EXCERPT: 'SuperFreakonomics,' by Steven Levitt and Stephen Dubner

Oct. 20, 2009— -- Economist Steven Levitt and journalist Stephen Dubner are at it again in the "freakquel" to their best-selling book, "Freakonomics." The duo managed to spin dense, dry data into best-selling cocktail party fodder by using crack dealers, sumo wrestlers and baby names to explain what people want and how things work under the law of unintended consequences.

"SuperFreakonomics: Global Cooling, Patriotic Prostitutes, and Why Suicide Bombers Should Buy Life Insurance" follows suit, exploring questions like: what does a street prostitute and a department store Santa Claus have in common? What's the best way to catch a terrorist? Can eating kangaroo meat save the planet?

Read an excerpt of the book below.

These days there is essentially a consensus among climate scientists that the earth's temperature has been rising over the long term and, increasingly, agreement that human activity has played an important role. "[W]e are now so abusing the Earth," writes James Lovelock, the renowned environmental scientist, "that it may rise and move back to the hot state it was in fifty-five million years ago, and if it does most of us, and our descendants, will die."

But the ways humans affect the climate aren't always as obvious as they seem. It is generally believed, for instance, that cars and trucks and airplanes contribute an ungodly share of green house gases. This has recently led many right-minded people to buy a Prius or other hybrid car. But every time a Prius owner drives to the grocery store, she may be canceling out its emission- reducing benefit, at least if she shops in the meat section.

How so? Because cows -- as well as sheep and other cud- chewing animals called ruminants -- are wicked polluters. Their exhalation and flatulence and belching and manure emit methane, which by one common measure is about twenty- five times more potent as a green house gas than the carbon dioxide released by cars (and, by the way, humans). The world's ruminants are responsible for about 50 percent more greenhouse gases than the entire transportation sector.

Even the "locavore" movement, which encourages people to eat locally grown food, doesn't help in this regard. A recent study by two Carnegie Mellon researchers, Christopher Weber and H. Scott Matthews, found that buying locally produced food actually increases greenhouse-gas emissions. Why?

More than 80 percent of the emissions associated with food are in the production phase, and big farms are far more efficient than small farms. Transportation represents only 11 percent of food emissions, with delivery from producer to retailer representing only 4 percent. The best way to help, Weber and Matthews suggest, is to subtly change your diet. "Shifting less than one day per week's worth of calories from red meat and dairy products to chicken, fish, eggs, or a vegetable- based diet achieves more greenhouse- gas reduction than buying all locally sourced food," they write.