Soot blamed for global warming underestimate

[dr. what]

Global warming looks set to be much worse than previously forecast, according to new research. Ironically, the crucial evidence is how little warming there has been so far.

Three top climate researchers claim that the greenhouse gases already in the atmosphere should have warmed the world more than they have. The reason they have not, they say, is that the warming is being masked by sun-blocking smoke, dust and other polluting particles put into the air by human activity.

But they warn that in future this protection will lessen due to controls on pollution. Their best guess is that, as the mask is removed, temperatures will warm by at least 6°C by 2100. That is substantially above the current predictions of 1.5 to 4.5°C.

“Such an enormous increase would be comparable to the temperature change from the previous ice age to the present,” says one of the researchers, Meinrat Andreae of the Max Planck Institute for Chemistry in Mainz, Germany. “It is so far outside the range covered by our experience and scientific understanding that we cannot with any confidence predict the consequences for the Earth.”

Cool estimate
The calculations assume a doubling of greenhouse gases such as carbon dioxide (CO2) in the atmosphere by 2100 compared to pre-industrial levels.

Andreae and his two British colleagues, Peter Cox and Chris Jones, are leading authors from the UN’s Intergovernmental Panel on Climate Change. These new findings are likely to be reflected in the IPCC’s next assessment of climate change science, scheduled for 2007.

The cooling effect of aerosols has been known for some time. But, says Andreae, past assessments have underestimated its influence. Because of this, they have also underestimated the sensitivity of the atmosphere to the warming effect of greenhouse gases.

The new modelling study finds that only high estimates of both aerosol cooling and greenhouse warming can explain the history of global temperatures over the past 50 years.

One foot on the gas
The problem for future climate is that the cooling aerosols only stay in the air for a few days, whereas the warming gases stick around for decades or centuries. So while the cooling effect is unlikely to grow much, the gases will accumulate and have an ever-bigger effect on global temperature.

The world, says Andreae, is “driving the climate with one foot on the gas and the other on the brake. When the brake comes off, it makes a hell of a difference".

The authors have added another previously unrecognised element to the temperature forecast - the effect of all this on nature and the natural carbon cycle.

Natural ecosystems are currently absorbing up to half of the CO2 that humans put into the atmosphere. Most climate models assume this will continue. But there is growing evidence that from about 2050, soils and forests will stop absorbing CO2 and start releasing it instead.

The authors calculate that this switch in the natural carbon cycle could accelerate the build-up of CO2 in the air by more than 50%, producing a total warming that “may be as high as 10°C” by 2100.


http://www.newscientist.com/article.ns?id=dn7607

[The Duchess of Zeon]

Couldn't we stop this by eliminating air pollution restrictions?

[The Duchess of Zeon]

Couldn't we stop this by eliminating air pollution restrictions?

Well, that really is more flippant than useful, but it seems that:

Injecting a fairly large amount of particulate matter into the upper atmosphere might actually be a solution to global warming, if it was done in a particular fashion.

[Gil Hamilton]

Well, that really is more flippant than useful, but it seems that:

Injecting a fairly large amount of particulate matter into the upper atmosphere might actually be a solution to global warming, if it was done in a particular fashion.

That idea isn't new, though the particulate matter is in orbit, not in the atmosphere.

http://bbs.stardestroyer.net/viewtopic.php?t=72290

That's the other thread going on that.

[Spambot Jedi]

Yeah, about that 10°C figure...

http://www.realclimate.org/index.php?p=115#more-115

Although I realize that the article detailed in the OP was published after the one at RealClimate, I would still take it with a grain of salt since they seem to be deferring to future IPCC studies (although, I am admittedly not an expert on the subject).

Injecting a fairly large amount of particulate matter into the upper atmosphere might actually be a solution to global warming, if it was done in a particular fashion.

More info on global dimming:

http://www.realclimate.org/index.php?p=105