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Multi‐model representation of the North Atlantic Oscillation in the 20th and 21st centuries

Ten coupled ocean‐atmosphere general circulation models (CGCM) are used to reproduce NAO mean sea level pressure and 2 meter air temperature fields highly correlated to the North Atlantic Oscillation index (NAOI), during a control period from 1961–1990. Three enhanced CO2 perturbation scenarios are compared to the control for 2070–2099, using pattern correlations and normalized root mean square errors between perturbation and control periods. It is found that models can successfully reproduce observed NAO sea level pressure and temperature anomaly fields. Model control SLP anomaly fields, however, more closely resemble the Arctic Oscillation than the expected NAO SLP distribution due to an expansion of the North Atlantic low pressure area. Analysis for the period 2070–2099 under the 3 enhanced CO2 scenarios shows intensification of the NAOI due to CO2 forcing, but with a weaker temporal trend relative to the control period.