Despite the complexity and unpredictability of the global climate system, there are factors that make some futures far more likely than others. In particular, we know that society’s introduction of more heat-trapping gases into the atmosphere will almost certainly lead to a warmer world, higher sea levels, and more intense droughts and storms. Furthermore, because half of each ton of carbon dioxide we emit today will be in the atmosphere a century from now, and because the thermal momentum of the oceans and the melting of glaciers we have already set in motion will continue for 3,000 years even if we stop burning fossil fuels immediately, some damages are inevitable. We also know that concerted efforts to reduce emissions and enhance the ability of terrestrial ecosystems to absorb carbon dioxide can minimize the rise in global temperature, thereby dampening the most severe consequences of global warming. Given the high probability of extremely adverse outcomes and our ability to forestall them, a prudent person would conclude that we should act now. Why, then, is the United States moving so slowly—and how might we change course?

The main reason for our political inertia is that proponents of policies to address global warming have struggled to translate climate-change science into a politically compelling story, while their opponents have effectively shifted attention to the potential costs of addressing the problem. For many years the U.S. environmental community lacked the elements of a narrative that could capture the public imagination: the villains were ordinary Americans, and the most affected victims were small island nations; the relationship between heat-trapping gases and global temperature was complex—mediated by many variables and amplified or dampened by highly uncertain feedbacks; and the crisis, should there be one, appeared to be at least a century away. Opponents countered this already weak narrative with a persuasive alternative storyline. They emphasized the uncertainties in climate-change science, actively supporting a handful of contrarians. As important, they claimed that instituting policies to curb emissions of carbon dioxide and other greenhouse gases would cripple the American economy. For a decade, these arguments—which were widely disseminated thanks to enormous infusions of cash from fossil-fuel-based industries—succeeded in defusing public concern.

Over the last five years, however, scientists have provided a steady stream of research that strengthens the global-warming story and decisively discredits the contrarians. First, a more visible and increasingly certain international scientific consensus about humans’ impact on the global climate has rendered absurd claims that scientists are divided. As the IPCC points out, in recent years the cause-effect relationship between human-caused carbon-dioxide emissions and rising global temperature has emerged unmistakably from the statistical noise. Scientists have corrected divergent satellite temperature measurements, quantified most climate-forcing factors, and tested and rebutted the most plausible alternative explanations for the observed temperature rise.

Second, scientists have sought to detect and forecast regional impacts of a changing climate and thereby highlight the extent to which Americans not only are the perpetrators but also will be the victims of global warming. They have generated scenarios that reveal the enormous local costs of regional climate changes; for example, the Northeast will experience severe flooding as the Atlantic Ocean rises; California will suffer severe disruptions in its water supplies as snow packs diminish; and throughout the West, droughts will become longer and more frequent, and wildfires will become more numerous and severe. As for the crisis, research indicates that it draws closer by the day: scientists are already documenting changes in the nesting and mating habits of species around the world and faster-than-expected melting of polar ice caps and glaciers from Greenland to Antarctica and tropical glaciers from the Andes to Kilimanjaro. Moreover, scientists are detecting unanticipated impacts of additional carbon dioxide, such as increases in the ocean’s acidity and phytoplankton declines that promise to be disastrous for marine ecosystems.

Less publicized but as important is the likelihood that addressing global warming could be relatively painless. It is true that to maintain concentrations of atmospheric carbon dioxide low enough to keep the global temperature from rising three times the amount it already has (1.2 degrees Fahrenheit)—an increase many scientists believe will destabilize the climate in dangerous ways—we must reduce global emissions by 75 percent or more. But although that figure sounds overwhelming, we can achieve it if the United States and other industrial economies reduce their emissions by three percent per year between now and mid-century. Continuing at this rate until the end of the century will bring our emissions down by nearly 95 percent, and as a result atmospheric carbon-dioxide concentrations will begin to fall back to today’s levels.

