Climate Change Slows Onset of Next Ice Age

The planet’s inexorable warming means there will be no new ice age for at least the next 100,000 years, scientists say.

Human beings have not just started to leave a unique geological stratum that will announce their existence long after the species has been extinguished.  They may have altered a climate cycle that has been stable for millions of years and even canceled – or certainly postponed – the next Ice Age.

Andrey Ganopolski and colleagues from the Potsdam Institute for Climate Impact Research in Germany report in Nature that they took a look at the conditions that determined the geologically recent cycle of Ice Ages.

The advance and retreat of vast glaciers over geological time are the consequence of a mix of factors involving sea, mountains, atmosphere, vegetation and the distribution of continents around the globe.

But ultimately what determines the rhythm of these events is what climate scientists call insolation: how much sun the Earth actually gets in a summer.  The Earth’s orbit is not a perfect circle but an ellipse, and the shape of the ellipse and the angle of the Earth’s tilt on its axis change subtly and imperceptibly over cycles lasting tens of thousands of years, which in turn alters the amount of sunshine striking the northern hemisphere.

And if the atmospheric levels of carbon dioxide are not high when the total insolation is near its lowest point, great thick sheets of ice begin to advance over Europe, Asia and North America.

This is enough to explain the last eight Ice Ages.  The sequence is punctuated by “interglacials” that tend to last roughly 10,000 years before the ice advances once more.

But at the end of the last Ice Age something happened:  humans had discovered fire, and then used it to invent agriculture and metal foundries, and then began to alter the carbon balance in the atmosphere, even before the discovery of fossil fuels.

Geologists have a name for this present interglacial epoch.  They call it the Holocene.  “Even without man-made climate change we would expect the beginning of a new ice age no earlier than in 50.000 years from now – which makes the Holocene as the present geological epoch an unusually long period in between ice ages,” Dr Ganopolski said.

“However, 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.

“The bottom line is that we are basically skipping a whole glacial cycle, which is unprecedented.  It is mind-boggling that humankind is able to interfere with a mechanism that shaped the world as we know it.”

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