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Science indicates that climate change is happening but says little about how well civilization will deal with it. In my recent article (“The Problem with Climate Catastrophizing,” March 21), I argue that those I term climate catastrophists—observers who regard climate change as an unprecedented, existential threat—badly underestimate humanity’s capacity to cope with change and thus overreact to the problem. Michael Mann’s response does not so much refute this argument as disregard it (“Climate Catastrophe Is a Choice,” April 21).
Mann begins by writing that "rather than assessing the legitimate range of views regarding climate change, Cass marshals a series of fallacies." But he points to no mischaracterizations of climate science in my essay. Instead, he extends a kind of scientific confidence to issues that lie outside of science’s domain. “It is true,” Mann writes, “that the projected effects of unmitigated warming might objectively be characterized as catastrophic.” But “true” and “objective” science describes effects in the physical world; a view of the human consequences of climate change and whether they constitute catastrophe requires economic and social assessments. More strikingly, Mann argues that I dismiss
“some scientists’ concerns about climate change as instances of ‘motivated reasoning.’ But science represents the opposite of that process: as the physicist and science communicator Neil deGrasse Tyson has put it, science is ‘true whether or not you believe in it.’”
Because “science” is true, this claim suggests, “scientists’ concerns” are beyond reproach. Yet scientists’ concerns about the societal consequences of climate change deserve no special deference. In many cases, after all, such concerns are neither based on the scientific method nor draw on unique expertise. In turn, far from being out of bounds, the unresolved question of climate change’s economic and social effects should be central to a reasoned policy debate.
The problem is less that Mann is unpersuasive in bridging the gap between scientific findings and the possibility of civilizational catastrophe and more that he doesn’t try to do so. Mann and I agree that climate change has real costs—but whereas I seek to explain why it is wrong to regard those costs as catastrophic, Mann simply restates the costs.
For instance, I argue that increased wealth and resilience will improve society’s ability to cope with natural disasters, reducing such disasters’ disruptive force faster than climate change can increase it. Mann does not directly respond to this claim, asserting instead that “a rapidly growing body of scientific literature show[s] clear connections between climate change and damaging extreme weather events.” Likewise, I argue that gains in agricultural productivity and water management will outpace the stresses that climate change might impose. Mann notes only that “[b]ecause climate change increases the stress on food, water, and habitable land, it is intensifying competition for those resources.” I also contextualize the economic impacts of unmitigated climate change with economists' models, which consistently project that increasing global prosperity will dwarf the costs created by the changing climate. Mann ignores this, too, instead highlighting a study finding that “climate change is already costing the economy more than one trillion dollars each year.”
In doing so, Mann makes three mistakes. First, he mischaracterizes the study, which attributes nearly half of those costs not to the changing climate but to the other effects of carbon-intensive activities, such as conventional air pollution. Second, he favors a single study over the weight of expert opinion. According to a report published by New York University’s Institute for Policy Integrity in 2015, only 41 percent of economists believe climate change is already damaging the global economy. (The trillion-dollar estimate is likewise unsupported by the range of models used in the Barack Obama administration's Social Cost of Carbon analysis.) But most important, Mann does not show what the cost he points to means. One trillion is a large number, but it represents less than one percent of global GDP, and, at its current rate of expansion, the global economy grows by that amount every few months.
Mann does make one attempt to show that the costs of climate change might overwhelm this progress, but it falls flat. “The fact that inaction on climate change costs far more than action does,” Mann writes, “betrays Cass’ claim that economic growth will more than compensate for the harms of environmental damage.” But even if Mann’s claim about the net benefits of action is correct, it bears no logical relationship to the question of whether economic growth will increase society’s wealth and resilience faster than climate change reduces it. Policies can have net benefits in a number of contexts; in none does that fact warrant concluding that the harm of inaction will overwhelm society and result in catastrophe. This is not a question of climate science, just common sense.