Jim Manzi has continued to argue that the cost in global GDP of climate change mitigation isn't worth the benefits (via). I tangled with this issue some time back (with a response here by Manzi), recalling that timely climate change adaptation measures can help abate total climate mitigation costs. Ultimately, however, cost-benefit runs up against other, non-monetary values, as it is wont to do. Here's the latest on this at The Economist:
...Jim Manzi's arguments that estimates of the cost of global warming to the world's GDP do not justify the estimated costs of slowing it down. Estimated differences in global GDP 90 years down the line simply do not seem to me to be a useful metric in addressing this question. If reasonable economic estimates produced figures showing that making meaningful climate change mitigation efforts, or declining to do so, would entail lowering global GDP by 30%, that would be one thing. But differences in the range of 3% or 6% on a 90-year timescale seem too uncertain and insignificant even to enter the calculation. The question of whether or not we want a world that is between 1.5 and 4 degrees Celsius warmer by 2100, with all the environmental destruction and extinction that entails, is one that needs to be answered on the basis of other values than that of global GDP. That we seem to find it difficult to discuss environmental risk or harm in any terms other than monetary ones seems to me rather depressing.And it has been depressing throughout the 20th and early 21st centuries. Not all value, and not necessarily the most important value, is economic.
UPDATE: More debunking here at ClimateProgress.