This week, Al Gore makes his action-hero debut in the movie An Inconvenient Truth. For a moment, let's not call the subject of the film climate change, or even global warming. Let's call it the most extensive science experiment of all time. It's been going on since the start of the Industrial Revolution. The entire planet serves as the lab. And you and 6.5 billion other people are the citizen-scientists working on it—oh, and the guinea pigs, too.
So hey, take a moment to be amazed that you're part of something big! Now adjust your goggles and focus on the details.
Over the last century, the planet's average surface temperature has risen by about 1 degree Fahrenheit. That may not sound like much, but it makes plenty of experts nervous. The increase is due to an overabundance of carbon dioxide and other gases in the atmosphere, which trap too much of the sun's heat. These gases can come from natural sources, including volcanoes, decaying plants, and flatulent farm animals, but humans are a major culprit. That's because we "burn fossil fuels"—by driving, heating our homes, using computers, buying goods that have been manufactured and shipped, and doing many other routine things.
Detractors say the temperature increase and the changes attributed to it—the fact, for instance, that 19 of the 20 hottest years on record have occurred since 1980—are part of normal patterns. While most have abandoned the argument that climate change isn't happening at all, they still insist that scientists disagree about humanity's role. But scientists apparently don't disagree: A 2004 review of 928 papers published on the topic in peer-reviewed journals between 1993 and 2003 found no article arguing against the notion that we are contributing to this trend.
Even President Bush, slow to jump on any bandwagon that doesn't run on oil, has acknowledged the reality of climate change. (Pay no attention to that Sharpie-wielding flack behind the curtain.) Prominent coverage in Time, USA Today,and other publications has recently added a layer of mainstream legitimacy. The question now is not whether the climate is changing, but when and where and how—and what we should do about it.
The Intergovernmental Panel on Climate Change—created in 1988 by the United Nations and the World Meteorological Organization—has estimated that the Earth's average temperature will rise between 2.5 and 10.4 degrees by the year 2100. The oft-used phrase "global warming" suggests that the world will roast, but the changes in store are more complex. The added heat will throw the whole system out of whack. We're in for heat waves and droughts, yes, but also cold snaps, floods, severe storms, and the spread of infectious diseases. As Gore puts it, the whole scenario is like "what someone has called 'a nature hike through the Book of Revelation.' "
The panoply of possibilities, all those "coulds" and "mights," is another reason doubters like to doubt. But this unfolding story is not all hypothetical. It's happening now. In the far north, Inuit hunters have fallen through ice, and villages have lost ground to swelling seas. In the tropics, deluged islanders are making plans for permanent evacuation. In Europe and India, heat waves have killed thousands. Climate-change models predicted these kinds of developments.
If that all sounds far from home, consider Hurricane Katrina. When it first reached Florida, it was a Category 1 storm. While traveling across the warmer-than-usual surface of the Gulf of Mexico, it brewed itself into a Category 5 then actually weakened to a Category 3 before causing the destruction still so fresh in our minds. Why were the Gulf's waters warmer than usual? You guessed it—and models had forecast this type of change, too.
Consider that seas worldwide have risen 4 to 8 inches in the last century, causing Massachusetts alone to lose 65 acres a year. They're expected to rise another 3.5 to 34.6 inches by 2100. Even moderate estimates allow for an 18-inch increase. More than half of U.S. residents live in coastal areas. We're not in Kansas anymore, but maybe we should be.
To brace for these changes, 141 of the world's 192 countries have ratified the Kyoto Protocol, which outlines emissions cuts for developed countries. The protocol isn't perfect—it's just a first step—but if nothing else, it serves as recognition of our collective plight. The United States, which has not ratified Kyoto, hammered out a separate agreement last year with Australia, China, Japan, India, and South Korea. But critics say that the weak and voluntary aspirations of that pact render it effectively meaningless. Meanwhile, the U.S. spews a quarter of the world's greenhouse-gas emissions and increased its carbon dioxide output 1.7 percent in 2004.