From the University of Michigan something I think Dr. Roy Spencer will be interested in as it is yet another case where models and satellite observations differ significantly. See the figure S1 at the end of this article – Anthony
Aerosols affect climate more than satellite estimates predict
ANN ARBOR, Mich.—Aerosol particles, including soot and sulfur dioxide from burning fossil fuels, essentially mask the effects of greenhouse gases and are at the heart of the biggest uncertainty in climate change prediction. New research from the University of Michigan shows that satellite-based projections of aerosols’ effect on Earth’s climate significantly underestimate their impacts.
The findings will be published online the week of Aug. 1 in the early edition of the Proceedings of the National Academy of Sciences.
Aerosols are at the core of “cloud drops”—water particles suspended in air that coalesce to form precipitation. Increasing the number of aerosol particles causes an increase in the number of cloud drops, which results in brighter clouds that reflect more light and have a greater cooling effect on the planet.
As to the extent of their cooling effect, scientists offer different scenarios that would raise the global average surface temperature during the next century between under 2 to over 3 degrees Celsius. That may not sound like a broad range, but it straddles the 2-degree tipping point beyond which scientists say the planet can expect more catastrophic climate change effects.
The satellite data that these findings poke holes in has been used to argue that all these models overestimate how hot the planet will get.
“The satellite estimates are way too small,” said Joyce Penner, the Ralph J. Cicerone Distinguished University Professor of Atmospheric Science. “There are things about the global model that should fit the satellite data but don’t, so I won’t argue that the models necessarily are correct. But we’ve explained why satellite estimates and the models are so different.”
Penner and her colleagues found faults in the techniques that satellite estimates use to find the difference between cloud drop concentrations today and before the Industrial Revolution.
“We found that using satellite data to try to infer how much radiation is reflected today compared to the amount reflected in the pollution-free pre-industrial atmosphere is very inaccurate,” Penner said. “If one uses the relationship between aerosol optical depth—essentially a measure of the thickness of the aerosols—and droplet number from satellites, then one can get the wrong answer by a factor of three to six.”
These findings are a step toward generating better models, and Penner said that will be the next phase of this research.
“If the large uncertainty in this forcing remains, then we will never reduce the range of projected changes in climate below the current range,” she said. “Our findings have shown that we need to be smarter. We simply cannot rely on data from satellites to tell us the effects of aerosols. I think we need to devise a strategy to use the models in conjunction with the satellite data to get the best answers.”
The paper is called “Satellite-methods underestimate indirect climate forcing by aerosols.” The research is funded by NASA.
PNAS Early Edition: http://www.pnas.org/content/early/recent
Joyce Penner: http://aoss.engin.umich.edu/people/penner
The University of Michigan College of Engineering is ranked among the top engineering schools in the country. At $180 million annually, its engineering research budget is one of largest of any public university. Michigan Engineering is home to 11 academic departments, numerous research centers and expansive entrepreneurial programs. The College plays a leading role in the Michigan Memorial Phoenix Energy Institute and hosts the world-class Lurie Nanofabrication Facility. Michigan Engineering’s premier scholarship, international scale and multidisciplinary scope combine to create The Michigan Difference. Find out more at http://www.engin.umich.edu/.
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You can read the full text of the paper here including the SI: http://www.pnas.org/content/early/2011/07/25/1018526108.full.pdf?with-ds=yes
This figure from the SI is quite interesting:
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Julian Braggins says:
August 3, 2011 at 6:18 am
“I have been led to believe that aerosols tend to remain in their respective hemispheres unlike CO2,
http://www.barrettbellamyclimate.com/page29.htm
compares the satellite record of temperatures graphically latitude by latitude from1976 to 2006. The southern hemisphere seems to have warmed ~.1°C in that time. The northern hemisphere ~.6°C”
Already been answered that the aerosol excuse is nonsense based on observed data. Looking at this a different way, which seems even more interesting. The northern hemisphere has warmed more than the southern hemisphere down to the land surface area being much larger. The idea this occurs because the energy is supposed to warm the ocean (never shown with scientific evidence except at the skin surface) and therefore because it has much higher heat capacity it takes longer to warm it. With the missing energy in the ocean and thus can’t suddenly skip the top 700m to deeper depths.
