Putting their money where their mouths are, a couple of Russian solar physicists have bet a British climatologist $10,000 that the average surface temperature of the Earth will decrease in the next decade. Read all about it here.
Now I'm not one to dispute that the Earth is warming. Nor will I argue that the ozone layer has some holes in it. I'll even stipulate that these are bad things. There's plenty of real evidence to support all three of the previous statements.
Where I differ is in the interpretation of the data. We've got 40 years of good satellite weather data. The Earth is 4.5 billion years old. The sun is 5 billion years old. Over the history of the Earth, there have been many ice ages. In between ice ages (that is, when it's comparatively warm), there are glacial periods. If we've had all of these eras of global cooling, who's to say that we haven't had eras of global warming? One nice thing about glaciers is they leave lots of evidence of their passing; less can be said for potential floods caused by warming.
My point is that periodic global warming may just be a normal thing for the Earth, and not a result of the industrial revolution, Aqua Net hair spray, and Freon. Since we're about 10,000 years past the end of the last glacial period, this may be pretty normal behavior. Or even if it's a few standard deviations off, that doesn't mean we're going to turn the planet into Venus before the next ice age.
Now having said that, I've got no problem making companies reduce the crap they're spewing into the air and water. I've gotta breathe, too. I just want our intentions to be clear, and not justified by scientific evidence that doesn't necessarily prove causation.
And having said that, there's an economic cost to reducing pollution. For the last 20 years or so, the arguably overly-stringent environmental laws in the US have simply forced chemical firms to go out of business or forced the entire industry abroad to eastern Europe, Asia and South America. Does it benefit the planet if, in our NIMBY-fueled attempts to reduce pollution, we just transfer the pollution elsewhere? I contend that there's an economically viable solution (i.e. acceptable level of pollution) that would benefit the ecosphere as a whole. But that's just me.
And finally, a corollary...I was talking to my dad, a chemical engineer, yesterday, and he posited that the banning of chlorofluorocarbons to make insulation foam resulted in the development of less-adhesive foam for the space shuttle boosters. How's about that for unintended consequences of the environmental movement?