skepticism

Dear EarthTalk: I keep meeting people who say that human-induced global warming is only theory, that just as many scientists doubt it as believe it. Can you settle the score? -- J. Proctor, London, UK

So-called "global warming skeptics" are indeed getting more vocal than ever, and banding together to show their solidarity against the scientific consensus that has concluded that global warming is caused by emissions from human activities.

Upwards of 800 skeptics (most of whom are not scientists) took part in the second annual International Conference on Climate Change -- sponsored by the Heartland Institute, a conservative think tank -- in March 2009.