Showing posts with label Flooding of Coast. Show all posts
Showing posts with label Flooding of Coast. Show all posts

Sunday, June 2, 2024

Recordes de secas e cheias mais que dobram de 2014 a 2023 em relação aos dez anos anteriores no Brazil

 

Porto Alegre RS 2014

 



Levantamento do Serviço Geológico do Brasil leva em conta dados de mais de 700 estações no país

 

Leonardo Fuhrmann
São Paulo

As enchentes provocadas em Porto Alegre pelo transbordamento do lago Guaíba não são um problema isolado. O Serviço Geológico do Brasil (SGB) aponta, em levantamento feito para a Folha, que recordes de enchentes e secas foram bem mais comuns na última década do que em períodos anteriores.

A quantidade de recordes de cheias sofreu um aumento expressivo. De 2014 a 2023, somaram 314. Nos dez anos anteriores, eram 182.

A de secas atingiu 406 de 2014 a 2023, mais do que quatro vezes a soma da década anterior, de 92.

A base de número de estações permaneceu estável nos últimos 50 anos, segundo Artur Matos, coordenador do Sistemas de Alerta Hidrológico do SGB. Por isso, a fonte de comparação no período é praticamente a mesma.

Mas o sistema do SGB é bem mais antigo, com informações de mais de um século. Em Manaus, por exemplo, os levantamentos são feitos desde 1900.


 Leidemar Plazido, 29, (camiseta preta) retira pertences de sua casa, atingida pela inundação no bairro Sarandi, um dos mais afetados de Porto Alegre, para levar para a casa dos amigos Otavio Henrique, 25, e Katiane Dias, 31, que o acompanham e o abrigam - Bruno Santos - 22.mai.2024/Folhapress

 Na avaliação de Matos, os dados da última década são prova de que as mudanças climáticas estão provocando uma alteração nos regimes de chuvas do país, com estas últimas mais intensas e períodos mais longos de estiagem.

 

Além de um maior número de picos de enchente e de secas, os dez últimos anos ficaram marcados por quebras consecutivas desses recordes.

Os rios Taquari e Caí, no Rio Grande do Sul, por exemplo, bateram os três maiores recordes de cheia nos dois últimos anos. Em Uruguaiana (RS), o rio Uruguai teve uma de suas seis maiores cheias neste ano. No ano passado e em 2017 o rio também alcançou dois de seus maiores índices. O estado também teve uma estiagem recorde em 2021.

A situação se repete em outras regiões do Brasil.

A maior cheia do rio Amazonas foi em 2021 e 6 das suas 10 maiores cheias foram nos últimos dez anos. O rio teve sua pior seca em 2023. O rio Branco, que banha e dá nome à capital do Acre, registrou suas duas maiores cheias em 2023 e 2024. O Madeira, que em Porto Velho (RO), apresentou sua pior seca em 2023 e seis dos maiores recordes de baixa vazão nos últimos dez anos.

Fonte: Serviço Geológico do Brasil/Ministério de Minas e Energia
 


Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
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Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
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Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
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Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
Veja mais em: https://www.jornaldotocantins.com.br/editorias/vida-urbana/recordes-de-seca-e-cheia-mais-que-dobram-de-2014-a-2023-em-rela%C3%A7%C3%A3o-aos-dez-anos-anteriores-1.2790095
Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
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Recordes de seca e cheia mais que dobram de 2014 a 2023 em relação aos dez anos anteriores - Jornal do Tocantins
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Fonte: Serviço Geológico do Brasil/Ministério de Minas e Energia

 

Matos afirma que o levantamento confirma uma ideia empírica que eles tinham de uma maior incidência dos recordes nos últimos anos e mostra uma tendência de mais secas e cheias. "Os dados apontam uma repetição de situações extremas, tanto de excesso como de falta de água", analisa.

Especialista em modelagem climática do Instituto Nacional de Pesquisas Espaciais (Inpe), Chou Sin Chan confirma que os fenômenos atuais fogem dos modelos climáticos tradicionais. Segundo ela, o desenvolvimento de novas equações meteorológicas têm sido um desafio para quem trabalha com previsões.

Para Chou, as mudanças climáticas estão por trás da alteração nos regimes de chuvas. O modelo atualmente aplicado pelo Inpe já leva em conta as projeções globais de concentração de monóxido de carbono e outros gases do efeito estufa em suas previsões. "A gente tem visto que as projeções que o Painel Intergovernamental sobre Mudanças Climáticas (IPCC) fez no início dos anos 2000 era bastante conservadora em relação à realidade que estamos vivendo", afirma.

