The Climate Left Attacks Nobel Laureate William D. Nordhaus

By Benjamin Zycher July 2020

Key Points

• William D. Nordhaus, having received the 2018 Nobel Prize in economics largely in recognition of his integrated assessment model of the science and economics of climate policies, now is under attack from the environmental left, almost certainly because that model does not support the policy preferences of the climate alarmists. • The alarmists’ assertions about prospective climate phenomena are driven by climate models that have predicted the past and present poorly, under a set of assumptions that are deeply dubious. Those assertions are inconsistent with the evidence, and the alarmists’ policy prescriptions have been based in part on the application of low (or zero) discount rates, on the grounds that such discount rates are appropriate as a tool with which to incorporate the interests of future generations. That premise is incorrect. • The proponents of the climate “crisis” attack on fossil fuels are driven by an imperative almost entirely ideological. That rather than any reliance on “science” explains why a dedicated scholar like Nordhaus finds himself under attack.

Having received the 2018 Nobel Prize in economics fronts.3 The same is true for Nordhaus’ policy argu- largely in recognition of his economic analysis of ment in favor of a carbon tax or other such pricing climate policy—in particular the development and policies, a policy prescription much more question- application of the Dynamic Integrated Climate- able than often asserted.4 But Nordhaus’ absolute Economy (DICE) model—William D. Nordhaus honesty and rigorous approach to economic analysis now is under attack from the environmental left.1 are beyond reproach, which is one general reason This emerging criticism of Nordhaus’ analytic that he now is under attack even though he favors framework is curious at a minimum. After all, is it such policies as the Paris agreement to reduce not more study and analysis—more “science”— greenhouse gas (GHG) emissions, with tariffs to be that the proponents of the “crisis” view of climate imposed on nations not participating.5 policy seek? The short answer to that question: decid- For reasons summarized below, Nordhaus’ argu- edly not.2 Nordhaus’ work is careful and detailed. ment for an international “climate club” enforcing Like any serious body of analysis, it raises more the Paris agreement is unlikely to prove workable.6 questions than it answers—there is good reason, But that is not the central issue here. Instead, for example, to question several of the underlying Nordhaus—by no stretch of the imagination a climate assumptions—and DICE can be criticized on several policy skeptic—is under attack more centrally

AMERICAN ENTERPRISE INSTITUTE 1 because DICE has not provided answers consistent 2 degree C limit is going to be achieved without any with the ideological demands of the climate alarmists, climate policies at all.11 Thus has the climate left and Nordhaus has refused to bend to the political moved the policy goalposts, a dynamic that has winds. In the DICE model under a wide range of received vastly less critical attention than it deserves.12 reasonable assumptions, and even under many not The proponents of the “crisis” justifications for plausible, climate policy cannot satisfy a benefit/cost climate policies usually fail to distinguish among test, and the same is true for the other two major the implications of the four central representative integrated assessment models.7 concentration pathway (RCP) scenarios of atmos- Accordingly, DICE provides no support for the pheric concentrations of GHGs, using only the most ideological attack on fossil fuels, on the freedom extreme (RCP8.5) of them.13 Rockstrom’s warning that they facilitate, or for such “net-zero” policies about 3 degrees C of warming may be the modeling as the Green New Deal.8 Notwithstanding the con- result under RCP6; that 3 degrees C is the average tinued references to “science,” it is the bottom line prediction for 2100 from the 102 CMIP5 climate in terms of climate ideology that motivates the envi- models tracked by the Lawrence Livermore National ronmental left. In that fundamental political context, Laboratory, under that scenario.14 But these models DICE is worse than useless, which means that as a crude generalization have overpredicted Nordhaus stands in the way regardless of his policy warming since 1975 (roughly the beginning of the arguments. satellite record) by a factor of about two.15 That the models predict the actual temperature The Politicized Criticisms of Nordhaus record and other climate phenomena poorly raises serious questions about the usefulness of their Should you consider that judgment too harsh, consider projections of future climate trends. Pat Michaels some recent criticism of Nordhaus and his work and Chip Knappenberger note that issued by the climate left, a concise summary of which is provided in the statement that “leading during all periods from 10 years (2006– 2015) to 65 (1951–2015) years in length, the scientists and economists, however, say there is observed temperature trend lies in the another impediment to climate action that merits lower half of the collection of climate closer scrutiny: the profoundly influential work of model simulations, and for several periods 9 2018 Nobel economics laureate William J. Nordhaus.” it lies very close (or even below) the (His middle initial actually is “D.” One would think 2.5th percentile of all the model runs. Over that the authors and editors at phys.org—supporters shorter periods, such as the last two decades, of “science” one and all—might at a minimum a plethora of mechanisms have been put bother to achieve accuracy with names and middle forth to explain the observed/modeled diver- initials. One would be wrong.) Some of those obser- gence, but none do so completely and many vations from the “leading scientists and economists”— of the explanations are inconsistent with 16 that is, those who agree with the climate alarmists’ each other. ideological demands—are as follows. Nordhaus’ work is a benefit/cost test—that is, Johan Rockstrom of the Postdam Institute argues an integration of climate science and economics. that the DICE benefit/cost policy failure “is simply not Rockstrom’s apparent argument is that only the aligned with climate science. It is an unequivocal views of the scientists in agreement with him matter, finding in the natural sciences that a 3C warming is a stance not to be taken seriously. Moreover, scientists 10 a disastrous outcome for humanity.” have no more claim to deference to their views of Whence the warning about 3 degrees C? The the relevant policy trade-offs than does anyone else. standard argument from the international advocates It is one thing to argue that the views of scientists— of climate policy for years was a need to limit anthro- which ones?—on science itself should be given pogenic warming to 2 degrees C by 2100, officially some degree of deference by nonspecialists. It is reduced by the Intergovernmental Panel on Climate quite another to argue that scientists’ views on policy Change (IPCC) in 2018 to 1.5 degrees C, for the obvi- questions should be given disproportionate ous reason that given ongoing and likely trends, the weight. Scientists have no greater, or lesser, claim

