http://www.sciencenews.org/view/download/id/49303/name/Gases_warming_potential_by_weight

http://www.sciencenews.org/view/generic/id/48940/title/Aerosols_cloud_the_climate_picture

Modeling the climate just got a little more complex. A new simulation that considers chemical interactions between various gases and atmospheric aerosols is giving scientists and policy makers better estimates of the climate-altering effects of those gases, scientists report.

Some atmospheric gases — known as greenhouse gases — trap heat and boost the planet’s surface temperature. This process keeps Earth habitable, but nowadays, many scientists say, the planet may be getting too much of a good thing. Though most climate simulations include the direct, heat-trapping effects of these atmospheric constituents, which can readily be measured in a lab, few account for how their presence either increases or decreases atmospheric concentrations of planet-cooling aerosols, says Drew Shindell, a climate scientist at NASA’s Goddard Institute for Space Studies in New York City. “These effects are generally understood but not well quantified,” he notes.

Aerosols, particles so small that they remain suspended in the air, come from natural sources such as volcanoes and sea spray, but also form in chemical reactions involving the gases spewing from tailpipes and smokestacks. Light-colored aerosols, such as sulfate droplets, scatter sunlight and reflect some of it back into space, cooling Earth’s surface just as natural clouds do.

ecently, Shindell and his colleagues modified a NASA climate model to consider chemical reactions among major atmospheric constituents and the resulting effect on aerosol concentration. Their report, in the Oct. 29 Science, reveals that some greenhouse gases have a substantially stronger warming effect than previously recognized because they take part in reactions that destroy aerosols, while others actually tend to boost concentrations of cooling aerosols.

The new study “shows that you can’t make efficient climate policy without considering the effects of air pollution,” says Almut Arneth, an ecosystem modeler at Lund University in Sweden.

New portions of the revised model consider the influence of methane, carbon monoxide and nitrogen oxides on the atmospheric concentration of hydroxyl radicals, highly reactive molecules sometimes referred to as the atmosphere’s detergent. Hydroxyl concentrations can be depleted as these radicals react with gases in the atmosphere, and this slows the reactions that produce light-colored, light-scattering sulfate aerosols, Shindell says. “And a lower number of aerosols means a lower cooling effect,” he notes.

Analyses using the revised model suggest that the aerosol-stifling power of methane and carbon monoxide considerably boosts the planet-warming effect of these gases. Previous studies have shown that a kilogram of methane, over the course of a century, warms Earth about 25 times more effectively than a kilogram of carbon dioxide does. But add in methane’s hydroxyl-consuming effect, and its planet-warming potential jumps to 28 times that of CO2, an increase of 12 percent, Shindell says. (Scientists use carbon dioxide as a baseline largely because it is a common, long-lived greenhouse gas in the atmosphere and its warming effects are well known.)

Similarly, carbon monoxide’s greenhouse warming potential rises from 2.2 times to 3.3 times that of CO2 when its hydroxyl-consuming effect is considered. If the inhibiting influence of these two gases on the formation of planet-cooling clouds is also incorporated into the model, their greenhouse effect increases even further.

But the news isn’t all bad: The team’s model suggests that various nitrogen oxides produced by fossil-fuel burning tend to increase aerosol concentrations through a complex series of reactions, thereby tripling their cooling power. NOx emissions are increasing in developing countries, but still play a relatively minor role in the overall global greenhouse effect.

Shindell and his colleagues haven’t yet used these new values to make long-term climate predictions under various emissions scenarios. For now, however, the new model could give scientists insight into recent climatic trends. For instance, Shindell notes, “We’ll be able to learn how much greenhouse gas warming that aerosols have been masking.” Recent studies have found that as much as 20 percent of the warming in Europe since the 1970s stems from a decline in aerosols, such as fog and haze, during that period (SN: 2/14/09, p. 9).

Results of the new model will also enable policy makers to better determine the possible climatic effects of significantly reducing specific types of emissions, especially those that substantially affect pollutants and other aerosols.

Because many greenhouse gases also trim aerosol concentrations, Arneth says, people will have to cut emissions even further to keep Earth’s average temperature from increasing 2 degrees Celsius above pre–Industrial Revolution levels. “We not only have to think about greenhouse gases, but about pollution too,” she says.

Burning Fossil Fuels Has A Measurable Cooling Effect On The Climate

ScienceDaily (Jan. 19, 2004) — Atmospheric researchers have provided observational evidence that burning fossil fuels has a direct impact on the solar radiation reflectivity of clouds, thereby contributing to global climate change.

