In this study, we apply causal discovery to analyse causal links among
key processes that contribute to Arctic-midlatitude teleconnections.
First, we calculate the causal dependencies from observations. We then
evaluate climate models participating in the Coupled Model
Intercomparison Project Phase 6 (CMIP6) via a comparison of their causal
graphs for the period of 1979-2019 with those derived from observations.
Based on observations, we show that the increase (decline) of
near-surface Arctic temperature is associated not only with the
reduction (increase) of sea ice over the Barents and Kara seas, but also
with the strengthening (weakening) of atmospheric blocking over central
Asia. We show that the near-surface westerly winds are strongly
associated with the phase of the North Atlantic Oscillation (NAO).
Observations show that the phase of NAO is connected with the polar
vortex (PV), which is affected by the strengthening of the poleward eddy
heat flux at 100 hPa. The analysis of CMIP6 historical simulations is in
good agreement with the observations but reveals a negative connection
between near-surface Arctic temperature and sea ice over Barents and
Kara seas, which was not found in observations during
December-January-February 1979-2019. Moreover, climate models simulate a
more robust link between Arctic temperature and Barents and Kara sea ice
towards the end of the century. The analysis of future changes in the
Arctic-midlatitude teleconnections during cold seasons 2059-2099 also
reveals that the connection between the Aleutian Low and the poleward
eddy heat flux is expected to become more robust than in the analysed