Read here and here. A team of 22 scientists, Willerslev et al., analyzed ice cores from southern Greenland and found that the southern Greenland ice sheet survived temperatures that were 9°F warmer than current temps. Even in this much warmer climate, the ice sheet remained at least 1,000 meters thick, which debunks the alarmist's claims of future ice sheet "tipping points."
Based on this analysis, the scientists concluded that the ice sheet's long-term stability is contrary to previous estimates of ice melt rapidity, such as those utilized by the IPCC climate models. The analysis also discovered that prior to ice sheet coverage, southern Greenland was a lush forest some 450,000 years ago, which is a 2 million year difference from previous expert estimates.
""What we've learned is that this part of the world was significantly warmer than most people thought,"....."If our data is correct, then this means that the southern Greenland ice cap is more stable than previously thought,"..."This may have implications for how the ice sheets respond to global warming." DNA extracted from ice cores shows that moths and butterflies were living in forests of spruce and pine in the area between 450,000 and 800,000 years ago.....The discovery pushes forward the date when the last forests were known to exist in Greenland by nearly two million years." [Eske Willerslev, Enrico Cappellini, Wouter Boomsma, Rasmus Nielsen, Martin B. Hebsgaard, Tina B. Brand, Michael Hofreiter, Michael Bunce, Hendrik N. Poinar, Dorthe Dahl-Jensen, Sigfus Johnsen, Jørgen Peder Steffensen, Ole Bennike, Jean-Luc Schwenninger, Roger Nathan, Simon Armitage, Cees-Jan de Hoog, Vasily Alfimov, Marcus Christl, Juerg Beer, Raimund Muscheler, Joel Barker 2007: Science]
Previous ice sheet-glacier and peer-reviewed postings.