Europe experienced a pronounced winter cooling of about −0.37°C/decade in the period 1989–2012, in contrast to the strong warming simulated by the Coupled Model Intercomparison Project Phase 5 multimodel average during the same period. Even more pronounced discrepancies between observed and simulated short‐term trends are found at the local scale, e.g., a strong winter cooling over Switzerland and a pronounced reduction in precipitation along the coast of Norway. We show that monthly sea level pressure variability accounts for much of the short‐term variations of temperature over most of the domain and of precipitation in certain regions. Removing the effect of atmospheric circulation through a regression approach reconciles the observed temperature trends over Europe and Switzerland and the precipitation trend along the coast of Norway with the corresponding multimodel mean trends.

The influence of atmospheric circulation on winter temperature and precipitation trends over Europe in the period 2006–50 is investigated in a 21-member initial condition ensemble from a fully coupled global climate model and in a multimodel framework consisting of 40 different models. Five versions of a dynamical adjustment method based on empirical orthogonal function analysis of sea level pressure are introduced, and their performance in removing the effect of atmospheric circulation on temperature and precipitation is tested. The differences in atmospheric circulation as simulated by different models in their control runs and under the historical and representative concentration pathway 8.5 (RCP8.5) forcing scenarios are investigated. Dynamical adjustment is applied to the multimodel ensemble to demonstrate that a substantial fraction of the uncertainty in projected European temperature and precipitation trends is explained by atmospheric circulation variability. A statistically significant response of sea level pressure to anthropogenic forcing is identified in the multimodel ensemble under the RCP8.5 scenario. This forced response in atmospheric circulation is associated with a dynamical contribution to the long-term multimodel mean temperature and precipitation trends. The results highlight the importance of accounting for the impact of atmospheric circulation variability on trends in regional climate projections.

The warming hiatus shows a strong seasonal and geographical asymmetry, with cooling in the Northern Hemisphere winter, especially over land, and warming elsewhere and in the other seasons. We show that the characteristics of the Northern Hemisphere winter cooling in 1998–2012 can mostly be explained by missing observations and by internal variability in the atmospheric circulation of the Northern Hemisphere extratropics. Estimates of the annual and seasonal temperature trends in 1998–2012 obtained by considering the concurrent effects of unforced natural variability and of coverage bias are much closer to the corresponding long‐term trends. Reanalyses suggest that the coverage bias was exceptionally pronounced during recent years and that an area of strong warming was missed due to the incomplete observational coverage. Coupled Model Intercomparison Project Phase 5 climate models indicate that trends in atmospheric circulation during the hiatus period did not occur as a response to anthropogenic forcing.

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A central role in the general circulation of the atmosphere is played by planetary-scale inertial fluctuations with zonal wavenumber in the range k=1-4. Geopotential variance in this range is markedly non-gaussian and a great fraction of it is non-propagating, in contrast with the normal distribution of amplitudes and the basically propagating character of fluctuations in the baroclinic range (3<k<15). While a wave dispersion relationship can be identified in the baroclinic range, no clear relationship between time and space scales emerges in the ultra-long regime (k<5, period >10 days). We investigate the hypothesis that nonlinear self-interaction of planetary waves influences the mobility (and, therefore, the dispersion) of ultra-long planetary fluctuations. By means of a perturbation expansion of the barotropic vorticity equation we derive a minimal analytic description of the impact of self-nonlinearity on mobility and we show that this is responsible for a correction term to phase speed, with the prevalent effect of slowing down the propagation of waves. The intensity of nonlinear self-interaction is shown to increase with the complexity of the flow, depending on both its zonal and meridional modulations. Reanalysis data of geopotential height and zonal wind are analysed in order to test the effect of self-nonlinearity on observed planetary flows.