Could an extremely cold central European winter such as 1963 happen again despite climate change?

Abstract

Central European winters have warmed markedly since the mid-20th century. Yet cold winters are still associated with severe societal impacts on energy systems, infrastructure, and public health. It is therefore crucial to anticipate storylines of worst-case cold winter conditions and to understand whether an extremely cold winter, such as the coldest winter on the historical record of Germany in 1963 (−6.3 °C or −3.4σ seasonal December–January–February (DJF) temperature anomaly relative to 1981–2010), is still possible in a warming climate. Here, we first show based on multiple attribution methods that a winter of similar circulation conditions to 1963 would still lead to an extreme seasonal cold anomaly of about −4.9 to −4.7 °C (best estimates across methods) under present-day climate. This would rank as the second-coldest winter in the last 75 years. Second, we conceive storylines of worst-case cold winter conditions based on two independent rare event sampling methods (climate model boosting and empirical importance sampling): a winter as cold as 1963 is still physically possible in central Europe today, albeit very unlikely. While cold winter hazards become less frequent and less intense in a warming climate overall, it remains crucial to anticipate the possibility of an extremely cold winter to avoid potential maladaptation and increased vulnerability.