AMERICAN ENTERPRISE INSTITUTE 2 than anyone else to expertise on policy questions, surprisingly small and cannot be statistically sig- with all the subjective trade-offs and value judgments nificant given the vagaries of economic forecasting that policy choices entail. and the number of years remaining before the end Notwithstanding Rockstrom’s assertion about of this century. (I exclude here Nordhaus’ “Stern “an unequivocal finding in the natural sciences,” discounting” policy scenario, as it assumes a discount there is no “consensus” among scientists about the rate effectively equal to zero, an analytic error addressed effects of increasing atmospheric concentrations below.21) Per capita consumption varies by about of GHG, whether at the 97 percent level commonly 1.3 percent, also a small number and almost certain asserted or any other number. Moreover, consensus not to be statistically significant.22 is irrelevant, in that scientific “truth” is not majori- The virtual independence of such economic aggre- tarian; science is a process of testing hypotheses gates and alternative climate policies is related to against evidence, whether derived from experimen- the reality that plausible policies can have only tation or empirical observations.17 trivial effects on climate phenomena, also a topic Joseph Stiglitz, professor at Columbia University discussed below. That is one central reason that and Nobel economics laureate for 2001, argues: climate policies cannot satisfy a benefit/cost test. DICE “is so badly flawed that it shouldn’t be taken The social cost of carbon (SCC) estimates in DICE seriously.” And DICE is “dangerous because we (and the other integrated assessment models)—in don’t have another planet we can go to if we mess a nutshell, a quantification of the marginal harm this up. The message [that Nordhaus has] been caused by GHG emissions—are highly sensitive to conveying is foolhardy.”18 the choice among discount rates; the higher the The “another planet” nostrum suggests that Stiglitz discount rate, the more heavily the future is dis- is oblivious to the scientific debate over anthropogenic counted relative to the present. In DICE, a shift climate change and that he views the prospective from a 3 percent discount rate to 7 percent reduces costs of climate policy as irrelevant to the policy the SCC calculation by about 80 percent, as shown question. Can he possibly believe that? Does he in Table 1.23 believe that only the most extreme of the climate As an aside, there are substantial benefits from model predictions should be included in an analytic modest anthropogenic warming, one of which is exercise? Notwithstanding Stiglitz’s “another planet” the “greening” or carbon dioxide fertilization effect.24 rhetoric, IPCC itself in the Fifth Assessment Report Neither DICE nor the other integrated assessment was deeply dubious about the various severe effects models incorporate that parameter in their respective often asserted to be looming as impacts of anthro- calculations of the SCC. pogenic warming.19 We return below to Stiglitz’s Because the choice among alternative discount rates apparent happiness to make empirical assertions in the economic analysis of climate policy affects unsupported by actual evidence. the attendant policy implications hugely, the advo- Gernot Wagner of New York University argues: cates of the “crisis” view have formulated arguments “If [Nordhaus] had won the Nobel Prize 20 years to the effect that low or zero discount rates are ago, it would have helped climate policy. But the appropriate for the evaluation of the benefits and fact that he won it two years ago is, in many ways, costs of climate policies. In other contexts, blatant a step back.”20 Translation: The timing with which inconsistency has been employed as a tool with Nordhaus received the economics Nobel Prize has which to achieve a preferred analytic outcome; not furthered our ideological policy goals, and those some such efforts would be amusing were they not rather than “science” are the paramount objective. so serious in their analytic effects.25 Consider for example the Obama administration regulatory im- Some Basic Analytics pact analysis of its Clean Power Plan.26 In Tables ES-9 and ES-10, we learn that the purported bene- Let us turn now to several related issues. Under fits of the rule were discounted at 3 percent, while DICE, global gross domestic product (GDP) in 2100 the costs were discounted at 5 percent. Is such in- varies by about 3 percent across policy scenarios, consistency supposed to be persuasive? including no climate policies at all, a figure that is

AMERICAN ENTERPRISE INSTITUTE 3 Table 1. DICE Average Baseline SCC, End Year 2300 (2019 Dollars) Year ———————————Discount Rate——————————— 2.5% 3% 5% 7% 2010 56.55 36.47 10.70 4.88 2020 69.12 45.88 14.69 7.13 2030 80.77 54.81 18.61 9.35 2040 93.43 64.69 23.09 11.96 2050 106.47 74.94 28.00 14.87 Source: Author’s computations.

The Interests of Future Generations choose to live on a pristine desert island; most people prefer closer proximity to family, employment, The advocates of low or zero discount rates in the entertainment, and all the other myriad beneficial context of climate policy argue that such a meth- dimensions of living in a world with environmental odological approach is needed to give sufficient quality less than pristine. weight to the interests of future generations, the In other words, the central interest of future members of which cannot vote currently. That is a generations is a bequest from previous generations fallacy: An artificially low discount rate applied to of the most valuable possible capital stock, of which current policy choices does not serve the interests environmental quality is one important dimension 27 of future generations. among many. There always are unavoidable trade-offs In a new book, Bjørn Lomborg notes that the among them. Satisfaction of that bequest preference IPCC itself estimates that global GDP adjusted for on the part of future generations requires efficient inflation if unconstrained by climate policies—that resource allocation by the current generation. If is, powered by fossil fuels—would be $509 trillion regulatory and other policies implemented by the higher annually by 2100 than global GDP would be current generation yield less wealth currently and under a “green” scenario. Per capita real GDP a smaller total capital stock for future generations— 28 would be $69,000 higher. defined broadly to include environmental values— The reason for that analytic prediction is then some additional emissions of pollutants and GHG straightforward: A green scenario means an artificial by the current generation would be preferred (efficient) constraint on the use of fossil fuels—that is, a policy- from the viewpoint of those future generations. driven reduction in the availability of energy resources, a condition that must reduce output. As noted below, the green scenario—the imposition of climate policies— The Mixed Evidence on Anthropogenic would yield environmental (climate) effects virtually Climate Change equal to zero, which means that any environmental The growing criticism now being directed toward improvement cannot offset the straightforward Nordhaus is driven by a quasi-religious view that a economic costs of the climate policies. climate “crisis” now is upon us. Back to Stiglitz: Another way to see this is to consider a baby born “Extreme events like hurricanes, fires, droughts in a cave some tens of thousands of years ago, in a that have been so clear in recent years . . . all of world with environmental quality virtually unaffected those things are really not adequately accounted by mankind. That child at birth would have had a for in [Nordaus’] analysis.” Stiglitz should explain life expectancy of about 10 years; had it been able the precise ways that DICE fails “adequately” to to choose, it willingly would have given up some account for the social cost of GHG emissions (or environmental quality in exchange for a longer life rising concentrations). One would think that a Nobel expectancy engendered by better housing, food, laureate in economics would pause to look at the water, medical care, and safety, ad infinitum. The actual evidence before making an empirical assertion. general proposition is straightforward: People will- In Stiglitz’s case, one would be wrong. ingly give up some environmental quality in exchange So let us do that work for him. That anthropogenic for lives longer, wealthier, and healthier. Few would climate change is “real”—that increasing GHG

