According to a recent study published in Nature which has been widely reported in the broadsheets such as The Guardian and New York Times, measures to clean up emissions from carbon sources such as vehicles and power stations could increase global warming. Known as Global Dimming, this latest study reveals that the effect of aerosol pollutants caused by particles under ten microns has been underestimated. These tiny particles float into the upper atmosphere forming clouds that reflect more light than normal clouds.These pollutants cause acid rain and are also harmful to human health. Over the last thirty years clean air laws in the industrialised countries have reduced these pollutants whilst CO2 emissions have continued to rise.
A conclusion that should be drawn from this is that it is futile and dangerous to take measures to control air pollution that are not also accompanied by strong measures to reduce CO2 emissions. In other words, tackling one and not the other could accelerate global warming.
The case for Prof Salter’s aerosol devices
John, the satellite analysis you refer to (of dimming) echoes the results of the Max Planck Institute’s computer model (also published in Nature this year), in saying that the climate models of a year or so ago (see Carbon Rationing discussion) were underestimating the cooling effect of man-made aerosols.
However, the man-made smogs largely persist for only a few days (see for example New Scientist, 14 May 2005). Whereas, correct me if I’m wrong, even today’s elevated levels of carbon dioxide are likely to take thousands of years to die back to pre-industrial ambience. While methane levels are probably on upward trajectory.
So we cannot avoid a step change upwards in the net warming resulting from our emissions to date. In short, we are considerably closer to hitting runaway warming than they thought a year ago.
With the prospect of averting catastrophe by emissions treaty alone ever receding, maybe there needs to be a huge R&D drive into Professor Stephen Salter’s wind driven aerosol machines. One kind would generate water mist (locally of benefit against water shortages) and the second kind would spray salt over tropical seas. He predicts that the latter, by generating more highly reflective cloud over ocean expanses, could dim the planet sufficiently to offset all forecast global warming effects. As I recall, he allowed for consequences of manufacture.
If these devices might help in dimming, then surely better to try now rather than later. It may all be a gamble, but by now surely a wiser bet than on emissions cuts alone not only (i) starting in time, but (ii) for total world f.f. extraction and cement-making to be wound to zero below the tipping total? Again, correct me if this thinking is wrong.
In particular there may be a possibility of slowing some of the polar feedbacks by deploying the mist machines there – I intend to ask the guy what he thinks on the subject.
An Aerosol Tour de Forcing
www.realclimate.org/index.php?p=245 discusses the discrepancy between the above mentioned research (Bellouin...) and other research published on the same day (Chung...) which found a smaller effect.