Winter 2009/2010 temperatures and a record-breaking North Atlantic Oscillation index

The 2009/2010 winter was notable for a number of reasons. While the global average temperature was close to a record high according to the analysis of Hansen et al. (2006; Figure 1(a)) and was the fifth highest (Figure 1(b)) in the 160-year record of Brohan et al. (2006), the UK had extensive snow cover and lower-than-average temperatures (National Climate Information Centre, 2010). The Central England Temperature (CET; Parker et al., 1992) for winter 2009/2010 was 2.43 °C, an anomaly of –1.65 degC compared with the 1961–1990 mean. Although there have been 56 colder winters in the CET record since 1659, none occurred during the last three decades and 2009/2010 was the coldest since 1978/1979.