If global warming isn't real

There are global-warming skeptics. Some of them are scientists. Some of them accept that some warming is happening, but argue that it's a temporary variation unrelated to greenhouse-gas emissions, similar to the Medieval Warm Period.

Whether any of the skeptics are actually credible, I don't know. But I find myself in the awkward position of hoping that they're wrong, and for pretty much the reason you'd expect: if it's conclusively demonstrated that global warming is nonexistent or that it won't get much worse before it cycles back, then all of those who have campaigned so hard to raise awareness about a supposedly impending catastrophe will be laughed out of their jobs. More broadly, the credibility of environmentalists worldwide will be almost completely destroyed. As a result, the political will to act on issues other than climate change is also likely to vanish.

To understand the severity of this problem, consider what the nonexistence of global warming would and wouldn't mean:

It would mean...	It wouldn't mean...
...that there's no pressing need to slow or halt carbon-dioxide emissions.	...that we can just stop worrying about the fact that the oil is running out, or ignore the health effects of coal-based power.
...that sea levels probably won't rise significantly this century.	...that there will always be enough land even as the scale of the human presence continues to expand.
...that the rate of severe droughts and resulting crop failures won't rise much further.	...that our current strategy of growing vast monoculture fields and destroying topsoil is a good idea.
...that the incidence of tropical diseases won't increase much more as a result of climate change.	...that the problems of AIDS, antibiotic-resistant bacteria, and illnesses caused by industrial chemicals in our environment will just go away.
...that the Amazon will not just dry up and blow away, and coral reef bleaching should slow down soon.	...that biodiversity loss due to deliberate habitat destruction will stop anytime soon, unless we do something about it.

So what can environmentalists do about all this? If the skeptics win, we will need to distance ourselves from climate scientists and rally around a new, more concrete cause, most likely the simple question of how to avoid using up our natural resources. On the other hand, if global warming is real but won't be indisputably obvious for another few decades, then we simply have to stay the course and knock down the skeptics one by one.

Clearly, it would be good to know for certain one way or the other, but science isn't like that. I'll post more when I've done my homework and come to a conclusion about which outcome seems more likely.