CCSP on Sea Level Rise
December 17th, 2008Posted by: Roger Pielke, Jr.
The U.S. Climate Change Science Program has released its report on Abrupt Climate Change, and it includes a chapter on “Rapid Changes in Glaciers and Ice Sheets and their Effects on Sea Level” (PDF), written by a team of leading scientists, and whose lead author is director of CIRES (where I work at CU) Koni Steffen.
What does the report say about our ability to predict future sea level rise (pp. 92-93)?
Considerable effort is now underway to improve the models, but it is far from complete, leaving us unable to make reliable predictions of ice-sheet responses to a warming climate if such glacier accelerations were to increase in size and frequency. It should be noted that there is also a large uncertainty in current model predictions of the atmosphere and ocean temperature changes which drive the ice-sheet changes, and this uncertainty could be as large as that on the marginal flow response.
So when asked . . . how high will sea levels rise in the 21st century?
. . . the scientifically correct answer, according to this report, is “we don’t know.” It could be large, but it also could be similar to that of the 20th century (and I am implying nothing of probability here). Of course, such a situation lends itself to cherrypicking and political Rorschaching. So the proper response might be “Well, what do you want it to be?”
December 17th, 2008 at 3:32 pm
“the scientifically correct answer, according to this report, is ‘we don’t know.’ It could be large, but it also could be similar to that of the 20th century”
Thanks for posting this, Roger. This sort of thing is what I had in mind in my comments on prediction & uncertainty in the other thread on IPCC projections. It’s far more useful to say,”we don’t know” than to make up a “best guess” when there is so much uncertainty. You worry about “political Rorschaching” but is there a better way to report uncertainty?
December 17th, 2008 at 4:04 pm
I think the CCSP did a nice job reporting the uncertainty (Koni is a straight shooter I can tell you). By contrast, others not so good with the same information:
http://climateprogress.org/2008/12/16/us-geological-survey-stunner-sea-level-rise-in-2100-will-likely-substantially-exceed-ipcc-projections-sw-faces-permanent-drying-by-2050/
Compare that breathless misrepresentation with the careful language reproduced above.
Now I have no illusions about getting rid of willful misrepresentations, but for those looking for a more complete picture it is helpful I think to see what the scientists — and in some cases the data — actually say.
December 18th, 2008 at 7:04 am
“I have no illusions about getting rid of willful misrepresentations” —
Exposure is the best antiseptic. With traditional news sources going bankrupt in a hurry, I hold out hope for the emergence of a more balanced and honest news source; one committed to exposing fraud and corruption without fear or favor. If such a news source should ever emerge, the willful misrepresentations would be less prevelant.
December 18th, 2008 at 9:11 am
[...] other comments on the report see Climate Progress and Bay and Environment. The Prometheus blog concluded from the report that we don’t know how fast sea level will rise in the 21st [...]
July 10th, 2009 at 8:39 am
[...] other comments on the report see Climate Progress and Bay and Environment. The Prometheus blog concluded from the report that we don’t know how fast sea level will rise in the 21st [...]