Figure 4.5 Historical trends in air temperature in the BCB region. Plots show spatially-averaged annual mean surface air temperature anomalies for the Chukotka region (based on RosHydromet, 2014); annual mean air temperature at Inuvik (from Environment Canada’s Adjusted and Homogenized Climate Data and based on Vincent et al., 2012); annual mean air temperature averaged across northern Canada (based on Wang et al., 2013); and change in regional average (relative to 1951-1960) of the 20-year return values of extreme high daily maximum temperature and extreme low daily minimum temperature and the annual mean temperature (Wang et al., 2013). Return values represent the level that is attained, on average only once in 20 years.