The ice core was drilled from a thick area of ice on Antarctica known as Dome C. The core is nearly 3.2km long and reaches to a depth where air bubbles became trapped in ice that formed 800,000 years ago.

"It's from those air bubbles that we know for sure that carbon dioxide has increased by about 35 per cent in the past 200 years. Before that 200 years, which is when man's been influencing the atmosphere, it was pretty steady to within 5 per cent," Dr Wolff said.

The core shows that carbon dioxide was always between 180 parts per million (ppm) and 300 ppm during the 800,000 years. However, now it is 380 ppm. Methane was never higher than 750 parts per billion (ppb) in this timescale, but now it stands at 1,780 ppb.

But the rate of change is even more dramatic, with increases in carbon dioxide never exceeding 30 ppm in 1,000 years -- and yet now carbon dioxide has risen by 30 ppm in the last 17 years.

"The rate of change is probably the most scary thing because it means that the Earth systems can't cope with it," Dr Wolff told the British Association meeting at the University of East Anglia in Norwich.

"On such a crowded planet, we have little capacity to adapt to changes that are much faster than anything in human experience."