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Blog: Science Report: CO2 Not Responsible for Past Warming
Michael Asher (Blog) - October 17, 2007 3:42 PM
Print E-mail del.icio.us 147 comment(s) - last by Andy35W.. on Nov 14 at 8:10 AM

New Research links retreating ice sheets to climate change -- not the other way around.
Major new study disputes primary link to greenhouse gas warming

Its the strongest evidence for the Greenhouse Gas theory of global warming -- that warm periods in the earth's past were typically accompanied by rises in atmospheric carbon dioxide.  But that evidence is under serious attack, from new research funded by the U.S. National Science Foundation.

The research team, led by Paleoclimatologist Lowell Stott, demonstrated CO2 levels after the last Ice Age started to rise some 1,300 years after the warming began.  According to Stott, earlier researchers had cause and effect reversed -- CO2 increases were the result of warming, and not the original cause.  Stott's paper is not the first to show CO2 rises followed warming trends, but it is one of the most detailed and thorough rebuttals of the linkage.

The work comes hot on the heels of other research downgrading CO2's importance in climate change.  Earlier this year, the Belgian Royal Meteorological Institute issued a study saying CO2 effects had been "grossly overstated."  Dr. Steven Schwartz of Brookhaven National Labs concluded that CO2-based warming had been overstated by some 400%, and a pair of Chinese researchers used mathematical modeling to demonstrate the majority of current warming was natural in origin.

Stott's findings are important for two reasons.  First, they directly challenge the correlation between CO2 and warming.  As Stott himself points out, CO2 is still likely a contributor to climate change, but its role needs to be reevaluated.

The results also weaken the belief that present-day atmospheric CO2 increases must be anthromorphic -- human-induced.  Stott's model showed how the warming generated changed ocean conditions, which then generated massive releases of CO2 from the ocean into the atmosphere.   As natural CO2 sources still constitutes more than 97% of all emissions, this may not come as much of a surprise.

But if CO2 didn't cause the warming, what did?  Stott's model links the forcing to periodic changes in the Earth's orbit which increase solar radiation over Antarctica.  This eventually causes ice sheet retreat, which lowers ocean albedo, reflectivity.  Additional warming is generated, a feedback effect which over 1,000 or more years, transports heat via deep-sea currents to the Northern Hemisphere.  The model also explains why surface measurements of solar insolation fail to correlate with warming ... the heat transport process is very slow, and thus surface warming lags centuries behind changes in solar output.

Stott is a professor at the University of Southern California, and a reviewer for the United Nations' Intergovernmental Panel on Climate Change. 

The Nobel Foundation recently announced the IPCC as a corecipient of the 2007 Nobel Peace Prize.

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This is not new!
By pliny on 10/18/2007 8:51:01 AM , Rating: 2
It is just not true to say that AGW implies a belief that past warmings were caused by CO2 forcing. Nor is the observation that CO2 lagged warming in past deglaciations new. The IPCC report (AR3) of 2001 had this to say
quote:
From a detailed study of the last three glacial terminations in the Vostok ice core, Fischer et al. (1999) conclude that CO2 increases started 600 ± 400 years after the Antarctic warming.
http://www.grida.no/climate/ipcc_tar/wg1/072.htm#2...




RE: This is not new!
By masher2 (blog) on 10/18/2007 9:04:22 AM , Rating: 2
You left out the most important part of that quote:

quote:
However, considering the large uncertainty in the ages of the CO2 and ice (1,000 years or more if we consider the ice accumulation rate uncertainty), Petit et al. (1999) felt it premature to ascertain the sign of the phase relationship between CO2 and Antarctic temperature at the initiation of the terminations. In any event, CO2 changes parallel Antarctic temperature changes during deglaciations.
This shows the IPCC clinging to the assumption that CO2 contributed greatly to ending those ice ages. This new study, however, shows the action was primarily over before CO2 rose substantially.


RE: This is not new!
By pliny on 10/18/2007 9:47:42 AM , Rating: 2
They are just saying that the 1999 evidence has enough error that you can't be certain of the phase relation. This isn't "clinging", because they never asserted the relation that you say they are clinging to. And they say CO2 "parallels" temperature, which is true. That is a neutral statement - doesn't say whether it is before or after.


RE: This is not new!
By LogicallyGenius on 10/20/07, Rating: 0
RE: This is not new!
By TomZ on 10/18/2007 9:06:33 AM , Rating: 3
I don't think you're paying very close attention to the AGW rhetoric. For example, in An Inconvenient Truth, Al Gore discusses at great length about past history rises in CO2 that "caused" past temperature rises. Then he goes on to talk about our current "skyrocketing" CO2 levels, saying that we are causing those, and therefore, we are causing the current global warming.

In addition, I just have to laugh at your statement in another post where you are basically saying that this time the temperature rise is different, i.e., there is a different mechanism in play now compared to other times in history. Obviously you are implying that humans are causing the current rise, but you completely ignore the fact that the current warming trend started some 250 years ago before humans had the technology to cause any sort of significant rise in CO2 or other GHGs.


RE: This is not new!
By pliny on 10/18/2007 9:24:57 AM , Rating: 1
I'm not sure what Al Gore says - he may have mis-stated it. I believe that this was one of the areas where the British judge said that he was out of line with the mainstream. I do know that scientists do not believe that past warmings were CO2 driven. I do imply that humans are causing the current rise, due to the 150 Gt of carbon we have put into the atmosphere. That is the CO2 forcing. It may be that there was some small temperature rise 250 years ago caused by something else.


