Image by Gerd Altmann from Pixabay

Hurricane Ida hit us and then moved north. Rainfall hit both areas and places in between. Why so much water? Climate change. Human caused.

You can chalk up Hurricane Ida’s devastating rainfall in southeast Louisiana – and now in New York City – at least in part to human-caused global warming, scientists agree. “We expect more extreme rainfall in hurricanes today from climate change,” said Allison Wing, a climate scientist at Florida State University. “And that rainfall will occur far away from where the storms make landfall, farther inland.” In the LaPlace area, 15 to 17 inches of rain on Sunday and Monday combined with Ida’s storm surge to flood the town. LaPlace sits 6.8 to 13 feet above sea level, and the National Weather Service reported that the water level at Pass Manchac, just north of town, reached 6.46 feet above sea level. With waves half again as high likely atop the surge, that conjures an image of water 9.69 feet deep pushing through LaPlace. Two days later and 1,200 miles from LaPlace, Ida’s still soggy remnants dropped 5 to 9 inches of rain Wednesday across parts of New Jersey and New York City, the National Weather Service said, “resulting in considerable to locally catastrophic flooding.” Four to 7 inches fell across much of southern Connecticut, northwest Long Island and the lower Hudson River Valley. Some areas saw phenomenal rainfall rates of 3 to 4 inches per hour.

Wee sort of expect the rain now – getting used to it? But they are not.

From Maryland to Connecticut, the storm killed 45 people Wednesday night and Thursday – including at least 11 in flooded basement apartments in New York City. Human-caused global warming has heated the atmosphere, so it holds more moisture. As thunderstorms occasionally grow into hurricanes in the Atlantic Basin and move onshore, the excessive moisture rains out for days on end. “The low end estimate of the increase [in rainfall] is 5% to 7% per 1 degree of warming,” said Colin Zarzycki, a climate and atmospheric dynamics research professor at Penn State University. “But it can go higher than that.”

How can we stop this? Ids there any way? The winds help blow the storms up toward the North East and they drop rain all along the way. But to still have 5-9 inches of rain after that journey?

Stopping this trend is a challenge for the world and, especially, for Louisiana. A recent LSU analysis found that 62% of the state’s greenhouse gas emissions – the kind that cause global warming – come from industrial plants that were built in Louisiana in large part because of tax breaks and access to deepwater ports. More research will be required to determine exactly how much wetter Ida was because of climate change. But there’s already a clear history linking intense rain during hurricanes, and at other times, to global warming, said S-Y Simon Wang, a professor of climate dynamics at Utah State University. “Hurricane Harvey [in 2017] in the Houston metro area had a 20 percent increase in its rainfall intensity because of the warming climate,” Wang said. He said the Louisiana Flood of 2016 in the Baton Rouge area also was estimated to be 40 percent more intense than it should have been because of global warming.

How much and what parts of Ida can be attributed to climate change?

Other characteristics of Ida’s fury are a bit more difficult to link directly to climate change, scientists say. Kevin Trenberth, a senior scientist with the National Center of Atmospheric Research, said hurricanes actually perform a role as ocean coolers. They pump heat out of the Atlantic Ocean, Caribbean Sea and Gulf of Mexico and deliver it to the atmosphere, where it disperses or is radiated into space. But at the height of summer, he said, cooler air from higher latitudes can’t filter into the tropics to cool and dehumidify the air, as occurs during the rest of the year. “So hurricanes turn out to be the most efficient mechanism to keep the oceans from getting too hot,” he said, pulling heat out of ocean waters yet in the process adding moisture to the atmosphere. “That moisture spirals into the storms and forms the heavy rain,” Trenberth said, and the latent heat acts as fuel to intensify the storms. He said the last big cleanout of heat in the Gulf of Mexico was in 2017, when Hurricane Harvey wrung enough up heat and moisture to dump 60 inches of rain on Houston over four days. Ever since, the Gulf heat has been building. By July, he said, the Gulf was exceptionally warm not just at the surface but as deep as 50 meters, or 164 feet. “The buildup of heat has a substantial climate change component, and as the hurricanes tap the surface waters, the strong winds stir up the waters and normally give rise to a cold wake,” that is, colder water pulled to the surface, which reduces the energy needed to keep a tropical storm going. “But with exceptionally warm subsurface waters, the hurricane is instead continually fueled and leads to more activity: more intense storm, possibly bigger and longer-lasting.”