Technological solutions are necessary but insufficient to reduce emissions by three percent per year; we will need to make lifestyle changes as well. But most of those adjustments will be negligible—and many will yield multiple benefits. For the American who drives 1,000 miles each month—the national average—driving 30 miles less per month for a year constitutes a three-percent reduction for that year. Most drivers could save those miles by occasionally sharing a ride to work or taking public transit. Others could achieve equivalent savings by driving less aggressively. Even better, by replacing an SUV with a fuel-efficient vehicle, a driver can instantaneously cut her emissions in half—the equivalent of an annual three-percent savings for 23 years. Similarly, it is relatively simple to reduce emissions from most existing buildings by 30 percent simply by adding insulation and energy-efficient lighting; we can make even greater reductions by replacing old appliances and installing modern windows and furnaces or ground-source heat pumps.

These changes are unlikely to come about in response to market forces alone; fortunately, however, as decades of experience with environmental regulation demonstrates, putting in place a set of policies that establish consistent and predictable rules can spur both rapid technological innovation and behavior change. As a first step, we should dismantle the web of policies that overwhelmingly favors fossil-fuel production and use and actively discriminates against new technologies and practices that would reduce harmful emissions. We routinely subsidize fossil fuels by allowing mining companies to extract coal by blowing off the tops of mountains and dumping the waste into Appalachian rivers; streamlining permits to develop oil and gas on publicly owned territory in the Rocky Mountain West and offshore Alaska; and using military force to prop up oil-producing regimes around the world. Similarly, policies that protect large, obsolete coal-burning power plants in the United States obstruct efforts to make a transition to newer, more efficient power sources, including renewables and distributed, combined heat and power systems.

The second step is to institute federal, state, and local policies that reverse the disincentives created by the existing policy structure and force users to pay the costs of extracting, transporting, and burning fossil fuels. The most straightforward and effective policy changes would include a carbon tax; an increase in the corporate average fuel economy (CAFE) standards; and a large increase in funding for mass transit, both within cities and along heavy travel routes on the East and West coasts. A less obvious policy change would be to require those who introduce energy-consuming technologies to offset or save one and a half times the amount of new emissions generated. State and local governments can adopt growth management policies that reflect the environmental costs of sprawling and inefficient development—such as upgrading building codes to ever-tightening Energy Star standards for renovations and new construction; creating incentives to increase urban densities and redevelop inner-city brownfields; downzoning rural areas; and putting areas of critical environmental concern, such as coastal and freshwater wetlands, off limits to development.

In deciding which technologies and behaviors to encourage, we will need to depart from our past practice of treating each remedy in isolation and instead think at a systems level. For example, widespread use of biofuels may reduce emissions from power plants and vehicles, but if their production entails clearing additional land or using more fertilizer, we could negate any benefits by eliminating carbon sinks and producing more heat-trapping nitrous oxide. Similarly, although some commentators have touted nuclear energy as a straightforward solution to global warming, no one has yet developed a credible plan for storing highly radioactive waste or dealing with the very real threats of natural disasters, technological failure, or the use of nuclear technology by terrorists or hostile states. In short, when choosing from the menu of available policy tools, we should give top priority to those that encourage reducing consumption and adopting technologies that minimize rather than shift environmental impacts.

Of course, devising effective policies is much easier than implementing them. Enacting major policy change entails political risk and is likely only if aspiring leaders perceive substantial public concern—and therefore the possibility of political support for their stands. Fortunately, although the public has been slow to react to the threat of global warming, public opinion—like the climate system—is subject to tipping points, and there is abundant evidence that the United States is nearing one. Actions taken at the state and local levels not only attest to widespread public concern but are also triggering positive economic and political feedbacks that strengthen demands for national policies. As the federal government responds and the United States demonstrates the benefits of environmentally friendly technologies and behaviors at home, we will gain the credibility to promote their adoption abroad.