A meticulous new analysis of Antarctic ice suggests that the sharp warming that ended the last ice age occurred in lock step with increases of carbon dioxide in the atmosphere, the latest of many indications that the gas is a powerful influence on the earth’s climate.
Previous research suggested that as the world began to emerge from the depths of the ice age about 20,000 years ago, warming in Antarctica preceded changes in the global carbon dioxide level by something like 800 years.
That relatively long gap led some climate-change contrarians to assert that rising carbon dioxide levels were essentially irrelevant to the earth’s temperature — a side effect of planetary warming, perhaps, but not the cause.
Mainstream climate scientists rejected that view and argued that carbon dioxide, while it certainly did not initiate the end of the ice age, played a vital role in the feedback loops that caused a substantial warming. Still, a long gap between initial increases of temperature and of carbon dioxide was somewhat difficult for the scientists to explain.
A wave of new research in the last few years has raised the likelihood that there was actually a small gap, if any.
The latest paper was led by Frédéric Parrenin of the University of Grenoble, in France, and is scheduled for publication on Friday in the journal Science. Using relatively new, high-precision chemical techniques, his group sought to reconstruct the exact timing of the events that ended the ice age.