Throughout Earth's history, 90,000 out of every 100,000 years have been ice ages - and it's been 12,000 years since the last one. You can thank global warming, it seems.

Future ice ages may be delayed by up to 500,000 years by greenhouse gas emissions from fossil fuels, according to recent work by Dr Toby Tyrrell of the University of Southampton.

If their numerical model is accurate, this sets a new standard for detailing the disruption of long-term planetary processes by human activity.

Dr Tyrrell's team used a mathematical model to study what would happen to marine chemistry in a world with ever-increasing supplies of the greenhouse gas, carbon dioxide.

The world's oceans absorb CO2 from the atmosphere but as they do so they become more acidic. This dissolves the calcium carbonate in the shells produced by marine life, adding even more carbon to the oceans. The outcome is elevated carbon dioxide.

The work confirms earlier ideas by David Archer of the University of Chicago, who first estimated the impact rising CO2 levels would have on the next ice age.

Dr Tyrrell said: "Our research shows why atmospheric CO2 will not return to pre-industrial levels after we stop burning fossil fuels. It shows that it if we use up all known fossil fuels it doesn't matter at what rate we burn them. The result would be the same if we burned them at present rates or at more moderate rates; we would still get the same eventual ice-age-prevention result."

Ice ages occur approximately every 100,000 years as the Earth's orbit changes over time. Alterations in the way the sun strikes the Earth allows for the growth of ice caps, plunging the Earth into an ice age. Their models contend it is not just variations in sunlight that determine an ice age; levels of atmospheric CO2 are also important.

Humanity has burned about 300 Giga-tons of carbon in fossil fuels. Their suggests that even if only 1000 Giga-tons are burned, 25% of climate capacity, then it is likely that the next ice age will be skipped. Burning all of the available fossil fuels could mean skipping the next five ice ages.

Funded by the Natural Environment Research Council

Source: University of Southampton