When will the ice age cometh?

University of Leeds and Cambridge research into climate change, published today (December 2nd) in Science Express, reveals that there is no regular pattern in the duration of warm phases (interglacials) on land over the last 350,000 years. This raises doubts over our ability to predict when the onset of the next ice age might occur.

For over 30 years it’s been thought that interglacials lasted about 10,000 years. On this basis, our current interglacial, already 11,500 years old, would appear to be already at the limit of its natural lifetime. However, recent work on the previous warm phase suggested that it lasted about 20,000 years, which implies that the onset of the next ice age would still be several millennia away. The Science paper shows that the duration of an interglacial can vary considerably, with some lasting only 6,000 years.

Researchers from the universities of Leeds and Cambridge examined land and marine fossils retrieved from the sea bed 180km off the Portuguese coast to reconstruct environmental changes over the last 350,000 years. They found some interglacials were cut short by the occurrence of sharp cooling events.

Leeds geography Professor Chronis Tzedakis said: “The origin of these climate events isn’t clear, but parallel declines in Antarctic temperatures and atmospheric methane levels suggest that these were global rather than local.

“Recent model experiments taking into account increased levels of atmospheric carbon dioxide have suggested that our current interglacial may last 50,000 years. However, until we understand the origin of abrupt and extensive climate coolings within warm phases, any such long-term projections remain uncertain”.