The Earth is in the midst of an unusually long spell between ice ages and the build-up of carbon dioxide emissions through the burning of fossil fuels may postpone the next glaciation event by at much as 100,000 years, according to new climate research.
Even without humans contributing to the rise in greenhouse gases, the next ice age would be unlikely for another 50,000 years, a paper by researchers based at the Potsdam Institute for Climate Impact Research in Germany found.
That's in part because of a reduced wobble in the Earth's orbit, which has served in the past to trigger ice ages as solar radiation is reduced.
There was also an unusually high level of atmospheric carbon dioxide for that stage of the cycle – even before the start of the Industrial Revolution around 1750.
"[Our study also shows that relatively moderate additional anthropogenic CO2 emissions from burning oil, coal and gas are already sufficient to postpone the next ice age for another 50.000 years," Andrey Ganopolski, lead author of the paper, said.
"The bottom line is that we are basically skipping a whole glacial cycle, which is unprecedented," Dr Ganopolski said. "It is mind-boggling that humankind is able to interfere with a mechanism that shaped the world as we know it."
The paper modelled different CO2 levels, with even the cumulative emissions of 500 gigatonnes – not much more than already released by human activities – enough to delay the evolution of northern hemisphere ice sheets by tens of thousands of years.
Should the emissions reach 1000-1500 gigatonnes, as some carbon projections suggest, the next glaciation period could be postponed by at least 100,000 years, the researchers said.
David Etheridge, a principal research scientist with the CSIRO and an ice core expert, said the paper underscores the unusual nature of Holocene epoch – which began 11,700 years ago.
"We would probably not get to a glacial set-up even without human-linked emissions" for much longer than usual in the glaciation cycle, Dr Etheridge said.
"With more CO2 emissions now, it's very unlikely we will have another ice age for tens of thousands of years."
The build-up of greenhouse gases might seem a plus far into the future but the near-term consequences are anything but positive, Dr Etheridge said.
"We don't want a glaciation but we certainly don't want several degrees' warming," he said.
Hans Joachim Schellnhuber, director of the Potsdam Institute, said ice ages had played a big role in shaping both the global environment and also human civilisation by creating fertile soil while carving out lakes and rivers.
"However, today it is humankind, with its emissions from burning fossil fuels, that determines the future development of the planet," Professor Schellnhuber said.
"This illustrates very clearly that we have long entered a new era – and that in the Anthropocene, humanity itself has become a geological force," he said.
