Abstract. While climate change mitigation targets necessarily concern maximum mean state changes, understanding impacts and developing adaptation strategies will be largely contingent on how climate variability responds to increasing anthropogenic perturbations. Thus far Earth system modeling efforts have primarily focused on projected mean state changes and the sensitivity of specific modes of climate variability, such as the El Niño–Southern Oscillation. However, our knowledge of forced changes in the overall spectrum of climate variability and higher-order statistics is relatively limited. Here we present a new 100-member large ensemble of climate change projections conducted with the Community Earth System Model version 2 over 1850–2100 to examine the sensitivity of internal climate fluctuations to greenhouse warming. Our unprecedented simulations reveal that changes in variability, considered broadly in terms of probability distribution, amplitude, frequency, phasing, and patterns, are ubiquitous and span a wide range of physical and ecosystem variables across many spatial and temporal scales. Greenhouse warming in the model alters variance spectra of Earth system variables that are characterized by non-Gaussian probability distributions, such as rainfall, primary production, or fire occurrence. Our modeling results have important implications for climate adaptation efforts, resource management, seasonal predictions, and assessing potential stressors for terrestrial and marine ecosystems.

Editor’s note: For easy download the posted pdf of the State of the Climate for 2019 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

Editor’s note: For easy download the posted pdf of the State of the Climate for 2017 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.

Intensification of El Niño-Southern Oscillation (ENSO)-rainfall variability in response to global warming is a robust feature across Coupled Model Intercomparison Project (CMIP) iterations, regardless of a lack of robust projected changes in ENSO-sea-surface temperature (SST) variability. Previous studies attributed this intensification to an increase in mean SST and moisture convergence over the central-to-eastern Pacific, without explicitly considering underlying nonlinear SST–rainfall relationship changes. Here, by analyzing changes of the tropical SST–rainfall relationship of CMIP6 models, we present a mechanism linking the mean SST rise to amplifying ENSO–rainfall variability. We show that the slope of the SST–rainfall function over Niño3 region becomes steeper in a warmer climate, ~42.1% increase in 2050–2099 relative to 1950–1999, due to the increase in Clausius–Clapeyron-driven moisture sensitivity, ~16.2%, and dynamic contributions, ~25.9%. A theoretical reconstruction of ENSO–rainfall variability further supports this mechanism. Our results imply ENSO’s hydrological impacts increase nonlinearly in response to global warming.