The whole carbon-footprint thing, for example. Is it better to eat a non-organic, local tomato than an organic one from Florida? Should I drive with the windows down and the a/c off above 50 mph? What about eating with a compostable fork and knife? Shouldn’t that corn be used to feed people instead?

You know the drill.

It’s bad enough that, thanks to global warming, all those beetles are chewing through trees in Alaska and the rest of western North America faster than Sarah Palin can mow down caribou with her AK-47. It turns out that the beetles are not only killing trees; they’re releasing tons of carbon at the same time. Something like 990 megatons in British Columbia alone over the next two decades.

Then we find out that methane is 20 times worse than carbon dioxide. Great. So let’s see: The permafrost holding up those trees in Alaska is thawing out, releasing enormous amounts of methane that’s been locked up for the past 11,000 years into the atmosphere, while thousands and thousands of dead trees are tipping over like guys at a Friday night kegger.

No wonder the governor wanted to get out of Wasilla and hit the campaign trail with McCain.

And then the good folks at Woods Hole tell us it’s nitrogen that we really have to worry about. Whose idea of a bad joke is this, anyways?

First it was carbon. Then it was methane. Now it’s nitrogen. Oh, and guess what? Tons and tons and tons of nitrogen are being released from … that’s right: the thawing permafrost.

As Gail Collins might put it, “There has been a lot of that going around this year, people.”

But not to worry. Just when it looks like all is lost, word comes from the University of Virginia that pond scum might be our salvation.

Pond scum. Algae. You know, the green stuff that floats on top when fertilizer runs off into the pond. The stuff that blooms like Mao’s hundred flowers when water has too much nitrogen. Which, of course, is the major ingredient in fertilizer.

According to the Charlottesville research team, algae can generate 15 times more oil per acre than other plants used for biofuel, such as corn or switchgrass. Take that, T. Boone Pickens. Who needs your wind plan? And I’m not making this up: Pond scum gobbles up carbon dioxide by the truckload at the same time. That’s called photosynthesis, remember?

So does that mean all we have to worry about is methane? Where’s Dave Barry when you need him?