Oct. 22 (UPI) -- When researchers at Columbia University developed a model to understand the global increase in runoff extremes -- or flash flooding -- they revealed a strong link between precipitation, human activity and climate change.
But the simulations also showed runoff extremes, not precipitation, correlated most closely with human-caused climate and land-use changes. In other words, the growing risk of flash flooding is outpacing the risk of extreme precipitation in most places around the the world.
The dynamic isn't explained by rising temperatures, alone, researchers determined. Land-use and land-cover changes also play a role.
"Our work helps explain the underlying physical mechanisms related to the intensification of precipitation and runoff extremes," Pierre Gentine, associate professor of earth and environmental engineering at Columbia, said in a news release. "This will help improve flood forecasting and early-warning alerts. Our findings can help provide scientific guidance for infrastructure and ecosystem resilience planning, and could help formulate strategies for tackling climate change."
The link between rising temperatures and precipitation extremes is relatively straightforward. As the atmosphere warms, it is able to hold more moisture, increasing the odds of extreme precipitation events.
But when scientists looked at the effect of anthropogenic changes on precipitation and runoff extremes, they found the influence of underlying physical mechanisms -- physical changes on Earth's surface -- are underestimated.
The research, published Monday in the journal Nature Communications, suggests the risk of flash flooding is likely to increase a faster clip than predicted by current climate models.
"We were trying to find the physical mechanisms behind why precipitation and runoff extremes are increasing all over the globe," said lead study author Jiabo Yin, a visiting student from Wuhan University in China. "We know that precipitation and runoff extremes will significantly intensify in the future, and we need to modify our infrastructures accordingly. Our study establishes a framework for investigating the runoff response."
Scientists hope followup research, and higher-resolution models, will help pinpoint which types of land-use changes have largest impact on the risk of flash flooding. The research team also plans to study the influence of thermodynamics and atmospheric dynamics on precipitation intensification, so as to improve the accuracy of models predicting the risk of runoff extremes.