Scientists working in Antarctica have confirmed that levels of key greenhouse gases that contribute to global warming, such as carbon dioxide and methane, are higher today than at any time in the past 650,000 years.

Humans Responsible for Global Warming

Their research also shows that human activity is the cause of the dramatic increase, which refutes the arguments of skeptics who claim that today’s global warming trend is merely part of a naturally recurring temperature cycle.

"The levels of primary greenhouse gases such as methane, carbon dioxide and nitrous oxide are up dramatically since the Industrial Revolution, at a speed and magnitude that the Earth has not seen in hundreds of thousands of years," said Ed Brook, an ice core expert at Oregon State University. "There is now no question this is due to human influence."

Dramatic Increases in Greenhouse Gases

According to the research, published in the journal Science in November 2005, carbon dioxide levels today are 27 percent higher than the highest previous level in the last 650,000 years, and methane levels are 130 percent higher.

The Chemistry of Global Warming

By analyzing the ice chemistry of a two-mile-long ice core they drilled and extracted in 10-foot sections, scientists were able to determine temperatures at various times from the past. Air bubbles trapped within the ice contain air and greenhouse gases from hundreds of thousands of years ago, enabling scientists to assess air quality at many points throughout the millennia.

Looking More Deeply Into the Past

Earlier ice cores gave scientists data for the past 440,000 years, so this new research extends the scientific view by another 210,000 years. Still, it falls short of a period scientists are eager to study when climate conditions were similar to those in our own time.

Brook is co-chairman of a group of European and American scientists that plan to start drilling an ice core in the future that could produce ice and air bubbles that are between 1.2 million and 1.5 million years old, which would more than double the length of the scientific record on global warming.