Oren Cass, a Senior Fellow at the Manhattan Institute, is one of the most informative analysts in the climate change policy debate. I love Cass’s work because he methodically investigates the various research studies being cited in a dispute in order to clearly explain to his readers where the headline results are coming from.

An excellent case in point is Cass’s May 16 testimony before the House Committee on Science, Space, and Technology in a hearing on climate change. Cass showed why some of the alarming warnings of impending climate catastrophe grossly understate the ability of humans to adapt, meaning that policymakers and the public should realize that the situation is not as dire as they have been led to believe. Cass achieves this result not through ideological assertions but merely by unpacking exactly how some of these leading studies derived their estimates of climate change damage. Once you understand where the numbers come from, you agree with Cass that these particular studies really don’t tell us very much.

Because Cass’s full testimony contains so much valuable information, I will spend three blog posts covering some of its best material.

Cass Isn’t Questioning the Science

Before diving into his critique of some recent estimates of impending climate change damage, Cass offered the following caveat to the House Committee:

Let me pause here to clarify that this issue does not concern climate science. I believe that mainstream climate science, particularly as summarized by the UN’s Intergovernmental Panel on Climate Change, provides the best available assessment of the changes to our physical environment that a given level of greenhouse-gas emissions will cause and that policymakers should use it as the starting point for their own work. But we depart the world of climate science for that of climate economics when we turn to the question of how those changes will affect human society via their influence on public health or infrastructure or the economy. [Bold added.]

This is a point worth emphasizing. These days on the internet, you can’t question the case for climate alarmism more than two minutes before someone says, “Give me a break, the science is settled; there’s a 97 percent consensus among experts in the field that humans are responsible for climate change. More CO2 causes the earth to get warmer. This is basic chemistry. Deal with it.”

Now for one thing, even that “97 percent consensus” figure is dubious, as David Friedman and others have pointed out, because it classifies authors using a very broad umbrella, such that “skeptics” like Pat Michaels and Richard Lindzen would fall under “the consensus.”

But that’s not the main point here. What Oren Cass is pointing out is that the physical science relationship between human-caused greenhouse gas emissions and the global climate is only the first link in the argument. In order to make the case for political intervention, it must also be demonstrated that (a) these physical relationships will harm human welfare and (b) these harms can be mitigated by government policy, using cures that are better than the disease.

These latter points are not the areas directly studied by climate science per se, but instead fall under the jurisdiction of economists. Of course, the economic considerations must be informed by the climate science, but the disciplines are not identical. It is entirely possible that a study warning of large climate change damages is based on very accurate physical science, but suffers from a basic methodological flaw that an outside analyst such as Oren Cass can illuminate.

Cass’s Testimony in a Nutshell: We Can’t Ignore Adaptation

To anticipate the theme of his testimony, Cass sums up like so:

The assumptions that we make about how human society will adapt to climate change are central to our understanding of the challenges that the phenomenon presents and the costs that it will impose. Relative to most problems that we encounter in public policy, climate change is a gradual process; its most dangerous effects will appear on decades- and even centuries long timescales. Yet analysts frequently analyze these effects as if they will happen now, without accounting for how our economy, society, and technology are likely to evolve independent of climate change and—especially—in response to climate change. Analyses that do not properly account for adaptation describe an alternative universe that does not exist; the estimates they produce are not plausible forecasts of future costs and should not be credited by policymakers. [Bold added.]

Some readers may feel inadequate to critically assess something as “official” as a formal study of the effects of climate change through the end of the century. And yet, just wait until you see the problems Cass exposes. It doesn’t take an expert to realize that these particular studies are heavily biased on the side of alarmism, because they grossly understate the ability of humans to adapt to a changing climate.

Will Ozone and Particulate Matter Cause Nearly a Trillion Dollars in Deaths Annually by 2100?

For the final component of this introductory post, let me summarize Cass’s critique of the way EPA used a 2015 study[i] to conclude that increased temperatures (from global warming) will cause higher mortality rates through the mechanism of increased concentrations of ground ozone (aka “smog”) and particulate matter (PM) (released into the atmosphere because of the hotter climate). Relative to a scenario with aggressive climate change mitigation policies, EPA estimated that business-as-usual would cause an excess 57,000 deaths annually by the year 2100, which carries a yearly cost of $930 billion. This is a staggering number, and to reiterate, this figure derives merely from the extra deaths ostensibly caused by warmer temperatures leading to increased conventional air pollution.

Yet Cass puts this result in context when he explains:

The paper estimated that unchecked climate change would increase ozone levels by 2.6 parts per billion and particulate-matter levels by 1.2 µg m−3, over the alternative scenario. But those concentrations have fallen since 2000, from 82 and 13.4, respectively. In 2009 alone, particulate matter fell by an amount almost equal to the increase that climate change would cause over the century. In most of the years from 2000 to 2015, ozone levels fluctuated by more than the climate-induced effect over a century. Put another way, the forecasted effect of climate change on air pollution is to return atmospheric quality from 2015 to 2011 levels. [Bold added.]

Cass illustrates this result with the following diagram:


Now to be sure, Cass’s Figure 2 doesn’t definitively rule out the possibility that increased smog and PM concentrations will have detrimental effects. But Cass’s point is that the model implicitly ignores the underlying processes that were leading these pollutants to rapidly fall, even over a relatively short 15-year period from 2000 – 2015. As with most arenas, what will probably happen is that progress will continue on these fronts as well, because the studies narrowly focusing on the factors that increase smog and PM are ignoring the factors that will decrease them.


In this opening blog post, I have laid out the framework of Oren Cass’s recent congressional testimony on adaptation and the costs of climate change. Cass is not challenging the actual science, but instead is showing how dubious are the projections that extrapolate from objective data into speculative warnings about the distant future.

For example, Cass showed that a recent EPA estimate of the costs of climate change via traditional air pollution was likely grossly overblown, because it ignored the stellar improvements in just 15 years. And this is no small item: The EPA’s estimate of excess mortality from smog and particulate matter (PM) worked out to a whopping $930 billion by 2100, out of total reported climate change damages of $1,391 billion. In other words, for those readers who understood the problems depicted in Figure 2, you must now consider that that calculation comprised about two-thirds of the EPA’s total estimate impact of unchecked climate change damage.

To challenge the alarmist case for aggressive government action in the name of climate change isn’t to deny science. As the work of Oren Cass demonstrates, one can often raise serious objections to “official” projections merely by reading the reports and seeing where their numbers come from.

Oren Cass’s testimony before the House Committee on Science, Space, and Technology can be viewed here:

[i] The study is Fernando Garcia-Menendez et al., “U.S. Air Quality and Health Benefits from Avoided Climate Change Under Greenhouse Gas Mitigation,” Environmental Science & Technology 49 (June 2015).

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