[I]n the new paper, the authors modeled glacial and non-glacial eras separately. And the best fit with the data suggests that climate sensitivity does indeed change depending on glaciation. In fact, during an ice age, the most probable climate sensitivity is six to eight degrees Celsius for a doubling of CO2, more than twice the previous estimate. Why do we care? As the authors drily put it, "Because the human species lives in a glacial interval of Earth history, this modeling result has more than academic interest."How much is "six to eight degrees"?
Six degrees isn't just a bit warmer here and there; it's a global catastrophe that would likely produce mass extinctions, dead oceans, large-scale desertification, coastal cities underwater, and billions dead. And unless something changes, we're well on pace for a doubling of CO2 before the end of the century.