I've already defended blanket skepticism about supposedly impending disasters. Here's a neat essay by Max More defending a "Proactionary Principle" against the far more popular "Precautionary Principle." Intro: "We can call this “the” Proactionary Principle so long as we realize that the underlying Principle is less like a sound bite than a set of nested Chinese boxes or Russian matroshka (babushka) dolls..." The best of the Russian dolls:
3. Triage: Give precedence to ameliorating known and proven threats to human health and environmental quality over acting against hypothetical risks.
4. Symmetrical treatment: Treat technological risks on the same basis as natural risks; avoid underweighting natural risks and overweighting human-technological risks. Fully account for the benefits of technological advances.
9. Prioritize (Prioritization): When choosing among measures to ameliorate unwanted side effects, prioritize decision criteria as follows: (a) Give priority to risks to human and other intelligent life over risks to other species; (b) give non-lethal threats to human health priority over threats limited to the environment (within reasonable limits); (c) give priority to immediate threats over distant threats; (d) prefer the measure with the highest expectation value by giving priority to more certain over less certain threats, and to irreversible or persistent impacts over transient impacts.
Underlying More's whole discussion is a deep appreciation for the great economic concept of opportunity cost. The progress you don't see because you didn't allow change is as much a cost as the losses you do see because you did. It's only because some places and times allowed drastic change that we can look back in time to 1000 A.D., or across the border at Third World countries, and realize how lucky we are that proaction prevailed over precaution.