O resultado é que, apesar de terem previstos fortes chuvas no Rio Grande do Sul, os levantamentos meteorológicos foram incapazes de apontar uma intensidade tão grande das chuvas e sua persistência ao longo do período.

Um dos motivos, segundo ela, foi a formação de uma massa de gases do efeito estufa que não permitiu que a frente fria seguisse para o Sudeste. Isso fez com que o período de chuvas na região se prolongasse além do previsto. "Lugares como o Rio e São Paulo, que geralmente são atingidos por frentes frias em abril e maio, tiveram calor e falta de chuvas ao longo destes dois meses", exemplifica.


 
Fonte: Serviço Geológico do Brasil 

 

Ela afirma que o obstáculo já causou outras enchentes nos últimos anos não só no Rio Grande do Sul e Santa Catarina, mas também no Uruguai e no norte da Argentina. "Esta situação tem provocado secas e recordes de calor no Sudeste, Centro-Oeste e até na Amazônia."

Outro desafio, de acordo com ela, tem sido prever chuvas muito intensas em uma região específica. É o caso das grandes chuvas que atingiram cidades da região serrana do Rio de Janeiro, como Teresópolis e Petrópolis, em 2011, 2022 e 2023. "As duas cidades ficam a menos de 100 quilômetros da capital fluminense, que não foi atingida pelas mesmas chuvas", afirma.

Pesquisador em Geociências do SGB, Marcus Suassuna aponta também para uma mudança no padrão das chuvas. "Muitas vezes, temos um recorde de chuva no meio de uma longa estiagem", diz. Segundo ele, a água cai em um mesmo lugar ou em um curto espaço de tempo, quando geralmente seria mais espalhada ao longo de uma estação.

 

Ele afirma que o problema é maior em regiões com pouca vegetação ou muito urbanizadas, onde o terreno é mais impermeabilizado. "Isto também acelera a velocidade com que a água das chuvas chegue aos rios, que não tem a capacidade de vazão daquele volume no mesmo ritmo."

Suassuna diz que a situação reforça a necessidade de aumentar a velocidade de informação e os pontos de monitoramento nas bacias hidrográficas, com atenção também para rios secundários que podem afetar bacias maiores ou grandes concentrações populacionais. Outros especialistas entrevistados pela Folha nas últimas semanas já haviam mencionado a necessidade de aprimoramento do sistema de alerta para evitar novas tragédias.

Vinculado ao Ministério das Minas e Energia, o SGB faz medições do volume das águas dos rios desde o início do século passado. Inicialmente, seus dados serviam fundamentalmente para a mineração, mas o monitoramento nas últimas décadas também passou a ser usado para a prevenção de eventos climáticos extremos.

Hoje, 75% do trabalho de monitoramento de bacias hidrográficas no país é feito pelo SGB. O Brasil conta com dados também do Instituto Nacional de Metereologia (Inmet), a Agência Nacional das Águas (ANA) e do Centro Nacional de Monitoramento e Alertas de Desastres Naturais (Cemaden).

Criado em 2011, o Cemaden é o único voltado diretamente para prevenção de eventos climáticos extremos, os demais produzem dados para a agropecuária e utilização de águas para o abastecimento de cidades e a geração de energia elétrica. Como foram criados para outras finalidades, esses monitoramentos não eram desenvolvidos para monitorar rios que provocam impactos em grandes concentrações populacionais

 

Wednesday, June 15, 2022

Methane leak at Russian mine could be largest ever discovered

About 90 tonnes of methane an hour were released from the Raspadskaya coalmine in January, data shows


Blast at the Raspadskaya cola mine, Russia. Photograph: Bloomberg/Getty Images Theguardian.com
 






Possibly the world’s biggest leak of methane has been discovered coming from a coalmine in Russia, which has been pouring out the carbon dioxide equivalent of five coal-fired power stations.

About 90 tonnes an hour of methane were being released from the mine in January, when the gas was first traced to its source, according to data from GHGSat, a commercial satellite monitoring company based in Canada. Sustained over the course of a year, this would produce enough natural gas to power 2.4m homes.

More recently, the mine appears to be leaking at a lower rate, of about a third of the highest rate recorded in January, but the leak is thought to have been active for at least six months before January’s survey.


