California's Volatile Hydroclimate: Lessons From the Paleoclimate Record

Abstract

Climate change is expected to decrease mean precipitation in California, but changes in hydroclimate extremes are likely to have more immediate and significant impacts on California water resources, ecosystems, and economy. Paleoclimate records can provide valuable baseline data for constraining natural hydroclimate variability and improving climate projections, but quantitative precipitation records are limited. A new study by de Wet et al. (2021) provides the first semi-quantitative record of early Holocene precipitation in central California, based on speleothem calcium isotope (δ44Ca) variations, that indicates that precipitation variability during and preceding the 8.2 kyr event approached or exceeded that of recent decades. This study outlines a new approach for developing more robust and quantitative hydroclimate records, and also highlights that precipitation “whiplash” is a ubiquitous feature of California's climate that we must prepare for, especially given the likelihood that human-caused climate change is already increasing the frequency and severity of hydrologic extremes.