Editor's letter: A tipping point for the Goldilocks zone

last updated 8 January 2015

Space scientists call it the Goldilocks zone: that temperate realm where a planet gets enough heat from its sun for water to exist in liquid form, not just as vapor or as ice. Earth’s orbit, about 93 million miles from the sun, has put us in that zone for at least 4.4 billion years. During that time, the planet’s climate has seesawed from ice ages, in which half the planet was covered by glaciers, to hothouse eras, when even the poles had tropical temperatures and humidity. Those wild swings have been driven by natural forces and taken place over millennia. But now we’re in the Anthropocene era, when the activities of 7 billion human beings are changing the climate rapidly. One study released this week warned of “tipping points” at which climate change becomes sudden and catastrophic. “Our planet can’t sustain the comfort zone to which we’ve become adapted unless we change our pace of emissions,” said meteorologist Martin Hoerling.

It’s enough to make human migration to other worlds start to look like more than just a fantasy, especially when you consider that Earth’s population is projected to grow to 11 billion by the end of the century. Mars is the closest prospect, but we learned this year that there are some 11 billion planets in the Goldilocks zone in our galaxy alone. Maybe that’s why so many billionaires are investing in private spaceflight these days. It’s likely that centuries will pass before humans can escape Earth in substantial numbers. It’s too bad we can’t figure out in the meantime how to do better by our planet, and make the Anthropocene an era of stewardship instead of recklessness.