The impact of climate change on the intensity of mid-latitude cold air outbreaks is a debated topic due to uncertainty associated with internal atmospheric dynamics. Here, we employ an event-based storyline approach in which the evolution of the large-scale atmospheric circulation is nudged to reanalysis data at different global warming levels based on historical and high-emission scenario simulations. We thereby quantify the thermodynamic climate-change effects of pre-industrial, 2ºC and 4ºC warmer climates compared to present-day climate for three cold surges in East Asia during the winter 2020/21. The strongest warming occurs over northeast Asia, reaching up to +12ºC in a +4ºC warmer climate and caused by the advection of less cold air from winter ice-free regions in the Arctic, where the change of surface air temperature exceeds +20ºC. In contrast, over southern China, a moderate cooling is present from pre-industrial to present-day climates, due to the observed and expected increase in aerosol concentration, which peaks by the mid-21st century and alters the radiative balances. This cooling effect is likely to persist well into a +2ºC-warmer climate; however, it may become undetectable at the end of the 21st century (+4ºC warming). In summary, our findings underscore the important thermodynamic impact associated with Arctic amplification and cooling effect of aerosol-induced changes in the radiation budget on East Asian cold extremes.

The Beaufort Gyre is an important feature of the Arctic Ocean. By accumulating or releasing freshwater, it influences ocean properties both within the Arctic and as far as the North Atlantic. Yet, its future remains uncertain: the gyre could strengthen as sea ice declines and allows increased wind stress on the ocean, or weaken along with the Beaufort High pressure system. Here, we provide a first evaluation of the Beaufort Gyre in historical and climate-change simulations from 27 available global climate models. We find that the vast majority of models overestimate the gyre area, strength, and northward extent. After discarding the models with too inaccurate a gyre and its drivers – namely, the sea ice cover and Beaufort High – we quantify changes in the Beaufort Gyre under two emission scenarios: the intermediate SSP2–4.5 and the high-warming SSP5–8.5. By the end of the 21st century, most models simulate a significant decline or even disappearance of the Beaufort Gyre, especially under SSP5–8.5. We show that this decline is mainly driven by a simulated future weakening of the Beaufort High, whose influence on the Beaufort Gyre variations is enhanced by the transition to a thin-ice Arctic. The simulated gyre decline is associated with an expected decrease in freshwater storage, with reduced salinity contrasts between the gyre and both Arctic subsurface waters and freshwater outflow regions. While model biases and unresolved processes remain, such possible stratification changes could shift the Atlantic-Arctic Meridional Overturning Circulation northward.

Effective adaptation to climate change requires detailed, tangible information about its impacts. This paper presents a novel simulation framework that combines storyline approaches based on spectral nudging with emerging kilometre-scale global climate modelling capabilities using the IFS-FESOM model. This approach allows for reconstructing recent extreme events and their potential evolution under different climate conditions while maintaining high-resolution local details. We demonstrate the system’s ability to reproduce observed variability on daily and longer timescales during the 2017–2023 period, particularly in the extratropics, and evaluate its performance using high-quality observations, including data from the MOSAiC expedition. To showcase the potential of this framework, we focus on two recent extreme events in Europe: the July 2019 heatwave and the July 2021 Ahrtal flooding. These examples highlight how kilometre-scale simulations can provide more granular, localized insights into climate change impacts, improving risk assessment and adaptation planning. This work, conducted as part of the European Union’s Destination Earth initiative, demonstrates how global, high-resolution simulations can be harnessed to support the development of digital twins of the Earth system, advancing both climate science and practical decision-making.