By Jim Steele – Re-Blogged From http://www.WattsUpWithThat.com
Dansgaard Oeschger Events and the Arctic Iris Effect
During the last Ice Age, Greenland’s average temperatures dramatically rose on average every 1500 years by 10°C +/- 5°C in a just matter of one or two decades, and then more gradually cooled as illustrated in Figure 1 below (8 of the 25 D-O events are numbered in red on upper graph; from Ahn 2008). These extreme temperature fluctuations between cold “stadials” that lasted about a thousand years and warm “interstadials” lasting decades are dubbed Dansgaard-Oeschger events (D-O events). These rapid temperature fluctuations not only rivaled the 100,000‑year fluctuations between maximum glacial cold and warm interglacial temperatures but D‑O warm events coincided with expanding Eurasian forests (Sánchez Goñi 2008, Jimenez-Moreno 2009), northward shifts of subtropical currents along the California coast (Hendy 2000), and shifts in belts of precipitation in northern South America (Peterson 2001).