Greg Kochanski

Proof and Global Warming

Proof

It's harder to really prove temperature changes than to prove that we are increasing the CO2 level.

The reason it's hard is that the most important greenhouse gas is water vapor, and that's closely tied in with predicting the weather. CO2 and methane are relatively easy: we (or cows) produce them, they go into the atmosphere, hang around for a while, then are slowly removed. Once a molecule of CO2 or methane is removed from the atmosphere, it's probably not coming back. And, these gases hang around long enough that they spread evenly across the planet.

But water, well, that's always evaporating and raining. The amount of water is very sensitive to the atmospheric temperature, to dust (which helps the initial condensation of rain drops and ice crystals), and other things. Convective activity, like thunderstorms, can push water up to the stratosphere. (Clouds affect global heating and cooling, too, not just the water vapor itself.)

So, it's a complicated business. People run big computer models to attempt to sort out all the effects, but all these models are simplifications of reality. They need to make assumptions to make the math simple enough to fit into a computer. I think we understand the basics of it all, and as far as I can tell, the computer models we have are reasonably trustworthy. So, I expect things to warm up. But, is it solid proof? Not quite yet.

Proof and Deniers

And, you need more than proof when you're dealing with people who have strong beliefs, like the people who run the JunkScience.com web site. Suppose you could prove that global warming would lead to giant man-eating mosquitos. If so, and if it got mentioned on JunkScience.com, I'm sure that they'd be talking about the economic benefits caused by stronger window screens. (Fewer cats would fall out of second-floor windows, I suppose.)

Proof and Politics

I am, personally, not entirely happy to be pushing for big social and economic changes on the basis of science that isn't 100% nailed down. It would be nice to wait 10 or 20 years until we really understand this stuff. But, the thing is, we need time to experiment with the ecology and society and economics.

Look at the recent (2008) spikes in food prices. Quite possibly, they were caused by the demand for biofuels. Nobody really anticipated it, right? That kind of unpleasant surprise is going to happen a lot over the next few decades as we re-arrange our energy production systems.

We need time to try policies, to make mistakes, and to back away from those policies that will eventually prove to be stupid. It's better to start early so that we don't have to try too many things at once. If you wait until global warming is certain, humanity will have that much less time to look for solutions.

And, besides, people are generally going to try the inexpensive, relatively painless solutions first. Change happens slowly. It takes time to develop new technologies and to get people to agree to things like carbon taxes. So, just in case global warming turns out to be wrong, we won't have wasted too effort and money. But, most likely, we really are changing the climate and it's time to start doing things.

(Thanks to Arun Bharatula for asking the question.)