Joyce Penner, professor in the University of Michigan Department of Atmospheric, Oceanic and Space Sciences, U-M graduate student Yang Chen, and assistant professor Xiquan Dong from the University of North Dakota Department of Atmospheric Science, reported their findings in the Jan. 15 issue of the journal Nature.

Most evidence that increased levels of fossil fuel particles (aerosols) affects the reflectivity of clouds, thereby producing a cooling effect on the climate, has been indirect. "This made it difficult to determine the impact this phenomena, known as the indirect aerosol effect, has on the global climate," Penner said. "Our data makes the direct connection and opens new areas of study."

Solar radiation, which adds to global warming, is reflected back into space by clouds. Cloud droplets are increased with higher levels of aerosols, allowing for less radiation, or heat, to reach the lower atmosphere. The end result is a measurable cooling effect on the climate.

Using atmospheric data gathered from a site in Oklahoma, a typical continental site with a high concentration of aerosols, and a typical Arctic site in Barrow Alaska with low aerosol concentration, the researchers were able to show that the difference in cloud reflectivity at the two sites was caused by the difference in aerosol levels. The researchers also provided important evidence that the computer simulation model used in the study was capable of estimating cloud optical properties determined over a broad range of aerosol concentrations.

"This study is important for two reasons," Penner said. "First, it provides evidence that there is some cooling of the climate due to anthropogenic aerosols. Second, the simulation model we used has been shown to be a valuable tool in determining more directly the impact of aerosols on the climate."

Penner cautioned that over longer time scales in the future, the climate cooling due to the indirect aerosol effect will be minimal when compared to the climate warming of carbon dioxide. "We've shown that there's more work to be done to discover all of the various ways we affect the climate."

For more information, visit http://aoss.engin.umich.edu/ and http://www.nature.com/

Nothing new in that.

You should try it.

There are, however, some things left unmentioned about the IPCC claims. For example, the observations are consistent with models only if emissions include arbitrary amounts of reflective aerosols or particles (arising, for example, from industrial sulfates) that are used to cancel much of the warming predicted by the models. Without such adjustments, the observations are consistent with there being sufficiently little warming as to constitute a problem not worth worrying about much.

Lindzen's full article here:
http://www.theaustralian.com.au/news/opinion/alarmists-keep-ringing-the-bell/sto...

It doesn't significantly affect the graph from AR4 that I posted earlier showing the forcings.

OK, N2O is affected by aerosols, but N2O is one of the less important greenhouse gases after water, CO2 and methane and in terms of overall effect.

The graph in FD's post doesn't account for relative abundance. The concentration of Nitrous Oxide in the atmosphere is about 320 parts per billion.

For those of you who prefer it in parts per hundred thousand and percent, that's  0.032 ppht (strange unit) and 0.000032 percent respectively.

Soren, do you want to get that rusty old argument about trace components out? You know - the one you were so enamoured with, but convinced no other rational person on this forum?

muso wrote on Apr 25^th, 2010 at 11:39am:



Muso, old pal, I am not in the business of hairsplitting. I am not sure what exactly stuck in your mind to be now called a rusty old agrgumnet.

CO2 is a relatively insignificant component, despite the gazillions of it being emitted. In the scheme of things it is still only one small elemenet in the climate balance. How it actually works its magic is open to not only research but conjecture - hence the reason for more research.

Here are a couple of rusty old statements:

CO2 does not control the climate.
The extent and mechanism of its influence is unknown IN THE CONTEXT of all other impact and variables. We may know what it does in isolation but we do not know how those effects actually work in the midsts of counter-effects by other climate elements.
CO2 does not cancel out all other climate effects to become the domonant effect on climate.
Even if none of us ever farted of exhaled, the climate would go on changing in ways we ouldn't quite understand.

Whatever we do is natural, if you are an atheist. Even if we blow th place up with nuclear weapon, that would b all part of nature as we are part of nature.
ANy moral panic over our evil influence is thinkable only if you are a closet theist and see our actions as supra-natural moral acts, rather than natural ones. Hence the obvious religious zeal in all AGW talk. But you can't have it both ways. Either we are neglecting our guardianship of nature, being put here in change of it by god - or we are mere animals and in that case que sera, sera.

I think ten days constitutes a deafening silence, does it not?

Soren wrote on May 7^th, 2010 at 11:06pm:

Exactly. What's so wrong about an old man getting round in a bear suit in the privacy of his own home, staying away from shopping malls and public conveniences as per the court order?