Even now, there is much we could do to parry the climate threat. We could enact stiff carbon taxes and mandate an accelerated phaseout of fossil fuels. We could undertake massive investments in renewable-energy sources, launch large-scale reforestation, and alter the mix of foods we eat. We could rush to develop scalable methods of carbon capture and sequestration. Yet on all of these fronts, we are taking only minimal action. The politics around climate change remain intractable, and human nature itself seems ill-suited to the challenge: Putting off solving the problem—or hoping it will somehow just go away—is easier than confronting it. “Call me a pessimist,” Jonathan Franzen wrote in a grim and widely read New Yorker essay on the climate crisis, “but I don’t see human nature fundamentally changing anytime soon.”

Having written periodically about climate issues for more than a decade, I have followed the scientific literature on the subject closely, and I understand the fatalist view that the window for an effective response is rapidly closing. But in the process, I’ve also arrived at a more hopeful perspective, one rooted in another side of human nature. Properly stoked and channeled, our instincts could help support a different trajectory.

Radical change can happen swiftly. I’m happy to report that none of my four adult sons is a smoker. But if they’d grown up when I did, I suspect that at least two of them would have taken up the habit. When my own stint as a smoker began—at age 14, in 1959—many of my friends had already been smoking for several years. My parents didn’t want me to smoke, but because they were smokers themselves, their objections rang hollow. At the time, more than half of American men and almost 30 percent of American women smoked. In some circles, it was just something that most people did.

Today, fewer than 15 percent of Americans smoke. Given the difficulty of quitting, few people imagined that such a precipitous reduction in smoking rates could occur so quickly. The decline was rooted in collective measures American society took to discourage the habit. States and the federal government raised taxes on tobacco products. In the ’50s, a pack of Camels could be had for as little as 25 cents in some locations—about $2.17 in today’s dollars. In many areas today, taxes have pushed that price close to $10. In New York City, a pack of cigarettes cannot be sold legally for less than $13. By the 1990s, many cities and states were banning smoking in restaurants, bars, and public buildings; some jurisdictions went so far as to prohibit the practice in outdoor public spaces as well.

These measures worked, but not necessarily in the way you might think. Taxes and bans made smoking more difficult and helped some people quit, yes. But far more important, these moves kick-started a virtuous cycle. One of the strongest predictors of whether someone will become a smoker is the smoking rate among his peers. With fewer people starting to smoke, Americans had fewer smoking peers, which reduced smoking rates still further. After carefully controlling for other factors, one study estimated that if the percentage of smokers among a teen’s close friends fell by 50 percent, the probability of her becoming (or remaining) a smoker would fall by about 25 percent.