June 19, 2025 by Max Planck Society edited by Gaby Clark , reviewed by Robert Egan scientific editor associate editor This article has been reviewed according to Science X's editorial process and policies . Editors have highlightedthe following attributes while ensuring the content's credibility: fact-checked peer-reviewed publication trusted source proofread Europe is facing increasingly frequent and intense extreme heat events, posing significant risks to human health, ecosystems, and agricultural productivity. Researchers at the Max Planck Institute for Meteorology have developed a novel method to improve the prediction of European hot summers, up to several years in advance. The key to unlocking these forecasts lies within the ocean – specifically, the North Atlantic. Previous research, led by Lara Wallberg at the Max Planck Institute for Meteorology, revealed a critical link: anomalously warm European summers are often preceded by a build-up of heat in the North Atlantic, occurring up to three years prior. This new study, published in Geophysical Research Letters, expands on this finding, identifying a measurable physical indicator that significantly enhances the accuracy of predicting extreme heat events across Europe. The research team, including Lara Wallberg, Laura Suarez-Gutierrez (ETH Zurich & LSCE Paris), and Max Planck researchers Daniela Matei, Daniel Krieger, and Wolfgang Müller, focused on quantifying the accumulation of heat in the North Atlantic. Their model calculations, using the climate model MPI-ESM-LR developed at the Max Planck Institute for Meteorology, incorporated ensemble simulations with slightly varied initial conditions. Crucially, they filtered these simulations, selecting only those that accurately represented the North Atlantic mechanism, as indicated by anomalies in the North Atlantic current. This meticulous approach yielded a remarkable result: only a handful of simulations reproduced the established relationship between North Atlantic heat content and heat wave summers. These models demonstrated a superior ability to depict past heat summers compared to those lacking this crucial link.

To rigorously assess the predictive power of this method, the researchers conducted a hindcast experiment, forecasting summers that had already occurred between 1964 and 2021, a period encompassing 18 above-average warm summers in Europe. The results were compelling: after applying the new method, ten of these summers were predicted with greater reliability, including a more precise assessment of the total number of hot summer days, the amplitude of the extremes, and the variability within those summers. This advancement has significant implications for understanding and mitigating the impacts of extreme heat. Currently, Lara Wallberg is investigating the potential to apply this approach to predict the regional characteristics of particularly impactful summers such as those of 2003, 2018, and 2022, up to three years in advance. A key area of focus is the utilization of growing degree days to assess the value of this method for agricultural applications, providing valuable insights for farmers and policymakers alike. Furthermore, she is actively collaborating with farmers through a dedicated project to translate these forecasts into practical, actionable information. This research represents a substantial step forward in our ability to anticipate and prepare for the growing threat of extreme heat in Europe.