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More Harvey-Sized Hurricanes Likely to Hit Texas
By Tim Radford
The probability that some city in the U.S. state of Texas will be hit again by Harvey-sized hurricanes, rainstorms that will dump half a meter of water in a short space of time, has increased sixfold in this century and will have increased 18-fold by 2100, thanks to climate change driven by global warming.
In the late summer of 2017, Hurricane Harvey dropped 65 cms of water on the city of Houston in Texas. It was the start of the largest natural disaster in the U.S. since Hurricane Katrina pounded New Orleans in 2005. Harvey claimed an estimated 70 lives, and created more than $150 billion in damage.
Kerry Emanuel, a meteorologist and professor of atmospheric science at Massachusetts Institute of Technology, asked a simple question: How likely is it that hurricane-induced flooding of such magnitude could happen again?
He reported in the Proceedings of the National Academy of Sciences that he looked again at the probabilities. Since 1899, only 11 U.S. hurricanes have brought with them rainfalls that measured more than 65 cms. Until Harvey, the most recent had been a hurricane called Patricia which dumped more than 50 cms in some parts of Texas.
For Texas alone, from 1981 to 2000, the chance of an event on the scale of Harvey or Patricia was 1 percent: that is, one chance in a hundred during any one year, with a high likelihood of such an event once every 100 years.
Harvey would once have counted as the storm of the century, and the chance of it hitting Houston made it an even more improbable event. Statistically, such a thing should happen once in 2,000 years.
But the past, Prof. Emanuel argues, is no longer a good guide to the future.
"When you take a very, very rare, extreme rainfall event like Hurricane Harvey, and you shift the distribution of rain toward heavier amounts because of climate change, you get really big changes in the probability of those rare events," he said. "People have to understand that damage is usually caused by extreme events."
He is not the only researcher to have looked at the statistics with alarm. More than one study has found that the Atlantic coast of the U.S. could face harder and more frequent battering as global temperatures creep up in response to ever-increasing use of fossil fuels that leave ever-growing ratios of the greenhouse gas carbon dioxide in the atmosphere.
One group has warned that coastal storms and floods could create new millions of U.S. climate refugees. The problem is not uniquely an American one: by the century's end, coastal flooding could be costing the nations of the world $100 trillion a year, as sea levels rise and extreme events such as tropical cyclones and storm surges become more intense, and more frequent.
Odds on Calamity
Some studies have concentrated on conditions for particular coastal cities such as Charleston or Seattle, where the once-in-500-year floods could in the next century happen 273 times more often.
Studies like these may sound alarmist: in fact, they have a simple, practical purpose. City authorities need to know if the odds of calamity are on the increase.
"Suppose you're the mayor of Houston, and you've just had a terrible disaster that cost you an unbelievable fortune, and you're going to try over the next few years to put things back in order in your city. Should you be putting in a more advanced storm-sewer system that may cost billions of dollars, or not.
"The answer to that question depends upon whether you think Harvey was a one-off—very unlikely to happen any time in the next 100 years—or whether it may be more common than you thought," Prof. Emanuel said.
"We are seeing for Texas an event whose annual probability was 1 percent at the end of last century, and it might be 18 percent by the end of this century. That's a huge increase in the probability of that event. So, people had better plan for that."
Reposted with permission from our media associate Climate News Network.
EcoWatch Daily Newsletter
By Julia Conley
Climate campaigners on Friday expressed hope that policymakers who are stalling on taking decisive climate action would reconsider their stance in light of new warnings from an unlikely source: two economists at J.P. Morgan Chase.
Tensions are continuing to rise in Canada over a controversial pipeline project as protesters enter their 12th day blockading railways, demonstrating on streets and highways, and paralyzing the nation's rail system
Colorado River Has Lost 1.5 Billion Tons of Water to the Climate Crisis, 'Severe Water Shortages' May Follow
California is headed toward drought conditions as February, typically the state's wettest month, passes without a drop of rain. The lack of rainfall could lead to early fire conditions. With no rain predicted for the next week, it looks as if this month will be only the second time in 170 years that San Francisco has not had a drop of rain in February, according to The Weather Channel.
The last time San Francisco did not record a drop of rain in February was in 1864 as the Civil War raged.
"This hasn't happened in 150 years or more," said Daniel Swain, a climate scientist at UCLA's Institute of the Environment and Sustainability to The Guardian. "There have even been a couple [of] wildfires – which is definitely not something you typically hear about in the middle of winter."
While the Pacific Northwest has flooded from heavy rains, the southern part of the West Coast has seen one storm after another pass by. Last week, the U.S. Drought Monitor said more Californians are in drought conditions than at any time during 2019, as The Weather Channel reported.
The dry winter has included areas that have seen devastating fires recently, including Sonoma, Napa, Lake and Mendocino counties. If the dry conditions continue, those areas will once again have dangerously high fire conditions, according to The Mercury News.
"Given what we've seen so far this year and the forecast for the next few weeks, I do think it's pretty likely we'll end up in some degree of drought by this summer," said Swain, as The Mercury News reported.
Another alarming sign of an impending drought is the decreased snowpack in the Sierra Nevada Mountain range. The National Weather Service posted to Twitter a side-by-side comparison of snowpack from February 2019 and from this year, illustrating the puny snowpack this year. The snow accumulated in the Sierra Nevadas provides water to roughly 30 percent of the state, according to NBC Los Angeles.
Right now, the snowpack is at 53 percent of its normal volume after two warm and dry months to start the year. It is a remarkable decline, considering that the snowpack started 2020 at 90 percent of its historical average, as The Guardian reported.
"Those numbers are going to continue to go down," said Swain. "I would guess that the 1 March number is going to be less than 50 percent."
The National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center forecast that the drier-than-average conditions may last through April.
NOAA said Northern California will continue deeper into drought through the end of April, citing that the "persistent high pressure over the North Pacific Ocean is expected to continue, diverting storm systems to the north and south and away from California and parts of the Southwest," as The Weather Channel reported.
As the climate crisis escalates and the world continues to heat up, California should expect to see water drawn out of its ecosystem, making the state warmer and drier. Increased heat will lead to further loss of snow, both as less falls and as more of it melts quickly, according to The Guardian.
"We aren't going to necessarily see less rain, it's just that that rain goes less far. That's a future where the flood risk extends, with bigger wetter storms in a warming world," said Swain, as The Guardian reported.
The Guardian noted that while California's reservoirs are currently near capacity, the more immediate impact of the warm, dry winter will be how it raises the fire danger as trees and grasslands dry out.
"The plants and the forests don't benefit from the water storage reservoirs," said Swain, as The Mercury News reported. "If conditions remain very dry heading into summer, the landscape and vegetation is definitely going to feel it this year. From a wildfire perspective, the dry years do tend to be the bad fire years, especially in Northern California."
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