Ever since analysts began in the 1980s trying to calculate the social costs of our dependence on carbon-based fuel, the results have been questioned. In 2010, basing its conclusions on three federal models, the Obama administration set the social cost of greenhouse gas emissions at $21 a ton. That matters because it's what is used by the Department of Energy to figure out, for example, the impact of tighter efficiency standards on kitchen appliances. It's also what the Environmental Protection Agency uses to calculate the impact of vehicle tailpipe emissions.
If the calculation is too low, it may make the cost of additional restrictions seem too expensive and provide ammunition for energy lobbyists and climate-change deniers to help defeat any attempt to tighten the rules. And they hardly need any more assistance in that realm.
However, a new (and controversial) look at the data used in federal models that set the social cost of has generated a new, much higher figure: $63 a ton.
Laurie Johnson, who is chief climate economist at the Natural Resources Defense Council, got her data from an updated version of the "Policy Analysis of Greenhouse Effect," or PAGE, model, one of three such models used to "blend physical and economic projections."
The older version assumes a one percent chance of catastrophe - such as the melting of a major ice sheet - should global temperatures rise above 2ºC (3.6ºF) compared to preindustrial levels, Johnson said.
The newer version, based on recent observations and science, assumes a 10 percent chance of catastrophe for the same threshold, among other refinements, she said.
The result: While the federal economists pegged a mid-range value of climate damages at $30 per ton of emissions using the 2002 version of PAGE, the revised version suggests the number is closer to $63, Johnson found.
That's $2 shy of the $65 estimate the federal Interagency Working Group on the Social Cost of Carbon identified last year as the "worst-case" impact of carbon emissions.
And even that may be low.
One catastrophe analysts have in mind is the stepped-up melting of Greenland or the West Antarctic, something which could raise global sea levels 20 feet or more.
Whether the actual per ton figure for the social costs is $21, or $30 or $63 will make little difference, however, as long as roadblocks are put up against any efforts to do anything to ameliorate those costs. And Congress, or at least the House of Representatives is the biggest roadblock of all for the next two years.