IPCC Report released September 27

The IPCC (Intergovernmental Panel on Climate Change) released its Summary for Policy Makers on September 27 as the first part of its fifth report on climate change called for short AR5. Its 4th report (AR4) was published in 2007. There is much commentary already by warriors on both sides in the "climate war." Two of the calmer commentators I like among academics are Judith Curry and Roger Pielke, Jr.

In Roger's post of today, he points out (among other things) that we can't know for certain what effect that efforts to curtail CO2 emissions will have until mid-century. That is true because the ranges of predicted earth temperatures for the best and worst cases overlap. Here are the numbers: In the best case (i.e., the most aggressive policy to curtail GHG (green house gases), the predicted temperature increase for 2046-2065 is 0.4 to 1.6 deg C (mean 1.0). For the least aggressive mitigation (i.e., no curtailment of GHG), it is 1.4 to 2.6 (mean 2.0). So, to the extent that we believe these predictions, it is possible that the increase in temperature could be 1.5 deg C regardless of what policy we follow.

Since the response to mitigation measures takes so long, it is silly to talk about short-term effects. He gives one example of such silliness in a quote by Al Gore of eight days ago:

Three years ago, Congress failed to put a price on carbon and, in doing so, allowed global warming pollution to continue unabated. We have seen the disturbing consequences that the climate crisis has to offer—from a drought that covered 60% of our nation to Superstorm Sandy which wreaked havoc and cost the taxpayers billions, from wildfires spreading across large areas of the American West to severe flooding in cities all across our country—we have seen what happens when we fail to act.