2013-03-01. Study of Ice Age Bolsters Carbon and Warming Link

posted Mar 1, 2013, 7:17 AM by Alan Gould
| Justin Gillis, The New York Times. Relevant to GSS Life and Climate chapter 10. Excerpt: ...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 ...led some climate-change contrarians to assert that rising carbon dioxide levels were essentially irrelevant to the earth’s temperature.... ...A wave of new research in the last few years has raised the likelihood that there was actually a small gap, if any. ...Scientists have long known that ice ages are caused by variations in the earth’s orbit around the sun. When an intensification of sunlight initiates the end of an ice age, they believe, carbon dioxide is somehow flushed out of the ocean, causing a big amplification of the initial warming. Since the 1980s, scientists have been collecting a climate record by extracting long cylinders of ice from the ice sheets in Greenland and Antarctica, and from glaciers.... Air bubbles trapped in the ice give direct evidence of the past composition of the atmosphere. And subtle chemical variations in the ice itself give an indication of the local temperature at the time it was formed. The trouble is that air does not get sealed in the ice until hundreds or even thousands of years after the snow has fallen, as it slowly gets buried and compressed. ...Instead of the 800-year lag between temperature and carbon dioxide increases found in some previous research, [Dr. Parrenin’s] work suggests that the lag as the ice age started to end was less than 200 years, and possibly there was no lag at all. ...“What this does, again and more clearly than ever, is to show that the large temperature changes are tightly coupled to the large CO2 changes,” ...said Richard B. Alley, a climate scientist at Pennsylvania State University. ...The tight relationship in past climate between temperature and carbon dioxide is a major reason scientists have warned that modern society is running a big risk by burning CO2-producing fossil fuels. The level of carbon dioxide in the atmosphere has jumped 41 percent since the Industrial Revolution began in the 18th century, and scientists fear it could double or triple.... Even at the current concentration of the gas, ...increases in sea level of 25 feet or more may have already become inevitable…. Read the full article: http://www.nytimes.com/2013/03/01/science/earth/at-ice-age-end-a-smaller-gap-in-warming-and-carbon-dioxide.html