Kevin Drum, a blogger at Mother Jones, visits his friend, Jeff Park, a geology professor at Yale, and learns about some new work with climate models that suggest it may be worse than we thought, much worse:

The model originally concluded that a doubling of CO2 produces a temperature increase just under three degrees Celsius, an estimate that’s in pretty good agreement with other models. So far, so good. But 500 million years is a long time, and several researchers have proposed that climate sensitivity might vary over that period depending on whether or not the earth is in an ice age. So in 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.” You see, the most recent ice age in human history is the one that started about 30 million years ago and continues to the present day. We’re living through a glacial interval right now, and that means that a doubling of CO2 in the atmosphere might produce a temperature increase of six to eight degrees Celsius, not the mere three degrees Celsius most commonly estimated.

Read Drum’s full article here.