Global warming episodes that were interspersed between prehistoric ice ages were caused by regular wobbles in the earth's tilt, according to new evidence from the University of Newcastle in Australia.
The research team, led by Russel Drysdale, suggest that the Earth emerges from ice ages due in large part to changes in the tilt of the planet in relation to the sun, otherwise known as its obliquity. This affects the total amount of sunlight each hemisphere receives in its respective summer, rather than the peak intensity of the solar radiation during the northern summer, according to the Discovery News.
The team studied sediment on the sea floor and compared the changes in the sea floor to similar material on the surface that can be accurately dated through samples taken from cave stalagmites.
The result is that the new date for the end of the second last ice age is thousands of years too early to be related to any increase in the intensity of the northern hemisphere summer as predicted by the Milankovitch Theory.
Instead, the researchers found that, in the past million years global warming events have occurred every second or third cycle of the Earth's changing obliquity, which occurs every 41,000 years.