If you are unable to use this captcha for any reason, please contact us by email at support@dreamwidth.org
This may be part of something bigger..
http://en.wikipedia.org/wiki/Dansgaard-Oeschger_events
A rapid rise in Greenland(Arctic) of 8 degrees C in less than 40 years, followed by prolonged cool downs with a periodicity of ~ 1500 years +/- 500.