This demonstrates at least some minor warming expected from CO2 in the northern hemisphere is only found over land. The little warming compared, observed in the southern hemisphere again only down to land. Thats why the land/ocean ratio between the two shows this difference. This would give scientific evidence that the oceans can’t warm due to longwave CO2 and what little affect occured was the known physics based on greenhouse gases, but only applies when not over ocean. Hence, this would apply that only atmosphere over land can demonstrate a little change in greenhouse effect and with it only covering around 29% of the planet, this would explain at least why the planet hasn’t warmed as much as expected via the models.
Richard Courtney
Thanks for the confirmation. Penner has shown that the aerosol forcing is too weak to expalin the 1940-1976 cooling using the model aerosol changes claimed by Charlson (1991). The Charlson paper does not agree with observations (e.g., Hoyt, D. V. and C. Frohlich, 1983. Atmospheric transmission at Davos, Switzerland, 1909-1979. Climatic Change, 5, 61-72). In davos there was no trend in aerosol loading from 1909 to 1979 and yet the Charlson paper claims that maximum increase in aerosol loading directly over Davos. So it is now a doublw whammy for the aerosol-cooling explanation – weaker than modelled forcing and weaker than claim trends.
There are other papers supporting the trend conclusions above. For example, MacDonald’s (1938) Atlas Of Climatic Charts of the Oceans shows the same geographical distribution of aerosols as are now seen in the satellites. There is just one exception and that is an aerosol cloud coming off England into the North Sea. It didn’t get as far as Norway or Belgium. This manmade aerosol cloud disappeared in the 1950s along with London fogs caused by coal burning. So the trend there is actually in the opposite direction of what the modellers assume.
Withe the small to non-existent aerosol forcing, the only remaining way to get the models to agree with observations for 1940-1976 is have a very low climate sensitivity as Lindzen, Spencer, and others have deduced.
Douglas Hoyt:
Your very fine post at August 3, 2011 at 3:32 pm includes this comment:
“Withe the small to non-existent aerosol forcing, the only remaining way to get the models to agree with observations for 1940-1976 is have a very low climate sensitivity as Lindzen, Spencer, and others have deduced.”
Yes! See
http://img36.imageshack.us/img36/8167/kiehl2007figure2.png
Richard
Matt G says:
August 3, 2011 at 3:11 pm
The difference can also be accounted for due to the fact that CO2 has essentially no greenhouse effect over the ocean. It only happens over land. The northern hemisphere has twice the land mass of the southern hemisphere. Since Antarctica doesn’t count because it radiates so little upwelling infrared there is nothing for greenhouse gases to absorb and reemit as downwelling IR it’s more like a 4:1 greater ratio of land in the northern hemisphere.
Nothing in climate science makes sense until it is understood that greenhouse gases don’t do any greenhousing over the ocean. Once that is understood all observations fall neatly in place.
The fact that greenhouse gases have no greenhouse effect over the ocean appears to be “the trade secret of climate science”. Not that climate boffins should be accused of keeping secrets, mind you (sarc sarc sarc). I’m reminded of the same thing happening in paleontology as famously and candidly admitted by perhaps the 20th century’s most distinguished paleontologist, Harvard’s distinguished professor Stephen J. Gould. I blogged about Gould’s admission here:
ttp://www.uncommondescent.com/intelligent-design/texas-mandates-teaching-the-trade-secret-of-paleontology/
What are the odds that there’s a scientist as distinguished in climate science as Gould was in paleotology admitting the secret? Slim to none is my guess.
The first time I read about “punctuated equilibrium” I thought I had stumbled on someone’s April Fool’s prank. When push came to shove, Gould was in the same boat as the Intelligent Design crew. Just more, you know, scientific about it all. Although, come to think of it, I never heard his explanation of what was doing the “punctuating.”
DJ H;
Since you seem to have a limited attention span, there’s a two-word answer: “population bottlenecks”. YCLIU, but you won’t.
Two word reply: “not quite”.
Even Eldredge and Gould admitted that the sudden appearance of higher order taxa was overeaching. The best you can hope for with population bottlenecks is the domination of previously random alleles because they were lucky enough to survive. It is sufficient to explain the tips of the branches. There’s no other mechanism elucidated for bringing up whole taxa. Wait, that sounds like another hypothosis we’ve been discussing…
“lucky enough” is only a part of it. Brutal winnowing of all but a few, with their valuable alleles, is entirely plausible. Not guaranteed; after all, only a few percent of one percent of species make it through the gauntlet(s).
There’s also, IMO, a form of “self-directed mutation” involved. Any of the “junk” DNA which usefully winnows the possible random mutation counts would be highly conserved. As much junk DNA is, contrary to all (purely statistical) expectation.