Greenland Warmer 1000 Years Ago

A recent paper by Vinther et al in Quaternary Science Reviews looks at ice cores from the Greenland ice cap and uses them to determine the past climate of the region.Two things are worth noting about this paper. The first is that it is yet more evidence that the Medieval Warm Period (MWP) of a thousand years ago was at least as warm, and very probably warmer, than today. The second thing to note is that sometimes you can’t tell everything about a research paper from just reading the abstract and the conclusions.By convention in scientific literature the abstract should be a concise summary of the whole paper written in a way so that someone in the field would be able to ascertain the method and outcome of the work, with someone not in the same field, but with scientific training, able to get a good overview of the research.At the other end of the paper are the conclusions, which is often the second section scientists turn to in order to get an understanding of what the research is all about.The researchers use data from 20 ice cores from 14 locations in medium to high accumulation areas of the Greenland ice sheet. The cores were analysed and seasonally resolved stable isotope measurements were extracted. All of them stretch back at least 200 years. They also incorporated near-surface air temperature data covering the same period from 13 locations on the southern and western coast of Greenland. An additional temperature data set was included from northwest Iceland.Looking at the three longest ice core records (designated DYE-3, Crete and GRIP) the authors say they are able to extend back temperatures for 1400 years.The abstract states that, “the warm period that began in the 1920s raised southern Greenland temperatures to the same level as those that prevailed during the warmest intervals of the Medieval Warm Period some 900– 1300 years ago.”The paper’s conclusions state that, “mid 20th century temperature conditions in southern Greenland were as warm as temperatures during the warmest parts of the Medieval Warm Period.”However, looking deeper inside the paper shows that what the researchers had found was actually that the warmest intervals of the MWP were as warm as, or slightly warmer, than present day Greenland temperatures.It’s a conclusion that independent analysis of the DYE-3 southern Greenland borehole confirms when it found that present temperatures, “were as warm as temperatures during the warmest parts of the Medieval Warm Period.” GRIP (Greenland Ice coring Project) also shows that central Greenland is cooler than the MWP.You will notice the subtle difference. The research found that the MWP was as warm, or slightly warmer than current day Greenland. But the abstract, all what most people would read, says that current temperatures were as warm as the MWP.The difference is not insignificant. One places current day as approaching the Medievel Warm Period, the other had the MWP approaching the present day. In leaving out the real possibility that the MWP was warmer than today, one of the paper’s findings, the abstract is misleading and incomplete.Feedback: david.whitehouse@netzerowatch.com