Before Harvey, it had been a record 12 years since a major hurricane made landfall in the United States, but that hasn’t stopped the climate change movement from blaming the Category 4 storm on global warming.
A torrent of claims linking Hurricane Harvey to climate change surfaced after the storm hit Corpus Christi, Texas, late Friday, bringing catastrophic flooding and an unprecedented 50 inches of rain by Tuesday as the system stalled over the Houston area.
“Harvey is what climate change looks like,” meteorologist and climate activist Eric Holthaus declared Tuesday in Politico magazine.
Climate Reality Project, founded by former Vice President Al Gore, argued that “climate change makes hurricanes more devastating,” while 350.org called the storm “an unnatural disaster” and “the product of both a hotter planet and this administration’s climate denial, racism and callousness.”
“[W]e can’t say that Hurricane Harvey was caused by climate change. But it was certainly worsened by it,” Michael E. Mann, Penn State professor of atmospheric science, said in a Monday op-ed headlined “It’s a fact: climate change made Hurricane Harvey more deadly.”
Begging to differ was Judith Curry, a climatologist and recently retired Georgia Tech professor, who cited data showing Harvey tied for 14th among strongest U.S. hurricanes since 1851 as ranked by pressure, along with storms from 1989 and 1954.
“Anyone blaming Harvey on global warming doesn’t have a leg to stand on,” Ms. Curry said on her Climate Etc. blog.
Roger Pielke Jr., a professor at the University of Colorado Center for Science & Technology Policy Research, pointed out that there were 14 U.S. landfalls of Category 4 or greater hurricanes — Category 5 is the highest — from 1926 to 1969, but only four from 1970 to 2017.
A specialist on extreme weather, Mr. Pielke said just four hurricanes of any size made landfall during the Obama administration for an average of 0.5 per year, the fewest of any presidential administration dating back to 1901.
The number was small despite rising greenhouse gas emissions in the atmosphere. Why? Mr. Obama was lucky, Mr. Pielke said.
“There is no reason to be debating Harvey and climate change in the context of an unfolding disaster, other than political opportunism and attention seeking,” Mr. Pielke said in a statement. “It’s not a good look for scientists or journalists who are promoting this issue.”
Assessments by the U.N. Intergovernmental Panel on Climate Change and others “are quite clear on this subject and one storm doesn’t change that. A better focus in the short term is on those with expertise in disaster response and recovery. The politicized debate over climate change can wait,” Mr. Pielke said.
Not everyone took his advice.
“As the inundation of Houston and other parts of the Texas Coast reached cataclysmic, probably unprecedented levels, it was clear that climate change played a role in worsening the storm,” InsideClimate News said Tuesday in an article.
San Francisco billionaire Tom Steyer, founder of NextGen Climate, said on Twitter that humans “must stop adding to the damage.”
What’s inconvenient for the climate change movement is that Harvey broke up a 142-month hurricane drought, which was the longest period without a major hurricane hitting the continental United States since the 96 months from September 1860 to August 1869, CNSNews reported.
Penn State’s Mr. Mann, a leader of the climate “consensus” camp, argued that rising sea levels and surface temperatures create more moisture in the atmosphere, which “creates the potential for much greater rainfalls and greater flooding.”
An ‘unprecedented’ event
“Harvey was almost certainly more intense than it would have been in the absence of human-caused warming, which means stronger winds, more wind damage and a larger storm surge,” Mr. Mann said in the [U.K.] Guardian.
Roy W. Spencer, principal research scientist at the University of Alabama in Huntsville, disagreed, saying he plotted the sea surface temperatures of all major Category 3 strikes in Texas since 1870 and found that “major hurricanes don’t really care whether the Gulf is above average or below average in temperature.”
He also challenged Mr. Mann’s assertion that global warming may explain why the storm stalled over Southeast Texas, producing record rainfall.
“This pattern, in turn, is associated with a greatly expanded subtropical high-pressure system over much of the U.S. at the moment, with the jet stream pushed well to the north,” Mr. Mann said. “This pattern of subtropical expansion is predicted in model simulations of human-caused climate change.”
Not so, said Mr. Spencer, who explained: “We didn’t have a warm August in the U.S. pushing the jet stream farther north.”
“The flooding disaster in Houston is the chance occurrence of several factors which can be explained naturally, without having to invoke human-caused climate change,” Mr. Spencer said on his Global Warming blog.
The National Weather Service reported Tuesday that Harvey had produced more than 50 inches of rain in Cedar Bayou, Texas, surpassing the measured single-storm rainfall record for the continental United States.
Then again, said Mr. Spencer, if the system had been moving a little faster, it would have dispersed the rainfall over a wider area and missed the record despite producing the same amount of precipitation.
“There is no aspect of global warming theory that says rain systems are going to be moving slower, as we are seeing in Texas,” Mr. Spencer said. “This is just the luck of the draw.”
The National Weather Service fueled the political debate with a Sunday tweet: “This is unprecedented & all impacts are unknown & beyond anything experienced.”
That may well turn out to be the case in terms of property damage and the size of the population affected — Houston is the fourth-largest city in the nation with 2.3 million — but it “won’t be because this was an unprecedented meteorological event,” said Mr. Spencer.
“‘Unprecedented’ doesn’t necessarily mean it represents a new normal,” Mr. Spencer said. “It can just be a rare combination of events.”
He noted that there were so many strong U.S. hurricanes in 2005, including the Category 5 Hurricane Katrina, that the National Hurricane Center ran out of names for the tropical storms. Then came the 12-year drought of major hurricanes.
“Weird stuff happens,” Mr. Spencer concluded.