In the past fifteen years global warming has moved from the esoteric scripts of scientists and mathematicians onto the real world stage. Record temperatures and devastating storms, droughts, and floods swamp the headlines. Scientists say it is neither hype nor coincidence. All these trends and events are in line with what mainstream modeling predicts for our disrupted climate.

We understand the problem’s primary cause: the addition of too much carbon dioxide (CO2) to the atmosphere, mostly through the burning of fossil fuel. Carbon dioxide traps solar energy that otherwise would radiate away from the Earth as heat. As we add CO2, the Earth’s temperature rises.

We understand many of the global consequences of climate disruption as well, and they are grave: increasingly intense and frequent storms, droughts, and heat waves; the rise of new illnesses such as SARS and West Nile Virus, and the spread to new places of old ones such as malaria and cholera; habitat displacement and extinctions of wild populations of plants and animals; the rise of sea levels and the battering and redefinition of our coasts. Climate disruption will wreak havoc on our water distribution system, our agricultural practices, and our basic ecosystem services, all fundamental to our economic and environmental welfare. The proportions of the problem make a reasonable person’s head spin.

We also know what could alleviate the problem of global warming. It is, sensibly, the reverse of the cause. To slow or stop climate disruption we need to reduce the amount of heat-trapping gasses in the atmosphere.

So much for all that we know. Now to the salient remaining mystery: Why, given our insights and knowledge, do we not respond appropriately? Why don’t we curb our carbon output?

The late philosopher David Love, who taught at Oberlin College, observed a key gap between merely knowing and what he called “taking knowledge to heart.” Knowing the truth is an accomplishment in itself, he said, and can lead to well-formed opinions. But taking the truth to heart is manifest in action. In Love’s formulation, we Americans have failed to take global warming to heart. That failure has already been costly. If it persists much longer, it will come at an astronomical price, a cost to be paid not only by ourselves, but by all people, plants, and animals in this and future generations. What mechanism of denial could allow us to carry on business as usual while accruing that kind of debt?

A frustrated dieter comes to mind. He too knows what he needs to do to solve his problem. For all the hand-wringing and pleading and promising that goes on, it boils down to a simple equation: reducing the ratio of calories going in to calories burned: eat less, exercise more, or both. Even though his doctor warns his weight may kill him, the man can’t lose weight. His family pleads. He tries, but he doesn’t stick to a program. Exercise is embarrassing, painful, time-consuming, and shows no immediate results. He reads books about Atkins, Ornish, vegetarianism, Weightwatchers, and other diets. Reading doesn’t help. He blames his difficulty on advertising, on food-loving friends who feed him, on the constant and pervasive marketing of fast and caloric food and on his own weight-induced depression.

Then one day his heart stops. As life slips away he thinks of his children, of his loves, his favorite places, favorite flavors, of the world’s excruciating beauty. How could he have done this to himself? He swears that if he lives he will change, will do whatever it takes to restore his health. Embarrassment? Inconvenience? Discomfort? How trivial they seem now.

We are something like that obese man on the eve of cardiac arrest. Our crazy weather is the warning sign. We understand our problem. We know the consequences. We know how to solve or minimize it. But somehow we just don’t take the predicament to heart. We have excuses: our politicians, the inconvenience, the expense, the impracticality of, say, walking or taking the bus to work.

But ultimately, our excuses and explanations aren’t worth a thing. Nor are our knowledgeable opinions of much use. What matters now is one thing: reducing greenhouse gas emissions by 70 percent before our own cardiac arrest. We can’t wait for politicians to take the lead. They live on two- or four-year election cycles and can’t afford to address a problem reaching forward decades and centuries. Nor can corporate heads, bound by duty to their quarterly reports, lead the way. It will have to be us, then. Ordinary people driven by knowledge and fueled by love for each other and the natural world and the epic story of life unfolding . . . or just plain old self-preservation.

—Gordy Slack