An ice core about two miles long -- the oldest frozen sample ever drilled from the underbelly of Antarctica -- shows that at no time in the last 650,000 years have levels of the greenhouse gases carbon dioxide and methane been as high as they are today.
The research, published in today's issue of the journal Science, describes the content of the greenhouse gases within the core and shows that carbon dioxide levels today are 27% higher than they have been in the last 650,000 years and levels of methane, an even more powerful greenhouse gas, are 130% higher, said Thomas Stocker, a climate researcher at the University of Bern and senior member of the European team that wrote two papers based on the core.
The work provides more evidence that human activity since the Industrial Revolution has significantly altered the planet's climate system, scientists said. "This is saying, 'Yeah, we had it right.' We can pound on the table harder and say, 'This is real,' " said Richard Alley, a Penn State University geophysicist and expert on ice cores who was not involved with the analysis.
Previous records, from an ice core drilled at the Russian Antarctic station Vostok, extended back 440,000 years. Extracting and analyzing that core was a major achievement, but the core stopped short of a time period scientists are anxious to study because it was like today's.
Climate scientists called the analysis of the older records spectacular because they were so clear and said they would become "canonical" additions to the climate record. "It's really important," Ed Brook, an ice core expert at Oregon State University said of the new research. "Those 200,000 years were a lot harder to get than the previous 400,000 -- and those were hard enough."
Ice cores are plugs drilled from glaciers and ice sheets. They are composed of tens of thousands of layers of fallen snow and air bubbles compressed over time. Ice cores are among the most powerful tools available to climate scientists. The chemistry of the ice reveals temperatures from the distant past, while bubbles within the ice are minuscule time capsules that capture air and greenhouse gases as they existed hundreds of thousands of years ago.
The ice core was drilled by the European Project for Ice Coring in Antarctica from a high plateau in East Antarctica called Dome C that rises about two miles above sea level. It is one of the driest, coldest parts of the continent, where summer temperatures can fall to 50 degrees below zero. Temperature records from the core were published in 2004, and scientists have been waiting for an analysis of the core's gases.
