The greenhouse gas problem is essentially a too-much-of-a-good-thing problem. In certain quantities, greenhouse gases--namely water vapor, nitrogen, carbon dioxide (CO2 ), ozone and methane--have allowed life on Earth to flourish by trapping some of the sun's heat. Their benevolent influence distinguishes our climate from that of, say, the moon, which has no comparable arrangement and suffers deadly cold on the dark side of its surface and searing heat on the sunny side.

But since those palmy days before the Industrial Revolution, CO2 has increased 30 percent and methanes have more than doubled. Chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs)--existing in relatively small quantities but very long-lived and excellent at trapping heat--have also taken up residence in the atmosphere. Collectively what all this means, explains Dr. Greg Smestad, professor of environmental policy at the Monterey Institute for International Studies, is that "we're putting more blankets on, but the amount of heat we're generating is the same."

Too many greenhouse gases form something akin to a cheap polyester bedspread that makes you sweat--heat comes in but it can't get back out.

Light from the sun enters the Earth's atmosphere at wavelengths spanning the electromagnetic spectrum, from ultraviolet to infrared. When the heat hits the Earth, Smestad explains, some is used and the extra is converted and sent back out as invisible, infrared light--the same stuff that shows up in Kirlian photographs.

But when greenhouse gases are excessive, Smestad says, the infrared heading back out to space meets up with what, to infrared light, appears to be an impenetrable black wall. That wall is made up of the greenhouse gases, which just happen to have molecular compositions that block infrared. So the infrared stays in the Earth's atmosphere, and it gets just a little warmer in here.

Further complicating matters is the fact that with time--"and by 'time' I mean billions of years," Smestad qualifies--the sun itself is getting hotter. In an ideal universe, our atmosphere would be letting out more heat than it did in the time of the dinosaurs--not less.

And finally, there's ozone depletion, a separate problem from the greenhouse effect, but one that compounds it and is related to it by a common perpetrator, the CFCs and the HFCs. Both of those molecules attack ozone, a natural sunlight filter. As a result of ozone depletion, a certain amount of raw, unfiltered sunlight is pouring onto the Earth's surface, further increasing the necessity of getting the extra heat back out of our atmosphere--which, of course, it's not.