Year 2010 surface air temperature observations around west and south Greenland are unprecedented in the instrumental record. Year 2010 and year 2003 temperatures dwarf high yearly averages occurring in the 1920s and 1930s.
Warming and Cooling
Over the full 171 years (1840-2010) of the reconstruction, the ice sheet average surface air temperature increased 1.26 C. The warming rate was 0.74 C/century. The recent 17 year Greenland ice sheet warming rate is 30% smaller in magnitude than a 17 year period in the 1920s. The intervening 63 year period (1932 to 1992) was cooling at -0.19 C/decade. This cooling can be attributed to a cooling phase of the Atlantic Multidecadal Oscillation (AMO) (e.g. Schesinger et al. 1994; Trenberth et al. 2006). Cold episodes in 1983-84 and 1991-92 enhance this cooling trend and are caused primarily by major volcanic eruptions (see Box, 2002) . West Greenland is a focus of sulfate aerosol-induced cooling (see Box et al. 2009). Another contributor to the 1932 to 1992 cooling is global dimming, that is, cooling at the surface induced by increases in atmospheric aerosols. Liepert et al (2002) estimated that there was globally a reduction of about 4% in solar radiation reaching the ground between 1961 and 1990. The Wikipedia Global Dimming article is worth reading. The recent (post-1994) warming, is attributable to: 1.) a growing absence of sulfate cooling because there has not been a major volcanic eruption since 1991; 2) recent warming phase of AMO; 3) an apparent reversal of the global dimming trend; and 4) ongoing and intensifying anthropogenic global warming (AWG), the elephant in the room, owing to a dominance of enhanced greenhouse effect despite other anthropogenic cooling factors such as aerosols and contrails (IPCC, 2007). The primary factor responsible for the warming trend is very likely to be AWG (IPCC, 2007).
It is scientific to question if year 2010 record setting temperatures are real or due to some spurious aspect of the measurements. Former television meteorologist Anthony Watts, for one, expended quite a lot of effort to discredit apparent record setting 2010 temperatures in Nuuk, Greenland. However, Watts seems in error, as one would not expect the same pattern at other locations and in independent periods of time (Fig. 2), if the Nuuk 2010 temperatures are spurious. Rather, record high temperatures are evident at other Greenland stations in the same months, for example, in May, August, September, November, December 2010. Watts implicates the fact that the Nuuk measurements are near an airport to discredit the anomalous year 2010 values. Heat spewing from airplanes seems a valid concern and incidentally Aasiaat measurements are also from the grounds of an airport. However, the Prince Christian Sound (a.k.a. Prins Christian Sund) data are not obtained from near any airport (J. Cappelen, DMI, personal communication).
We are fortunate to have continuous temperature records from Greenland’s capital Nuuk beginning in 1866 in addition to century-plus records from other locations in Greenland (Box 2002; Vinther et al. 2006; Cappelen 2010; Box et al. 2009), providing instrumental climate records rivaling many of the longest records on Earth. I have used these data record and others available from the Danish Meteorological Institute and NASA to reconstruct Greenland ice sheet average surface air temperatures (see Box et al. 2009). I update the Box et al. (2009) reconstruction and make further analysis in this blog entry. This work is in preparation for my 7th consecutive annual Greenland entry for the Bulletin of the American Meteorological Society’s “State of the Climate” report published each June.
- Box, J.E., 2002: Survey of Greenland instrumental temperature records: 1873-2001, International Journal of Climatology, 22, 1829-1847. PDF
- Box, J.E., L. Yang, D.H. Browmich, L-S. Bai, 2009: Greenland ice sheet surface air temperature variability: 1840-2007, J. Climate, 22(14), 4029-4049, doi:10.1175/2009jcli2816.1. PDF
- Cappelen J., 2010: DMI Monthly Climate Data Collection 1768-2009, Denmark, The Faroe 263 Islands and Greenland Dansk Meterologisk Institut Technical report No. 10-05
- Intergovernmental Panel on Climate Change (IPCC) (2007), Climate Change 2007: The Physical Science Basis, edited by S. Solomon et al., Cambridge Univ. Press, New York.
- Liepert, B. G. (2002), Observed reductions of surface solar radiation at sites in the United States and worldwide from 1961 to 1990, Geophys. Res. Lett., 29(10), 1421, doi:10.1029/2002GL014910.
- Schlesinger, M.E. and Navin Ramankutty (1994): An oscillation in the global climate system of period 65-70 years. Nature, 367, Issue 6465, pp. 723-726, DOI: 10.1038/367723a
- Trenberth, K.E. and D.J. Shea (2006): Atlantic hurricanes and natural variability in 2005. Geophysical Research Letters 33, L12704, doi:10.1029/2006GL026894 PDF
- Vinther, B. M., K. K. Andersen, P. D. Jones, K. R. Briffa, and J. Cappelen, 2006: Extending Greenland temperature records into the late eighteenth century. J. Geophys. Res., 111, D11105,