Once upon a time, about 650m years ago, our planet was covered in ice. Glaciers stretched as far as the tropics, and equatorial regions were as cold as modern day Antarctica.
Life clung on, huddling around geothermal springs and in pockets of liquid water under the ice caps. Ancient rock deposits suggest our planet entered this snowball state multiple times.
So what tipped Earth’s climate into such frigid conditions, and how did it revert to the warm temperatures of today? These questions have perplexed scientists for decades.
Using a climate model to investigate the unstable melancholia states between warm and snowball, Prof Valerio Lucarini from the University of Reading and his colleagues show that ice stretched as far as mid-latitudes during melancholia phases.
Their results, published in Physical Review Letters, reveal that when Earth is in a melancholia state, small changes in solar radiation are enough to tip the climate into snowball or warm states.
Today’s big concern is global warming. Lucarini and his colleagues intend to use a similar model to explore whether another melancholia state exists between a warm and very hot climate state.
