By Usha Lee McFarling, Times Staff Writer

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.