WHEN DID GLOBAL WARMING START? An Editorial Comment

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: ice core
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.84.1683; http://stephenschneider.stanford.edu/Publications/PDF_Papers/Crowley2003.pdf

With a bolt from the blue William Ruddiman has forced scientists and broader elements of society to contemplate the possibility that the anthropogenic era of greenhouse forcing began thousands of years ago. Even as a long-time admirer of Bill Ruddiman, I admit to having been almost taken aback when I first read the title of the paper in this issue (‘The Anthropogenic Greenhouse Era Began Thousands of Years Ago’). But when I started reading the paper, I could not help but wonder whether he just might be on to something. The origin of the ‘outrageous hypothesis ’ begins with Ruddiman’s analysis of the Pleistocene CO2 record from the Vostok ice core. His long time experience in analysis of Pleistocene time series gives him a great deal of credibility in this analysis. He concludes that the CO2 interglacial life cycle in the present interglacial has been different than the three other interglacials in the last 400,000 years in the sense that CO2 levels tended to peak in the early part of the interglacial and then either stabilized or gradually decreased. For the Holocene interglacial, however, an early downdip follows the first peak and then CO2 levels start to go back up.