The leak, which comes from the Raspadskaya mine in Kemerovo Oblast, the largest coalmine in Russia, is about 50% bigger than any other leak seen by GHGSat since it started its global satellite monitoring in 2016. The company believes it is bigger than any leak yet traced to a single source.

Brody Wight, director of energy, landfill and mines at GHGSat, said that methane was an often overlooked side-effect of coalmining that added to the climate impact of burning coal. The Raspadskaya leak would add about 25% to the greenhouse gas emissions of burning any coal produced from the mine, he estimated.

“We are seeing an increase in methane from this site generally, which could be the result of increased coal production, linked to global trends in coal use,” he said.

Russia is one of the world’s biggest sources of methane from fossil fuel extraction. The country’s gas infrastructure, including production facilities and pipelines, is notoriously leaky despite calls for the government to take action.

Paul Bledsoe, a former White House adviser to Bill Clinton and now with the Progressive Policy Institute in Washington DC, said: “Deeply cutting methane is the only sure way to limit near-term temperatures and prevent runaway climate change, yet every month brings new evidence that Russia is hiding the world’s most massive and destructive methane leaks. Putin is desperately hiding these enormous emissions so he can continue to profit from sales of Russian coal, oil and gas and fund his war-making regime. But those nations like China who continue to buy Putin’s oil and gas are equally abetting his climate and war criminality.”

All underground coalmines produce methane, which can cause explosions if it builds up. A blast at the Raspadskaya mine in 2010 killed 66 people.


Venting methane can be done for safety reasons. However, there are ways of capturing methane when it is produced at a high rate, or venting through oxidisation, so that it causes less harm to the climate.

Methane is about 80 times more powerful as a greenhouse gas than carbon dioxide, though it degrades in the atmosphere over about 20 years. In February, the International Energy Agency warned that most countries were under-reporting their methane emissions, and the true amounts pouring into the atmosphere were far greater than had been thought.

Recent studies have shown that cutting methane could be one of the fastest ways of holding down global temperature rises, and that sharp cuts now could prevent a rise of about 0.25C by 2050.

Durwood Zaelke, the president of the Washington-based Institute for Governance, said the Raspadskaya leak showed the urgent need for action. “It’s critical to set up a comprehensive satellite monitoring system for methane. We also need to deploy a system of incentives and sanctions that can remedy these emissions, focusing first on the super emitters,” he said.

The IEA also found that at current high gas prices, the cost of capturing methane was far less than the value of using it or selling it as a fuel source, which should give companies and governments an incentive to capture the gas rather than venting or flaring.


At the Cop26 UN climate summit in Glasgow last November, more than 100 countries agreed to reduce their methane emissions by at least 30% by 2030. Russia was not among them, however.

GHGSat said it measured 13 distinct methane plumes, ranging in size from 658 to 17,994 kg an hour, from the mine. The discovery was made on 22 January, but the company took time to verify its findings and contact the operator of the mine, which has not responded.




Sunday, September 4, 2016

‘Oh, God, it is real.’” - Flooding of Coast, Caused by Global Warming, Has Already Begun.

Scientists’ warnings that the rise of the sea would
eventually imperil the United States’ coastline are no
longer theoretical.
By JUSTIN GILLISSEPT. 3, 2016. (NYtimes)

A house in Norfolk, Va., that has been repeatedly hit by tidal floods sat on temporary supports as workers prepared to elevate it permanently in June.
Credit Eliot Dudik for The New York Times
NORFOLK, Va. — Huge vertical rulers are sprouting beside low spots in the streets here, so people can judge if the tidal floods that increasingly inundate their roads are too deep to drive through.
Five hundred miles down the Atlantic Coast, the only road to Tybee Island, Ga., is disappearing beneath the sea several times a year, cutting the town off from the mainland.
And another 500 miles on, in Fort Lauderdale, Fla., increased tidal flooding is forcing the city to spend millions fixing battered roads and drains — and, at times, to send out giant vacuum trucks to suck saltwater off the streets.
For decades, as the global warming created by human emissions caused land ice to melt and ocean water to expand, scientists warned that the accelerating rise of the sea would eventually imperil the United States’ coastline.
Now, those warnings are no longer theoretical: The inundation of the coast has begun. The sea has crept up to the point that a high tide and a brisk wind are all it takes to send water pouring into streets and homes.
Federal scientists have documented a sharp jump in this nuisance flooding — often called “sunny-day flooding” — along both the East Coast and the Gulf Coast in recent years. The sea is now so near the brim in many places that they believe the problem is likely to worsen quickly. Shifts in the Pacific Ocean mean that the West Coast, partly spared over the past two decades, may be hit hard, too.
These tidal floods are often just a foot or two deep, but they can stop traffic, swamp basements, damage cars, kill lawns and forests, and poison wells with salt. Moreover, the high seas interfere with the drainage of storm water.
In coastal regions, that compounds the damage from the increasingly heavy rains plaguing the country, like those that recently caused extensive flooding in Louisiana. Scientists say these rains are also a consequence of human greenhouse emissions.
“Once impacts become noticeable, they’re going to be upon you quickly,” said William V. Sweet, a scientist with the National Oceanic and Atmospheric Administration in Silver Spring, Md., who is among the leaders in research on coastal inundation. “It’s not a hundred years off — it’s now.”
Local governments, under pressure from annoyed citizens, are beginning to act. Elections are being won on promises to invest money to protect against flooding. Miami Beach is leading the way, increasing local fees to finance a $400 million plan that includes raising streets, installing pumps and elevating sea walls.

