Ecologists love doomsday predictions. We are destroying our planet, they shout, and running out of food, space, species -- you name it. In the United States, the predicted shortages have yet to arrive. Obesity not starvation is our problem. So it is no surprise that most Americans have not jumped on the global-warming bandwagon. We still send more greenhouse gases into the sky than any other nation, in part because scientists crying wolf have made us skeptical of scientists crying climate change. And that's too bad because the very real juggernaut of global warming is coming our way.
Tim Flannery -- professor, scientist, author and director of the South Australia Museum -- forcefully warns about the dangers of global warming in "The Weather Makers." He marshals fact after fact and skillfully weaves them into a very readable book. Flannery also avoids much of the hyperbole that is an occupational hazard for ecology writers. There's no reason to exaggerate; the case for global warming is a slam dunk.
The greenhouse effect is scientific fact. Nearly 150 years ago, a Scottish physicist named John Tyndall established that some gases absorb infrared radiation while others do not. The greenhouse gases -- methane, water vapor and carbon dioxide, for example -- do, while nitrogen and oxygen, the main components of our atmosphere, do not. Visible light in the form of sunlight passes through the atmosphere. It warms the Earth, which re-emits it as infrared radiation. Greenhouse gases absorb this radiation and turn it into heat.
Another scientific fact is the increase of one of these greenhouse gases -- carbon dioxide -- in the atmosphere. It has grown from 280 parts per million (ppm) at the beginning of the Industrial Revolution, when we began burning fossil fuels for energy, to 380 ppm in 2004.
Skeptics attack this data in two ways. Some argue that such small amounts of a gas (it's measured in parts per million, for God's sake), could not change Earth's climate. However, without the smidgen of greenhouse gases we have, the Earth would be a frosty ball unable to retain enough heat to support life. And if carbon dioxide in the atmosphere grew to just 1 percent, Flannery tells us, "it would -- all other things being equal -- bring the surface temperature of the planet to the boiling point."
Even higher concentrations could put us in the same sorry state as Venus. With an atmosphere of 98 percent carbon dioxide, the temperature on Venus is a toasty 891 degrees Fahrenheit. As expected, the steady climb of atmospheric carbon dioxide is raising the temperature of Earth. Using 17,000 thermometers scattered around the world, scientists have concluded that the planet is warming at a rate of about 1 degree Fahrenheit every 30 years.
Other skeptics admit that warming is occurring but say we do not know the cause. However, there is no plausible explanation for this phenomenon besides human activity.
If the science is solid and if global warming is already under way, why do some people, including most of our leaders, believe they can ignore climate change? The answer lies in Flannery's cautionary statement, "all other things being equal." If all other things were equal, scientists could calculate exactly how much the Earth's temperature would rise as atmospheric carbon dioxide increases. However, all things are not equal. Many variables -- clouds and volcanic eruptions, for example -- can dramatically affect climate and makes predictions iffy. Which leaves us in a bit of a pickle. We know that rising carbon dioxide and the greenhouse effect it causes is a certainty; the continued increase in Earth's temperature is virtually certain; but how much, how fast and where temperatures will rise are far less certain.
Flannery summarizes the history and future of Earth's climate in a graph, a plot of temperature over time from 1000 A.D. to 2100. It is called the "hockey stick" graph because of the sharp upturn in temperatures that began in the 20th century. Computer models on which the graph is based project Earth's temperature will rise 4.5 degrees Fahrenheit in this century. The model's uncertainty ranges from a minimum projected increase of 2.5 degrees to a maximum of 5.8 degrees. But this small uncertainty can produce dramatic changes. It could grow colder in Europe, devilishly hot in North America, and dust dry in Africa. Sea levels could rise 4 inches or 20 feet, depending on how fast the polar ice sheets melt. And that is the problem in a nutshell: The uncertainty in predicting the effects of surging temperatures coupled with Earth's regional sensitivity to climate change allows politicians to do nothing. Everything will turn out fine, they say. Ecologists are always predicting catastrophe, and they are always wrong.
Many, maybe most, Americans agree with this do-nothing approach. So far, global warming has caused us few problems. Maybe hurricanes are getting stronger, but who knows why. Sea levels are rising -- but slowly. Higher ocean temperatures are killing coral reefs, but that doesn't affect us much. This Pollyannaish attitude is a mistake. Global warming is happening, it's almost certain to continue, and we should be acting to ameliorate it. You don't wait for a fire to buy fire insurance.
One thing is certain; even if we stopped all greenhouse gas emissions immediately, it would take 50 years for the climate to stabilize as oceans warm and glaciers melt. Of course, we aren't stopping; we are spewing more and more of it into the air. "Half the energy generated since the Industrial Revolution," writes Flannery, "has been consumed in just the last twenty years."
Now, the good news: carbon dioxide doesn't last forever. It has an average life in the atmosphere of about 100 years. If we reduce emissions, atmospheric carbon dioxide levels will eventually stabilize. And if we can pull that off, our children and our children's children will certainly thank us.
Flannery trots out the usual options for encouraging nations to reduce carbon emissions: Build on the Kyoto Protocol; adopt carbon-emissions trading; or impose a carbon tax. He also discusses alternative energy sources and carbon sequestration. But he is more enthusiastic about what individuals can do. "You can in a few months," he claims, "attain the ... reduction in emissions required to stabilize the Earth's climate." Use renewable energy where available, opt for solar hot water, and buy energy-efficient appliances. So outraged was Flannery by the coal-fired utilities in his area that he installed solar panels on his house and now generates his own electricity. But if all that seems too much bother, he says we can do our part simply by trading in our SUVs for fuel-efficient hybrids.
Flannery makes it clear that what we choose to do about global warming is crucially important to us and future generations. As his title states, we are "The Weather Makers," and tomorrow's climate depends on what we do today.
(Phillip Manning is a Chapel Hill writer; his book reviews and essays on science are available on line at www.scibooks.org.)