Storylines of Marine Heatwaves: Relatable and tangible climate simulations for real-world decision-making

Heatwaves in the ocean, called Marine Heatwaves, are expected to increase both in frequency and intensity in a warming world, with major impacts on ecosystems and coastal societies. The occurrence of such ocean extremes usually raises the following key questions: Was this extreme event influenced by anthropogenic climate change? How would this ocean extreme unfold in an even warmer climate?

Here we propose a new, relatable way to answer these questions. We use novel “storyline simulations”, which re-create real extreme weather and ocean events if they were to unfold in past, present, and future warmer climates. By imposing (or "nudging") the real large-scale winds in the model to mimic observed events, the storyline approach isolates the role of thermodynamic changes due to climate warming while minimizing uncertainties linked to large-scale wind changes. We showcase the potential of this unique, event-centred approach for a sample set of Marine Heatwaves across the globe.

We also introduce a prototype web tool that continuously provides and displays storylines of extremes for any place on Earth, and only a few days behind real-time—when major Marine Heatwaves are still salient. This publically available near-real-time tool (https://climate-storylines.awi.de) has already shown great potential for climate change communication.

The storyline approach thus offers accessible “what if” scenarios that make the effects of climate change more tangible for diverse audiences, and support evidence-based ocean and climate policies.