Attribution of the exceptionally warm summer of 2024 in Northern Norway

In the summer of 2024, Northern Norway experienced an exceptionally warm season, leading to a drought that affected important regional industries, such as reindeer herding and hydropower operations. The Arctic has been warming at a rate exceeding the global average in recent decades, putting its vulnerable ecosystems under considerable stress due to the changing climate. Understanding the role of climate change in altering the intensity and frequency of extreme events, such as the summer of 2024, is vital for mitigating impacts to ecosystems and informing societal adaptation strategies in the Arctic.

In this study, we analyse the 2024 event and attribute its changes to human-induced climate change. We employ a probabilistic attribution approach, fitting a non-stationary Generalized Extreme Value (GEV) distribution to an annual time series of the warmest 60-day period across the affected region, using global mean temperature (GMT) as a covariate. The methodology integrates observational data with an ensemble of downscaled and bias-adjusted climate model outputs.

Preliminary results reveal a significant positive trend in the warmest annual 60-day period in Northern Norway with global warming. When comparing the current climate to a couter-factual pre-industrial climate, we find that such extreme events like the summer of 2024 are at least five times more likely to occur in today's climate. Further investigations will explore the influence of climate modes and teleconnections on the 2024 event, as well as a compounding effect with marine heatwaves in the Barents Sea. 

This research is part of a broader initiative to develop a national extreme event attribution service at the Norwegian Meteorological Institute.