In many of the worst-hit cities, mayors of both parties are sounding an alarm.

“I’m a Republican, but I also realize, by any objective analysis, the sea level is rising,” said Jason Buelterman, the mayor of tiny Tybee Island, one of the first Georgia communities to adopt a detailed climate plan.
golink:   http://www.nytimes.com/interactive/2016/09/04/science/global-warming-increases-nuisance-flooding.html
But the local leaders say they cannot tackle this problem alone. They are pleading with state and federal governments for guidance and help, including billions to pay for flood walls, pumps and road improvements that would buy them time.
Yet Congress has largely ignored these pleas, and has even tried to block plans by the military to head off future problems at the numerous bases imperiled by a rising sea. A Republican congressman from Colorado, Ken Buck, recently called one military proposal part of a “radical climate change agenda.”
The gridlock in Washington means the United States lacks not only a broad national policy on sea-level rise, it has something close to the opposite: The federal government spends billions of taxpayer dollars in ways that add to the risks, by subsidizing local governments and homeowners who build in imperiled locations along the coast.
As the problem worsens, experts are warning that national security is on the line. Naval bases, in particular, are threatened; they can hardly be moved away from the ocean, yet much of their land is at risk of disappearing within this century.
“It’s as if the country was being attacked along every border, simultaneously,” said Andrea Dutton, a climate scientist at the University of Florida and one of the world’s leading experts on rising seas. “It’s a slow, gradual attack, but it threatens the safety and security of the United States.”
‘We’re Living It’
One night eight years ago, Karen Speights, a Norfolk resident, was sitting at the dinner table with her mother, eating crab legs dipped in butter and a tangy sauce. She felt a tingle.
“Ma!” she cried. “My feet are wet!”


Her mother laughed, but then she felt it, too: a house that had not flooded since the family moved there in 1964 was soon awash in saltwater. Ms. Speights initially hoped that flood was a fluke. Instead, it turned out to be the first of three to hit their home in less than a decade.
ontinue reading thNowadays, Ms. Speights, an administrative worker at a utility company, is wondering how to get her and her mother out of the neighborhood before the water comes again, without taking too much of a financial hit. And she pays more attention to problems that once seemed remote, like warnings from scientists about the rising sea.
“I believe it because we’re living it,” Ms. Speights said as she sat on her sofa, nodding toward the nearby tidal marsh that sent water into her living room. “The water has to be rising if we never flooded, and all of a sudden we’ve flooded three times in eight years.”
Because the land is sinking as the ocean rises, Norfolk and the metropolitan region surrounding it, known as Hampton Roads, are among the worst-hit parts of the United States. That local factor means, in essence, that the region is a few decades ahead in feeling the effects of sea-level rise, and illustrates what people along the rest of the American coast can expect.
The biggest problems involve frequent flooding of homes and roads. As the sea rises, hundreds of tidal creeks and marshes that thread through the region are bringing saltwater to people’s doorsteps.
This summer, on a driving tour of Norfolk and nearby towns, William A. Stiles Jr. pointed to the telltale signs that the ocean is gradually invading the region.
He spotted crusts of dried salt in the streets, and salt-loving marsh grasses that are taking over suburban yards. He pointed out trees killed by seawater. He stood next to one of the road signs that Norfolk has been forced to install in recent years, essentially huge vertical rulers so people know the depth of floodwaters at low-lying intersections.
“There’s just more and more visible impacts: water on the street, water that won’t clear from the ditch, these intense rain events, higher tides,” Mr. Stiles said.
“It’s beginning to catch the attention of citizens, restaurant owners, business people, politicians. There’s just much more of a conversation, and it’s not just in the politically safe places. It’s everywhere.”
Mr. Stiles, known as Skip, heads a local environmental group, Wetlands Watch. At his suggestion, students at two local universities began looking at the neighborhood where Ms. Speights lives, Chesterfield Heights. It has had little history of flooding, but that is starting to change as the water rises.
The plan the students developed has morphed into an ambitious program to safeguard the neighborhood, and another nearby, for decades. The Obama administration recently gave Virginia more than $100 million to carry the plan out. The administration has also enlisted one of the universities, Old Dominion in Norfolk, to spearhead a broad effort at better planning.
But the size of that grant illustrates the scope of the problem confronting the region, and the country: protecting a single neighborhood from rising water can easily cost tens of millions of dollars. Sea walls and streets may have to be raised, or movable gates built along waterways so they can be closed at times of high water.
While the Obama administration is trying to create a few showcase neighborhoods, there is no sign Congress is prepared to spend the money that cities and states say they need: tens of billions of dollars just to catch up to the current flooding problems, much less get ahead of them. Norfolk alone, a town of 250,000 people, has a wish list of $1.2 billion — or about $5,000 for every man, woman and child in the city.
As the national response lags, experts warn that the flooding is putting the country’s defense at risk.
Several studies have concluded that Naval Station Norfolk, the world’s largest naval base, is profoundly threatened by rising seas, as are other coastal bases. 

