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Book Summary: Superfreakonomics Global Cooling, Patriotic Prostitutes and Why Suicide Bombers Should Buy Life Insurance

Authors: Steven Levitt and Stephen Dubner

Substory: Mount Pinatubo

One of the unlikeliest positive externalities on record came cloaked in a natural disaster.

In 1991, an eroded, wooded mountain on the Philippine island of Luzon began to rumble and spew sulfuric ash. It turned out that beloved old Mount Pinatubo was a dormant volcano. The nearby farmers and townspeople were reluctant to evacuate, but the geologists, seismologists, and volcanologists who rushed in ultimately persuaded most of them to leave.

Good thing, too: on June 15, Pinatubo erupted for nine furious hours. The explosions were so massive that the top of the mountain caved in on itself, forming what is known as a caldera, a huge bowl-shaped crater, its new peak 850 feet lower than the original mountaintop. Worse yet, the region was simultaneously being lashed by a typhoon. According to one account, the sky poured down “heavy rain and ash with pumice lumps the size of golf balls.” Around 250 people died, mainly from collapsed roofs, and more died in the following days from mudslides. Still, thanks to the scientists’ warnings, the death toll was relatively small.

Mount Pinatubo was the most powerful volcanic eruption in nearly one hundred years. Within two hours of the main blast, sulfuric ash had reached twenty-two miles into the sky. By the time it was done, Pinatubo had discharged more than 20 million tons of sulfur dioxide into the stratosphere. What effect did that have on the environment?

As it turned out, the stratospheric haze of sulfur dioxide acted like a layer of sunscreen, reducing the amount of solar radiation reaching the earth. For the next two years, as the haze was settling out, the earth cooled off by an average of nearly 1 degree Fahrenheit, or .5 degrees Celsius. A single volcanic eruption practically reversed, albeit temporarily, the cumulative global warming of the previous hundred years.

Pinatubo created some other positive externalities too. Forests around the world grew more vigorously because trees prefer their sunlight a bit diffused. And all that sulfur dioxide in the stratosphere created some of the prettiest sunsets that people had ever seen.

Of course it was the global cooling that got scientists’ attention. A paper in Science concluded that a Pinatubo-size eruption every few years would “offset much of the anthropogenic warming expected over the next century.”

Even James Lovelock conceded the point: “[W]e might be saved,” he wrote, “by an unexpected event such as a series of volcanic eruptions severe enough to block out sunlight and so cool the Earth. But only losers would bet their lives on such poor odds.”