't listen. And the public, being very impatient of depth, aren't going to listen to anything but your best argument, if that. The second is that predicting societal and technological changes past 100 years is impossible. Even 100 years is pushing it, but further is just too much.

Anonymous said...

It is a bit troubling that the "real" line tends so often these days to be outside the WCS estimates....

John Mashey said...

There are arguments both pro and con, but I've found this useful more as a response to "but SLR will only be xx by 2100."

"Yes, but do you think the world ends in 2100?"

I.e., I do run into the "If only it's OK in 2100, all is well" thing.

I'd also observe that younger folks than we actually seem to care what 2100 looks like.

David B. Benson said...

I'll claim that 'the world', meaning modern civilization, will end far, far sooner than that.

Say 2034 CE.

Anonymous said...

I don't spose the talks were videotaped, were they?

I would love to be able to see Alley's.

Michael Tobis said...

You can see Lonnie Thompson's presentation on the AGU site; unfortunately the camera stayed on his face and not his slides so it's really pretty frustrating.

As far as I know most of AGU is unrecorded.

Nobody said we are great at PR. The contrary, alas, is true...

Alley's closing remark was memorable, something like "On the whole, I'm an optimist, but I have to say that if you warm ice enough, it will melt."

Simon Donner said...

That was my favourite part of Alley's presentation. It may be hard to relate the distant future to the public -- 2100 is hard enough to wrap your mind around -- but the fact is there's likely to be a lot of residual warming in the pipeline even in a stabilization scenario. In our study on climate change and coral reefs in the Caribbean, we found that hardy / more "adaptable" corals (which may not exist, mind you) may not experience chronic bleaching in a scenario in which concentrations stabilize at 550 ppm in 2100. But if you run the model out another hundred years, the residual warming becomes a serious problem for the corals.