My colleague Jim Pethokoukis deserves applause for his recent argument that the effects of increasing greenhouse gas (GHG) concentrations are uncertain, notwithstanding the loud assertions of many, and that incremental policy interventions are vastly to be preferred to “abrupt and expensive changes in public policy.” Incrementalism in this context reasonably can be interpreted (or defined) as adaptation over time as the body of evidence on climate change becomes clearer, about which more below.
So far, so good. But Jim then argues that “uncertainty about the degree of damage . . . argues for reasonable, precautionary action.” That sentence contains three fundamental problems.
Jim Pethokoukis’ take: Climate change, risk, and conservatives
First, it accepts the assumption that increasing GHG concentrations will engender “damage,” and the only issue to be determined is the attendant magnitude over time. Sorry, but that is not what the integrated assessment models of climate change and economic growth tell us. Instead — even apart from the poor predictive record of the climate models — the near-term effects appear to be positive, particularly in terms of “greening,” agricultural productivity, and the like, while the longer-term effects, which are far more speculative, may be negative or strongly negative. Or perhaps not negative at all: No one knows.
The climate industry simply assumes, based again on the climate models, that the longer-term effects are strongly negative. And that is why economic analysis of the “social cost” of GHG emissions (“carbon”), or SCC, is so highly sensitive to the choice of the discount rate. Notice that the Obama administration in its analysis of the SCC refused to use a 7 percent discount rate despite the requirement in OMB Circular A-4 that federal benefit-cost analyses do so. From the perspective of the federal climate bureaucracy — very much an interest group and decidedly not a group of truth seekers devoid of an agenda of its own — the 7 percent discount rate is inadmissible because under that parameter the SCC falls to zero or even becomes negative, that is, GHG emissions ought to be subsidized.
The climate industry argues that the refusal to use the 7 percent discount rate is not driven by its ideological pursuit of a SCC larger rather than smaller; it is instead a moral choice in favor of the interests of future generations. Sorry: that argument is deeply dubious. Future generations prefer to inherit a capital stock more rather than less valuable, and the capital stock comprises a myriad of dimensions among which environmental quality is only one important component. (Would future generations prefer to give up some environmental quality in return for a sufficiently large increase in some other component of the capital stock? The obvious answer is “yes.”) Accordingly, satisfaction of the preference of the future generation for a bequest of a capital stock larger rather than smaller requires efficient resource allocation by the current generation, that is, the use of a discount rate that reflects the long-run opportunity cost of capital rather than one artificially low.
Credit: Twenty20
Second, Jim does not delve into the fundamental benefit-cost question: Whether the chosen policies are abrupt or incremental, what benefits would they yield in terms of future temperatures and attendant climate effects? The climate industry desperately prefers to avoid that question for the obvious reason that the effects of any set of policies politically plausible would range from small to effectively zero; that is, such policies impose substantial costs but offer no benefits.
If we apply the Environmental Protection Agency’s own climate model, the entire Obama climate action plan would reduce global temperatures in the year 2100 by 0.015 of a degree Celsius, under a set of assumptions that exaggerate the effect of reducing GHG emissions. (The standard deviation of the surface temperature record is a bit more than 0.1 degree.) If we assume that the pseudo-agreement with China is meaningful (it is not), we get another 0.01 degree. If we assume that every promise made in the Paris COP-21 agreement is fulfilled by 2030 and then maintained fully until the end of the century, the temperature effect would be 0.17 of a degree by 2100.
But why stop there? Let us exercise our imaginations: In addition to the Obama climate action plan and the additional US emissions cut agreed with China, assume a Chinese cut of 20 percent, a 30 percent cut by the rest of the industrialized world, and a 20 percent cut by the rest of the developing world, all by 2030. The temperature effect by 2100: a bit more than half a degree. How much is that worth?
I shunt aside here the obvious truth that such policies, whatever benefits they might yield, would hardly be costless, with all of the rent-seeking, redistribution incentives, and other massive perversities characteristic of both democracies and autocracies.
Third, let us turn instead to the “damage” argument, that is, the assertion in so many pronouncements on climate policy that the evidence of the negative effects of increasing GHG concentrations is clear.
Really? It certainly is true that anthropogenic climate change is “real” in the sense that increasing atmospheric concentrations of GHG are having a detectable effect, important evidence of which is declining temperatures in the lower stratosphere.
But the surface and lower-atmosphere temperature records are not consistent with a looming crisis view: Surface temperatures have been roughly flat since 1998 (or perhaps since the early 2000s, as 1998 was a strong El Niño year). The satellite record is very similar. More generally, the record of temperature anomalies since the late 19th century does not correlate well with increasing GHG concentrations; how, for example, do the proponents of GHG reductions propose to explain the warming from 1910 through roughly 1940?
