"Last week the Biden Administration announced “a return to science” in the form of “evidence-based estimates of the benefits of reducing climate pollution.”
... such estimates are called the social cost of carbon (SCC).
The SCC is a quantification of the economic consequences of the emissions of carbon dioxide for use in benefit-cost analyses of proposed Federal regulations.
... Unfortunately, the U.S. government’s estimates for the social cost of carbon have compromised scientific integrity.
With its SCC announcement last week, rather than a “return to science,” the Biden Administration has continued a long-standing charade that not only violates its claim to uphold scientific integrity, but leaves its carbon price extremely vulnerable to legal challenge.
... (in) 2008, when a federal court ruled that the U.S. Department of Transportation was in error in conducting a benefit-cost analysis when it assigned a value of zero to the economic consequences of carbon dioxide emissions, concluding, “while the record shows that there is a range of values, the value of carbon emissions reduction is certainly not zero.”
This judgment meant that the government would subsequently need to develop a defensible estimate of economic consequences of carbon dioxide emissions.
... in 2010 the IWG (Obama interagency working group) estimated the SCC at $26 (in 2007$ for 2020) per ton of carbon dioxide, and following several updates,
in 2016 set the value at $42 (in 2007$ for 2020) per ton in 2016. In March, 2017, the Trump administration disbanded the IWG and issued a new and much lower estimate for the SCC of $7 per ton (in 2018$ for 2020).
Last week the Biden administration restored the final estimate of the Obama administration (now $51 per ton in inflation-adjusted 2020$ for 2020), as an “interim step” to issuing updated estimates sometime in the next year.
The current SCC is science-y — it has the appearance of rigor, sophistication and is calculated under a mindbogglingly complex set of methods.
But looking behind the curtain reveals that it is much closer to quantification theater than to scientific rigor.
... there can be no empirical or objective basis for many of the assumptions that must be made to produce a estimate of the SCC.
... Richard Tol, of the University of Sussex and whose work is central to the IWG methodology, observes that “published estimates [of the SCC] range from -[$]771 / tC to +[$]216,035 / tC.
Research cannot reduce the span of credible estimates by much, as the future is uncertain and ethical parameters are key.”
... it is based on climate scenarios that are not just badly out of date, but reflecting a set of fictional worlds.
Consequently, any SCC derived from such implausible scenarios simply cannot be justified as reflecting “best available science and data.”
... in order to estimate future damages resulting from the emissions of carbon dioxide into the atmosphere, plausible estimates of how that future might unfold are necessary.
The IWG based its original 2010 SCC on eight different scenarios of the climate future, developed more than a decade ago.
These outdated scenarios have never been updated in the IWG methodology.
All of them, including the policy scenario, envisage enormous emissions of carbon dioxide from the burning of fossil fuels to 2300.
None of these futures are remotely plausible, in fact they are laughable.
... The difference between plausible expectations for future emissions and the imaginary worlds of the scenarios underpinning the IWG SCC is important because most of the cumulative damage projected due to climate change occurs well after the end of the 21st century.
For instance, 55% of total damage estimated by the integrated assessment model with the largest damages from carbon dioxide occurs from about 2100 to 2300 (under a discount rate of 3%).
Put another way, more than half of the Biden’s administration’s estimate of the social cost of carbon is based on damages that occur under temperature changes of 3 degrees Celsius at the end of the current century to greater than 9 degrees Celsius by 2300.
If the world economy does not actually emit into the atmosphere tens of thousands of gigatons of carbon dioxide, as envisioned by the IWG, then the majority of the IWG SCC estimates are simply imaginary ...
In 2017, the National Academy of Sciences recognized that many aspects of the IWG methodology were dated or unsupported, and recommended a range of actions to update and improve the SCC estimate.
... The Biden administration is relying “in particular” on a consortium of researchers whose “cookbook” for estimating future damage from climate change relies on using another implausible, extreme scenario (called RCP8.5).
... it will again produce a SCC that looks like science but would be more accurately described as fiction."