The world’s atmosphere is warming, but — fortunately — for the past century it’s been warming at a relatively slow rate (in California, on average about one degree Fahrenheit in the last fifty years). But some scientists now suspect that our atmosphere would be warming much faster were it not for particulate matter — soot. This "global dimming" was observed in this country after 9/11, when plane flights were shut down completely for three days…and temperatures at thousands of weather stations across the country jumped, averaging a degree’s warming in a matter of days.
In the words of this report from the BBC:
While the greenhouse effect has been warming the planet, it now seems Global Dimming has been cooling it down. So the warming caused by carbon dioxide has been hidden from us by the cooling caused by air pollution. But that situation is starting to change.
The trouble with global warming stories is that they tend to depress people. (Believe it or not, the movie "The Day After Tomorrow" was intended to be cynically amusing, in the "Dr. Strangelove" style. But that a style easier to admire than it is to imitate.) Thanks to Global Dimming, however, we now have an alternative to fear — pollution!