By Howard Kunreuther and Paul Slovic
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It’s easy to project a pattern of smooth, linear growth: one person gets the coronavirus today, another person contracts it tomorrow, a third person gets it on the third day, and the process continues in this manner, the cases simply adding. But most people, including leaders and policymakers, have a harder time imagining exponential growth, which means you can have two cases of coronavirus tomorrow, four on the third day, hundreds after the seventh day and thousands soon after—a situation that’s challenging to anticipate and manage. That’s the nature of pandemics.
It’s also how climate change works. And if there’s any silver lining in this mess, it’s that the coronavirus pandemic is teaching us a valuable lesson about the perils of ignoring destructive processes—and perhaps even larger, longer-term disasters—that increase exponentially. Even if growth looks mild in the moment—think of the earliest segments on an exponential curve like the red line shown in the illustration above—it will soon enough be severe. In other words, delay is the enemy.
The human mind does not easily grasp the explosive nature of exponential growth. This was demonstrated more than 40 years ago in a series of pioneering psychological experiments conducted in the Netherlands by Willem Wagenaar and his colleagues. In one study, participants were shown a hypothetical index of air pollution beginning in 1970 at a low value of 3 and rising yearly in an exponential way to 7, 20, 55 and, finally, 148 by 1974. Asked to intuitively predict the index value for 1979, many of the respondents produced estimates at or below 10 percent of the correct value of about 21,000 (which can be determined from the underlying exponential equation). Subsequent experiments have observed similarly dramatic underestimation of exponential growth and showed that it typically results from straight-line projections based on early small increases.
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Obviously, dealing with the present dangers from the coronavirus must be everyone’s top priority at this moment. We will eventually get control of this demon and begin to restore some semblance of normal life. When we do, the world must turn its attention to reducing CO2 emissions and stopping the further exponential havoc that climate change will wreak, far sooner than we expect.
Michael Oppenheimer, Andrew Quist, Quinlyn Spellmeyer, Carol Heller and Cameron Slovic contributed to this article.