08:55 NZDT Fri Mar 1 2013
French researchers say carbon dioxide levels rose hand-in-hand with warming at the end of the last Ice Age.
Levels of carbon dioxide rose hand-in-hand
with warming at the end of the last Ice Age, according to a study that
deals a blow to climate sceptics.
French researchers say they have answered a riddle that has perplexed scientists.
The question arises from bubbles of atmospheric air, trapped in cores of ice drilled from Antarctica that date back to the last deglaciation, which ended some 10,000 years ago.
These tiny bubbles are closely scrutinised, for they contain carbon dioxide (CO2), the principal greenhouse gas behind global warming.
The higher or lower the CO2, according to the conventional benchmark, the greater or lower the atmospheric temperature.
The anomaly is this: the CO2 in the bubbles do not correspond to the level of warming indicated by the surrounding snowfall of that time.
Climate sceptics argued this showed the CO2 rose after Earth's atmosphere warming.
It would imply global warming today may come, at least in part, from natural means - not from carbon emissions from fossil fuels as the scientific consensus maintains.
Writing in the US journal, Science, a team led by French glaciologist Frederic Parrenin looked at ice from five deep drilling expeditions in Antarctica.
By analysing the isotopic composition of the nitrogen gas in these samples, the researchers said they were able to filter out the confusing signal from the data.
During the last deglaciation, the temperature rose by 19C while at the same time CO2 levels in the atmosphere rose by about 100 parts per million, they said.
The discrepancy comes from the physical process by which CO2 bubbles are formed in successive layers of snow.
Further work will be carried out on different ice samples taken from different eras to see whether this result holds.
French researchers say they have answered a riddle that has perplexed scientists.
The question arises from bubbles of atmospheric air, trapped in cores of ice drilled from Antarctica that date back to the last deglaciation, which ended some 10,000 years ago.
These tiny bubbles are closely scrutinised, for they contain carbon dioxide (CO2), the principal greenhouse gas behind global warming.
The higher or lower the CO2, according to the conventional benchmark, the greater or lower the atmospheric temperature.
The anomaly is this: the CO2 in the bubbles do not correspond to the level of warming indicated by the surrounding snowfall of that time.
Climate sceptics argued this showed the CO2 rose after Earth's atmosphere warming.
It would imply global warming today may come, at least in part, from natural means - not from carbon emissions from fossil fuels as the scientific consensus maintains.
Writing in the US journal, Science, a team led by French glaciologist Frederic Parrenin looked at ice from five deep drilling expeditions in Antarctica.
By analysing the isotopic composition of the nitrogen gas in these samples, the researchers said they were able to filter out the confusing signal from the data.
During the last deglaciation, the temperature rose by 19C while at the same time CO2 levels in the atmosphere rose by about 100 parts per million, they said.
The discrepancy comes from the physical process by which CO2 bubbles are formed in successive layers of snow.
Further work will be carried out on different ice samples taken from different eras to see whether this result holds.
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