Climate change is the critical challenge facing humanity. The impacts of global warming will predominantly be experienced on continents, where the rapidly increasing risk of severe heatwaves represents an existential threat to societies and ecosystems. The exceptional summers of 2018 (the UK’s joint hottest on record) and 2019 (which featured the UK’s hottest-ever day) represent ominous portents of the future.
Fundamental understanding of continental heatwaves remains limited, despite the severe impacts on human health, wildfire risk and food production. Average warming over continents is up to 60% larger than over oceans (Sutton et al, 2007), and this enhanced warming is tightly linked to ocean temperatures and land aridity (Byrne & O’Gorman, 2018). But how climate change will affect extreme continental temperatures and heatwaves is highly uncertain, particularly in the extratropical regions poleward of 30N/S that are home to a large portion of the world’s population.
The key hypothesis underlying this project is that the response of extratropical continental heatwaves to climate change is controlled by ocean temperatures and land aridity. Moisture transport and convection in the atmosphere link the surface climates over continents and oceans, such that energy profiles over continents and oceans are tightly coupled (Byrne & O’Gorman, 2013). This energy constraint underpins recent quantitative theories for how average and extreme tropical continental temperatures respond to climate change (Byrne & O’Gorman, 2018; Byrne, 2021). Yet the potential of this energy constraint to unlock the problem of extreme extratropical temperatures in a changing climate is untested and unknown.
The goal of this IAPETUS2 project is to transform understanding of extratropical heatwaves in a changing climate. The project will build on recent studies – led by Dr Michael Byrne – of tropical temperatures in a changing climate (Byrne & O’Gorman, 2018; Byrne, 2021), and will combine new climate simulations and theory to tackle three key objectives:
A. Determine the relative influences of ocean temperatures vs land aridity in controlling extratropical continental heatwaves using a novel set of climate simulations.
B. Develop the first quantitative theory for extratropical continental heatwaves.
C. Diagnose the physical drivers of uncertainties in extratropical heatwave projections across state-of-the-art climate models.