David Leonhardt considers the benefits and costs of oil spill prevention and climate change (Spillonomics):

... The people running BP did a dreadful job of estimating the true chances of events that seemed unlikely — and may even have been unlikely — but that would bring enormous costs.

... For all the criticism BP executives may deserve, they are far from the only people to struggle with such low-probability, high-cost events. Nearly everyone does. “These are precisely the kinds of events that are hard for us as humans to get our hands around and react to rationally,” Robert N. Stavins, an environmental economist at Harvard, says. We make two basic — and opposite — types of mistakes. When an event is difficult to imagine, we tend to underestimate its likelihood. This is the proverbial black swan. Most of the people running Deepwater Horizon probably never had a rig explode on them. So they assumed it would not happen, at least not to them.

... When the stakes are high enough, it falls to government to help its citizens avoid these entirely human errors. The market, left to its own devices, often cannot do so. Yet in the case of Deepwater Horizon, government policy actually went the other way. It encouraged BP to underestimate the odds of a catastrophe.

In a little-noticed provision in a 1990 law passed after the Exxon Valdez spill, Congress capped a spiller’s liability over and above cleanup costs at $75 million for a rig spill. Even if the economic damages — to tourism, fishing and the like — stretch into the billions, the responsible party is on the hook for only $75 million. (In this instance, BP has agreed to waive the cap for claims it deems legitimate.) Michael Greenstone, an M.I.T. economist who runs the Hamilton Project in Washington, says the law fundamentally distorts a company’s decision making. Without the cap, executives would have to weigh the possible revenue from a well against the cost of drilling there and the risk of damage. With the cap, they can largely ignore the potential damage beyond cleanup costs. So they end up drilling wells even in places where the damage can be horrific, like close to a shoreline. To put it another way, human frailty helped BP’s executives underestimate the chance of a low-probability, high-cost event. Federal law helped them underestimate the costs.

I should know this, but how did that $75 million cap come about? It seems like a silly thing to add in, even ex-ante.

Next, Leonhardt applies the risk perception logic to climate change:

Then, of course, there are the greenhouse gases that oil wells (among other things) send into the atmosphere even when the wells function properly. Scientists say the buildup of these gases is already likely to warm the planet by at least three degrees over the next century and cause droughts, storms and more ice-cap melting. The researchers’ estimates have risen recently, too, and it is also possible the planet could get around 12 degrees hotter. That kind of warming could flood major cities and cause parts of Antarctica to collapse.

Nothing like that has ever happened before. Even imagining it is difficult. It is much easier to hope that the odds of such an outcome are vanishingly small. In fact, it’s only natural to have this hope. But that doesn’t make it wise.

In other words, we shouldn't underestimate the likelihood that something awful might happen, and bias downwards the expected benefits of climate change mitigation policy, just because it has never happened before.

In other words, in other words, don't be Matt Lauer:

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