Thanks Chris for an excellent post. Dr. Hanson is a great scientist and hero.

There are a few issues to deal with:

1) Note on fig. 2, the temperature charts for the past several interglacials, that trough to peak involves temperature changes of 10 deg. C., or 18 F. Note also that in all but the Holocene there were immediate and progressive declines in warmth, as the interglacial slid inexorably back into the grinding ice age.

If not for anthropomorphic changes since the ancient Greeks, we would probably right now be sliding back into a world where ice sheets were grinding Canada and northern Europe back down to bedrock. As Greg Easterbrook noted in "A Moment on the Earth," an ice sheet is an environmental catastrophe in anyone's book.

If CO2 emissions do not continue to progressively expand after PO, we may actually arrive at a happy medium; no new ice age, and no run away greenhouse warming.

2) I really have to dispute Dr. Hanson's guesstimate about a "50% extinction rate" caused by a 3 deg. C. rise in temp. As noted above in fig 2, the world has periodically seen rapid temperature rises of three times that amount (admittedly from a lower threshold).

We know from the Younger Dryas, as well from earlier temperature shocks, that these changes have happened with startling rapidity, and yet the 17 or so interglacials saw few extinctions until the beginning of the Holocene, which saw an enormous die off of mega fauna, but few changes in micro fauna. (As Tim Flannery put it in "North America: The Eternal Frontier" -- 65 million years of ecological history -- the megafauna disappeared into a black hole; the black hole between the nose and chin of paleolithic hunters.)  

3) Note in fig. 6; there is a 50% decline of CO2 levels (from emissions) in a mere 20 years. 66% reduction in a century, and 78% in 500 years. If an economic crash accompanies PO, GW gas emissions will decline markedly. CO2 levels will have more time to balance. Also, with a crash it will be far more difficult to come up with investment capital to figure out how to exploit shale oil and methane hydrates.

4)which brings us to coal. As Dr. Hanson shows, oil and gas aren't as likely to destroy the climate, but coal may. This suggests two very different objectives:

a) It is imperative that we funnel money and political power to those forces opposing mountain top removal, and which block greater coal exploitation. Further, we need to oppose switching transportation from oil to coal based electricity.

b) We need to be honest about the psychological division in each of our minds. On the one hand we are horrified by runaway climate warming, but we also are horrified by the prospect that PO may cause our global economy to collapse.

This isn't just on our site; it pervades institutional thinking, as typified by The Economist. The Economist has gotten the bug on stopping global warming, but they are not only in denial about PO, but they favor doing everything in their power to increase power supplies to increase the chances for exponential economic growth.

We can't have it both ways. If we demand exponential economic growth (and what other kind is there?) then we must accept all the consequences of global warming and the literal rape of the land from strip mining. But if we accept the limitations of  both global warming and PO, then we must radically change our conception of what constitutes an acceptable economic model.