http://www.grist.org/
by David Roberts
Mr. Tucker,
Your story about transitioning from climate skepticism to climate realism has gotten quite a bit of attention and interest among folks on "my side" of that debate, as you can imagine. I had wondered if it were still possible for people to be "defeated by facts" and change their minds about issues tangled in America's contentious partisan warfare. I don't know your whole story, but if that's what you've done, you're to be commended. Intellectual self-discipline and courage are rare in U.S. politics these days.
I write not only to thank you, but to encourage you to keep going. Keep pursuing this line of inquiry. Keep thinking about changes in the climate and what they mean for America and the world. Recognizing the problem is the first step in a long journey, and no one, not even the most devoted climate advocate, is certain where that journey ultimately leads.
As you dig, you'll discover that there's some disagreement over just how much climate change is "too much" -- how much humans ought to tolerate/adapt to vs. how much they should try to prevent. That issue has not been and can not be settled with any certainty. Ultimately it's a question of values, and different people will value risk, economic growth, and social justice differently.
Nonetheless, climate scientists have done their best to identify the level of CO2 in the atmosphere that would risk pushing the climatic system over dangerous, irreversible thresholds. Over time, their consensus has changed, but it's always been to revise the level downward. First it was 550 parts per million of CO2 in the atmosphere. Then it was 450, which remains the general U.N. target and what's reflected in the 2007 IPCC report. Now many people are arguing that the report is conservative and out-of-date and the latest science suggests 350 ppm. (Currently, we're at 392 ppm.)
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