The Pentagon has managed to build floodgates and other protective measures at some facilities. But attempts by the military to develop broader climate change plans have met fierce resistance in Congress.
That was the case this summer, when an effort by the Pentagon to appoint officers to take charge of climate resilience led to a House vote prohibiting taxpayer money from being spent on the plan.
Andrea Dutton, a University of Florida climate scientist, beside an ancient coral reef in the Florida Keys, evidence that the sea level was once far higher than today.
Credit Joshua Bright for The New York Times

“When we distract our military with a radical climate change agenda, we detract from their main purpose of defending America from enemies” like the Islamic State, said Mr. Buck of Colorado, the Republican congressman who sponsored the measure. His amendment passed the House 216 to 205, though the Senate has yet to agree to it.
Many people in Congress, almost all of them Republicans, express doubt about climate science, with some of them promulgating conspiracy theories claiming that researchers have invented the issue to justify greater governmental control over people’s lives. So far, this ideological position has been immune to the rising evidence of harm from human-induced climate change.
The Obama administration has been pushing federal agencies, including the Pentagon, to take more aggressive steps. But without action in Congress, experts say these efforts fall far short of what is required.
“In the country, certainly in the Congress, it hasn’t really resonated — the billions and perhaps trillions of dollars that we would need to spend if we want to live on the coast like we’re living today,” said David W. Titley, a retired rear admiral who was the chief oceanographer of the Navy, and now heads a climate center at Pennsylvania State University.
“I haven’t seen any evidence that there is serious thought about this: What does a world of three, four, five feet of sea-level rise look like?”

Mounting Evidence

Deep in a thicket of trees on an out-of-the-way island in the Florida Keys, a diesel engine roared to life. Soon a drill bit was chewing through ancient limestone, pulling up evidence from the geological past that might shed light on the future of the planet.
On a sultry day in March, Dr. Dutton, the University of Florida scientist, stood watch over the drilling operation, inspecting her samples as they emerged from the ground. She spotted fossilized corals, proof that what is now the dry ground of Lignumvitae Key was once underwater.
With taxpayer funding from the National Science Foundation, Dr. Dutton is chasing what might be the most urgent question in climate science: How fast is the ocean going to rise?
“Is it going to happen in decades, or centuries, or a thousand years?” Dr. Dutton asked as she took a break to eat lunch on a tarpaulin spread under the trees. “This will give us an example to say, ‘Well, the last time this happened, here is how long it took.’”
The opponents of climate science in Congress, and the tiny group of climate researchers allied with them, have argued that the concerns of thousands of mainstream scientists about the future are based on unproven computer forecasts.
In reality, their concerns are based in large part on mounting evidence of what has happened in the past.
Water from a tidal stretch of the Potomac River flooded Old Town Alexandria in Virginia during high tides in early June.
Credit Gabriella Demczuk for The New York Times

