Superfreakonomics_ global cooling, patri - Steven D. Levitt [74]
The big fear was a collapse of the agricultural system. In Britain, cooling had already shortened the growing season by two weeks. “[T]he resulting famines could be catastrophic,” warned the Newsweek article. Some scientists proposed radical warming solutions such as “melting the arctic ice cap by covering it with black soot.”
These days, of course, the threat is the opposite. The earth is no longer thought to be too cool but rather too warm. And black soot, rather than saving us, is seen as a chief villain. We have cast endless streams of carbon emissions skyward, the residue of all the fossil fuels we burn to heat and cool and feed and transport and entertain ourselves.
By so doing, we have apparently turned our tender planet into a greenhouse, fashioning in the sky a chemical scrim that traps too much of the sun’s warmth and prevents it from escaping back into space. The “global cooling” phase notwithstanding, the average global ground temperature over the past hundred years has risen 1.3 degrees Fahrenheit (.7 degrees Celsius), and this warming has accelerated of late.
“[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.”
There is essentially a consensus among climate scientists that the earth’s temperature has been rising and, increasingly, agreement that human activity has played an important role. But the ways humans affect the climate aren’t always as obvious as they seem.
It is generally believed that cars and trucks and airplanes contribute an ungodly share of greenhouse 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 greenhouse 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 gas 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.
You could also switch from eating beef to eating kangaroo—because kangaroo farts, as fate would have it, don’t contain methane. But just imagine the marketing campaign that would be needed to get Americans to take up ’roo-burgers. And think how hard the cattle ranchers would lobby Washington to ban kangaroo meat. Fortunately, a team of Australian scientists is attacking this problem from the opposite direction, trying to replicate the digestive bacteria in kangaroos’ stomachs so it can be transplanted to cows.
For a variety of reasons, global warming is a uniquely thorny problem.
First, climate scientists can’t run experiments. In this regard, they are more like economists than physicists or biologists, their goal being to tease out relationships from existing data without the ability to,