AMERICAN ENTERPRISE INSTITUTE 4 concentrations are having detectable effects—is about the various severe effects often asserted to incontrovertible, but that does not tell us the mag- be looming as impacts of anthropogenic warming.44 nitude of the observable impacts, which must be measured empirically. Temperatures are rising, The Climate Effects of Climate Policies but as the Little Ice Age ended around 1850, it is not easy to separate natural from anthropogenic The proponents of various climate policies almost effects on temperatures and other climate phe- never specify the future effects of their proposals nomena.29 The latest research in the peer-reviewed in terms of temperatures and such other important literature suggests that mankind is responsible for climate phenomena as sea levels. The implicit asser- about half a degree of the global temperature increase tion is that the given policies upon implementation of about 1.5 degrees C since 1850.30 will yield significant beneficial effects. The reality There is little trend in the number of “hot” days is that even policies aggressive in terms of reducing for 1895–2017; 11 of the 12 years with the highest GHG emissions would have effects effectively number of such days occurred before 1960.31 The equal to zero by the end of the century, using the National Oceanic and Atmospheric Administration US Environmental Protection Agency climate model has maintained since 2005 the US Climate Reference under highly favorable assumptions, in particular an Network, comprising 114 meticulously maintained equilibrium climate sensitivity of 4.5 degrees C.45 temperature stations spaced more or less uniformly Full implementation of the Obama administration across the lower 48 states, 21 stations in Alaska, climate action plan would have reduced temperatures and two stations in Hawaii.32 They are placed to in 2100 by 0.015 degrees C.46 The most prominent avoid heat island effects and other such distortions recent proposals for a US carbon tax are those pro- as much as possible; the reported data show no moted by the Alliance for Market Solutions and the trend over the available 2005–20 reporting period.33 Climate Leadership Council; the temperature A reconstruction of global temperatures over the reduction in 2100 yielded by each proposal would past one million years, using data from ice sheet be 0.015 degrees C.47 The entire Paris agreement, if formations, shows that there is nothing unusual implemented immediately and enforced strictly: about the current warm period.34 0.17 degrees C.48 The contemporaneous agreement Global mean sea level has been increasing for between the Obama administration and China, if one thousands of years at about 3.3 mm per year; it may were to take the agreement seriously: an additional or may not be accelerating, and any such acceleration 0.01 degrees C.49 The electricity component of the might be the result of anthropogenic or natural causes.35 Green New Deal: 0.17 degrees C.50 A net reduction The Northern and Southern Hemisphere sea ice to zero of GHG emissions by the entire Organisation changes tell different stories.36 US tornado activity for Economic Co-operation and Development: shows either no trend or a downward trend since 0.35 degrees C.51 1954.37 Tropical storms, hurricanes, and accumulated Assume a truly serious international effect to cyclone energy show little trend since satellite reduce GHG emissions: a 20 percent reduction by measurements began in the early 1970s.38 The China, a 30 percent reduction by the rest of the number of US wildfires shows no trend since 1985, industrialized world, and 20 percent by the rest of and global acreage burned has declined over past the developing world, all in addition to the US reduc- decades.39 The Palmer Drought Severity index tions as envisioned in the Obama climate action shows no trend since 1895.40 US flooding over the plan, and all by 2030. The temperature effect by past century is uncorrelated with increasing GHG 2100: a bit more than 0.5 degrees C.52 Can anyone concentrations.41 The available data do not support argue that policies yielding such reductions in the ubiquitous assertions about the dire impacts of emissions—or ones even greater—are even remotely declining pH levels in the oceans.42 Global food plausible as a political matter? availability and production have increased more or Accordingly, Nordhaus’ support for a carbon tax less monotonically over the past two decades on a is difficult to understand, particularly given the per capita basis.43 As noted above, the IPCC itself benefit/cost implications of DICE. His “climate club” in the Fifth Assessment Report was deeply dubious proposal for tariffs as a tool to induce international

