We'll, sometimes the scientists are wrong, or the results are manipulated to get the desired result. I clearly remember studying the coming ice age when I was in junior high school, we had long discussions about how the human race would survive. They missed the boat on that one. Then global warming came along with it's unique set of problems and results that may or may not have been completely accurate, then they changed the name to "climate change", which sounds pretty vauge.
So it's not so much the science being denied, as the conclusions being questioned.
With climate change, the worst possible proponent was the the guy leading the charge. Al Gore personally took what may have been very solid science, and made it into a dog and pony show. His motivation was extremely questionable, and his never ending assertion that he was "carbon neutral" was such an absurd joke that it brought scorn and disbelief to the entire concept. So in this particular case, it wasn't so much the message that was denied, it's that the messenger made it sound like he was lying.