Climate change is indeed a danger in the US
By: Marshall Burke
US EPA recently invited public comment on it’s proposal to rescind the 2009 Endangerment Finding (henceforth, EF). The EF concluded at the time that greenhouse gases, through their effect on the climate, endanger human health and welfare in the US, and thus concluded that GHGs can and should be regulated under the Clean Air Act. The EF subsequently served as an important legal underpinning of subsequent administrations’ (specifically, the Obama and Biden administrations) efforts to regulate emissions of GHGs from a range of sources.
Trump EPA’s proposed rollback of the EF is part of a broader strategy to undermine the federal goverment’s ability to make any progress in addressing climate change. Sol Hsiang and I wrote an initial op-ed describing the overwhelming strength of the scientific evidence on the dangers posed by GHGs and their effect on the climate. We, along with Jen Burney, Chris Callahan, Lisa Rennels, and Andrew Wilson, also wrote a public comment on the proposed rollback, alongside 351,346 others (!!). Either EPA got a lot of great international submissions, or about 0.1% of the US submitted a comment — or maybe even more than 0.1%, given that most folks teamed up. It’s not clear whether EPA plans to actually read these comments, even though they are basically required to do so, but content in the comments will help litigators who take the proposed rulemaking up in court.
I wanted to summarize our main arguments, and then provide some of my own reflections (not speaking for my colleagues). Our comment focuses on three central arguments in the Proposal: (1) that GHGs should not be regulated under the Clean Air Act (CAA) because unlike some other air pollutants, the impacts of GHGs on health are not “direct” and the causal chain linking GHGs to human damages is too long and uncertain; (2) that the relative contribution of U.S. vehicle emissions to global climate change is too small to warrant attention; and (3) that since the original Endangerment Finding, scientific evidence on the dangers of GHGs to human health and related outcomes has become more rather than less uncertain. We argue in our comment that each of these arguments is either internally inconsistent, inconsistent with the scientific literature, or both.
A broader recurring error in the Proposal — and one I want to reflect on a bit — is the implicit argument made in the Proposal that if the effects of a warming climate are not clearly detectable for all relevant outcomes, at all scales, and in all places—for example, if warming is implicated in some climate extremes but not others, or in worsening some health outcomes but not others—then this calls into question the prior finding of endangerment, as well as the broader enterprise of understanding the impacts of a changing climate. If climate science cannot state confidently that the number of landfalling hurricanes will increase under a changing climate or that the decline in cold-related deaths from warming will be outweighed by increasing heat deaths — both cases where the science on US specific impacts is indeed uncertain — then we can’t say anything reliable about impacts.
This argument is, of course, incorrect: Endangerment does not require that a warming climate negatively affects everything, but instead that on balance its effects on public health and welfare are negative and substantial. And the evidence here is very clear. For some key outcomes (e.g. temperature-related mortality), it’s probably the case that the net effect of warming will be close to zero. For most other outcomes that have been studied, including temperature-related morbidity, wildfire smoke related mortality and morbidity, ozone-related mortality and morbidity, and a range of other health-related impacts due to changes in dust, fungi, infectious disease, a warming climate is expected to worsen impacts. We have no health outcomes for which, on net, we expect benefits from warming in the US.
A broader challenge with this argument, though, is that it elicits what in my opinion is an unfortunate response on the part of the scientific community. If it’s the case that null effects or uncertainty for one impact can call into question the reliability of knowledge on all other impacts, then the implication is that we can’t be uncertain about any impact: we have to argue that everything gets worse. But this is not the case: not everything gets worse, and some things get way worse than others. Not being able to say this out loud distorts our own understanding of impacts, and makes it difficult to prioritize adaptation efforts.
This was brought home to me in repeated discussions with colleagues (many of whom were writing their own comments) around temperature-related mortality. Even folks who work on very closely related issues or impacts are surprised to learn, and often very hesitant to believe, that the “direct” effect of warming temperatures on mortality in the US will likely be a wash, at least this century. The best available evidence suggests that declines in cold-related deaths will perhaps slightly outweigh increases in heat-related deaths across the US as a whole, but with confidence intervals on these estimates that contain zero. Again, the conclusion is not that climate change doesn’t matter for health, but instead that it might not matter (on net) in this one specific way. And that there are a dozen other ways in which it does matter.
Part of the goal at Trump’s EPA appears to be to waste the time of the scientific community. A special committee of contrarians were assembled at DOE to produce a report on the “scientific” underpinnings of the proposed EF rollback, and in response there was a huge and quickly organized scientific effort to point out errors, resulting in a 400+ page rebuttal by something like 85 scientists. Similarly for the proposed EF rollback: many very smart people spent many weeks assembling comments, and now it looks like the EPA might not even read them. But I worry that the style of argument in these documents and proposals from EPA — where if one piece of evidence is in question, then everything is in question — also makes it harder for scientists to be clear about what we know and what we don’t know. In effect, this undermines science itself.
What if instead we were just really clear about the impacts where we are uncertain, or where it looks like impacts will be small or even positive? Hypothesis: saying these things plainly, which we often do not do, will make it more clear that our claims about “the balance of evidence” are actually a balanced view of the evidence. They will also help us focus more clearly on impacts where evidence is really clear that we have a lot to worry about.