Clean Air Act: Inflection Point For Global Warming?

Click on this graph with the date of the Clean Air Act noted.





It could be one of those funny coincidences like falling in love with a girl who you've ignored for years just as she meets "the one."

Dr Drew Shindell of NASA's Goddard Institute of Space Studies has led a new study which indicates that much of the general upward trend in temperatures since the 1970s - particularly in the Arctic - may have resulted from changes in levels of solid "aerosol" particles in the atmosphere, rather than elevated CO2. Arctic temperatures are of particular concern to those worried about the effects of global warming, as a melting of the ice cap could lead to disastrous rises in sea level - of a sort which might burst the Thames Barrier and flood London, for instance.

In other words, we cleared the air and allowed the sun to shine in.

Shindell's research indicates that, ironically, much of the rise in polar temperature seen over the last few decades may have resulted from US and European restrictions on sulphur emissions. According to NASA:

Sulfates, which come primarily from the burning of coal and oil, scatter incoming solar radiation and have a net cooling effect on climate. Over the past three decades, the United States and European countries have passed a series of laws that have reduced sulfate emissions by 50 percent. While improving air quality and aiding public health, the result has been less atmospheric cooling from sulfates.

Meanwhile, levels of black-carbon aerosols (soot, in other words) have been rising, largely driven by greater industrialisation in Asia. Soot, rather than reflecting heat as sulphates do, traps solar energy in the atmosphere and warms things up.

Given the choice between acid rain and global warming, I'll take the acid. The oceans are acidifying anyway due to the increasing CO2, so might as well blow up those bag plants and burn that juicy eastern coal.