what is at stake in climate policy?

The website, ourenergypolicy.org, currently posts five issues with questions
of interest to key decision makers.

One question they ask is ==========================

Despite a comprehensive climate bill passing the House in 2009, the enactment of some policies that may reduce CO2 emissions over the long-term, and continuing Congressional discussion of a clean energy standard, it seems that clear paths forward on climate change are not emerging.

Nevertheless, in spite of some debate as to the phenomenon’s authenticity, climate change does not seem to be going away. June 2012 was the 328th straight month above 20th Century temperature averages, Greenland’s glaciers are melting more than ever..
....
How would you characterize the state of the climate discourse? What are the stakes of acting, or not acting, to mitigate climate change? Is there a politically viable, effective path forward on this issue?

=================

My response (one of the comments you can see on that website):


NOT representing NSF — I had a whole lot of contact with both sides of the usual debate when I worked for an office attached to the EPW committee of the the Senate in 2009.
Regarding the stakes — I am worried that the polarization of the debate is blinding us to the really biggest risks, where we need more information but our very survival might be at stake.
People urging inaction have often said “The world has done perfectly well for a billion years with CO2 levels much higher than what we see today.” That’s true … but there were about a dozen times when “doing well” has meant mass extinctions. In one of them,
90% of the species on the land of the earth were totally wiped out; all but one of the protomammals went extinct. H2S and radiation (from ozone depletion) reached levels so high that every single human on earth would be killed if it happened again. One of the world’s top experts on this event, Peter Ward, believes that we are well on course to repeating that same kind of event.
I agree with some critics that Ward’s book, Under a Green Sky, panders a bit too much to some of the usual CO2 politics, but his primary sources do check out, and there is good reason to worry. It all seems to hinge on changes in deep ocean currents, which are a kind of mirror image of the Gulf Stream debate led by Bryden of Southampton a few years ago. NOAA is beginning to do a few pilot studies on how to use satellite data to keep track of these currents in real time, for the Pacific ocean, but we need to know what is happening in other areas (like the North Atlantic) and we need new empirical models in order to have any kind of advance warning of whether such an extinction phenomenon could be as close as Ward asserts. It could conceivably be even closer, based on the limited circumstantial evidence at hand — like faster warming of the Arctic than of the tropics, occasional signs of sputtering in the Gulf stream, and no shortage of nutrient
runoff to cause anoxia. The Black Sea already has a poison rich zone, which has risen steadily over the past few decades, and I am surprised I do not see more analysis of what might happen when it reaches breakout.
Regarding response — that’s extremely important, but this comment is already a bit long. Certainly I agree with Ward that consideration of the long history of the earth is a key input to trying to understand the ocean currents better… including possibilities for tipping points.