Why do ice ages end

The angle of this tilt varies on a cycle of about 41, years, which changes how extreme the seasons are, Maslin said. Third, there's the wobble of Earth's tilted axis, which moves as if it were a spinning top.

That wobble occurs on a 20,year cycle. Milankovitch identified that orbital conditions for cool summers were especially important precursors to ice ages. But, to transition into an ice age, orbital phenomena alone aren't enough. The actual causation of an ice age is the fundamental feedback in the climate system, Maslin said.

Scientists are still teasing apart how various environmental factors influence glaciation and deglaciation , but recent research has suggested that greenhouse gas levels in the atmosphere play an important role. For instance, scientists at the Potsdam Institute for Climate Impact Research PIK in Germany have shown that the onsets of past ice ages were triggered mainly by decreases in carbon dioxide and that the dramatic increase of carbon dioxide in the atmosphere, because of human-caused emissions, has likely suppressed the onset of the next ice age for up to , years.

However, today it is humankind with its emissions from burning fossil fuels that determines the future development of the planet. Original article on Live Science.

Of course, modern global warming stems from a clear cause—rising levels of CO2 and other greenhouse gases from fossil fuel burning, cutting down forests and other human activities. And, in the past rising CO2 levels at the very least magnified global warming, ushering in the relatively balmy, stable climate sometimes called the " long summer " that has allowed human civilization to flourish.

Humanity has now raised global CO2 levels by more than the rise from roughly to ppm at the end of the last ice age, albeit in a few hundred years rather than over more than a few thousand years. In fact, the amount of global warming already guaranteed by existing concentrations of CO2 in the atmosphere— ppm and still rising —will also play out over centuries, if not millennia. It will be many centuries and beyond to feel the full effects.

David Biello is a contributing editor at Scientific American. Follow David Biello on Twitter. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Fall Flash Sale. Get smart. CO2 works as an intensifier. Ice cores from both Antarctica and Greenland show that the last ice age started to become milder Climate ripples between north and south There is however another, more dramatic climate variation: The abrupt climate shifts in the ice age.

The climate, especially in the high northern latitudes has, so to say, gone into overdrive. We have counted up to 30 such sudden shifts in Greenland. These shifts cannot be explained by solar radiation. The shifts are much stronger in the north with a temperature change of degrees; but in the south they are between degrees.

The changes are not simultaneous either: When it is cold in the north it is warmer in the south and when it is warmer in the north is colder in the south. More we do not know just now. The last cold ripple ended