Recent record-breaking rainfall in the northeastern United States is part of a broader trend. From Maine to West Virginia, the Northeast has seen a sharp increase in precipitation extremes—heavy rain and snow resulting in about 1 to 2 inches of water per day depending on the location—since 1996, which has coincided with warming sea level in the North Atlantic. Northeast extreme rainfall is typically caused by tropical cyclones, storms along fronts, and extratropical cyclones such as The Norwegian. A recent study published in Extreme weather conditions and climate finds that the increase in extreme precipitation after 1996 was caused by greenhouse gases from human activity and the variability of the surface temperature of the North Atlantic Ocean, known as Atlantic variability.
“Our previous work showed that northeast extreme precipitation has increased dramatically over the past 25 years, but this study is among the first to show that this increase is partly due to anthropogenic climate change,” said lead author Huanping Huang, former graduate student. in earth sciences and a graduate of the Applied Hydroclimatology Group at Dartmouth. Huang is currently a postdoctoral fellow in the Department of Climate and Ecosystem Sciences at Lawrence Berkeley National Laboratory.
This study builds on previous work by Huang and co-authors, who found that the northeastern region has experienced 53% increase in extreme rainfall since 1996, and that the main driver of the increase is enhanced heavy rainfall from tropical cyclones. The team linked the enhanced heavy rainfall from tropical cyclones to both a warmer atmosphere, which increases the amount of water the air can hold, and a warmer Atlantic Ocean, which creates stronger and more frequent hurricanes. “Our results demonstrate that multidecadal variability in Atlantic sea surface temperatures, a major driver of Atlantic warming, along with anthropogenic greenhouse gases and aerosols, also contributed to the increase in Northeast precipitation extremes after 1996.” , Huang added.
To determine the causal factors of increased extreme precipitation in the Northeast and warming of Atlantic sea surface temperatures from 1929 to 2018, the research team used two large sets of global climate model simulations provided by the National Center for Atmospheric Research, as and precipitation data from US weather stations from the World Historical Climatic Network compiled by the National Centers for Environmental Information of the National Oceanic and Atmospheric Administration.
To isolate the causes of the extreme increase in precipitation, the team used a set of global climate model simulations that reproduce the historical climate by including the evolution of all natural and anthropogenic forcings. Natural forcings include solar radiation and volcanoes, while anthropogenic forcings include greenhouse gases, industrial aerosols (particles from burning fossil fuels), aerosols from biomass burning, and land use and land change. In the other set of simulations, all but one of the four anthropogenic forcings were included. Through this leave-one-out approach, researchers could isolate the effects of external forcing and internal variability (natural climate changes) on the observed changes in North Atlantic sea surface temperature and Northeast extreme precipitation . The researchers then applied a statistical method called “optimal fingerprinting,” often used in climate change research, to determine the extent to which external forcings have affected the regional climate.
The findings revealed that the extreme increase in rainfall observed after 1996 was caused by greenhouse gases from human activity and a warmer North Atlantic Ocean. The warming of the North Atlantic Ocean since the 1990s can be attributed to multidecadal variability, reduced industrial aerosols and increased greenhouse gases. As air quality improved due to the Clean Air Act of 1970, aerosols that pollute the atmosphere and reflect sunlight decreased. This reduced cooling from fewer aerosols, combined with warming from increased greenhouse gases from human activity, warmed the North Atlantic.
“Our analysis shows that reduced aerosols and increased greenhouse gases from human activity have contributed to both the rise in extreme precipitation and North Atlantic sea surface temperatures,” said co-author Jonathan Winter, associate professor in geography and principal investigator of Applied. Hydroclimatology Group at Dartmouth. “Our research team has been investigating this dramatic increase in extreme rainfall for several years, and this study confirms that humans are, in fact, partly responsible for the increase in extreme rainfall we've been experiencing over the past two and a half decades.”
More information:
Huanping Huang et al, Rise in Northeast US Precipitation Extremes Driven by Atlantic Variability and Climate Change, Extreme weather conditions and climate (2021). DOI: 10.1016/j.wace.2021.100351
Reference: Increase in extreme precipitation in the Northeast due to Atlantic variability and climate change (2021, 4 August) Retrieved 24 July 2024 from
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