AMERICAN ENTERPRISE INSTITUTE 5 cooperation (or to reduce incentives for free riding) Terrorist use of bioweaponry. Nuclear war. Gamma is unworkable, even apart from the trivial climate ray storms. Massive crop failures. Does Nordhaus impacts of the policies enforced by the “club.”53 It or his critics among the climate alarmists believe is not clear how Nordhaus’ “climate club” tariff that we should spend 2 percent or more of annual would be implemented in the case of nations without GDP as insurance against each?57 For Nordhaus, it carbon pricing systems but with regulations, subsidies seems likely that he does not; perhaps he would argue for such alternative energy sources as wind and solar that it is increasing atmospheric concentrations of power, or other policies that are purported to reduce GHG about which we can do something. That GHG emissions.54 Such adjustments for nontax stance, if indeed it is his view, is deeply problematic, policies would be enormously complex, requiring again because of the trivial effects of plausible climate an estimate of the tax-equivalent value of the given policies. For the climate alarmists, it would seem policies under examination. Does Nordhaus believe that they also do not, for a different reason: It is that the bureaucracies producing these estimates the potential climate problem alone within that will be unpressured to adjust them in various direc- list, the “solutions” to which would further the ide- tions depending on which interests are being affected? ological opposition to fossil fuels and increasing The larger problem is that of the international supply human flourishing. chain phenomenon: Goods imported from a given The environmental left displays no reluctance nation are likely to embody components and other to increase economic and physical suffering among inputs from other nations—perhaps many other ordinary people to further its goals. Witness the nations—in vastly differing proportions, and those happiness about the reduced emissions of GHG nations’ policies on GHG emissions almost certainly and conventional pollutants attendant upon the will vary considerably. The “climate club” tariff calcula- sharp decline in economic activity worldwide tion would have to estimate transfer prices—always caused by the COVID-19 pandemic.58 Instead of a a subjective and problematic calculation—and the central hope that the economic suffering will end, effects of shifting exchange rates, changing input we have instead the central left-wing fear that an proportions, and a host of other complexities to arrive economic revival will increase emissions.59 This at a tariff to be imposed on imports from a given celebration of suffering exposes the fundamental economy. And even that is an abstraction that shunts antihuman core of the climate movement, which aside various political pressures that inexorably views ordinary people—climate kulaks, as it were— will be felt and incorporated. as only mouths to feed wreaking environmental This means that a new bureaucracy, or perhaps destruction, rather than as individuals with moral an expanded one at the IRS, will have a vast value and as the ultimate resource yielding ingenuity amount of work to do, with important implications and inventiveness driving a dynamic process of for the allocation of resources. This is only one reason finding solutions to problems.60 among several that the purported “efficiency” of a These issues and questions are among the compo- carbon tax is illusory.55 nents of a debate for another day. The central point Perhaps Nordhaus has an “insurance” argument here is that the attacks on Nordhaus reveal little in mind: Given the uncertainties, we should implement about him but provide powerful evidence that the a carbon tax as a hedge against the possibility that proponents of the climate “crisis” attack on fossil serious climate impacts will emerge. But that fuels are driven by an imperative almost entirely framework fails analytically, again because of the ideological rather than by the “scientific” framework trivial effects of plausible climate policies, a reality that they claim in support of their policy preferences. independent of the underlying scientific questions.56 That a brilliant, honest, and dedicated scholar like Nordhaus finds himself in the environmentalist Conclusions crosshairs makes it clear that only a willingness to toe the party line can provide immunity from attack It is not difficult to list several low-probability catas- for those of us unlikely to win a Nobel Prize or any trophes. Asteroid impacts. Mass volcanic eruptions. other. Powerful earthquakes. Tsunamis. Mass contagion.

AMERICAN ENTERPRISE INSTITUTE 6 About the Author

Benjamin Zycher is a resident scholar at the American Enterprise Institute. Notes

1. For the announcement of the 2018 Nobel Memorial Prize in Economic Sciences, see Nobel Prize, “The Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel 2018,” https://www.nobelprize.org/prizes/economic-sciences/2018/summary/. For materials on the Dynamic Integrated Climate-Economy (DICE) model, see William Nordhaus, “Scientific and Economic Background on DICE Models,” February 3, 2020, https://sites.google.com/site/williamdnordhaus/dice-rice. See also William Nordhaus, “Home Page of William D. Nordhaus,” http://www.econ.yale.edu/~nordhaus/homepage/homepage.htm. 2. See Benjamin Zycher, “Earth Day 2020: The Exhaustion of the Climate Left,” RealClearMarkets, April 22, 2020, https://www.realclearmarkets.com/articles/2020/04/22/earth_day_2020_the_exhaustion_of_the_climate_left_489297.html. 3. See Benjamin Zycher, “The Social Cost of Carbon, Greenhouse Gas Policies, and Politicized Benefit/Cost Analysis,” Texas A&M Law Review 6 (2018): 59–76, https://www.aei.org/wp-content/uploads/2019/01/SCC-TAMU-LR-Final-fall-2018.pdf; Kevin D. Dayaratna, Ross McKitrick, and David Kreutzer, “Empirically Constrained Climate Sensitivity and the Social Cost of Carbon,” Climate Change Economics 8, no. 2 (2017), https://www.worldscientific.com/doi/abs/10.1142/S2010007817500063; and Kevin D. Dayaratna and David Kreutzer, “Loaded DICE: An EPA Model Not Ready for the Big Game,” Heritage Foundation, November 21, 2013, https://www.heritage.org/environment/report/loaded-dice-epa-model-not-ready-the-big-game. 4. See Benjamin Zycher, “The Deeply Flawed Conservative Case for a Carbon Tax,” American Enterprise Institute, March 7, 2017, https://www.aei.org/research-products/report/the-deeply-flawed-conservative-case-for-a-carbon-taxconservatives-endorse-the- broken-windows-fallacy-reject-evidence-and-rigor/; and Benjamin Zycher, “Observations on the Alliance for Market Solutions’ ‘Conservative’ Case for a Carbon Tax,” American Enterprise Institute, May 28, 2019, https://www.aei.org/research-products/report/ observations-on-the-alliance-for-market-solutions-conservative-case-for-a-carbon-tax/. 5. See William Nordhaus, “The Climate Club: How to Fix a Failing Global Effort,” Foreign Affairs, May/June 2020, https://www.foreignaffairs.com/articles/united-states/2020-04-10/climate-club. 6. See Benjamin Zycher, “Trump Is Absolutely Correct to Withdraw from the Paris Climate Agreement,” InsideSources, November 12, 2019, https://www.insidesources.com/trump-is-absolutely-correct-to-withdraw-from-the-paris-climate-agreement/. 7. Details of the Climate Framework for Uncertainty, Negotiation, and Distribution (FUND) model can be found at Fund- Model.org, “FUND Model,” http://www.fund-model.org/. For details of the Policy Analysis of the Greenhouse Effect (PAGE) model, see Chris Hope, “The Marginal Impact of CO2 for PAGE2022: An Integrated Assessment Model Incorporating the IPCC’s Five Reasons for Concern,” Bridging Sciences & Policy 6, no. 1 (2006): 19–56, https://journals.sfu.ca/int_assess/index.php/iaj/article/view/ 227/190. 8. Indur Goklany, “Fossil Fuels, and Human and Environmental Well-Being,” International Conference on Climate Change, March 2017, https://www.researchgate.net/publication/324761275_Fossil_Fuels_and_Human_and_Environmental_Well-Being. See also Zycher, “Earth Day 2020”; Loren E. Lomasky, “Autonomy and Automobility,” Independent Review II, no. 1 (Summer 1997): 5–28, https://www.independent.org/pdf/tir/tir_02_1_lomasky.pdf; and Benjamin Zycher, The Green New Deal: Economics and Policy Analytics, American Enterprise Institute, April 2019, https://www.aei.org/spotlights/the-green-new-deal-economics-and-policy- analytics/. 9. See Marlowe Hood, “Climate Economics Nobel May Do More Harm Than Good,” phys.org, July 6, 2020, https://phys.org/news/2020-07-climate-economics-nobel-good.html. 10. Hood, “Climate Economics Nobel May Do More Harm Than Good.” 11. For a history of the long-asserted 2 degree C safety limit, see Carbon Brief Staff, “Two Degrees: The History of Climate Change’s Speed Limit,” carbonbrief.org, December 8, 2014, https://www.carbonbrief.org/two-degrees-the-history-of-climate- changes-speed-limit. The report from the Intergovernmental Panel on Climate Change (IPCC) justifying the highly publicized change to the asserted 1.5 degree C safety limit is Valerie Masson-Delmotte et al., “Global Warming of 1.5°C,” Intergovernmental Panel on Climate Change, 2019, https://www.ipcc.ch/site/assets/uploads/sites/2/2019/06/SR15_Full_Report_High_Res.pdf. For my critique of that IPCC report, see Benjamin Zycher, “Hearken Sinners: The End Is Near,” American Enterprise Institute, October 22, 2018, https://www.aei.org/articles/hearken-sinners-the-end-is-near/. 12. Benjamin Zycher, “The Climate Empire Strikes Out: The Perils of Policy Analysis in an Echo Chamber,” American Enterprise Institute, September 26, 2018, https://www.aei.org/research-products/report/the-climate-empire-strikes-out-the-perils-of-policy- analysis-in-an-echo-chamber/; and Benjamin Zycher, “Observations on Volume 2 of the Fourth National Climate Assessment,” American Enterprise Institute, November 29, 2018, https://www.aei.org/articles/observations-on-volume-2-of-the-fourth-national- climate-assessment/. See also Patrick J. Michaels, “Comments on the Fourth National Climate Assessment,” Cato Institute, 2018,

