Seasonal to Multi-year Predictability and Prediction of Statistics of Marine and Terrestrial Heat Waves

Marine and terrestrial heat waves (MHWs, THWs) are critically recognized as a dominant threat to marine, socioeconomic and human systems. Estimating the predictability and improving prediction of the frequency, duration, and intensity of these extremes on seasonal to multi-year timescales are crucial for proactive planning and adaptation. However, climate prediction at regional scales remains challenging due to the complexity of the climate system and limitations in model accuracy. Here we use a large ensemble of simulations, assimilations, and reforecasts of Community Earth System Model version 2 (CESM2) to assess the predictability of statistics of MHWs and THWs with lead times of up to 5 years. We show that the frequency of MHWs and THWs during local summer in specific regions is predictable up to several months to years, and that the prediction skill of the cumulative intensity and duration for various MHW hot spots remains high even after the second lead year and across seasons. Sources of long-term predictability include not only external forcings but also modes of climate variability beyond human-induced climate change across time scales such as El Niño and Southern Oscillation, Pacific Decadal Variability, and Atlantic Multidecadal Variability. This study implies opportunities to deepen our scientific understanding of sources for long-term prediction of statistics of climate extremes and the potential for the associated disaster management.