End-of-century heat and drought stress is approaching Europe swiftly

Extreme heat and drought levels typical of an end-of-century climate could occur soon, and repeatedly. Despite the European climate being potentially prone to multi-year successive extremes due to the influence of the North Atlantic variability on multi-year timescales, it remains unclear how the likelihood of such successive extremes changes under warming, how early could they reach end-of-century levels, and how this is affected by internal climate variability. We use the MPI Grand Ensemble to perform a systematic assessment of how soon different forms of highly impactful, end-of-century single and compound heat and drought stress could occur over Europe, and the role that the decadal variability in the North Atlantic plays in this outcome. Our ultimate goal is to determine how worst-case successive and compounding heat and drought stress accumulates to produce the most extreme decades, and how soon into the near future such heat and drought loaded decades could bring a taste of the end-of-the-century reality.

We find that even under moderate warming, end-of-century heat and drought levels virtually impossible 20 years ago reach 1-in-10 likelihoods as early as by the 2030s. By 2050-2075, single and compound end-of-century extremes occurring unprecedentedly for two successive years exceed 1-in-10 likelihoods; while Europe-wide 5-year megadroughts reach non-negligble odds. Moreover, our results show that the range of all plausible conditions that we may come to experience under the same global warming levels is growing wider by the decade. The range of potential heat and drought stress accumulated over a whole decade increases to the point that experiencing heat and drought loaded decades typical of an end-of-century climate could become a reality in Europe as early as 2040, and this is highly influenced by the state of the North Atlantic. Under a concurrent warm North Atlantic state, exceeding end-of-century single and compound heat and drought stress during decades starting as early as in 2030 becomes twice as likely.