A comprehensive study of tree-ring data from more than 600 years in the San Joaquin Valley shows that the region faces more extreme climate variability than has been recorded in recent history. The study highlights the combined impact of natural variability and human-induced climate change in shaping these extreme climates, suggesting that the impact of climate disasters may be underestimated in the future when assessed on the basis of current records.
According to the latest study of the 600-year growth rings in California's San Joaquin Valley, the valley has experienced great variability in climate extremes, with droughts and floods exceeding modern records in severity and duration.
This new approach combining paleontological information with synthetic weather generation could help policymakers and scientists better understand and ** California's flood and drought risks, and how climate change will exacerbate them. The research team's ** was recently published in the journal of the American Geophysical Union, The Future of the Earth.
Located in the southern part of California's ** River Valley, the San Joaquin Valley is an important agricultural center from which most of the country derives its produce. Patrick Reed, a professor of engineering at Cornell University, is the co-first author of the article.
These models show how flood and drought extremes in the San Joaquin Valley have evolved and help elucidate how natural variability and climate change exacerbate each other's impacts.
Reid said"It is often desirable to distinguish internal variability from climate change in order to understand the changes in signals brought about by anthropogenic warming. But when we plan in a complex water system, both happen. We need to understand what happens when the two work together. The result is that we will encounter extreme situations that we have never seen before. This opens the door to a viable future in a broader sense. "
These findings include:
Much of the variability in flood and drought extremes in the San Joaquin Valley can be attributed to natural variability in the short term, but human-driven climate change has implications for flood and drought extremes that last more than 30 years.
Over the past 600 years, there have been periods of continuous alluvial and drought for decades.
Estimates of drought incidence and severity over the past 30 years are comparable to those of the most severe megadrought periods in 600 years of reconstruction, but estimates of modern drought duration are slightly shorter than paleoclimatic records.
Therefore, modern instrumental records alone may not adequately reflect hydroclimatic hazards. The combination of natural variability and climate change can lead to more frequent, severe, and long-lasting extreme floods and droughts than in the past 600 years.