Insure against risk of climate catastrophe

Go Set a Watchman isn’t the only book this year that brings new perspective to an old story line. Climate Shock: The Economic Consequences of a Hotter Planet should shift our narrative on climate change.

The old story line: People need to worry about climate change because doubling the atmosphere’s concentration of carbon dioxide relative to its preindustrial level would probably raise global average temperatures by 2.7 to 8 degrees Fahrenheit.

The new story line: We should worry because of the risk that the changes will be catastrophic.

Acting now is thus urgent not because of the expected outcome, but because of the risks associated with the worst possible outcomes, as authors Gernot Wagner of the Environmental Defense Fund and Martin Weitzman ofHarvard Universitywell explain.

Let’s put some numbers to this argument. Preindustrial levels of carbon dioxide amounted to 280 parts per million. Today, we’re at 400 ppm, and the annual increase is 2 ppm. Without drastic action, we will reach 700 ppm by 2100, according to the International Energy Agency.

Wagner and Weitzman helpfully translate the scientific research on climate sensitivities into probabilities of very bad outcomes, and they conclude that at 700 ppm, there is an 11 percent chance of an increase in global temperature exceeding 11 degrees Fahrenheit.

What would happen with that kind of temperature increase? No one knows exactly, but Wagner and Weitzman properly view the outcome as “near-certain disaster.” “‘Catastrophic’ no longer seems to do it justice, they say.