Carbon emissions ‘will defer Ice Age’
Human emissions of carbon dioxide will defer the next Ice Age, say scientists.
The last Ice Age ended about 11,500 years ago, and when the next one should begin has not been entirely clear.
Researchers used data on the Earth’s orbit and other things to find the historical warm interglacial period that looks most like the current one.
In the journal Nature Geoscience, they write that the next Ice Age would begin within 1,500 years - but emissions have been so high that it will not.
“At current levels of CO2, even if emissions stopped now we’d probably have a long interglacial duration determined by whatever long-term processes could kick in and bring [atmospheric] CO2 down,” said Luke Skinner from Cambridge University.
Dr Skinner’s group - which also included scientists from University College London, the University of Florida and Norway’s Bergen University - calculates that the atmospheric concentration of CO2 would have to fall below about 240 parts per million (ppm) before the glaciation could begin.
The current level is around 390ppm.
Other research groups have shown that even if emissions were shut off instantly, concentrations would remain elevated for at least 1,000 years, with enough heat stored in the oceans potentially to cause significant melting of polar ice and sea level rise.
The root causes of the transitions from Ice Age to interglacial and back again are the subtle variations in the Earth’s orbit known as the Milankovitch cycles, after the Serbian scientist Milutin Milankovic who described the effect nearly 100 years ago.
Glaciation and its reverse are related to cycles discovered by Milutin Milankovic
The variations include the eccentricity of the Earth’s orbit around the Sun, the degree to which its axis is inclined, and the slow rotation of its axis.
These all take place on timescales of tens of thousands of years.
The precise way in which they change the climate of the Earth from warm interglacial to cold Ice Age and back every 100,000 years or so is not known.