New Publication
Centennial intensification
Centennial-scale intensification of wet and dry extremes in North America
Posted by Jim Stagge on September 06, 2024
Access the paper: Centennial-Scale Intensification of Wet and Dry Extremes in North America
Our study titled “Centennial-Scale Intensification of Wet and Dry Extremes in North America”, was recently published in the journal, Geophysical Research Letters. Congratulations to Kay Sung, the study’s lead author.
Press release
Severe drought in the American Southwest and Mexico and more severe wet years in the Northeast are the modern norm in North America, according to new research – and the analysis suggests these seasonal patterns will be more extreme in the future.
The middle of the United States, meanwhile, can expect bigger swings between wetter wet periods – high-rainfall years known as pluvials – and drier summers through the rest of this century, the study predicts.
Researchers at The Ohio State University say the findings, based on modern precipitation data, historical tree rings and climate models spanning the years 850 to 2100, suggest climate change has shifted precipitation patterns across North America to extremes that were not experienced before industrialization began around the mid-1800s.
It’s very much a tale of Southwest versus the Northeast for most of the seasons. Mexico and the American Southwest tends to get drier across more or less all seasons, whereas we’re seeing in the Northeast – and Ohio is included in that – a trend toward wetter, particularly in the winter and early spring. - Jim Stagge
Percent precipitation change compared to the pre-Industrial baseline (1840–1860) for drought years (SPI = −1.5) during the current era (2000–2020), and future under ssp1–2.6 and ssp5–8.5 scenarios (2080–2100). Exposed color (no stipples) represents statistically significant trends, while stipples represent a lack of statistically significant trends.
Key Findings
- This study models seasonal drought and pluvial trends, merging reconstructions, observations, and projections from 850 to 2100 CE
- Results show widespread exacerbation of both extremes with overall drying (wetting) in southern (northeastern) North America.
- Modern drought and pluvial distributions are outside pre-Industrial (1850) conditions, and exhibiting substantial shifts in some regions
Modeled precipitation changes at Los Angeles, CA, USA. (Left) Fitted Gamma distributions. (Right) Time series of underlying data, the bias-corrected mean, drought and pluvial thresholds. Gray shaded region: pre-1400, a period with greater NASPA uncertainty. MRI, MIROC, Gridmet are plotted individually using a darker gray color..
Study Summary
Managing water resources has become challenging due to the effect of human-caused climate change on precipitation. This study examines trends in droughts and pluvials from the distant past (850 CE) to the projected future (2100 CE) to determine whether precipitation extremes in the modern, Industrial era and future are beyond what is typical of natural climate variability in North America. Trends were generated by merging information from tree rings, observations, and climate models using a novel statistical approach. Results indicate the widespread intensification of both drought and pluvials–especially summer drought and winter pluvials during the modern and future periods. Spatially, southern and western regions of North America are becoming drier, while the northeast is getting wetter, and central areas of North America show a wider range between drought and pluvial years. Our study suggests that anthropogenic climate change has already modified drought and pluvial extremes beyond natural, pre-Industrial conditions and these ongoing trends are projected to intensify through the future.
Access the Publication
The full publication is available in Hydrology and Earth System Sciences.