Good News: I was Wrong About Global Dimming

Yippee! There’s great news. The TV show NOVA scared me a few weeks ago by describing the phenomenon called “global dimming.” I blogged about it basing my story on the NOVA presentation. Three smart readers, Manuel Rozental, Gary Boyd, and "Anonymous" entered useful comments on my blog. I’m not sure who “Anonymous” is, but he pointed out that some recent discoveries have disconfirmed much of the NOVA thesis, and he directed me to his web site, http://www.scientificblogging.com/the_soot_files. (This seems to have been written by one Lee Rodgers (AKA “Leebert”) His argument, which I presume is well-founded, though I have not sought further evidence, is that the atmospheric pollutants are of two types: (a) regular water-vapor clouds and (b) soot – and that contrary to NOVA, the soot element does not contribute to global cooling but rather to global warming. Such soot emanates from industrial particulates, and is especially conspicuous in Asia, where it is described as the “Asian brown cloud” (see photo).

Whereas according to NOVA, clouds generally shield the earth from the sun’s rays and offset some of the global warming effects of the greenhouse gases, Rodgers’s web site argues the contrary: that the soot element actually accounts for a large part of the global warming effect.

This will be very welcome news if it is established, since soot is easier to remove from the atmosphere than greenhouse gases. Whereas NOVA implied that we should avoid removing particulates too rapidly, since that would even intensify global warming, Rodgers’s web site calls for the opposite, arguing that a quick reduction in soot will slow down the GHG effects and give us longer to fix that problem.

Rodgers argues that soot from Asia is the main factor behind the melting of glaciers, for soot impairs the albedo (reflectivity) of the white surface. Citing Professor V. Ramanathan (one of the main researchers cited by the NOVA program too), Rogers claims that the deglaciation of the Himalayas largely results from the effects of airborne soot in the region. The sooty brown clouds seem to inhibit the formation of low-altitude cumulus clouds that provide a true net cooling benefit. Much of the soot comes from Asian and Pacific-region coal-powered industries and cooking fires, possibly accounting for up to 12 percent of global warming, worldwide. Add to that the melt-off of the Arctic,

“we might readily account for 33 percent of all human-caused global warming being due to soot.

“Were another 10-15 percent of all global warming found to result from other sources of soot in the industrialized West and in the tropics and subtropics (wood burning, slash and burn agriculture), we might be looking at a net 45-48 percent of global warming thus far being due to readily-mitigated soot....

[If the soot is eliminated] “We could observe tangible, meaningful results in addressing climate change, with the Arctic and Greenland ice sheets regenerating and the monsoon cycles in Asia resuming their normal patterns.“

So where does this soot originate? I found a brief article and map in the September 2007 issue of New Scientist (page 15). The Blacksmith Institute in New York, has released its annual list of the world’s most toxic places. They created a database of 600 polluted sites, then pared it down to the worst ten places on earth, in terms of the number of people harmed by the emissions. Six of these were in Asia, India, and Russia. The list includes Linfen, the heart of China’s coal industry; Sukinda, in India, which affects 2.6 million people with its chromite mines; and Dzerzhinsk, Russia, where people are exposed to the toxic by-products of chemical weapons. This list of 400 sites would provide a good list of the major sources of soot in the world. It will give us an excellent starting point for solving a big part of Earth’s problems.

Thanks to you, Lee Rodgers.