"I'm not a global warming believer. I'm not a global warming denier. I'm a global warming agnostic who believes instinctively that it can't be very good to pump lots of CO2 into the atmosphere but is equally convinced that those who presume to know exactly where that leads are talking through their hats.
Predictions of catastrophe depend on models. Models depend on assumptions about complex planetary systems -- from ocean currents to cloud formation -- that no one fully understands. Which is why the models are inherently flawed and forever changing. The doomsday scenarios posit a cascade of events, each with a certain probability. The multiple improbability of their simultaneous occurrence renders all such predictions entirely speculative."
-- Charles Krauthammer
This is the best summary quote on the global warming issue that I have seen. I am just quibbling about words, but global warming is not a matter of belief or denial. It's a matter of science and the proper response is to be skeptical -- or to be agnostic, as Krauthammer put it.
I also support his instinctive response, when he said, "it can't be very good to pump large amounts of CO2 into the atmosphere."
Here, again, Krauthammer used the right word, "instinctively." He might have said that he trusted his own intuition, or that it was common sense, or an assertion.
But it's not a fact, not yet. Mounting evidence suggests that it is a fact, and we ought to do something about it.
But at no time, now or in the future, will it ever be a matter of belief.