(a) Linear trend (°C per 10 years) in winter SAT from 1990/91–2013/14. Figure is repeated from Cohen et al. (2014). Linear regression coefficients of winter mean SAT (units: °C; shaded) upon the simultaneous negative AO (b) and NAO (c) index from 1990/91–2013/14. Stippled regions indicate the regression coefficients are statistically significant at 90% confidence level, as estimated using the Student