A silver lining.

It could be that clouds are also helping to turn down the heat. It's been calculated that a 10% increase in the amount of low-level cloud could completely cancel the warming that is typically predicted to occur as a result of a doubling of the air's [CO.sub.2] content. How? By reflecting more solar radiation back to space. It's also been shown that the warming-induced production of high-level clouds over the equatorial oceans almost totally nullifies the powerful greenhouse effect of water vapour there. Just as the human body sweats when it's hot as a means of cooling down, nature might have it's own self-cooling system. Warm weather creates more clouds to keep the heat in check.

Investigators have found another cooling mechanism involving clouds. It seems that warming increases the amount of oceanic phytoplankton, which, in turn, produces more dimethyl sulfide (DMS). DMS then finds its way into the atmosphere where it creates more clouds which -- you guessed it -- reflect more solar radiation back to space, cooling the earth, and countering the initial impetus for warming.

Hold on though. There's another view. Some observers think increased cloud cover would exaggerate the greenhouse effect by trapping more outgoing radiation beneath it.