AMERICAN ENTERPRISE INSTITUTE 7 https://www.cato.org/sites/cato.org/files/pubs/pdf/pat-michaels-national-climate-assessment.pdf; and Marlo Lewis Jr., “National Climate Assessment Still Needs a Reset,” Competitive Enterprise Institute, November 30, 2018, https://cei.org/blog/national- climate-assessment-still-needs-reset. 13. For discussions of the representative concentration pathways (RCP), see Intergovernmental Panel on Climate Change, Data Distribution Centre, “Scenario Process for AR5,” https://sedac.ciesin.columbia.edu/ddc/ar5_scenario_process/RCPs.html; G. P. Wayne, “The Beginner’s Guide to Representative Concentration Pathways,” Skeptical Science, August 2013, https://skepticalscience.com/docs/RCP_Guide.pdf; Judith Curry, “Is RCP8.5 an Impossible Scenario?,” Climate Etc., November 24, 2018, https://judithcurry.com/2018/11/24/is-rcp8-5-an-impossible-scenario/; Kevin Murphy, “Reassessing the RCPs,” Climate Etc., January 28, 2019, https://judithcurry.com/2019/01/28/reassessing-the-rcps/; Keywan Riahi et al., “RCP8.5—A Scenario of Comparatively High Greenhouse Gas Emissions,” Climatic Change 109, no. 33 (August 13, 2011), https://link.springer.com/article/ 10.1007/s10584-011-0149-y; and Zeke Hausfather and Glen P. Peters, “Emissions—The ‘Business As Usual’ Story Is Misleading,” Nature 577 (January 30, 2020), https://media.nature.com/original/magazine-assets/d41586-020-00177-3/d41586-020-00177-3.pdf. 14. “CMIP5” stands for Coupled Model Intercomparison Project, Phase 5. For a discussion of the CMIP5 climate models, see Lawrence Livermore National Laboratory, Department of Energy, “Coupled Model Intercomparison Project 5 (CMIP5),” Earth System Grid Federation, https://esgf-node.llnl.gov/projects/cmip5/. 15. On the overprediction of temperatures by these models, see John R. Christy, testimony before the US House Committee on Science, Space, and Technology, US House of Representatives, March 29, 2017, https://science.house.gov/imo/media/doc/ Christy%20Testimony_1.pdf?1; and Ross McKitrick and John Christy, “A Test of the Tropical 200- to 300 hPa Warming Rate in Climate Models,” Earth and Space Sciences 5 (September 21, 2018): 529–36, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/ 2018EA000401. Note that the Christy analysis is for the tropical troposphere and the McKitrick and Christy analysis is for the tropical 300–200 mb layer, or roughly 30,000 to 40,000 feet. See also Roy W. Spencer, “Hot Summer Epic Fail: New Climate Models Exaggerate Midwest Warming by 6X,” drroyspencer.com, July 3, 2020, https://www.drroyspencer.com/2020/07/hot- summer-epic-fail-new-climate-models-exaggerate-midwest-warming-by-6x/. See also Ross McKitrick and John Christy, “Pervasive Warming Bias in CMIP6 Tropospheric Layers” (working paper, Earth and Space Science, Washington, DC, June 4, 2020). 16. Pat Michaels and Chip Knappenberger, “Climate Models Versus Climate Reality,” Climate Etc., December 17, 2015, https://judithcurry.com/2015/12/17/climate-models-versus-climate-reality/; and Pat Michaels and Chip Knappenberger, “Quantifying the Lack of Consistency Between Climate Model Projections and Observations of the Evolution of the Earth’s Average Surface Temperature Since the Mid-20th Century” (presentation, American Geophysical Union fall meeting, San Francisco, 2014), https://agu.confex.com/agu/fm14/meetingapp.cgi/Paper/20121. 17. For a discussion of the purported “97 percent” scientific consensus about anthropogenic climate change, see Frank Hobbs, “What Is There a 97% Consensus About?,” Climate Etc., December 20, 2015, https://judithcurry.com/2015/12/20/what-is-there-a-97- consensus-about/. See also Richard Tol, “Global Warming Consensus Claim Does Not Stand Up,” March 24, 2015, http://richardtol.blogspot.com/2015/03/now-almost-two-years-old-john-cooks-97.html. In the original paper by John Cook and colleagues, their claim was that 97 percent of the abstracts reviewed—not 97 percent of scientists—that took a position supported the anthropogenic climate hypothesis, a conclusion vastly less interesting than commonly asserted. See John Cook et al., “Quantifying the Consensus on Anthropogenic Global Warming in the Scientific Literature,” Environmental Research Letters 8, no. 2 (May 15, 2013), https://iopscience.iop.org/article/10.1088/1748-9326/8/2/024024/pdf. See also David R. Legates et al., “Climate Consensus and ‘Misinformation’: A Rejoinder to Agnotology, Scientific Consensus, and the Teaching and Learning of Climate Change,” Science & Education 24 (2015): 299–318, https://link.springer.com/article/10.1007/s11191-013-9647-9. On the analytically sound nature of Donald Trump’s views (or instincts) on climate policy, see Zycher, “Trump Is Absolutely Correct to Withdraw from the Paris Climate Agreement.” 18. Hood, “Climate Economics Nobel May Do More Harm Than Good.” 19. See Matthew Collins et al., “Long-Term Climate Change: Projections, Commitments and Irreversibility,” in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge, UK: Cambridge University Press, 2013), Table 12.4. 20. Hood, “Climate Economics Nobel May Do More Harm Than Good.” 21. See Nicholas Stern, The Economics of Climate Change: The Stern Review (Cambridge, UK: Cambridge University Press, January 2007), https://www.cambridge.org/us/academic/subjects/earth-and-environmental-science/climatology-and-climate-change/economics- climate-change-stern-review?format=PB. 22. See William Nordhaus and Paul Sztorc, “DICE 2013R: Introduction and User’s Manual,” Yale University, Department of Economics, October 2013, Figure 4 and Table 1, http://www.econ.yale.edu/~nordhaus/homepage/homepage/documents/ DICE_Manual_100413r1.pdf. 23. See Zycher, “The Social Cost of Carbon, Greenhouse Gas Policies, and Politicized Benefit/Cost Analysis.” 24. See Zaichun Zhu et al., “Greening of the Earth and Its Drivers,” Nature Climate Change 6 (April 25, 2016): 791–95, https://www.nature.com/articles/nclimate3004; Antonio Gasparrini et al., “Mortality Risk Attributable to High and Low Ambient

