Rising temperatures and human activity increase storm flows and flash floods

Hurricanes Florence and Michael in the United States and Typhoon Mangkhut in the Philippines have shown the widespread and adverse impact of extreme weather conditions on ecosystems and built communities, with sudden floods causing more deaths than property losses and in agriculture. risks related to bad weather. These losses have increased over the last 50 years and have exceeded $ 30 billion annually over the last decade. Globally, nearly one billion people now live in flood plains, which puts them at greater risk of flooding caused by extreme weather events, and stresses the urgency of understanding and predicting these events. events.

Columbia Engineering researchers demonstrated for the first time that runoff extremes have increased dramatically in response to climate change and human-induced changes. Their findings, published today in Nature Communications, show a sharp increase in precipitation and runoff extremes due to both human activity and climate change. The team, led by Pierre Gentine, associate professor of earth and environmental engineering and affiliated with the Institute for the Earth, also found that runoff has a stronger response than rainfall to induced change. by the man etc). This suggests that the expected responses of stormwater runoff extremes to climate and anthropogenic changes will increase dramatically, posing major threats to the ecosystem, affecting community resilience and infrastructure systems.

The researchers found that changes in storm runoff extremes in most parts of the world are similar to or greater than extreme precipitation extremes. They noted that different reactions of rainfall and runoff to temperatures can be attributed not only to warming, but also to factors such as land use and change changes, land management, and land use. Water and land and vegetation changes that have altered the underlying surface conditions and hydrological feedbacks that, in turn, have increased runoff.

"Our work is helping to explain the underlying physical mechanisms associated with intensification of precipitation and extreme runoff," said Gentine. "This will help improve flood prediction and early warning alerts, our results can help provide scientific guidance for planning resilience of infrastructure and ecosystems, and could also help formulate strategies." to deal with climate change. "

Precipitation is generated after condensation of water vapor in the atmosphere, and the intensity of precipitation is governed by the availability of atmospheric water vapor. Since the atmosphere can retain more moisture as the temperature increases, climatologists expect an intensification of extreme precipitation with climate change.

As previous studies focused on the response of precipitation, the Gentine team decided to examine the response of extreme precipitation and storm runoff to natural and anthropogenic changes in surface temperature and atmospheric moisture content. They performed a hydrological analysis on a global scale to characterize the responses and their underlying physical mechanisms. The researchers then assessed the influence of variability over decades on the scale of runoff extremes and temperature, and then systematically compared it with changes in precipitation extremes. Their daily flow observation data came from the Global Runoff Data Center (GRDC) data sets and daily precipitation and near-surface air temperature data from the ground. Global Summary of the Day (GSOD).

"We were trying to find the physical mechanisms causing increased rainfall and runoff around the world," said the study's lead author, student Jiabo Yin. guest of Wuhan University and working in the group of Gentine. "We know that precipitation and runoff extremes will greatly intensify in the future, and we need to modify our infrastructure accordingly.Our study establishes a framework for studying stormwater response."

Rainfall is governed by both thermodynamics (relationship between water vapor and temperature) and atmospheric dynamics. The Gentine team then plans to spread the effects of thermodynamics and dynamics on precipitation to better understand the intensification of precipitation. They will also focus on detecting changes due to warming from those due to human activity in order to establish an adaptive water resource management system.

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More information:
Jiabo Yin et al., Increased global runoff extremes caused by climate and anthropogenic changes, Nature Communications (2018). DOI: 10.1038 / s41467-018-06765-2