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Fact-free he began and fact-free he remains.
Fact-free he began and fact-free he remains.
Herewith, some observations on Professor Jeffrey Sachs’s response to my critique of his criticism of the recent State Department analysis of the proposed Keystone XL pipeline in the context of greenhouse gas (GHG) emissions. A summary of his original criticism of Keystone XL is as follows:
• “The world is on a trajectory to raise the mean global temperature by at least 3 degrees C by the end of the century.”
• “The world is experiencing a rapidly rising frequency of extreme climate-related events such as heat waves.”
• “The Keystone pipeline is crucial to the global carbon budget,” that is, an effort to limit the use of fossil fuels to an amount that would yield a global temperature increase of no more than 2 °C.
In my critique, I argued that the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5) presents no temperature data — that is, an actual temperature trend, which is the only definition of the phrase “on a trajectory” that is meaningful analytically — even remotely consistent with Sachs’s assertion of a temperature trajectory yielding an increase of “at least 3 degrees C by the end of the century.” I pointed out that the data on tornado, hurricane, and cyclone activity, wildfires, sea-level increases, droughts, and flooding are inconsistent with the assertion of “a rapidly rising frequency of extreme climate-related events.” I added that the data on the Arctic ice cover are ambiguous, in part because the satellite record begins in 1979, that is, at the outset of the warming period that began in the late 1970s and continued through 1998. I noted also that it is not plausible to argue that Keystone XL “is crucial to the global carbon budget” (about which more below) given the vanishingly small contribution of the proposed pipeline to aggregate GHG emissions even under the most extreme assumptions.
Sachs again offers no actual evidence in support of his assertions.
In his response, Sachs again offers no actual evidence in support of his assertions, and makes no attempt to refute my point about the absence of any such trend in the AR5 data. Instead, he defines his “trajectory” as the modeling result of the most extreme of four IPCC emissions scenarios; it is a set of modeling assumptions that together are defined in the scientific literature as the Representative Concentration Pathway 8.5 (RCP8.5). (The 8.5 figure is 8.5 watts per square meter, the theoretical surface warming resulting from the radiative forcing caused by rising GHG concentrations under the RCP8.5 assumptions. The others are RCP6, RCP4.5, and RCP2.6.) In this scenario, atmospheric GHG concentrations are assumed (or modeled) to rise from about 370 ppm in 2000 (or about 396 ppm in 2013) to 1370 ppm in 2100; accordingly, that long-term increase assumes annual increases (from 2013) of about 11 ppm on average. For the period 1959-2013, the highest such annual change in GHG concentrations was less than 3 ppm (in 1998). In the RCP8.5, annual GHG emissions triple between 2000 and 2100; about three-quarters of that increase is the result of rising carbon dioxide emissions from the energy sector. But that assumption already is problematic due to the ongoing shift from coal to natural gas and other energy sources that are less GHG-intensive. (Sachs here engages in some sleight of hand in his assertion that under RCP8.5, “emissions continue to rise rapidly as they are now doing.” Nope: Under RCP8.5, emissions rise much faster than is now the case.) In any event, Sachs may sincerely believe the assumptions and projections of RCP8.5 as a scenario, but a “trajectory” it is not.
Similarly, Sachs in his response offers no evidence in support of his assertion that “The world is experiencing (emphasis added) a rapidly rising frequency of extreme climate-related events such as heat waves.” No, it is not; see this for a summary of the evidence. Instead, Sachs offers a table from the AR5 Technical Summary of projections of the various adverse effects of increased GHG emissions, from warmer weather to extreme high sea levels, with asserted confidence levels for this century ranging from low confidence to virtual certainty. This has nothing to do with what the world “is experiencing,” and neither the table nor Sachs offers actual evidence that the purported trends are anthropogenic. The table is a set of conjectures. Another table (p. 12-78) from the same AR5 working group offers a different set of potential adverse effects that really are “extreme”: a collapse of the Atlantic Meridional Overturning Circulation (“very unlikely” with “high confidence”), ice sheet collapse (“exceptionally unlikely” with “high confidence”), permafrost carbon release (“possible” with “low confidence”), clathrate methane release (“very unlikely” with “high confidence”), tropical forests dieback (“low confidence” in such projections), boreal forests dieback (“low confidence” in such projections), disappearance of summer Arctic sea ice (“likely” with “medium confidence”), long-term droughts (“low confidence” in such projections), and a collapse in monsoonal circulations (“low confidence” in such projections).
So: The worst of these potential extreme events is the possible disappearance of the summer Arctic ice, an outcome that IPCC now views only as “likely” with “medium confidence,” and only under an RCP8.5 scenario. “Extreme” may be in the eye of the beholder; but even in the AR5 there is little confidence in the inevitability of such events, let alone in the broader scientific debate, Sachs’s assertions notwithstanding.
Can anyone possibly believe that emission reductions of 80 percent are anything other than a fantasy?
Finding himself unable to defend the proposition that approval of Keystone XL would have any measurable effect on temperatures — even in the extreme case, the marginal GHG emissions from the pipeline would raise temperatures by something on the order of one ten-thousandth of a degree — Sachs attempts to change the subject by tying Keystone XL with a global “carbon budget” that purportedly would limit temperature increases to 2 °C. Based upon somewhat dated analysis by Professor Richard S.J. Tol of the economic effects of climate change, the carbon budget, however much a political construct, nonetheless is irrelevant in terms of Keystone XL, since the GHG emissions from the pipeline, again, would be trivial.
What truly is shocking is how little thought Sachs seems to have devoted to the policy issues raised by the carbon budget. Recall Sachs’s asserted global “trajectory” of 3-3.7 °C of warming under RCP8.5. If he really believes that, then the carbon budget — no more than 2 °C of warming — means that emissions must be reduced by an amount averting about 1.5 °C of warming. By how much would emissions have to be cut?
If we apply the MAGICC/SCENGEN climate simulator developed at the National Center for Atmospheric Research, and used by both IPCC and the EPA, and assume an 80 percent reduction in GHG emissions by the OECD90 (North America, Western Europe, Australia, New Zealand, and Japan), the warming averted by 2100 would be about 0.3 °C. If Asia also reduces emissions by 80 percent, that would increase the averted warming by about another 1.1 °C , for a total close to the goal envisioned in the carbon budget relative to RCP8.5. Can anyone possibly believe that emission reductions of 80 percent are anything other than a fantasy?
Sachs’s not-so-subtle shift of emphasis from the pipeline itself to the “carbon budget” belies his denial that he and his allies simply oppose fossil fuels. Given his reliance on the worst-case RCP8.5 scenario, it is axiomatic that the use of fossil fuels must be reduced dramatically in order to adhere to the “carbon budget.” At the end of his response, Sachs asserts the existence of a “globally agreed objective of avoiding dangerous anthropogenic interference with the climate system.” Really? Unless this is just a tautology driven by the term “dangerous,” the agreed objective to which Sachs refers is entirely obscure. We have just observed the end of the 19th(!) Conference of the Parties in Warsaw, at which the only “agreement” was on the restaurants to be patronized at the 20th and 21st COPs in Lima and Paris. Professor Sachs would be well advised to adhere to scholarly standards of skepticism and a close alliance with evidence rather than ideology.
Benjamin Zycher is a resident scholar at the American Enterprise Institute.
Image by Dianna Ingram / Bergman Group
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