For most people, driving with a seat belt tightly strapped around their bodies is a smart habit. Not only is racing down the highway without it illegal—"click it or ticket," as the slogan goes—but seat belts also " reduce serious crash-related injuries and deaths by about half ." Yet as we've previously estimated , your chances of dying in a car crash are at least 9.5 times lower than dying in a human extinction event.

If this sounds incredible—and admittedly, it does—it's because the human mind is susceptible to cognitive biases that distort our understanding of reality. Consider the fact that you're more likely to be killed by a meteorite than a lightning bolt, and your chances of being struck by lightning are about four times greater than dying in a terrorist attack. In other words, you should be more worried about meteorites than the Islamic State or al-Qaeda (at least for now).

The calculation above is based on an assumption made by the influential "Stern Review on the Economics of Climate Change," a report prepared for the UK government that describes climate change as "the greatest and widest-ranging market failure ever seen." In making its case that climate change should be a top priority, the Stern Review stipulates a 0.1 percent annual probability of human extinction.

This number might appear minuscule at first glance, but over the course of a century it yields a whopping 9.5 percent probability of our species going extinct. Even more, compared to estimates offered by others, it's actually quite low. For example, a 2008 survey of experts put the probability of human extinction this century at 19 percent. And the co-founder of the Centre for the Study of Existential Risk, Sir Martin Rees, argues that civilization has a 50:50 chance of making it through the current century—a mere coin toss!

How could the probability of a global disaster be so much greater than that of dying in a car accident?

How is this possible? How could the probability of a global disaster be so much greater than that of dying in a car accident? To be sure, these estimates could be wrong. While some existential risks, such as asteroid impacts and super-volcanic eruptions, can be estimated using objective historical data, risks associated with future technologies require a good dose of speculation. Nonetheless, we know enough about certain technological trends and natural phenomena to make at least some reasonable claims about what our existential situation will look like in the future.