Study Finds Human-Caused Climate Change Made Hurricane Harvey Record Rainfall Three Times More Likely

World Weather Attribution’s (WWA) scientific analysis has found that human-caused climate change made the record rainfall that fell over Houston during Hurricane Harvey roughly three times more likely and 15 percent more intense.

Homes sit surrounded by flood waters brought on by Hurricane Harvey near Houston, Texas, Aug. 31, 2017. U.S. Air Force photo by Master Sgt. Jason Robertson/Released

The recent study, Attribution of extreme rainfall from Hurricane Harvey, August 2017, focused primarily on the changes in extreme rainfall in the US Gulf Coast region, applied to the rainfall during Hurricane Harvey that caused record flooding in Houston.

Between 25 and 30 August, 2017, Hurricane Harvey stalled over Texas and caused extreme precipitation, particularly over Houston and the surrounding area between 26 and 28 August. Baytown recorded 1043.4 mm of rain over a 3 day period.

The study found that the three-day rainfall sums responsible for most of the flooding were extremely rare, with a return time for station observations of more than 9000 yr (97.5% CI) in the current climate, taking the trend into account. This would have caused flooding in any city.

Secondly, the study found strong evidence that global warming over the last century, primarily caused by anthropogenic greenhouse gas emissions, increased the intensity of the three-day rainfall extremes on the Gulf Coast.

The study also acknowledged that other factors have likely also contributed to increased flood risk in Houston, including relative sea level rise and changes in land use and land cover in the region.

Members of the South Carolina’s Helicopter Aquatic Rescue Team (SC-HART) perform rescue operations in Port Arthur, Texas, August 31, 2017. Credit: U.S. Air National Guard photo by Staff Sgt. Daniel J. Martinez

About World Weather Attribution (WWA)

WWA is an international coalition of scientists that objectively and quantitatively assesses the possible role of climate change in individual extreme weather events.

Previously WWA found that global warming increased the likelihood of the heavy precipitation associated with Storm Desmond that hit the UK in the winter of 2015 to 2016 and the heavy rain that caused major flooding in the Seine and the Loire River basins in France during May 2016.

Research into the floods in southern India of December 2015 however found no connection to global warming. The WWA said “No effect of human-induced climate change was detected in the the extreme one-day rainfall that caused widespread flooding in Chennai, India on December 1, 2015”