We've generally come to the conclusion that the CO2 output went into the oceans first which may partially explain what you pointed out about the lack of warming during the first decade of the millennium (and has resulted in coral bleaching.) The ironic thing about the climate models is that they're now proving to be TOO conservative as far as sea level rise is concerned. I've always been of the philosophy that we need to be proactive and make changes (for a multitude of reasons) BEFORE the science was settled, and there have always been good reasons to do that (regarding air pollution and health, which we've already gone over.) And it's important for us to present a united front to the general public, which either doesn't have access to this data or doesn't have the time to sift through it. There's many reasons to end the consumption of fossil fuels, and climate change is only one of them. On top of that, if you want to wait until everything is 100% settled, it'll be too late. It almost is already. Perfection is the enemy of the good.
Regarding Siberia, I think we're now seeing the accelerated temperature rise that has long been predicted. Not only that, we are also seeing it in other northern regions, including Vermont and other parts of Northern New England. A good analogy is that the attic is on fire and the fire is now spreading to other parts of the house.