Greenland Near-Surface Air Temperature Datasets: What Should We Use to Evaluate CMIP6?

Greenland has, like the Arctic region as a whole, seen rapid warming since the end of the 20^th century. Mass loss from the Greenland ice sheet has made a major contribution to sea level rise in recent decades. Near-surface air temperature (SAT) plays an important role in ice sheet mass balance, but due to a lack of weather stations over most of the 20^th century and a relatively sparse monitoring network even now, the picture of Greenland SAT history is incomplete.

A number of gridded SAT datasets have the potential to complete the picture, but it is unclear which are reliable in the region. In our recently published work (Reeves Eyre and Zeng, 2017) we used extensive in situ SAT measurements (∼1400 station-years) to assess monthly mean SAT from seven global reanalysis datasets, five gridded SAT analyses, one satellite retrieval and three dynamically downscaled reanalyses.

Strengths and weaknesses of these products are identified, and their biases are found to vary by season and between high and low elevations on the ice sheet. MERRA2 reanalysis overall performs best with mean absolute error less than 2 °C in all months. Ice sheet-average annual mean SAT from different datasets are highly correlated in recent decades, but their 1901–2000 trends differ even in sign. Compared with the MERRA2 climatology combined with gridded SAT analysis anomalies, thirty-one earth system model historical runs from the CMIP5 archive reach ∼ 5 °C for the 1901–2000 average bias and have opposite trends for a number of sub-periods.