1176. Hydroclimate Volatility on a Warming Earth 

At the beginning of 2025, Los Angeles was hit by severe wildfires, which some researchers have likened to a "hydroclimate whiplash," and have pointed to "hydroclimate whiplash" as the background. After several years of severe drought, the area around Los Angeles experienced record flooding in the winter of 2022-2023, resulting in increased vegetation. The record-breaking heat wave in 2024 was followed by a dry start to the rainy season of 2025, and the dry vegetation exacerbated a series of devastating wildfires.

A paper published in Nature Reviews Earth & Environment reviewed the hydroclimate volatility due to anthropogenic warming.

Hydroclimate volatility refers to the extremely frequent and abrupt transition from wet to dry or from dry to wet relative to local criteria. From the point of view of water balance, such an extreme situation can be seen as a state of "oversupply" (i.e., an excess of water due to heavy rainfall) and "undersupply" or "excess demand" (i.e., a shortage of water due to low or high evapotranspiration).

Global warming is expected to increase the variability of the hydrologic climate by causing extreme variability in precipitation and evapotranspiration through increased atmospheric water vapor retention and potential evaporative demand. Indeed, increased hydrologic climate variability amplifies hazards (floods, wildfires, landslides, and disease outbreaks) related to the rapid fluctuations in wet and dry conditions, posing threats to human health, public safety, food and water security, and infrastructure. More than when droughts and floods occur in isolation, the impacts of hydrologic climate change can increase in physical magnitude as well as extend over a wider geographic area.

It may accelerate the shift in water management towards co-management of drought and flood risk. To understand the trajectory of future hydroclimate variability, large-scale climate model simulations, high-resolution models, and new machine learning techniques need to advance research on atmospheric circulation responses to regional and global forcing, as well as land-sea-atmosphere feedback.

Reference
Swain, D.L., Prein, A.F., Abatzoglou, J.T. et al. Hydroclimate volatility on a warming Earth. Nat Rev Earth Environ 6, 35–50 (2025). doi.org/10.1038/s43017-024-00624-z , www.nature.com/articles/s43017-024-00624-z

Contributor: IIYAMA Miyuki, Information Program