Partial reversal of European summer precipitation decline in stabilisation scenarios: where does the moisture come from?

Over the last few years, there has been increasing interest in the long-term climate stabilisation response that we might expect when net-zero emissions of greenhouse gases are achieved. These studies often explore the stabilisation response across multiple global warming levels (GWLs). Several studies have now shown that regional patterns of change at given GWLs can be very different between transiently warming through a GWL and stabilising at that same GWL.

In a recent study with the UK Earth System Model 1.0, we showed that stabilising the external forcings and running the model forward for 500 years at various GWLs can stop the decline of southern European summer precipitation and reverse the sign of the trend. In northern Europe, the wetting trend is more substantial, and precipitation projections in UKESM1.0 overshoot the pre-industrial baseline in the second century after stabilisation (Dittus et al. 2024).  

In this presentation, we explore the mechanisms contributing to this spring and summertime increase in precipitation in the stabilisation simulations with UKESM1, relative to the transient projections from ScenarioMIP. We show that the frequency of different atmospheric circulation types is changing during the 500 years of stabilisation, and also highlight the important role of the land surface and soil moisture feedbacks onto the hydrological cycle.

Dittus, A. J., Collins, M., Sutton, R., & Hawkins, E. (2024). Reversal of projected European summer precipitation decline in a stabilizing climate. Geophysical Research Letters, 51, e2023GL107448. https://doi.org/10.1029/2023GL107448