RE: This is not new!
By masher2 (blog) on 10/18/2007 9:29:31 AM , Rating: 1
> "I do know that scientists do not believe that past warmings were CO2 driven"

From IPCC 2001 (your own link, above):

quote:
This is consistent with a significant contribution of these greenhouse gases to the glacial-interglacial changes...


RE: This is not new!
By pliny on 10/18/2007 9:39:01 AM , Rating: 2
To complete the quote:
quote:
This is consistent with a significant contribution of these greenhouse gases to the glacial-interglacial changes by amplifying the initial orbital forcing (Petit et al., 1999).

ie something else (orbital forcing) started the warming, and the gases that were driven out by warming provided positive feedback which caused further warming. but that is feedback, not a forcing. And as they (IPCC) say, that is consistent with a delayed CO2 rise, observed by both Petit (1999) and Stott.


RE: This is not new!
By masher2 (blog) on 10/18/07, Rating: -1
RE: This is not new!
By pliny on 10/18/2007 10:05:51 AM , Rating: 3
No, Stott is careful about timing, he says:
quote:

nor can its early onset between 19-17 ka B.P. be attributed to CO2 forcing
. That is consistent with the possibility of later amplification.

The earlier result was between 200 and 1000 years delay; Stott says 1300 (with no error limits). Not very much difference there.


RE: This is not new!
By pliny on 10/18/2007 10:14:39 AM , Rating: 2
Incidentally, the fact that we're trying to glean the IPCC's view from a single non-committal paragraph buried deep in the AR3 is a clear indication that it is not true that
quote:
Its the strongest evidence for the Greenhouse Gas theory of global warming -- that warm periods in the earth's past were typically accompanied by rises in atmospheric carbon dioxide.

If that were their strongest evidence, they would be much more upfront with it!


RE: This is not new!
By masher2 (blog) on 10/18/2007 10:39:18 AM , Rating: 1
> "If that were their strongest evidence, they would be much more upfront with it! "

If you believe they have stonger evidence for CO2's role in forcing, then put it forth here. A simple radiative forcing calculation doesn't give rise to anywhere near the level of warming the IPCC predicts.

The only evidence for CO2's role in climate change is the correlation in the geologic record, and the projections of GCM models. Remove the geologic correlation, and that leaves only the GCMs, which are based on thousands of ad-hoc parameters, and have failed utterly in predictive ability.


RE: This is not new!
By pliny on 10/18/2007 10:58:41 AM , Rating: 2
No the primary evidence for CO2's role in climate change is the greenhouse effect. You can calculate, by a fairly simple 1D analysis, the IR heat absorbed. And you can verify, by looking at the satellite-measured spectrum of outgoing IR, the radiation that has been absorbed. Comes to roughly 2 W/m2. Arrhenius could see that in 1896. And sure, you then need to adjust for clouds, aerosols, feedback etc, which is where the GCM's come in.

There were essentially no pre-instrumental temperature or CO2 estimates to correlate in the 1980's, when AGW gained widespread scientific acceptance, leading to the Kyoto meeting.


RE: This is not new!
By masher2 (blog) on 10/18/2007 11:13:33 AM , Rating: 1
> "the primary evidence for CO2's role in climate change is the greenhouse effect. You can calculate, by a fairly simple 1D analysis, the IR heat absorbed"

Which is what I said. However, that calculation results in an expected rise of only 0.6 - 1.0 degrees for the first doubling of CO2. The IPCC predicts 2.5 degrees, possibly more.

The difference is anticipated feedback effects, which are extrapolated from GCM models, whose parameters derived from "best guess" estimates of climate response, taken largely from analysis of the Earth's response to past conditions. Where else would they come from?

If one removes the geologic record from the equation, a simple radiative forcing delta calculation (aka "greenhouse effect") leads only to a minor degree of warming, most of which we've already experienced.


RE: This is not new!
By pliny on 10/18/2007 6:10:35 PM , Rating: 2
Yes, it's true that positive feedback amplifies the GHG effect by a factor of 2 or more, and that ultimately the best estimate of this factor comes from the climate history. But that has little to do with what is discussed here. The strongest feedback by far is from water vapor. More heat, more vapor, which is a GHG, then more heat. The feedback role (as opposed to the driver role) of CO2 is minor in comparison.


RE: This is not new!
By masher2 (blog) on 10/18/2007 6:50:43 PM , Rating: 2
> "The feedback role (as opposed to the driver role) of CO2 is minor in comparison. "

You might want to inform the IPCC of your theories, as they clash strongly with their own opinion. Again, from your earlier link:

quote:
This is consistent with a significant contribution of [CO2] to the glacial-interglacial changes by amplifying the initial orbital forcing


RE: This is not new!
By pliny on 10/18/2007 7:43:32 PM , Rating: 2
No need to do that - they know!
quote:
Water vapour feedback continues to be the most consistently important feedback accounting for the large warming predicted by general circulation models in response to a doubling of CO2. Water vapour feedback acting alone approximately doubles the warming from what it would be for fixed water vapour (Cess et al., 1990; Hall and Manabe, 1999; Schneider et al., 1999; Held and Soden, 2000). Furthermore, water vapour feedback acts to amplify other feedbacks in models, such as cloud feedback and ice albedo feedback.

http://www.grida.no/climate/ipcc_tar/wg1/268.htm