The Cooling of Greenland over the past 8000 Years

A 2009 paper¹ plots GISP2 paleoclimate icecore data from central Greenland over the past 8000 years, finding at least 6 periods of warming exceeding that of the 20th century. In addition, the rate of warming 900-1000 AD leading up to the Medieval Warming Period exceeds the rate of warming in the 20th century. The authors find close agreement between two analysis methods of the temperature proxies for GISP2 data, stable isotope analysis² and Oxygen 18/16 variability³. The Medieval, Roman, and Minoan warming periods are all found to be hotter than the 20th century, in addition to other unnamed periods of warming over the past 8000 years.

¹Florides GA, Christodoulides P Global warming and CO2 through sciences. Environ Int. 2009 Feb;35(2):390-401.

²Alley RB. GISP2 ice core temperature and accumulation data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-013. NOAA/NGDC Paleoclimatology Program, Boulder CO,USA;2004. http://www1.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gisp2_temp_accum_alley2000.txt

³Grootes PM, Stuiver M. Oxygen 18/16 variability in Greenland snow and ice with 10^3 to 10^5-year time resolution. JGeophysRes1997;102:26455–70 ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/summit/gisp2/isotopes/gispd18o.txt

Related: Melting the facts about Greenland's Ice Sheet

Related: Greenland Glacier Trend:

If you look at this graph in detail, you can see that the retreat in the period 1929-1953 (24 years) was faster than in 1953-2003 (50 years).



Thus all together, the retreat of Greenland ice is the result of global warming at least since 1850, and the retreat was faster around 1930-1940 than today, when GHGs were not playing any important role.



Moreover, the summer temperatures around Greenland in recent years (still) are slightly less than in the 1935-1950 period...