Read here. As the Climategate and "Hockey Stick" frauds have shown, there was a concerted effort by a group of paleo-climate scientists to rid climate history of the Little Ice Age and Medieval Warming Periods. To do so would make it much easier for global warming alarmists to claim that modern temperatures are "unprecedented." Fortunately for the world, there still remains a minority of scientists who pursue empirical evidence and truth, regardless of the impact on the current favorite political agenda. These scientists continue to provide actual scientific evidence of the impact of major climatic events on the continent of Antarctica.
"In addition, her data "indicate ice advance after ~650 cal. yr BP (AD ~1300)," which she notes is "broadly contemporaneous with the 'Little Ice Age', as defined in Europe." Hall also says that this was "the only advance that extended beyond the present ice margin in the last 3500 years, making the Little Ice Age in that part of the world likely the coldest period of the current interglacial. And the fact that "the present ice cap margin ... is still more extensive than it was prior to ~650 cal. yr BP" leads her to conclude that the climate prior to that time -- which would have comprised the Medieval Warm Period -- may have been "as warm as or warmer than present." These observations help to demonstrate the worldwide nature of the millennial-scale oscillation of climate that has alternately brought the planet century-scale warm and cold periods independent of any variations in atmospheric CO2 concentration."