Ida, like many before her, intensified rapidly as she moved across the Gulf.

Ida’s strength when it hit in Louisiana resulted from meteorologists call rapid intensification: Its wind speed increased from Category 1 to Category 4 strength in just 24 hours, from the time it left the northern tip of Cuba to its landfall Sunday at 11:55 a.m. at Port Fourchon. Like Trenberth, other researchers point to the higher water temperatures deeper in the Gulf of Mexico as a key factor in rapid intensification. Ida might not have been able to access cooler water that would have reduced its intensification. But there’s a more natural ringer that’s likely the cause of the rapid intensification in Ida: the “loop current,” chunks of the Gulf Stream that break off each year and meander in the Gulf of Mexico. The Gulf Stream is a 200-meter-deep river of warm water that snakes from the Caribbean Sea around the Florida Keys and up the East Coast. The loops that spin off from it hang onto a portion of that warm water. This year, Ida traveled directly over part of one of those loops, causing rapid intensification in less than a day as the storm kept pulling up warm water. The loop acted like a burner beneath a pot of boiling water, increasing the energy feeding the storm.

The general warming of the oceans may also be a factor in the problem. That is a common factor that is seen today.

Zarzycki, the Penn State scientist, said there’s a chance the Gulf Stream and its loops might be warming a bit as a result of the broader warming of oceans from rising global temperatures. But how big a factor that increase was in intensifying Ida is unclear. Equally unclear, said Chris Landsea, science officer for the National Hurricane Center, is whether Ida’s intensity – 150 mph at landfall – was significantly more than the historical record for hurricanes. He said research does show that there’s likely to be a 5 percent increase in the intensity of hurricanes through the end of the current century, as global temperatures continue to rise. But he points to other reasons for the seeming trend of more intense storms in recent years: the lack of modern tools to identify tropical storms and hurricanes before 1980, and the dramatic improvement in those tools in identifying storms and their intensities today. Equally problematic is identifying whether Hurricane Ida, the ninth named storm of 2021, is part of a trend of more named storms every year. “It’s awful difficult to pick out any particular storm and say, ‘Well, there’s climate change,’” said Kerry Emanuel, a climate scientist at the Massachusetts Institute of Technology. “I don’t consider Ida meteorologically extraordinary. It was on the high end of intense storms, but did not break any records.” “Globally, the numbers of storms occurring each year around the globe have been very stable since accurate counts began in 1980,” he said. He said a measurably higher number occurring in the Atlantic beginning in the 1970s is actually the result of an environmental improvement: the reduction of particulate matter by stricter environmental laws in the northern hemisphere.

What part does the industry of Louisiana play? Especially the refineries.

The particulates, a byproduct of burning for industrial processes, actually reduced storm formation before then, a trend mirrored in years when major volcanic eruptions have pumped large quantities of particulates in the air. Also clearly the result of rising temperatures are present and future increases in the height of storm surge that accompanies hurricanes. On Louisiana’s coast, surge impacts are expected to increase in future years as the normal water level rises almost 2 feet by 2050, according to a NASA estimate combining subsidence and new sea level projections. Another key factor is what’s in the path of hurricanes such as Ida, said Wang, the Utah State scientist. “If another Katrina hit New Orleans again, there’s no question that New Orleans learned from Katrina, strengthened its protections,” he said. “But other small communities may have built a new school, planned for new generators, taken other steps” – which might or might not have been equal to either Ida or a Katrina repeat. “One must always weigh the societal factor when it comes to damage,” he said.

The societal factor. I am in North Carolina with a daughter. I know other in Texas and other areas around Louisiana. The city is moving people out of the city. There is limited gas and food for those remaining, Yes this is not caused by the hurricane but rather the power loss during the storm but it all blends together. I hope the city is factoring all this in.

New Orleans to New York – both hit by climate change
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