Read here and here. Fredrik Charpentier Ljungqvist, a Stockholm University scientist recently published a peer-reviewed study that found there were previous warming periods that produced a warmer climate than our current climate, over the past 2,000 years . As a followup to that study, Ljungqvist has published additional information for the past 1,200 years that examines paleo-reconstructed temperatures for specific Northern Hemisphere regions.
This new data clearly reveals that both the Medieval Warming and the Little Ice Age cooling were significant climate events across the entire northern portion of the globe. In the majority of regions, modern temperatures are yet to reach the level and extent of the MWP.
"The presently available palaeotemperature proxy data records do not support the assumption that late 20th century temperatures exceeded those of the MWP in most regions.....Previous conclusions (e.g., IPCC, 2007) in the opposite direction have either been based on too few proxy records or been based on instrumental temperatures spliced to the proxy reconstructions. It is also clear that temperature changes, on centennial time-scales, occurred rather coherently in all the investigated regions – Scandinavia, Siberia, Greenland, Central Europe, China, and North America.....Assumptions that, in particular, the MWP was restricted to the North Atlantic region can be rejected."
This new data, combined with his other recent research, establishes without any doubt the existence of substantial climate change prior to 20th century's large emission of CO2. This research completely invalidates the UN's IPCC attempt to falsify historical climate change via the Climategate team of scientists. (click on images to enlarge)
Note: Original graphs had instrumental temperatures superimposed on top of proxy reconstruction during 20th century period. The instrumental data was removed and a reconstruction of the proxy reconstruction was done in order to make them visible - our re-do is close enough for NASA/GISS government work. ;-)
Historical temperature charts. Other climate history postings. Modern temperature charts. List of peer-reviewed study postings.