Well, because I have seen the statistics, for one thing.
Because there's every bit as much doubt in the relevent scientific community about global warming - in essence, not in specifics - as there is about evolution, that smoking causes cancer, and of the heliocentric theory of the solar system. That you can find "scientists" that have opposed all three of those means precisely about as much. The majority of scientific studies that you'll find about climate change at this point are not trying to prove it exists, but to study its already extant effects on flora, fauna, specific areas and climatological models, et al.
Because it's simple common sense that if when you have made a more than measurable dent in the forestation of the planet (which we have), and when you have released untold amounts of carbon dioxide into the atmosphere (which we have and do), it will have an effect on the planet's climate. Why people who refuse to believe in global warming think that the consumption of 84 million barrels of petroleum a day (to say nothing of the other sources of released carbon, and there's more than a few) will never have a significant effect on climate is very much beyond me. It strikes me as similar to the notion that "It's impossible to catch all the fish in the sea", a belief that didn't turn out too well.
Because there's a scary amount of "rapid acceleration" factors that could release an untold amount of carbon into the atmosphere within a relatively small amount of time, such as the northern hemisphere permafrost.
Because the snows of Kilimanjaro are gone. So are most of the coral reefs.
Because, quite frankly, there is no good reason to think there a pro-global-warming conspiracy, as very, very few people benefit financially from it (especially up until this point). But there's a hell of a lot of reasons for people to deny it exists and a hell of a lot of people with financial reasons to keep denying it exists.
Because there's every bit as much doubt in the relevent scientific community about global warming - in essence, not in specifics - as there is about evolution, that smoking causes cancer, and of the heliocentric theory of the solar system. That you can find "scientists" that have opposed all three of those means precisely about as much. The majority of scientific studies that you'll find about climate change at this point are not trying to prove it exists, but to study its already extant effects on flora, fauna, specific areas and climatological models, et al.
Because it's simple common sense that if when you have made a more than measurable dent in the forestation of the planet (which we have), and when you have released untold amounts of carbon dioxide into the atmosphere (which we have and do), it will have an effect on the planet's climate. Why people who refuse to believe in global warming think that the consumption of 84 million barrels of petroleum a day (to say nothing of the other sources of released carbon, and there's more than a few) will never have a significant effect on climate is very much beyond me. It strikes me as similar to the notion that "It's impossible to catch all the fish in the sea", a belief that didn't turn out too well.
Because there's a scary amount of "rapid acceleration" factors that could release an untold amount of carbon into the atmosphere within a relatively small amount of time, such as the northern hemisphere permafrost.
Because the snows of Kilimanjaro are gone. So are most of the coral reefs.
Because, quite frankly, there is no good reason to think there a pro-global-warming conspiracy, as very, very few people benefit financially from it (especially up until this point). But there's a hell of a lot of reasons for people to deny it exists and a hell of a lot of people with financial reasons to keep denying it exists.