Writing in National Affairs, Ben Zycher argues that Republicans need to stop ignoring climate science and instead become staunch advocates of “climate realism.” On that point, Mr. Zycher is correct. But the version of climate science that he offers is anything but realistic. Following Zycher would bring conservatives backward in their approach to climate.
Where, recently, policymakers on the right have begun to accept the reality of climate risk, Zycher would have them regress to fighting about the science. It is fair to note, as he does, that some commentators have made exaggerated claims about impending climate doom, but mainstream assessments are themselves dire enough to warrant action. The truth is: industrial emissions are causing harmful global warming, and rapid decarbonization of the economy is justified to avoid the risks imposed by continued climate change. Zycher wrongfully encourages his readers to dispute that view and the scientific understanding that leads to it.
For example, the conclusion that we should reduce emissions to reduce future risks depends on carbon being a driving force for climate change. That is what scientific evidence has shown for decades. Yet Zycher argues otherwise. He writes, “it is important to recognize that the assumption of many politicians, environmental groups, and no small number of scientist-activists — that humans are the single most significant cause of climate change — is simply unsupported by the available science.“ He’s wrong.
If anything, the available science linking warming to greenhouse gas emissions has grown stronger in recent years. The fresh-off-the-presses Sixth Assessment Report from the Intergovernmental Panel on Climate Change gives the best summary of the available science, reviewed and synthesized by working scientists. It offers the following statement: “The likely range of human-induced warming in global-mean surface temperature (GSAT) in 2010-2019 relative to 1850-1900 is 0.8°C–1.3°C, encompassing the observed warming of 0.9°C–1.2°C, while the change attributable to natural forcings is only −0.1°C–0.1°C.” That means that all of the temperature change measured over the past century and a half can be explained by human activity. The natural factors that could have driven changes over that time period are minimal compared to warming.
What might cause one to think the IPCC overstates the human contribution? Zycher lists a number of climate phenomena that contribute to variability in global temperatures, recounts the history of rising global temperatures since the 19th century, and cites warming in the early 20th century as an example that wasn’t driven exclusively by greenhouse gas increase. But variability in global temperature caused by phenomena in the ocean and atmosphere, such as the El Nino cycles in the Pacific Ocean or the Atlantic Multidecadal Oscillation does not explain long-term warming. Those shorter-frequency signals are properly seen as being superimposed on other longer-term trends of human and natural origins. The result is to produce decades in which warming goes faster and slower than the long-term average (the history the Zycher recounts). That combination also explains the rapid warming in the early 20th century, which scientists estimate was about half due to natural factors and half due to increased greenhouse gases, while longer-term warming falls to human influence.
Zycher says that other, yet unknown, natural factors might be to blame for warming. He cites climate scientist Roy Spencer, who says those factors are not studied enough to reveal their role. But neither Zycher nor Roy explain what gaps in understanding those factors need to explain or how such unknown sources of warming are stronger or more significant than the increase in greenhouse gases. We know those have been increasing for the past century and a half, so any alternative needs to both explain warming and discount human influence as it is currently understood. Scientists have looked, and they simply don’t see any evidence to pursue. Without evidence, critics like Spencer and Zycher are left with speculation and insinuation.
Science doesn’t say things with certainty. The many studies on which the latest IPCC report is based give ranges of possible outcomes, not point estimates. Theoretically, then, it is possible—although highly improbable—that trends in temperature, sea level, and the like are near the bottom of the ranges that the IPCC report gives, or even below their lower bound, as Zycher says (unconvincingly, in my view). But stepping back from science to public policy, why should that small chance determine the decisions we make? We are weighing the small chance that emissions are only partly making global warming worse against the much more likely chance that they are the dominant signal. This is risk management. And even if warming does turn out to be trending in the lower rather than the higher part of the likely range, reducing emissions on the margin will have benefits because of avoided warming.
The shakiness of Zycher’s scientific interpretation extends to his other claims.
On extreme heat, Zycher writes, “there is no observable upward trend in the number of “hot” days between 1895 and 2017; 11 of the 12 years with the highest number of such days occurred before 1960.” That might be true, for example in a limited geography or a certain dataset, but it is false for the world. The findings for extreme heat and its relationship to climate change are amongst the strongest climate scientists have found. Here the IPCC says, “It is virtually certain that hot extremes (including heatwaves) have become more frequent and more intense across most land regions since the 1950s.” Moreover, increases in extreme heat are one of a few extreme weather phenomena where climate change signals have been detected and formally attributed to increasing greenhouse gas concentrations at global scales.
Regarding sea level, Zycher offers a poor rebuttal of the evidence that the observed rise is human-caused and accelerating. He writes, “[i]t is of course possible there has been an acceleration in sea-level rise, but even still, it would not be clear whether such a development stemmed primarily from anthropogenic or natural causes; clearly, both processes are relevant.” The acceleration in sea level rise between the 20th and early 21st century has been observed in satellite data, tide gauge records, and in comparisons between the two. As the new IPCC report states, “GMSL [global mean sea level] is rising, and the rate of GMSL rise since the 20th century is faster than over any preceding century in at least the last three millennia.“ On attributing sea level rise, the scientists are more qualified, but still clear on human influence, saying “we conclude that the main driver of the observed GMSL rise since at least 1970 is very likely anthropogenic forcing.” Thus, it is clear that humanity’s contribution is making it worse.
On the decline in Arctic sea ice, Zycher writes “Since 1979, Arctic sea ice has declined relative to the 30-year average (again, the degree to which this is the result of anthropogenic factors is not known).” The IPCC report refutes the parenthetical, stating “we conclude that it is very likely that anthropogenic forcing mainly due to greenhouse gas increases was the main driver of Arctic sea ice loss since 1979.”
Zycher is correct that climate realism does not have to result in climate catastrophism. While there are substantial risks to warming—and damages already being felt—the world isn’t going to end in 10 years because people still drive cars powered by fossil fuels. Rather, a reasonable scientific interpretation tells us that a great deal of observed climate change is being driven by industrial emissions. There is emerging evidence that it is having the effects scientists warned about regarding sea level rise, extreme heat, and precipitation events (not to mention drought and the extent of wildfires in the Western United States). Those impacts will get more significant and more pervasive as time goes on. But critically, the expectation for just how significant and pervasive depends strongly on the quantity of greenhouse gases emitted for the rest of this century.
As climate models and the physical understanding that underlies them tell us, the human impact on climate will continue to grow, whether at a faster or a slower rate, until net emissions stop. Conservatives have a role to play in designing policies to deal with this. They can design all manner of platforms around the need to minimize the costs of climate regulations, the need to avoid the kind of special-interest distortions that introduce inefficiencies into efforts to promote green power, and the need to take adaptation and resilience seriously rather than focusing exclusively on mitigation. Conservatives can also help design smart interventions to reduce the costs of decarbonization, incentivize low-carbon development, and fix the regulations and standards that distort insurance and housing prices and place people in harm’s way. Already, some conservatives are embracing carbon pricing, which has great promise for improving the efficiency and effectiveness of efforts to reduce emissions. A carbon tax of $25 per ton would lead to substantial emissions reductions, and even a modest carbon tax of a few dollars would improve the cost-effectiveness of regulations and green incentives. Carbon revenue can be rebated or used to cut other taxes, as some Republican members of Congress have proposed in recent years.
Those kinds of initiatives do not require that conservatives adopt the most dire projections regarding greenhouse gas emissions and their effects. They are just the kinds of policies that would be justified even if warming were to proceed in the mid-to moderate part of the ranges that the IPCC projects. But arguing the science in the style of Mr. Zycher is wrong on the details and useless on the merits.