Actually, few intelligent people can deny that there is, most definately, a problem. The Earth is growing warmer. The question is, how much of that warming is caused by man's activities? In my opinion, very little. Sure there is a lot of localized effects of industry, smog and acid rains among others, but global effects? I've seen no definitive proof of it.
The article I saw today about the UN's statement also said that the earth is now the warmest it's been for the last 12,000 years. And we are only 1.8 degrees cooler than the highest temperature in the last million years. This clearly points to the fact that the Earth has undergone these kinds of warming cycles in the past. What makes us think it's our actions that are causing it this time?
Scientists have shown that the planet has undergone several periods of glaciation over its lifetime. To my knowledge there is no definitive understanding of what caused the glaciers to grow out of control, nor any understanding of why they stopped. But it wasn't mankind's doing, that's certain.
There is even one area of thought which hypothesizes that global warming can trigger an ice age. I don't know if this is true or not, but one thing I do know. The future will be different. Maybe worse, maybe better, but certainly different. And regardless of what you believe, I suggest you sell that beachfront property and move inland a good ways. About five feet higher up, if that UN report is accurate. Looks like Venice isn't going to be the only canal city anymore.