March 18, 2008
You Can't Make This Stuff Up
Posted to Author: Pielke Jr., R. | Climate Change | Prediction and Forecasting | Science + Politics
Now according to Grist Magazine's Joe Romm I am a "delayer/denier" because I've asked what data would be inconsistent with IPCC predictions. Revealed truths are not to be questioned lest we take you to the gallows. And people wonder why some people see the more enthusiastic climate advocates akin to religious zealots.
I am happy to report that it is quite possible to believe in strong action on mitigation and adaptation while at the same time ask probing questions of our scientific understandings.Posted on March 18, 2008 10:51 AM
I believe we should take action too.
What precisely does Romm think you are saying?
When compared to data that actually arrive, IPCC appear to over estimate the warming trend. This is probably because they understate the uncertainties in the trend at least in the near term.
People can embrace "El Nino makes things uncertain" all they want. But there are ways to account for that in the IPCC's uncertainty estimates, and there are ways to communicate the large uncertainties in the near term.
When the uncertainties are due to known factors (like, evidently, El Nino), this can be communicated also.
However, the IPCC either a) didn't recognize the true uncertainty, b) recognized it, but elected not to communicate it or c) over estimated warming.
Now that they are aware of how the data look to people who know how to apply a linear regression using EXCEL, maybe they can elect to better explain their projections to policy makers and the public.
Posted by: lucia at March 18, 2008 12:33 PM
Coincidentally, Joseph D’Aleo, CCM, wrote today,
What label would Romm apply to the IPCC which which, from time to time, adjusted its predictions in response to observations, as you pointed out on January 26, 2008 in “Updated IPCC Forecasts vs. Observations”?
Romm should read, “Rhetorical Excess in the Case Against Global Warming” at:
Brian M. Flynn
Posted by: BRIAN at March 18, 2008 03:06 PM
BRIAN --- Its not cooling:
Posted by: David B. Benson at March 18, 2008 04:18 PM
Lucia L. continues to write with clarity and purpose:
Compare that to the responses of Romm and Connolley. There is an incredible difference in tone and content.
David B. we updated the Rahmstorf et al. analysis here in January. Lucia's analysis is completely consistent with that.
Posted by: Roger Pielke, Jr. at March 19, 2008 12:46 AM
Another thing that needs to be looked at more closely is CO2eq emissions and trends in CO2eq concentrations. Emissions are accelerating, but the increase in concentrations doesn't seem to be.
I'm not confident that there is a strong correlation.
Posted by: aaron at March 19, 2008 11:15 AM
David Benson has cited the last of the links in his post above (to a commentary on Rahmstorf et al 2007) on several other websites. I'll take the liberty of pasting in here the response I've made on one of those sites (other comments differ slightly):
David Benson, Thanks for your suggestion that I read the recent 'Skeptical Science' posting on 'Comparing IPCC Scenarios to Observations', which draws on Rahmstoorf [sic] et al (2007) to argue, inter alia, that the IPCC's 2001 projections 'underestimated temperature rise with observations warmer than all projections.'
Unfortunately, the authors of Rahmstorf et al misunderstood the basis of the 'projections' for 1990-2000 in the TAR. As explained in the Special Report on Emissions Scenarios (2000), 'the 1990 and 2000 emissions scenarios were standardized in all the SRES scenarios, with emissions diverging after the year 2000' (Box 5.1, p. 243).
The SRES went on to explain that 'The standardized scenarios share the same values for emissions in both 1990 and 2000', and that 'The 1990 and 2000 emissions estimates for all gases, except SO2, were set to be equal to the initial values in the unadjusted four marker scenarios.' So, for example, the projections for emissions AND FOR TEMPERATURE for the A1FI scenario, which was not a marker, were set BY ASSUMPTION as equal to those of the average of the four markers.
As an indication of the possible scale of the effect of this procedure, the A1FI scenario assumed that the global energy supply from coal would increase by 30% between 1990 and 2000, compared with an increase of about 5% for the A1B and B1 scenarios.
Posted by: Ian Castles at March 20, 2008 10:50 PM
I share Ian's interpretation of how Rahmstorf et al. identified the SRES scenarios. Rahmstorf et al. present multiple scenarios in the past when in reality, we can specify what emissions actually were, and then compare the particular scenario that best matched.
Posted by: Roger Pielke, Jr. at March 21, 2008 05:55 AM
For the record, I agree with Ian Castles's interpretation, and encouraged him to post here.
Posted by: David B. Benson at March 21, 2008 12:46 PM
Thanks David Benson. Yes, you did.
Posted by: Ian Castles at March 21, 2008 04:37 PM
I'm not sure whether this is going to post twice. I got a message that the first attempt was rejected.
You write, "Unfortunately, the authors of Rahmstorf et al misunderstood the basis of the 'projections' for 1990-2000 in the TAR. As explained in the Special Report on Emissions Scenarios (2000), 'the 1990 and 2000 emissions scenarios were standardized in all the SRES scenarios, with emissions diverging after the year 2000' (Box 5.1, p. 243)."
But if one goes to the Rahmstorf et al. paper in Science, one sees (if one squints hard enough!) that the temperature projections for the IPCC scenarios only diverge after the year 2000 (i.e., they are all the same from 1990 to 2000). This can be better seen from the (apparent) reprint/blowup on the "Skeptical Science" website.
So the temperature projections attributed to the IPCC scenarios in the Science paper only diverge after the year 2000, which seems completely consistent with the fact that the forcings in the IPCC scenarios only diverged after the year 2000.
Or am I missing something?
Posted by: Mark Bahner at March 21, 2008 06:31 PM
No Mark, you're not. The TAR estimates/projections for emissions, concentrations and forcings for each of the six illustrative scenarios are identical for 1990. They're also identical for 2000. They were made identical in both years through the scenario standardization process described in my posting above. The 'projected' increase in temperature between 1990 and 2000 is also the same for all six scenarios. For all of these variables, the divergence between scenarios only begins after 2000: see Appendix II for the details.
The Rahmstorf et al 2007 comparison of observations to outcome is invalid for the 1990-2000 decade, because the projected emissions, concentrations, forcings and temperatures for each of the scenarios was originally different. The original model outputs for these variables has been replaced, for all six of the illustrative scenarios, with a simple average of four scenarios.
The example I gave of the differences between scenarios in the trends in energy output from coal shows that the original estimates/projections of fossil CO2 emissions would also have differed between scenarios. And the translation of any given level of cumulative emissions into concentration levels would also have differed initially, because five different models were used to produce the six scenarios. And the translation of atmospheric concentration levels into forcings, and from forcings into global mean temperatures, would also have differed between the scenarios produced by the different modelling teams. .
As the IPCC removed all of these differences BY ASSUMPTION for the 1990-2000 decade, Rahmstorf et al 2007 did not in fact evaluate model projections against observations for this period. As for the subsequent decade, all six scenarios projected INCREASES in global mean temperature. This doesn't square with the observations.
Posted by: Ian Castles at March 21, 2008 08:56 PM
My last sentence is clumsy. I meant to say that the statement in Rahmstorf et al 2007 that the global mean surface temperature increase is at the upper end of the IPCC predictions doesn't square with observations.
Posted by: Ian Castles at March 22, 2008 05:52 PM
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