An area is flooded in Galveston, about 75 kilometers southwest of Houston, the United States, Aug. 29, 2017. Tropical storm Harvey has broken the record of rainfall from a cyclonic storm in the U.S. mainland, with 132 centimeters of rain observed in the state of Texas, authorities said on Tuesday.(Xinhua/Robert Stanton)
by Xinhua writers Yang Shilong, Lin Xiaochun, Li Ming
NEW YORK, Aug. 30 (Xinhua) -- Although it might be hard to directly blame climate change for Hurricane Harvey, which has wreaked havoc in the U.S. state of Texas, human-caused global warming has enhanced some of the impacts of the tropic storm, climate scientists say.
EXTREME RAINFALL EXACERBATED BY CLIMATE CHANGE
"It's hard to put a figure on the amount that climate change has contributed to Harvey's impacts but we've definitely exacerbated the flooding impacts in particular," Andrew King, climate extremes research fellow at School of Earth Sciences, University of Melbourne, told Xinhua via email late Tuesday.
"Limiting the future damage from this kind of event could definitely be seen as an incentive to follow the Paris Accord and attempt to keep global warming below the 2C (2 degrees Celsius) level," King said.
Harvey's biggest effect is through its intense and prolonged rainfall, the scholar noted, a low pressure system to the north is keeping Harvey over southern Texas, resulting in greater rainfall totals.
"We know that climate change is enhancing extreme rainfall. As the atmosphere is getting warmer, it can hold more moisture -- roughly 7 percent more for every 1 degree Celsius rise in temperature," King explained.
"This means that when we get the right circumstances for very extreme rainfall to occur, climate change is likely to make these events even worse than they would have been otherwise."
"Without a full analysis, it is hard to put exact numbers on this effect, but on a basic level, wetter skies mean more intense rain," he added.
According to local media reports, Harvey's rainfall total reached 49.32 inches (125.27 cm) in Friendswood, Texas, in less than a week. That is about as much rain as the metropolitan region normally sees in a year.
Harvey is "unusual" because it "continued to strengthen in the Gulf of Mexico until it made landfall...This is almost definitely linked to the anomalously high sea surface temperatures there as it developed," noted Sir Brian Hoskins, chairman of the Grantham Institute for Climate Change at Imperial College London and professor of Meteorology at the University of Reading.
DAMAGE WORSENED BY HUMAN ACTIVITIES
Many scientists have pointed to Hurricane Harvey as further evidence of the dangers of climate change.
"Climate change due to increased greenhouse gases in the atmosphere makes the occurrence of the warm waters in the Gulf of Mexico (and elsewhere) more likely, and so it has increased the chances of occurrence of a hurricane like Harvey, and the devastating impacts that go with it," Hoskins said.
"Whether we can attribute Harvey to global warming, as with any individual weather event, is a questionable proposition," said Dr. Jeffrey Kargel, Department of Hydrology & Atmospheric Sciences at the University of Arizona.
"But it is very likely that many more storms like Harvey and Katrina and bigger ones yet are on the way. The expected higher frequency of such storms is "an effect of global climate change" brought on mainly by burning of fossil fuels," Kargel said.
One cannot say climate change "caused" Hurricane Harvey but the severity of the storm and associated damage were "worsened" by human activities, particularly the substantial emissions of greenhouse gases that are warming the oceans and the air above, said Richard Allan, professor of climate processes at the University of Reading.
A warmer ocean and the air above were able to inject greater quantities of moisture into the storm leading to an intensification of the already extreme rainfall, he said.
Additionally, sea level rise driven by climate warming combined with coastal subsidence related to human activities increased the storm surge while urban development such as paving over grasslands and prairies are likely to have exacerbated flooding, according to Allan.
DEBATE RENEWED OVER TRUMP'S CLIMATE POLICIES
Hurricane Harvey, likely to end up being one of the most costly disasters in U.S. history, has also renewed hot debate over the U.S. climate policies under the administration of President Donald Trump.
"The scenes from Texas are shocking. Such extreme rainfall events are likely to get even more intense as our climate warms. When the flood waters finally recede, and the rebuilding of homes, businesses and lives begins, climate resilience needs to be (at the) front and centre," noted Dave Reay, professor of Carbon Management at the University of Edinburgh.
"President Trump may have withdrawn the U.S. from the Paris Climate Agreement, but he can't opt out of the laws of physics," Reay said.
Trump's actions are an "extreme outlier" in an "era of extreme weather" as the United States "flies blindly into a world of rising waters and storms our coastal cities won't be able to withstand," wrote Silvio Marcacci in his comment "Trump's climate policy legacy will be making disasters like Harvey worse" carried by thehill.com on Wednesday.
"Count me among the disbelievers when Trump says America will be stronger than ever before, and among those who fear his actions will harm our communities, country and climate," Marcacci said.
Conservative groups, however, shrug off any link between Harvey and climate change.
Myron Ebell, director of environmental policy at the Competitive Enterprise Institute, said the last decade has been a "period of low hurricane activity" and pointed out that previous hurricanes occurred when emissions were lower, according to a report by theguardian.com.
"It is unfortunate, but not surprising, that the left is exploiting Hurricane Harvey to try and advance their political agenda, but it won't work," said Bette Grande, a heartland research fellow and a Republican who served in the North Dakota state legislature until 2014.
The Texans are also split over the issue.
"I believe humans have messed with the environment for sure...(yet) I feel like global warming is something which is not as serious as a lot of people say," Marc Guzman, a Trump supporter at Austin, Texas, told Xinhua.
His town fellow Caroline disagreed:" When I moved down here in 1980, usually by September, it was starting to get cool weather, but now in September it just is hot. September is as August and July. And we are not having much of winter any more."
Trump's pulling out of the global climate deal "is first of many bad decisions he's making", she said.
"My only hope is that people living in Houston, some of whom did vote for Trump, now realize (they did it wrong,) because they are affected first hand," said Abigail Lindsey.
"It's terrible, but I think that's the only way that people are going to realize that the climate change is real. They are physically affected by it. So I hope there's some good come out of this," she added.
"It's fine (for Trump) to say America First as a campaign slogan...But the slogan we should always say is Earth First, not America First, we are all part of the same planet, and what we were doing is impacting the planet in the negative way that can ultimately destroy the future," Brian Greene, professor of physics and mathematics at Columbia University, told Xinhua on June 1 when Trump announced withdrawal from the Paris climate accord.
"What does it mean to put one country first when there is no future for us, so rather think it is an economic issue, why don't think it's a political issue, think it as a human issue, think what kind of planet we are leaving for the next generation?" asked Greene.