AMERICAN ENTERPRISE INSTITUTE 8 Temperature: A Multicountry Observational Study,” Lancet 386, no. 9991 (May 20, 2015): 369–75, https://www.thelancet.com/ journals/lancet/article/PIIS0140-6736(14)62114-0/fulltext; National Aeronautics and Space Administration, “Carbon Dioxide Fertilization Greening Earth, Study Finds,” April 26, 2016, https://www.nasa.gov/feature/goddard/2016/carbon-dioxide- fertilization-greening-earth; and Marlo Lewis Jr., “Climate Change, Fossil Fuels, and Human Well Being,” Competitive Enterprise Institute, July 11, 2018, https://cei.org/blog/climate-change-fossil-fuels-and-human-well-being. 25. See Zycher, “The Social Cost of Carbon, Greenhouse Gas Policies, and Politicized Benefit/Cost Analysis.” 26. See US Environmental Protection Agency, Regulatory Impact Analysis for the Clean Power Plan Final Rule, October 23, 2016, 75, https://www3.epa.gov/ttnecas1/docs/ria/utilities_ria_final-clean-power-plan-existing-units_2015-08.pdf. 27. See Zycher, The Green New Deal; and David Kreutzer, “Discounting Climate Costs,” Heritage Foundation, June 16, 2016, https://www.heritage.org/environment/report/discounting-climate-costs. 28. Bjørn Lomborg, False Alarm: How Climate Change Panic Costs Us Trillions, Hurts the Poor, and Fails to Fix the Planet (New York: Basic Books, 2020), 129–31. See also David Kreutzer, “Book Review: False Alarm by Bjorn Lomborg, Institute for Energy Research,” July 7, 2020, https://www.instituteforenergyresearch.org/climate-change/book-review-false-alarm-by-bjorn-lomborg/. 29. On the surface (land/ocean) temperature record, see UK Met Office, Hadley Centre/University of East Anglia Climatic Research Unit, “Tim Osborn: HadCRUT4 Global Temperature Graphs,” https://crudata.uea.ac.uk/~timo/diag/tempdiag.htm. On the Little Ice Age, see Michael E. Mann, “Little Ice Age,” in Encyclopedia of Global Environmental Change, Volume 1: The Earth System: Physical and Chemical Dimensions of Global Environmental Change, ed. Michael C. MacCracken, John S. Perry, and Ted Munn (Chichester, England: John Wiley & Sons, 2002), http://www.meteo.psu.edu/holocene/public_html/shared/articles/littleiceage.pdf. 30. See, for example, Ross McKitrick and John Christy, “A Test of the Tropical 200- to 300 hPa Warming Rate in Climate Models”; Nicholas Lewis and Judith Curry, “The Impact of Recent Forcing and Ocean Heat Uptake Data on Estimates of Climate Sensitivity,” Journal of Climate 31 (August 2018): 6051–71, https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-17-0667.1; and John R. Christy and Richard McNider, “Satellite Bulk Tropospheric Temperatures as a Metric for Climate Sensitivity,” Asia-Pacific Journal of Atmospheric Sciences 53 (2017): 511–18, https://link.springer.com/article/10.1007/s13143-017-0070-z. For a chart summarizing the recent empirical estimates of equilibrium climate sensitivity as reported in the peer-reviewed literature, see Patrick J. Michaels and Paul C. Knappenberger, “The Collection of Evidence for a Low Climate Sensitivity Continues to Grow,” Cato Institute, September 25, 2014, https://www.cato.org/blog/collection-evidence-low-climate-sensitivity-continues-grow. 31. For the reconstruction of the NASA data, see John R. Christy, “Average per Station (1114 USHCN Stations) 1895–2017: Number of Days Daily Maximum Temperature Above 100˚F and 105˚F,” drroyspencer.com, http://www.drroyspencer.com/wp- content/uploads/US-extreme-high-temperatures-1895-2017.jpg. 32. For the Climate Reference Network program description, see National Centers for Environmental Information, “U.S. Climate Reference Network,” https://www.ncdc.noaa.gov/crn/. 33. For a visualization of a prototypical station, see Willis Eschenbach, “NOAA’s USCRN Revisited—No Significant Warming in the USA in 12 Years,” Watts Up with That?, November 8, 2017, https://wattsupwiththat.com/2017/11/08/the-uscrn-revisited/. For the monthly data and charts reported by the National Oceanic and Atmospheric Administration (NOAA), see National Oceanic and Atmospheric Administration, “National Temperature Index,” https://www.ncdc.noaa.gov/temp-and-precip/national-temperature- index/time-series?datasets%5B%5D=uscrn¶meter=anom-tavg&time_scale=p12&begyear=2005&endyear=2020&month=8. 34. See R. Bintanja and R. S. W. van de Wal, “North American Ice-Sheet Dynamics and the Onset of 100,000-Year Glacial Cycles,” Nature 454, no. 7206 (August 14, 2008): 869–72, https://www.researchgate.net/publication/23171740_Bintanja_R_van_ de_Wal_R_S_W_North_American_ice-sheet_dynamics_and_the_onset_of_100000-year_glacial_cycles_Nature_454_869-872. NOAA published the underlying data at R. Bintanja and R. S. W. van de Wal, “Global 3Ma Temperature, Sea Level, and Ice Volume Reconstructions,” National Oceanic and Atmospheric Administration, August 14, 2008, https://www.ncdc.noaa.gov/paleo- search/study/11933. For a chart showing the temperature record over one million years, see Institute for Energy Research, “Temperature Fluctuations over the Past Million Years,” https://www.instituteforenergyresearch.org/wp-content/uploads/2020/ 03/temperature-flucturations.png. 35. See Judith Curry, “Sea Level and Climate Change,” Climate Forecast Applications Network, November 25, 2018, https://curryja.files.wordpress.com/2018/11/special-report-sea-level-rise3.pdf. Curry cites research from Xianyao Chen and colleagues, the central finding of which is that “global mean sea level rise increased from 2.2 ± 0.3 mm/year in 1993 to 3.3 ± 0.3 mm/year in 2014.” See Xianyao Chen et al., “The Increasing Rate of Global Mean Sea-Level Rise During 1993–2014,” Nature Climate Change 7 (June 26, 2017): 492–95, https://www.nature.com/articles/nclimate3325. Whether the trend from a 21-year period can yield important inferences is a topic not to be addressed here. For a different empirical conclusion from the tidal gauge record, see J. R. Houston and R. G. Green, “Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses,” Journal of Coastal Research 27, no. 3 (May 2011): 409–17, https://meridian.allenpress.com/jcr/article-abstract/27/3/409/28456/Sea- Level-Acceleration-Based-on-U-S-Tide-Gauges?redirectedFrom=fulltext. For an example of temporary rapid sea-level rise in the 18th century, see W. R. Gehrels et al., “A Preindustrial Sea-Level Rise Hotspot Along the Atlantic Coast of North America,” Geophysical Research Letters 47 (2020), https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL085814. For further

