The analysis, announced by researchers with the British Antarctic Survey (BAS), is further evidence that humans are adding large amounts of the heat-trapping gas to the planet's atmosphere and causing significant changes to the climate.
Ice cores provide scientists critical records of the climate over time. (Photo courtesy NASA)
But the current peak levels are far above anything seen in past cycle and the rate of change is alarming, the scientists said.
"Ice cores reveal the Earth's natural climate rhythm over the last 800,000 years," said Eric Wolff a BAS ice core chemist. "Over the last 200 years human activity has increased carbon dioxide to well outside the natural range and we have no analogue for what will happen next."
Wolff is the leader of the science team for the European Project for Ice Coring in Antarctica, which drilled the ice core.
Analysis of the ice core showed that the levels of carbon dioxide in the atmosphere ranged between 180 parts per million (ppm) and 300 ppm over the past 800,000 years.
But the amount of carbon dioxide remained relatively steady, the researchers said, until about 200 years ago - when humans began widely burning fossil fuels.
Levels of atmospheric carbon dioxide have jumped 35 per cent in the past two centuries and are rising at an unprecedented rate.
Carbon dioxide levels have risen 30 ppm in the past 17 years - an increase that used to take 1,000 years.
Furthermore, methane had never tipped 750 parts per billion (ppb), but is now 1,780 ppb.
Methane is considered the second-most significant greenhouse gas - it is more powerful than carbon dioxide, but released at much lower levels. It contributes about 20 per cent of the warming from all greenhouse gases and is released by humans through burning of grasslands, forest and wood fuel as well as by intense livestock activity, rice cultivation, and industrial sources.
A study released last year by American and Australian scientists found that methane levels in the atmosphere have risen nearly 300 per cent since the 1700s.
The BAS researchers cautioned that natural carbon sinks in the ocean and on land could reach capacity if greenhouse gas emissions continue to increase at current rates.
"Our land and oceans may well become less efficient carbon sinks as concentrations increase," said Dr. Corrinne Le Quéré, a physicist and BAS carbon cycle expert. "We cannot rely on them to solve the problem."
The new ice core analysis was released at the British Association for the Advancement of Science's Science Festival in Norwich, a public gathering of more than 300 of the United Kingdom's leading scientists and engineers.
In her opening message at the festival, BA President Frances Cairncross warned that climate change is inevitable and the world must be ready to adapt.
"Adaptation policies have had far less attention than mitigation, and that is a mistake," said Cairncross, who is also chair of Britain's Economic and Social Research Council. "We need to think now about policies that prepare for a hotter, drier world, especially in poorer countries. That may involve, for instance, developing new crops, constructing flood defenses, setting different building regulations, or banning building close to sea level."
Improved international cooperation is vital, Cairncross said, but the Kyoto Protocol is insufficient to address the reality of climate change.
Policymakers and educators must persuade "this generation to accept sacrifices on behalf of posterity" and convince all nations to share the burden, she told delegates.
This means "persuading countries that will gain from climate change, or lose little, to take action not on behalf of their own grandchildren but of the descendants of people in other nations," Cairncross said.
"Of course, there are important areas where no adaptation is possible," she says. "We cannot relocate the Amazon or insulate coral reefs and so we need mitigation too. But the government could and should put in place an adaptation strategy right away."
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