Fig. 5: Change in the frequency of extreme NAO events at 4 × CO2.
From: More positive and less variable North Atlantic Oscillation at high CO2 forcing

Extreme (a) NAO- and (b) NAO+ events for DJF (first set of bars) and JJA (second set of bars). The total change (gray) is decomposed into contributions from changes in the NAO mean (red), standard deviation (blue) and the non-normality of the distribution (green). Extreme events are defined as those occurring once per decade.