Posted on 08/11/2007 12:40:50 AM PDT by neverdem
Climate scientists are used to skeptics taking potshots at their favorite line of evidence for global warming. It comes with the territory. But now a group of mainstream atmospheric scientists is disputing a rising icon of global warming, and researchers are giving some ground.
The challenge to one part of the latest climate assessment by the Intergovernmental Panel on Climate Change (IPCC) "is not a question of whether the Earth is warming or whether it will continue to warm" under human influence, says atmospheric scientist Robert Charlson of the University of Washington, Seattle, one of three authors of a commentary published online last week in Nature Reports: Climate Change.
Instead, he and his co-authors argue that the simulation by 14 different climate models of the warming in the 20th century is not the reassuring success IPCC claims it to be. Future warming could be much worse than that modeling suggests, they say, or even more moderate. IPCC authors concede the group has a point, but they say their report--if you look in the right places--reflects the uncertainty the critics are pointing out.
Twentieth-century simulations would seem like a straightforward test of climate models. In the run-up to the IPCC climate science report released last February (Science, 9 February, p. 754), 14 groups ran their models under 20th-century conditions of rising greenhouse gases. As a group, the models did rather well (see figure). A narrow range of simulated warmings (purple band) falls right on the actual warming (black line) and distinctly above simulations run under conditions free of human influence (blue band).
But the group of three atmospheric scientists--Charlson; Stephen Schwartz of the Brookhaven National Laboratory in Upton, New York; and Henning Rodhe of Stockholm University, Sweden--says the close match between models and the actual warming is deceptive. The match "conveys a lot more confidence [in the models] than can be supported in actuality," says Schwartz.
To prove their point, the commentary authors note the range of the simulated warmings, that is, the width of the purple band. The range is only half as large as they would expect it to be, they say, considering the large range of uncertainty in the factors driving climate change in the simulations. Greenhouse-gas changes are well known, they note, but not so the counteracting cooling of pollutant hazes, called aerosols. Aerosols cool the planet by reflecting away sunlight and increasing the reflectivity of clouds. Somehow, the three researchers say, modelers failed to draw on all the uncertainty inherent in aerosols so that the 20th-century simulations look more certain than they should.
Modeler Jeffrey Kiehl of the National Center for Atmospheric Research in Boulder, Colorado, reached the same conclusion by a different route. In an unpublished but widely circulated analysis, he plotted the combined effect of greenhouse gases and aerosols used in each of 11 models versus how responsive each model was to a given amount of greenhouse gases. The latter factor, called climate sensitivity, varies from model to model. He found that the more sensitive a model was, the stronger the aerosol cooling that drove the model. The net result of having greater sensitivity compensated by a greater aerosol effect was to narrow the apparent range of uncertainty, as Schwartz and his colleagues note.
"I don't want certain interests to claim that modelers are dishonest," says Kiehl. "That's not what's going on. Given the range of uncertainty, they are trying to get the best fit [to observations] with their model." That's simply a useful step toward using a model for predicting future warming.
IPCC modelers say they never meant to suggest they have a better handle on uncertainty than they do. They don't agree on how aerosols came to narrow the apparent range of uncertainty, but they do agree that 20th-century simulations are not IPCC's best measure of uncertainty. "I'm quite pleased with how we're treating the uncertainties," says Gabriele Hegerl of Duke University in Durham, North Carolina, one of two coordinating lead authors on the relevant IPCC chapter, "but it's difficult to communicate" how they arrived at their best uncertainty estimates.
Hegerl points out that numerical and graphical error ranges in the IPCC report that are attached to the warming predicted for 2100 are more on the order expected by Schwartz and his colleagues. Those error bars are based on "a much more complete analysis of uncertainty" than the success of 20th-century simulations, she notes. It would seem, as noted previously (Science, 8 June, p. 1412), IPCC could improve its communication of climate science.
How about hedge your bets on global warming?
review
Mars is getting warmer too.
It must be the Martians tooling around in SUV's.
Well, I am certain that simulations (God they love their sims dont they?, easy science, no field work) for a mere 100 years of earths climate history compared to measured data with margins of error itself is nothing impressive to me.
Many models were made in the long ago past to explain movements of planets, sun, moon. Some worked pretty good too. But the bigger picture blew them out of the water.
The “simulations” of those days could not explain the grand picture at all with any accuracy.
Now we have come a long way since then.
But we cannot experiment on planetary levels with climate over vast time spans.
They are gazing into crystal balls constructed of equations and processors, and attempting to predict the future of something that I strongly suspect truly do not have a complete grasp of the massive complexity of.
Oh, and gotta love the language...
“Comes Under Attack”
Questioning, testing, proving, disproving, is not an “attack”.
Lawrence Solomon's "The Deniers" (a series of articles on the view of scientists who have been labelled "Global Warming Deniers"):
Other References:
The thing is, if they don’t have other factors included like the varying activity of the sun and cosmic rays affects on cloud formation they had to tweak the other inputs to their model so that it came up with the right results. Which in short means their model will fail to predict the future because it is simply wrong.
They can’t even accurately predict the past. How do they expect to handle the future?
“they can’t even accurately predict the past. how do they expect to handle the future?”
how dare you have even the slightest doubt of the brilliance, the sheer intellectual intensity, the wonderful sensitivity, the deep god-like understanding of these wonderfully superior human beings who are on a plane way above the rest of humanity? you should be ashamed of yourself for not kneeling before such brightness, such glowing insight, such rousing hope for mankind that is represented by these special humans who power-walk on the beach and the bay. shame on you!!!
(heil hillary!)
/sarcasm off/
That's a minimum 10% error across the entire period modeled (the 20th Century).
Are we supposed to ignore that part or what?
Exsqueeze me?
Does that mean it could be as bad, worse or better than currently predicted?
I bet he’s a corporate toady and a traitor
:)
Can we please just cut funding to all these studious idiots?!?
It is most certainly an absolute posibility, maybe.
Click on POGW graphic for full GW rundown
New!!: Dr. John Ray's
GREENIE WATCH
Ping me if you find one I've missed.
We cannot experiment on planetary levels with climate over short periods of time. One need only look as far as the local weather forecast and how consistently inaccurate it is to see proof of this concept.
Add to this all the various weather stations that are set next to exhaust ports of air conditioning ducts, next to trash burning barrels, in areas near major airports where they are subjected jet blasts, tied to chimneys, and placed in asphalt parking lots, along with the complete absence of precipitation and it's effects on temperature in the models, and you have nothing more than fraud. I also read recently that many, if not most, of the weather reporting stations in the former Soviet Union were abandoned after the collapse and that loss of data has also not be included.
This "global warming" nonsense is like peeling back an onion. The deep you dig into the "facts" the more layers off corruption you find.....
‘more complete analysis of uncertainty’? How the hell do you do an analysis on that which is uncertain? Hedging your bets is more likely looking for cover when their predictions don’t come true. When is doesn’t happen, they will cay there was too much ‘uncertaintanty’
It is considered an attack by template driven journalists who are as familiar with the principles of the scientific method as Bill Clinton is to the truth.
I look around, see changes in the land, weather, animals myself. We also had a serious cold spell last winter, 3 weeks it was minus 65 every morn at 6am.
Back in 1950’s fishwheels caught 400 king salmon a day, today a good day is 20-30. I don’t know if its global warming or off shore intercept fishery that our govt regulates that is responsible. But if the govt doesn’t do any better job with environment than they do with the fish; we better watch & worry.
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