Late last month, the Interagency Working Group on Social Cost of Greenhouse Gases quietly released a three-paragraph memo on how agencies should determine the social cost of greenhouse gas emissions.  I hesitate to call it “guidance.”  Here’s the operative language:

As agencies consider applying the SC-GHG in various contexts, agencies should use their professional judgment to determine which estimates of the SC-GHG reflect the best available evidence, are most appropriate for particular analytical contexts, and best facilitate sound decision-making.

I know about states as the laboratories of democracy, but since when did each agency become its own laboratory for determining how to measure the SC-GHG?  I’ve always been told by government attorneys that we have a unitary government at the federal level.  But now each agency gets to measure the cost of carbon according to its own judgment?

According to ClimateWire (subscription required), the IWG memorandum “opened the door for agencies to use EPA’s figures”.  As those following this issue know, EPA put a much higher price on carbon than that previously developed by the IWG under Obama.  I happen to think that EPA’s estimate of the SC-GHG is closer to the mark than the prior IWG figures, but if the Administration really believes that, then why doesn’t it have the courage of its convictions and adopt the EPA estimate as the government’s estimate, rather than leave it to the “professional judgment” of EPA and whichever agencies want to go along with EPA.

Is this any way to determine how to calculate the social cost of greenhouse gases?