There are a lot of problems with the claims...so many it's hard to determine exactly what is going on. The 'science' behind all this relies on catastrophic numbers for continued funding, and they've been caught cooking the books more than once. I would go so far as to admit the earth is warming...but only slightly, and our contribution to that is, if anything, minimal.

The earth's climate is always in a state of flux, there's simply no such thing as a stable climate. There never has been, there never will be. Ten minutes reviewing data that goes back more than 1 billion years should convince anyone of this. CO2 level fluctuate, and do not track temperatures reliably, nor do CO2 concentrations precede changes in temperature.

Glaciers have been in decline since the 1700's, the 'mythical' northwest passage, which was made much of in the media lately, has opened a number of times since about 1800. And we just don't know how often prior to that it was navigable.

The IPCC goes so far as to admit that increases in CO2 can push worldwide temperatures up by approximately 1 degree by 2100. Which would be very difficult to isolate from random climate 'noise'. It would, at most, be a nuisance. Most people won't notice it at all. How they get the upwards of 9 degree C increases is by adding positive feedback mechanisms to their models. These are known collectively as 'forcings'. However, most are purely conjectural, and have not been measured. The IPCC also famously ignores negative feedback mechanisms, (which are MUCH more likely to exist), because a system dominated by positive feedback mechanisms is very unstable. Nuclear fission weapons are an easy to understand example. Negative feedback, in nuclear power plants is also easy to understand. In the former case, a run away reaction...positive feedback at work. In the later, no....fairly stable.

Another brief review of historical climate data will also demonstrate that the earth's climate is not dominated by positive feedbacks....if it were, this planet would resemble Venus, and it would have happened billions of years ago.