German climate scientists studying past ice ages in Earth's geologic history have concluded that we probably won't see another ice age for at least 100,000 years. That's because of global warming, a consequence of all the carbon we've been pouring into the atmosphere for decades. Predicting the future is always tricky, but researchers at the Potsdam Institute for Climate Impact Research had help from the past. In studying past ice ages, they have been able to come up with a relationship between the amount of energy the Earth absorbs from the sun, the amount of carbon dioxide in the atmosphere and the world's glacial cycles. In a paper published in Nature today, they conclude that "moderate anthropogenic cumulative CO2 emissions of 1000 to 1500 gigatonnes of carbon will postpone the next glacial inception by at least 100,000 years".
At first glance, that seems fantastic. The last ice age occurred between 110,000 years ago and 12,000 years ago, as glaciers swallowed up large tracts of inhabited land. And while we may not like the sound of them, we're reaping the benefits of past ice ages right now. Glaciers aren't as static as they appear. They trap dirt and debris, they're filled with openings and internal flows, and they actively grind against earth below them. When they retreat, they leave soil that's highly fertile. They also carve out channels in the Earth, creating rivers and lakes with which to irrigate that soil. Too much time without an ice age and Earth could become relatively barren and dry.
That means humans may have to take the term "Anthropocene" seriously. If we have entered a period in which human activities shape the globe, we need to consider working towards the kind of globe that we want to have. We can't cut nature out of the picture when it's convenient, yet still expect natural cycles to provide a liveable planet for us. If we're cutting ice ages out of the picture, we need to learn how to keep soil healthy and fertile, maintain rivers, or even sculpt the globe ourselves. Future humans will have to do the work of the ice ages that we're eliminating.