Moreover, almost all of the climate models have overestimated the recent temperature record. Global temperatures appear to be on a long-term upward trajectory, but the degree to which that trend is anthropogenic is far from clear, as the earth since roughly 1850 has continued to emerge from the Little Ice Age. The degree to which warming over, say, 1977–98 was anthropogenic — the “climate sensitivity” of the atmosphere — is unsettled in the scientific literature; and the Intergovernmental Panel on Climate Change (IPCC) in its fifth assessment report (AR5) has reduced its estimated range of the effect in 2100 of a doubling of GHG concentrations from 2.0–4.5 to 1.5–4.5 degrees C.
More to the point, there is little evidence of severe or even “strong” climate effects attendant upon increasing GHG concentrations. Increases in sea levels have been roughly constant at about 3.3 mm per year since the early 1990s, despite increasing GHG concentrations. There appears to be a close correlation between sea levels and the El Niño/Southern Oscillation. The data presented in the IPCC AR5 for the 20th century are not consistent with the crisis view, and increases in sea levels appear to have been more or less constant for the last 8,000 years. For the more recent decades: as we do not know the extent to which rising temperatures are anthropogenic, the same follows for temperature effects on sea levels, as the latter can be due to ice melt and thermal expansion not anthropogenic in origin.
The data on the Arctic and Antarctic sea ice extents are mixed. Relative to the 1981–2010 average, the Arctic sea ice in recent years crudely is below or at the bottom of the 95 percent confidence interval surrounding that mean, although the newest data show that the 2017 Arctic sea ice is at the same level as in 2006. For the Antarctic, recent years are above or at the top of the confidence interval. There is some evidence that the eastern Antarctic ice sheet (about two-thirds of the continent) is gaining mass, while the western ice sheet and the peninsula are losing mass, with a net gain for the continent as a whole. There does not appear to be an accepted explanation for this phenomenon in the peer-reviewed literature.
There has been no trend in total US tornado activity since 1954, and a declining trend in strong-to-violent tornadoes. There has been no trend in the frequency of tropical cyclones since the early 1970s, no trend in the frequency of global hurricanes, and no trend in tropical accumulated cyclone energy (crudely, the destructiveness of cyclones and the cyclone season), but an increase in accumulated cyclone energy in 2016 to the level observed in 2006. The annual number of US wildfires shows no trend since 1985. The Palmer Drought Severity Index shows no trend since 1895. There is no correlation between US flooding and increasing GHG concentrations.
IPCC in the AR5 is deeply dubious (Table 12.4) about the various severe effects often hypothesized (or asserted) as future impacts of increasing GHG concentrations. Table 1 summarizes the AR5 analysis.
| Table 1 |
| IPCC AR5 on Proposed Abrupt/Irreversible Earth System Changes |
| ________________________________________________________________________ |
| Climate System Component Projected Likelihood 21st Century Confidence Level |
| ________________________________________________________________________ |
| Collapse of Atlantic Meridional Overturning Circulation very unlikely high confidence |
| Ice sheet collapse exceptionally unlikely high confidence |
| Permafrost carbon release possible low confidence |
| Clathrate methane release very unlikely high confidence |
| Tropical forests dieback not estimated low confidence |
| Boreal forests dieback not estimated low confidence |
| Disappearance of summer |
| Arctic sea ice under RCP8.5 likely medium confidence |
| Long-term droughts not estimated low confidence |
| Monsoonal circulation [collapse] not estimated low confidence |
| ________________________________________________________________________ |
| Note: The representative concentration pathways — alternative scenarios of increases in atmospheric concentrations of GHG over time — are described here. A simplified discussion can be found here. For the AR5 analysis of the disappearance of the summer Arctic sea ice, RCP8.5 is the most extreme of the four RCPs used in the AR5, useful for sensitivity analysis but far less so for purposes of policy formulation. Under RCP8.5, GHG concentrations are assumed to grow to about 1,370 ppm by 2100, from about 404 ppm in 2016, or an average annual increase of about 11.5 ppm. Since 1959 the single largest annual increase in GHG concentrations was about 3 ppm, in 2015. Accordingly, under RCP8.5 the average annual increase is almost four times larger than the single largest increase observed since 1959. |
| Source: Intergovernmental Panel on Climate Change, “Working Group I Contribution to the IPCC Fifth Assessment Report Climate Change 2013: The Physical Science Basis,” Final Draft Underlying Scientific-Technical Assessment, September 30, 2013, p. 12-78, Table 12.4. |
| ________________________________________________________________________ |
In short, IPCC views only the disappearance of the summer Arctic sea ice as “likely,” with “medium confidence,” and only under the most extreme assumption about future GHG concentrations.
Again, Jim Pethokoukis deserves real applause for his resistance to the “crisis” justifications for large and costly shifts in US and global energy policies, and for his willingness to recognize the important role of scientific uncertainty. But he concedes too much, perhaps without realizing it, a sin with respect to which he is not alone in the climate policy congregation.
Benjamin Zycher is the John G. Searle scholar at the American Enterprise Institute.