Rising Carbon Dioxide Could Prevent Ice Age Cycle

Humans have put so much extra carbon dioxide into the atmosphere that the normal pattern of recurring ice ages is probably going to be disrupted for the next 100,000 to 500,000 years, according to new research from the University of Southampton in the U.K.

Toby Tyrrell of the university's School of Ocean and Earth Science at the National Oceanography Centre in Southampton used a mathematical model to determine how rising levels of atmospheric carbon dioxide would affect the world's oceans. He found that, as the oceans absorb more carbon dioxide from the air and the water becomes more acidic, the calcium carbonate in shelled creatures dissolves, which adds even more carbon to the oceans. The result is that higher levels of carbon dioxide are likely to persist even if humans drastically reduce their burning of fossil fuels.

"Our research shows why atmospheric CO2 will not return to pre-industrial levels after we stop burning fossil fuels," Tyrrell said. "It shows that it if we use up all known fossil fuels it doesn't matter at what rate we burn them. The result would be the same if we burned them at present rates or at more moderate rates; we would still get the same eventual ice-age-prevention result."

From the start of the Industrial Age through the present, humans have burned about 300 gigatons (a gigaton is 1 billion tons) of fossil fuels. Tyrrell's research suggests that, if people eventually burn a total of 1,000 gigatons of fossil fuels, the next regular ice age cycle will not occur. If humans burn all the fossil fuel reserves left, believed to total about 4,000 gigatons, the Earth could skip the next five ice ages.

During the present geological epoch, known as the Pleistocene, which began about 1.8 million years ago, ice ages have normally occurred every 100,000 years or so. The last ice age ended about 10,000 years ago, meaning the Earth wouldn't expect another glacial period for another 90,000 years or so. The timing of ice ages is believed to be affected by a variety of factors, including atmospheric composition, changes in the Earth's orbit around the sun, variations in the sun's output, continental drift and volcanic activity.

Since humans began burning fossil fuels in the 19th century, atmospheric carbon dioxide levels have increased from 284 parts per million in 1832 to 387 parts per million as of this July, according to the National Oceanic and Atmospheric Administration.University of Southampton, "Next Ice Age Delayed by Rising CO2 Levels." URL: (http://www.soton.ac.uk/mediacentre/news/2007/aug/07_100.shtml)