Economists have quantified the economic risks of climate "tipping points." It's grim.

A trickle of transcripts!

First up, an administrative note: many, many people have requested written transcripts of the Volts podcasts. And I want to provide them. But it’s going to take a while.

I could produce the transcripts in a few hours if I were willing to simply send the sound files through a robot transcriber like Otter and accept the somewhat choppy results (which are generally around 85 percent accurate).

However, I’m way too anal retentive to do that. And Volts readers deserve better! I want to clean the transcripts up — remove all the “sort of’s” and “kind of’s,” delete aborted or repeated sentences, polish up the grammar — so that they are as pleasant to read as they are to hear. (I’m not that precious about preserving the exact original words; I’m more interested in clearly capturing meaning in readable form.)

That means closely copyediting these files, some of which are more than 10,000 words. So far, with a little help, I’ve gotten through … one. And it took about 10 people-hours of work. Sigh.

Here’s the full transcript of my podcast with Rep. Sean Casten on “Hot FERC Summer” (and here’s a PDF version). For those who’d like a more compact version, here’s a highlight reel running on Canary.

Hopefully these will get somewhat faster and easier going forward. I will let you know as they come out. Now, on to the main event.

Pulling tipping points into climate economics

Just about everyone familiar with climate change has heard about “tipping points.” Famed climate scientist Wallace Broecker first raised the possibility way back in 1987, and ever since then, they’ve loomed large in the climate discussion.

The idea behind tipping points is fairly simple and familiar: as heat accumulates in the atmosphere, Earth’s geophysical systems may not simply adjust in linear fashion, alongside the incrementally rising temperature; in some cases, they may “tip over” some unpredictable threshold and enter a fundamentally new state, sometimes called a “phase shift.” Think of ice that has slowly cracked suddenly shattering, or “the straw that broke the camel’s back.”

The commonly cited examples of potential tipping points are the Greenland and West Antarctic ice sheets. As warming has progressed, they have been shedding water and developing deep fissures. It is possible that at some (unpredictable) point, one or both will lose integrity and begin breaking apart altogether, irreversibly, raising global sea level dozens of feet in relatively short order.

Because the consequences of some oft-discussed tipping points are rather apocalyptic, they have been used and misused for a long time in climate communications. It has somewhat annoyed climate scientists, because not only are these tipping points not a sure thing, each one is, in its own right, relatively unlikely.

Civilization-ending changes are not likely, but they’re not zero probability either. Legendary Harvard economist Martin Weitzman called these low-probability, high-impact possibilities “tail risks” and was famous for warning that economists are not taking them into account — and are thus underestimating the need for rapid decarbonization.

In his book Climate Shock, co-authored with his protégé, New York University’s Gernot Wagner, he argued that the right way to think about climate mitigation is not through a cost-benefit lens, as though particular levels of spending avoid specific levels of damages, but instead as a kind of insurance. We purchase insurance to cover against tail risks all the time, not because we think they’re likely to happen, but because the consequences would be so dire if they did.

Weitzman has passed away, but Wagner and others have carried on this argument long enough that it has begun to break through in mainstream climate economics. However, it leaves a key question unanswered: yes, the risk of tipping points raises the value of mitigation, but how much? It has never been quantified.

Into that breach comes a new paper in the Proceedings of the National Academy of Sciences (PNAS), from Wagner and a group of colleagues: Simon Dietz and Thomas Stoerk of the Grantham Research Institute on Climate Change, and James Rising of the University of Delaware.

“Economic impacts of tipping points in the climate system” represents the first formal attempt to quantify the economic impacts of tipping point risks. The results are startling: the economic impact of carbon emissions is much higher than appreciated, as is the value of reducing emissions.

Not that we needed much more evidence, but this study makes it clear that there is virtually no way we could overdo it on decarbonization. As Wagner told me when I called him to discuss the results, “I don't see a downside to doing too much too quickly.”

The devilishly difficult task of quantifying risks

The PNAS authors adopt a common definition of tipping points: “subsystems of the Earth system that are at least subcontinental in scale and can be switched—under certain circumstances—into a qualitatively different state by small perturbations.”

They included the eight that have been studied by the IPCC:

Thawing of permafrost leading to carbon feedback resulting in additional carbon dioxide and methane emissions, which flow back into the carbon dioxide and methane cycles.

Dissociation of ocean methane hydrates resulting in additional methane emissions, which flow back into the methane cycle.

Arctic sea ice loss (also known as “the surface albedo feedback”) resulting in changes in radiative forcing, which directly affects warming.

Dieback of the Amazon rainforest releasing carbon dioxide, which flows back into the carbon dioxide cycle.

Disintegration of the Greenland Ice Sheet increasing sea-level rise.

Disintegration of the West Antarctic Ice Sheet increasing sea-level rise.

Slowdown of the Atlantic Meridional Overturning Circulation modulating the relationship between global mean surface temperature and national mean surface temperature.

Variability of the Indian summer monsoon directly affecting GDP per capita in India.

It’s important to note that these are not all possible tipping points, just the ones that have been studied, so the PNAS study’s results are, as the authors emphasize, a “probable underestimate, given the literature we synthesize has yet to cover some tipping points and misses possible impact channels and interactions even for those it does cover.”

In their survey of existing literature, the authors found 52 papers that quantified the economic impacts of one or more tipping points, but over half of those were based, not on geophysical data or analysis, but on highly stylized adjustments to model parameters. The authors put those aside. In the end, they focused on 21 papers that actually linked the geophysical mechanisms of tipping points to economic damages.

The whizbang procedural move of the paper is to pull these dif