DisastersClimate change made Hurricane Harvey's rainfall three times more likely

Climate change did not cause Hurricane Harvey, but two independent studies have concluded that global warming dramatically increased the probability of a storm of its magnitude occurring ahead of its appearance, and intensified the severity of its impact when it arrived.

“Did climate change make this event more likely than in the past? Yes,” said Dr. Karin van der Wiel of the Royal Netherlands Meteorological Institute, who co-authored one of the studies, published Environmental Research Letters.

CNN reports that the researchers compared Hurricane Harvey’s rainfall to the historical records, concluding that such an extreme weather event should only be expected once every 9,000 years. The researchers then used climate models to run simulations which showed different levels of climate change.

Comparing historical weather records with the results of the simulations allowed the scientists to assess the impact different levels of climate change had on the probability of the hurricane’s rainfall.

CNN says that the other study, carried out by the Lawrence Berkeley National Laboratory, used computer simulations to analyze Harvey’s heavy rains over a week, They calculated that global warming increased the storm’s rainfall by nearly 20 percent.

The findings were presented at the American Geophysical Union meeting in New Orleans. 

While Harvey was battering Texas, scientists suspected the storm had been made more intense by global warming, but they did not have the data to confirm their suspicions.

The scientists say that the increase in rainfall may be linked to increases in the ocean’s heat content. Most of the heat which greenhouse gasses trap in the atmosphere is absorbed by oceans, and this trapped heat fuels hurricanes.

“[One of the studies] suggests that the extreme rainfall component of Hurricane Harvey was made 15 percent more intense due to climate change, which is broadly in agreement with the atmospheric theory that has been developed in this area,” said Dr. Dann Mitchell, a climate physicist at the University of Bristol who was not involved in the study. 

The research is but the latest addition to a growing body of evidence that extreme weather events are exacerbated and made more intense by climate change.

Understanding the role that global warming plays in natural disasters is a developing area of science, and one that plays a vital role in shaping public narratives about climate change.

Earlier this week, the U.K. Energy and Climate Intelligence Unit issued a report which found extensive links between climate change and extreme weather events. 

“Two years’ worth of studies shows that climate change is affecting heatwaves, droughts and rainfall right now,” Richard Black, director of the Energy and Climate Intelligence Unit, told the Independent.

Scientists note that while events such as heatwaves and droughts are relatively easy to link with increases in global temperatures, the question of the links between hurricanes and climate change is more complicated.

“Attribution of hurricane characteristics to climate change is extremely challenging, and the authors have focused only on the precipitation response, which is perhaps the most well understood, and is particularly important given the nature of the flooding in Texas due to Harvey,” said Dr. Mitchell.

He said that further investigation of hurricane dynamics will be vital going forward.

“Such research is needed for understanding future changes in cyclones and avoiding impacts if we follow the Paris Agreement on climate change, rather than current, high greenhouse gas emission pathways,” he said.