Sydney, Aug 25 - Warm summers in the northern and southern hemispheres may have knocked out the ice ages, says a new study.

'It is already known that wobbles in the earth's orbit drive the ice age cycle but there are several theories as to how they do this,' said study co-author John Hellstrom, University of Melbourne's School of Earth Sciences.

'The most popular one suggests that ice ages end during a period when the intensity of northern hemisphere summer insolation is greatest,' Hellstrom added.

The results of the new study, which focussed on the end of the penultimate ice age, questions this theory and attributes the variations to the earth's axial tilt.

Previous research had identified precisely when these orbital 'wobbles' occurred, but could accurately date the records of the earth's response to them, which are found in marine sediment on the ocean floors.

Russell Drysdale from the University of Newcastle's School of Environmental and Life Sciences (SELS), who led the research with colleagues from Italy, France, Germany and Britain, said ocean sediment cores contain a wealth of information about past global climate.

But beyond about 50,000 years ago it is difficult to determine the exact age of these sediments.