There’s a vigorous debate going on about how bad it would be if the Earth warms. You might not know it from the general tone of politics or the media. But to its credit, Australia’s ABC News reports that even some economists who believe in fairly significant man-made climate change actually think we could adapt to as much as 4°C of warming without much difficulty. One prominent economist compared the worst case of warming to the difference between adapting to life in Perth versus Melbourne. Others think even 2°C would be disastrous. Seems there’s still something to debate after all. If we’re allowed to.
ABC points to William Nordhaus, “a renowned American economist” and winner of the 2018 Nobel Prize in Economics. Nordhaus is what some call a climate worrier: He thinks human emissions of GHGs are having a harmful effect and he’s a leading proponent of internationally coordinated carbon tax. But he’s also, as befits an economist, one who talks and thinks about tradeoffs and marginal costs and benefits. Indeed, he says we should not act quickly to reduce emissions because the magic of compound interest means increasing wealth faster now will dramatically increase our ability to act decisively later. In fact he’s on record saying the “optimal” (economese for “best”) policy response would aim at limiting warming to around 3°C by 2100 and 4°C by 2150.
One might be permitted polite skepticism at our capacity so precisely to twirl the dial on the planetary thermostat. But Nordhaus is not some kooky Nobel-prize-winning outlier. ABC notes that Richard Tol, an economics professor at the University of Sussex and a lead author with the IPCC for over a quarter of a century, holds the same view.
On the other hand, ABC quotes Australian economist Steve Keen, who blogged that “I am personally not coping well with climate change”, who feels the “same generalised anxiety about the future felt by Greta Thunberg and the young people she's inspired” and says Nordhaus and others dramatically underestimate the severity of the impact of climate change.
Of course his technical expertise as an economist is in what to do about changes in climate not in how severe the effects of a temperature increase are likely to be. But as ABC notes, Tol was one of the authors of Chapter 10 in its 2014 Assessment Report, whose look at the economic impacts of climate change suggested a 2°C increase might cost between 0.2 and 2.0 per cent of global income (meaning any policy to prevent such an increase that costs more is a bad idea) unless of course it was more. That is, if there were some “tipping point” where the damage suddenly accelerated. Nobody knows. Decide your preference and pick your model.
As ABC added antiseptically, “a summary chapter of that report used far stronger language”. Indeed. Because the summaries are written by activists expressly to scare politicians and voters by exaggerating the warnings of scientists and economists. A habit to which Professor Tol objected at the time, calling parts of the summary “too alarmist”. To drive it home, Tol said if the Earth warms by 6°C not 4 it’s no big deal, that “6°C is the difference between Melbourne and Perth”. Only if you live there are you likely to know which is warmer. But both are plainly habitable.
Turns out Perth is the hotter one. As Tol adds, “If it were to warm by 6°C degrees in a century — it will not — you have about 100 years to upgrade Melbourne's air-conditioning, drainage, etc, to Perth standards. That costs money, but it won't ruin the economy.” Whereas Keen says humans never lived on a planet with an average temperature 6°C higher than we see today (which is true, though our primate ancestors flourished on one) and denies that technology can advance fast enough to save us. He adds colourfully that Nordhaus calls a simple, low carbon tax “a Magnum 44 for shooting climate change” while “In reality, climate change is armed with a howitzer”. And Keen is far from alone in critiquing Nordhaus’s methodology, if others lack his flair for the dramatic phrase.
There’s a great deal more that one could debate including the inability of the models to predict the past because of their overreliance on CO2 as the driver of temperature. Or the vexed question of the unpredictability of “tipping points” in direction as well as magnitude and timing. But here’s something one cannot debate: There is a debate.
Even among those who accept the broad outlines of the alarmist position, there is a great deal of debate over what’s happening, what it means and what to do. Nothing is “settled”.