Apr
23
2009

Hey, why not: pollution saves the planet!

An environmentalist's dream: The rat-filled cans are too small to see in this picture.
An environmentalist's dream: The rat-filled cans are too small to see in this picture.Courtesy steven.buss
Here at Science Buzz, we sometimes have what might seem like a Through the Looking Glass attitude towards Earth Day and environmentalism. I, for one, litter filthy old cans all over my yard, comfortable in the knowledge that these cans will provide wonderful little shelters for the population of rats in my neighborhood. Sort of counter-intuitive, huh? Well check this out: after I get rats living in those cans, I’m going to use highly toxic chemicals to poison the little suckers in their homes. I will then plant sunflower seeds in my dead rat filled cans. So litter + poison + patience = a beautiful garden + delicious sunflower seeds.

Sophisticated environmentalism can be complicated like that.

It feels good though, doesn’t it? A little weird, but good.

Here’s another one (and this one comes from scientists who published in the journal Nature, not just from, you know, me):
Air pollution is fighting global warming!

Say what? We thought global warming was caused by air pollution.

Yes, but… think back to flowers growing from cans of dead rats. It’s like that, kind of.

See, yes, air pollution in the form of carbon dioxide (and other gases, but we’re dealing with CO2 here) is warming the planet. But CO2 isn’t the only junk we’re burping up into the atmosphere. Think about the grey brown haze you see over some big cities. Co2 is invisible, so what’s that stuff? Some of the chemicals we put into the atmosphere have the effect of absorbing sunlight, or reflecting it back into space. Some particles form the nucleus of water droplets in clouds, and cause the same amount of water in a cloud to be spread out among a much larger number of droplets, and more droplets cause light to be reflected and scattered more. It’s all part a phenomenon sometimes referred to as “global dimming”.

Some scientists believe that “global dimming” has had the effect of partially masking global warming; we aren’t as warm as we might otherwise be for the amount of greenhouse gasses in the atmosphere because a significant amount of solar energy has been prevented from reaching the Earth by other pollutants. So there’s that.

The Nature article, however, focuses on something else entirely. While many people might assume that plants have a harder time growing in our pollution-dimmed world, it turns out that they actually seem to grow better under a hazy blanket of pollution. The light-scattering effect of many air pollutants actually causes light to reach more plant leaves. So more photosynthesis is taking place under this diffused light than under direct sunlight. That means that plants are growing more, and growing plants suck up more carbon dioxide.

The scientists behind the study estimate that global dimming could be responsible for as much as a one quarter increase in plant productivity from 1960 to 1999, causing a 10% increase in the amount of carbon stored by the land.

This also means that as we have stricter air pollution controls, the rate of global warming probably won’t decrease as much as we’d have thought—there’d be less CO2 in the air, but because other pollutants would be reduced as well plants would be less productive, and suck up less of the CO2 that is released.

Well, shucks.

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