You're looking at Less Wrong's discussion board. This includes all posts, including those that haven't been promoted to the front page yet. For more information, see About Less Wrong.

drnickbone comments on Global warming is a better test of irrationality that theism - Less Wrong Discussion

-2 Post author: Stuart_Armstrong 16 March 2012 05:10PM

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (112)

You are viewing a single comment's thread. Show more comments above.

Comment author: steven0461 16 March 2012 07:49:58PM 46 points [-]

Here's the main thing that bothers me about this debate. There's a set of many different questions involving the degree of past and current warming, the degree to which such warming should be attributed to humans, the degree to which future emissions would cause more warming, the degree to which future emissions will happen given different assumptions, what good and bad effects future warming can be expected to have at different times and given what assumptions (specifically, what probability we should assign to catastrophic and even existential-risk damage), what policies will mitigate the problem how much and at what cost, how important the problem is relative to other problems, what ethical theory to use when deciding whether a policy is good or bad, and how much trust we should put in different aspects of the process that produced the standard answers to these questions and alternatives to the standard answers. These are questions that empirical evidence, theory, and scientific authority bear on to different degrees, and a LessWronger ought to separate them out as a matter of habit, and yet even here some vague combination of all these questions tends to get mashed together into a vague question of whether to believe "the global warming consensus" or "the pro-global warming side", to the point where when Stuart says some class of people is more irrational than theists, I have no idea if he's talking about me. If the original post had said something like, "everyone whose median estimate of climate sensitivity to doubled CO2 is lower than 2 degrees Celsius is more irrational than theists", I might still complain about it falling afoul of anti-politics norms, but at least it would help create the impression that the debate was about ideas rather than tribes.

Comment author: drnickbone 27 April 2012 10:53:54PM 0 points [-]

Wouldn't denial of AGW equate to one of the following beliefs?

  1. Climate sensitivity to doubled CO2 is zero, less than zero, or so poorly defined that it could straddle either side of zero, depending on the precise definition.
  2. Increased levels of CO2 have nothing to do with human activity.

Anyone who believes in ~1 and ~2 must believe in some degree of AGW, even if they further believe it is trivial, or masked by natural climate variations.

Belief that sensitivity is below 2 degrees doesn't seem utterly unreasonable, given that the typical IPCC estimate is 3 degrees +/- 1 degree, the confidence interval is not more than 2 sigma either way ("likely" rather than "very likely" in IPCC parlance) and building that confidence interval involves conditioning on lots of different sorts of evidence. Belief that sensitivity is below 1 degree does seem like having an axe to grind.

All this is Charney or "fast feedback" sensitivity. The biggest concern is the growing evidence that ultimate (slow feedback) sensitivity is much bigger than Charney (at least 30% bigger, and plausibly 100% bigger). Also, that there are carbon cycle and other GHG feedbacks (like methane), so the long-run impact of AGW includes much more than our own CO2 emissions. Multiplying all the new factors together tuns a central estimate of 3 degrees into a central estimate of more than 6 degrees, and then things really do look very worrying indeed (temperatures during the last ice age were only 5-6 degrees less than today; at temperatures 6 degrees more than today there have been no polar ice caps at all).