AMERICAN ENTERPRISE INSTITUTE 9 reported evidence of an acceleration, see Hans-Otto Pörtner et al., Special Report on the Ocean and Cryosphere in a Changing Climate, Intergovernmental Panel on Climate Change, 2019, https://www.ipcc.ch/srocc/. 36. See Patrick J. Michaels, “Spinning Global Sea Ice,” Cato Institute, February 12, 2015, https://www.cato.org/blog/spinning- global-sea-ice. 37. For the historical data reported by the NOAA, see National Ocean and Atmospheric Administration, “Historical Records and Trends,” https://www.ncdc.noaa.gov/climate-information/extreme-events/us-tornado-climatology/trends. 38. For data on global tropical cyclone activity, see Ryan N. Maue, “Global Tropical Cyclone Activity, climatlas.com, July 15, 2020, http://climatlas.com/tropical/. 39. For US wildfire data reported, see National Interagency Fire Center, “Total Wildland Fires and Acres (1926–2019),” https://www.nifc.gov/fireInfo/fireInfo_stats_totalFires.html. On the decline in global area burned over past decades, see Stefan H. Doerr and Cristina Santin, “Global Trends in Wildfire and Its Impacts: Perceptions Versus Realities in a Changing World,” Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 371, no. 1696 (2016), https://www.ncbi.nlm.nih.gov/ pmc/articles/PMC4874420/pdf/rstb20150345.pdf. 40. See US Environmental Protection Agency, “Climate Change Indicators: Drought,” https://www.epa.gov/climate- indicators/climate-change-indicators-drought; and US Department of Commerce, National Climatic Data Center, “Divisional Data Select,” https://www7.ncdc.noaa.gov/CDO/CDODivisionalSelect.jsp. 41. See R. M. Hirsch and K. R. Ryberg, “Has the Magnitude of Floods Across the USA Changed with Global CO2 Levels?,” Hydrological Sciences Journal 57, no. 1 (2012): 1–9, https://www.tandfonline.com/doi/full/10.1080/02626667.2011. 621895?scroll=top&needAccess=true&. 42. See CO2 Science, “Ocean Acidification Database,” http://www.co2science.org/data/acidification/results.php. See also Alan Longhurst, Doubt and Certainty in Climate Science, 214–25, https://curryja.files.wordpress.com/2015/09/longhurst-print.pdf. 43. See Food and Agriculture Organization of the United Nations, World Food and Agriculture Statistical Pocketbook 2018, 2018, Charts 28 and 46, http://www.fao.org/3/CA1796EN/ca1796en.pdf. See also Kevin D. Dayaratna, Ross McKitrick, and Patrick J. Michaels, “Climate Sensitivity, Agricultural Productivity and the Social Cost of Carbon in FUND,” Environmental Economics and Policy Studies 22 (2020): 433–48. 44. Julie M. Arblaster et al., “Long-Term Climate Change: Projections, Commitments and Irreversibility—Final Draft Underlying Scientific-Technical Assessment,” in Working Group I Contribution to the IPCC Fifth Assessment Report (AR5), Climate Change 2013: The Physical Science Basis, September 23–26, 2013, 12–78, http://www.climatechange2013.org/images/uploads/WGIAR5_WGI- 12Doc2b_FinalDraft_Chapter12.pdf. 45. On the near-zero effects of any plausible climate policy, see Zycher, “The Climate Empire Strikes Out.” On the US Environmental Protection Agency (EPA) climate model, see Magicc, “The Climate System in a Nutshell,” http://www.magicc.org/. On the 4.5 degree C upper bound of the IPCC estimated range for equilibrium climate sensitivity, see Lisa V. Alexander et al., “Summary for Policymakers,” in Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, ed. T. F. Stocker et al. (Cambridge, UK: Cambridge University Press, 2013), 16 and Table SPM.2, http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf. 46. White House, Executive Office of the President, “The President’s Climate Action Plan,” June 2013, https://obamawhitehouse.archives.gov/sites/default/files/image/president27sclimateactionplan.pdf. For the temperature effect of the Obama climate action plan, see Dan Utech, “Three Years of Action Under the Climate Action Plan,” White House, June 28, 2016, https://obamawhitehouse.archives.gov/blog/2016/06/28/third-anniversary-climate-action-plan; and author’s computations using the EPA climate model. 47. See, respectively, Zycher, “Observations on the Alliance for Market Solutions’ ‘Conservative’ Case for a Carbon Tax”; and Zycher, “The Deeply Flawed Conservative Case for a Carbon Tax.” 48. See Benjamin Zycher, “The Absurdity That Is the Paris Climate Agreement,” American Enterprise Institute, May 25, 2017, https://www.aei.org/articles/the-absurdity-that-is-the-paris-climate-agreement/. 49. See Benjamin Zycher, “Observations on the US-China Climate Announcement,” Hill, November 14, 2014, https://thehill.com/blogs/pundits-blog/energy-environment/224076-observations-on-the-us-china-climate-announcement; and Benjamin Zycher, “The US-China Climate Agreement Hangover,” Hill, December 8, 2014, https://thehill.com/blogs/pundits- blog/energy-environment/226272-the-us-china-climate-agreement-hangover. 50. See Zycher, The Green New Deal. 51. Author’s computations using the EPA climate model. 52. Author’s computations using the EPA climate model. 53. See William Nordhaus, “Climate Clubs: Overcoming Free-Riding in International Climate Policy,” American Economic Review 105, no. 4 (2015): 1339–70, https://pubs.aeaweb.org/doi/pdfplus/10.1257/aer.15000001.

