The magnitude of future Arctic amplification is highly uncertain. Using the Norwegian Earth System Model, we explore the effect of improving the representation of clouds, ocean eddies, the Greenland ice sheet, sea ice, and ozone on the projected Arctic winter warming in a coordinated experiment set. These improvements all lead to enhanced projected Arctic warming, with the largest changes found in the sea ice retreat regions and the largest uncertainty found on the Atlantic side.

Strong disagreement exists in the scientific community over the role of Arctic sea ice in shaping wintertime Eurasian cooling. The observed Eurasian cooling can arise naturally without sea-ice loss but is expected to be a rare event. We propose a framework that incorporates sea-ice retreat and natural variability as contributing factors. A helpful analogy is of a dice roll that may result in cooling, warming, or anything in between, with sea-ice loss acting to load the dice in favour of cooling.

Climate models still struggle to correctly represent blocking frequency over the North Atlantic–European domain. This study makes use of five large ensembles of climate simulations and the ERA-Interim reanalyses to investigate the Greenland blocking frequency and one of its drivers, namely cyclonic Rossby wave breaking. We particularly try to understand the discrepancies between two specific models, out of the five, that behave differently.

The single-column version of the shared ALADIN-HIRLAM numerical weather prediction system, called MUSC, was developed by Météo-France in the 2000s and has a growing user-base. Tools to derive the required input, to run experiments and to handle outputs have been developed within the HARMONIE-AROME configuration of the ALADIN-HIRLAM system. We also illustrate the usefulness of MUSC for testing and developing physical parametrizations related to cloud microphysics and radiative transfer.