Almost any scientist looking at a new idea views it with deep skepticism and doubts it, and that skepticism is only overcome by a consistent preponderance of evidence that keeps supporting the idea that that might be important – that global climate change driven by humans might actually be occurring. As that evidence has been accumulated, skeptic after skeptic among the scientists have decided, "Well, I'd better pay more attention to this." The physics of this is much more well understood. The models that incorporate all of our known aspects of physics and atmospheric chemistry and and climatology and so on, all predict that what we're doing is going to lead to climate change. All these bits of evidence keep falling into place. They all keep saying, "Gee, we'd better pay more attention to this global climate change idea," because when we look at some data that maybe would have rejected it, it doesn't. It supports that idea. I guess what I would say is that the idea is so real now.
There have been so many attempts to test it, so many attempts to reject the idea that we might be causing climate change which have not been successful, which keep supporting that hypothesis. I think it is now incumbent upon us to take it seriously and to do things to help slow the rate of climate change and hopefully stop it. If we find out in the long-term that climate change is not going to happen, we won't have done much to harm ourselves. But if we don't act now, we could have a runaway climate change that could basically greatly decrease the livability of the earth. The science is now solid enough that any reasonable person examining the scientific evidence would decide, "We have to pay attention to it. It's time to have some action.".