Projected Changes in Precipitation, Temperature, and Drought across California’s Hydrologic Regions in the 21st Century

Abstract

This study investigated potential changes in future precipitation, temperature, and drought across 10 hydrologic regions in California. The latest climate model projections on these variables through 2099 representing the current state of the climate science were applied for this purpose. Changes were explored in terms of differences from a historical baseline as well as the changing trend. The results indicate that warming is expected across all regions in all temperature projections, particularly in late-century. There is no such consensus on precipitation, with projections mostly ranging from −25% to +50% different from the historical baseline. There is no statistically significant increasing or decreasing trend in historical precipitation and in the majority of the projections on precipitation. However, on average, precipitation is expected to increase slightly for most regions. The increases in late-century are expected to be more pronounced than the increases in mid-century. The study also shows that warming in summer and fall is more significant than warming in winter and spring. The study further illustrates that, compared to wet regions, dry regions are projected to become more arid. The inland eastern regions are expecting higher increases in temperature than other regions. Particularly, the coolest region, North Lahontan, tends to have the highest increases in both minimum and maximum temperature and a significant amount of increase in wet season precipitation, indicative of increasing flood risks in this region. Overall, these findings are meaningful from both scientific and practical perspectives. From a scientific perspective, these findings provide useful information that can be utilized to improve the current flood and water supply forecasting models or develop new predictive models. From a practical perspective, these findings can help decision-makers in making different adaptive strategies for different regions to address adverse impacts posed by those potential changes.

Microclimate and demography interact to shape stable population dynamics across the range of an alpine plant

“…Buffered population response may lead to reduce range shifts as long as climatic conditions stay within the range currently experienced across this species’ distribution. Currently, the large magnitude of spatiotemporal microclimatic gradients is larger than the predicted changes from climate change in this region (He et al ., ), suggesting that this species’ range may not contract with climate change, but instead the populations may shift their demographic strategies for persistence (Pironon et al ., ). Further, range shifts studies need to consider the potential for life‐history components to interact with changing climatic conditions in different ways (Doak & Morris, ; Csergő et al ., ).…”

Potential Changes in Runoff of California’s Major Water Supply Watersheds in the 21st Century

“…In contrast, there is a clear warming signal in all temperature projections (Figure A5 Appendix C) [44], though the warming magnitude varies across different projections and two different future periods. In general, higher increases in temperature and larger variation ranges are projected for late-century rather than in mid-century.…”

“…When assessing potential changes in runoff projections from historical runoff, following a previous study focusing on changes in precipitation and temperature across California's hydrologic regions in the 21st century [44], a parsimonious metric was applied in the current study to quantify those changes: Percent differences from the baseline. The same 40-year historical period, water year 1951-1990, was used as the baseline period.…”

“…There are large uncertainties on how future precipitation differs from the historical baseline ( Figure A5 in Appendix C) [44,55]. There is no consensus among projections which would indicate a wetter (positive difference) or drier (negative difference) condition.…”

The California Tree Mortality Data Collection Network — Enhanced communication and collaboration among scientists and stakeholders

“…In some areas the recent drought was the most severe to occur in the past 1,200 years (Griffin and Anchukaitis 2014). With more frequent and extreme drought conditions predicted with a changing climate (He et al 2018), a better understanding of drought-induced tree mortality is essential, as are the forest management strategies that can minimize future tree mortality (Stephens et al 2018). As the waves of red trees drop their needles and fade into the background, we hope individuals, agencies and institutions will stay engaged to promote healthy, productive and resilient forests and communities.…”