Climate science: Earth's narrow escape from a big freeze.

Abstract

An equation has been derived that allows the timing of the onset of glaciations to be predicted. This confirms that Earth has just missed entering a new glacial period, and is unlikely to enter one for another 50,000 years. See Letter p.200 Despite decades of research, the conditions responsible for the inception of a glacial period have remained unclear. Why, for example, did the Earth not enter a glacial period in recent times, when Northern Hemisphere insolation patterns resembled those often associated with other inceptions? These authors use a climate model of intermediate complexity, constrained by evidence from ice cores, to quantify the insolation required to trigger a glacial period for any level of atmospheric CO2: high CO2 levels, such as in the late Holocene, demand that insolation fall below an unusually low level. The simulations suggest that in the absence of human perturbations to the climate system, the present interglacial would persist for tens of thousands of years. With human-generated releases of carbon, there appears to be little chance of a new glacial period over the next 100,000 years.