In The discovery of global warming Spencer Weart elaborates extensively about the discovey of large climate swings, inferred from the ice core research in Greenland. You can read the book online there, but also here. A few quotes from the chapter Rapid climate changes, A similar plot can be found in the price winning book http://press.princeton.edu/titles/6916.html [Broken] of Richard Alley. The isotope jumps in question look like these: http://www.ipsl.jussieu.fr/GLACIO/hoffmann/Texts/jouzelJGR1997.pdf [Broken], ) showing clear strong temperature jumps, especially at around 15,000 years ago, known as the Bolling Allerod interstadial. However some doubts remainded, although one had to very audaciously ignore the strong expressions of undesirabilty of sharing those doubts with others, but nevertheless that happened in threads like these: https://www.physicsforums.com/showthread.php?t=125669 https://www.physicsforums.com/showthread.php?t=333159 accumulating into the idea that these isotope jumps were not about temperature but aridity: https://www.physicsforums.com/showthread.php?t=333747 Now all of a sudden we see this published: [URL [Broken] U. Clark, et al. (2009) The Last Glacial Maximum, in Science Vol 325, 710-714, doi:10.1126/science.1172873 [/url] which states: So, with this publication, it seems now official those doubts, the ice sheets retreating a considerable time before the isotope temperature increased. So no warming of a shocking 7°C within a span of less than 50 years. Somebody has a lot of explaining to do. One of the messages seems to be: the interpretation of "proxies" is much trickier than it looks, justifying a sincere doubt about the value of other "proxies", one of the corner stones of global warming.