AMERICAN ENTERPRISE INSTITUTE 10 54. Nordhaus suggests that “countries might agree that each country will implement policies that produce a minimum domestic carbon price of $25 per ton of carbon dioxide (CO2). Countries could meet the international target price requirement using whatever mechanism they choose—carbon tax, cap-and-trade, or a hybrid.” See Nordhaus, “Climate Clubs.” How would policies not imposing an explicit “price” be treated? It is far from clear that wind and solar power systems actually reduce emissions of greenhouse gas or conventional pollutants, as the unreliability of such alternative power requires using backup generation units that must be cycled up and down depending on wind and sunlight conditions. Accordingly, the backup units must be operated inefficiently. See, for example, Bentek Energy, “How Less Became More: Wind, Power, and Unintended Consequences in the Colorado Energy Market,” April 2010, https://docs.wind-watch.org/BENTEK-How-Less-Became-More.pdf. See also Zycher, The Green New Deal. 55. Zycher, “The Deeply Flawed Conservative Case for a Carbon Tax”; and Zycher, “Observations on the Alliance for Market Solutions’ ‘Conservative’ Case for a Carbon Tax.” 56. See Benjamin Zycher, “Has Irwin Stelzer Asked the Right Question on Climate Change?,” American Enterprise Institute, October 1, 2019, https://www.aei.org/articles/has-irwin-stelzer-asked-the-right-question-on-climate-change/. 57. See Zycher, The Green New Deal, Table ES1. 58. See, for example, Tony Barboza, “Coronavirus Shutdowns Are Lowering Greenhouse Gas Emissions; History Shows They’ll Roar Back,” Los Angeles Times, March 19, 2020, https://www.latimes.com/environment/story/2020-03-19/coronavirus-shutdowns- are-lowering-greenhouse-emissions-history-shows-theyll-come-roaring-back. 59. See Steve Milloy, “Never Waste a Crisis: Climate Alarmism Surfs Coronavirus,” ClimateRealism, April 7, 2020, https://climaterealism.com/2020/04/never-waste-a-crisis/. 60. See Benjamin Zycher, “Earth Day and the Celebration of Suffering,” American Enterprise Institute, April 21, 2015, https://www.aei.org/articles/earth-day-and-the-celebration-of-suffering/; and Julian L. Simon, The Ultimate Resource 2 (Princeton, NJ: Princeton University Press, 1998).

The American Enterprise Institute (AEI) is a nonpartisan, nonprofit, 501(c)(3) educational organization and does not take institutional positions on any issues. The views expressed here are those of the author(s).

AMERICAN ENTERPRISE INSTITUTE 11