I'm really not going to get involved with this, and I hesitate to even post, but this is the biggest problem I have with the claims:
"The effects of global warming on local weather patterns are unknown, and even as two-thirds of the world has heated up, another one-third has shown a gradual cooling over the past 250 years, he says."
We have no accurate records from 250 years ago. There were no weather stations on the oceans, and none in the arctic. Weather stations in Africa were in the teens for the entire continent. How are we going to analyze global climate data when we don't have accurate records from like 90% of the world?
Really we don't even have great information from 100 years ago. Over the last 70 years or so, we do have good statistcal data, and the warming is there, but not as great as the claims of the warming from 250 years ago or even 100 years ago. The warming that we do see over that time could be explained by higher solar output.
I am not arguing against the science, the consensus is that the warming is there and that it is man-made, but I don't trust people that talk about warming from 250 years ago, and I don't trust weather models that have been nothing but completely inaccurate.