New ice core data has revealed a stronger link between CO2 and temperature during the end of the last ice age.
The study, published in the journal Science, appears to answer questions over previous data that showed temperature increases occurring before CO2 levels went up. It also suggests CO2 could trigger warming, not just reinforce it.
The previous understanding was due to the lag time between when snow falls and when it has been compacted enough by subsequent snow to trap the air inside it.
By using data about the nitrogen in the Antarctic ice cores, the researchers have been able to reduce this uncertainty.
“Scientists had been saying the CO2 was an amplifier of global warming, but not the initial cause,” said lead author Frederic Parrenin, Laboratory of Glaciology and Geophysics of the Environment. “Now we’re saying it could be the cause.”
A study last year by Dr Joel Pedro of the University of Tasmania used five ice cores from the coast of Antarctica where there is greater snowfall and a shorter lag time between the CO2 and the age of the snow, to produce a more accurate record.
“The take home message from this [Parrenin’s] paper is that temperature and CO2 increased in lock step during the warming out of the last glacial period,” said Pedro.
“We came to the same conclusion using independent methods and different ice cores. In terms of advancing the science this is good.
“We now have two studies by different groups of authors using different methods and several different ice cores coming to the same key result: that Antarctic temperature and atmospheric CO2 increased essentially in synchrony as the Earth warmed out of the most recent glacial period,” added Pedro.