Through decades of research, it has become clear that human civilization, roughly 6,000 years old, developed during an unusually stable period for global sea levels. But over longer spans, coastlines have been much more dynamic.
During ice ages, caused by wobbles in the Earth’s orbit, sea levels dropped more than 400 feet as ice piled up on land. But during periods slightly warmer than today, the sea may have risen 70 or more feet above the current level.
Dr. Dutton and other leading scientists are focused on the last sea-level high point, which occurred between the last two ice ages, about 125,000 years ago.
After years of surveying ancient shorelines around the world, scientists determined that the sea level rose by something like 20 to 30 feet in that era, compared with today. But how long did it take to make that jump? That is the question Dr. Dutton, using improved research techniques, wants to answer.
Large parts of the Florida Keys are simply ancient coral reefs that grew during the period of high seas, and were exposed when the levels fell. Trees, roads and houses now sit atop the old reefs. By recovering samples, Dr. Dutton hopes to date a sequence of corals as they grew along with the rising sea, potentially revealing the rate at which the water rose.
The research, likely to take years, may supply a figure for how quickly the ocean was able to rise under past conditions, but not necessarily a maximum rate for the coming decades. The release of greenhouse gases from human activity is causing the planet to warm rapidly, perhaps faster than at any other time in the Earth’s history. The ice sheets in both Greenland and West Antarctica are beginning to melt into the sea at an accelerating pace.
Scientists had long hoped that any disintegration of the ice sheets would take thousands of years, but recent research suggests the breakup of West Antarctica could occur much faster. In the worst-case scenario, this research suggests, the rate of sea-level rise could reach a foot per decade by the 22nd century, about 10 times faster than today.
In 2013, scientists reached a consensus that three feet was the highest plausible rise by the year 2100. But now some of them are starting to say that six or seven feet may be possible. A rise that large over a span of decades would be an unparalleled national catastrophe, driving millions of people from their homes and most likely requiring the abandonment of entire cities.
In essence, by revealing how sensitive the ice sheets have been to past warming, Dr. Dutton’s research may answer the question of whether such a rapid jump is possible.
Along those parts of the United States coast that are sinking at a brisk clip, including southern Louisiana and the entire Chesapeake Bay region, including Norfolk, the situation will be worse than average. On the Pacific Coast, a climate pattern that had pushed billions of gallons of water toward Asia is now ending, so that in coming decades the sea is likely to rise quickly off states like Oregon and California.
Along the East Coast, scientists with the National Oceanic and Atmospheric Administration say that many communities have already, or will soon, pass a threshold where sunny-day flooding starts to happen much more often.

 Highway 80, the only road to Tybee Island, Ga., in June. High tides are forcing the road to close several times a year. Credit Stephen B. Morton for The New York Times





At the City Market in Charleston, S.C., one of the most popular spots in town, shoppers dodged seawater that bubbled up from storm drains during high tide in June.
CreditHunter McRae for The New York Times

“When you look at the historical record, there’s no trend saying the flooding is going down,” said Dr. Sweet, the NOAA expert. “The trends are all very clear. They’re going up, and they’re going up in many of these areas in an accelerating fashion.”
Late last year, in Paris, nations reached a landmark global agreement to cut emissions. It is fragile, and might not survive if Donald J. Trump is elected president in November; he has pledged to scrap it.
But the air is already so full of greenhouse gases that most land ice on the planet has started to melt. So even if the deal survives, it will, at best, slow the rise of the sea and perhaps limit the ultimate increase. Many climate scientists, including Dr. Dutton, believe a rise of at least 15 or 20 feet has already become inevitable, over an unknown period.

Facing Hard Decisions

As Brad Tuckman walked the piece of land in Fort Lauderdale where he is building a grand new house, he pointed toward the canal that wraps around three sides of the property.
It is scenic, with yachts plying the water, yet as the sea has risen, street flooding in the area has become a recurring nuisance. So before starting construction, Mr. Tuckman said he spent nearly a half-million dollars to raise the sea wall and truck in dirt to elevate the land.
“The predictions of what’s going to happen over the next 20, 30, 40 years — it’s real,” said Mr. Tuckman, the founder of a company offering creative services to the retail industry.
In South Florida, among the worst-hit parts of the country for sunny-day flooding, people are not waiting for state or federal help. Those who can afford it are starting to act on their own. A company, Coastal Risk Consulting, has cropped up to advise them, and is offering its services nationally.
Cities and counties in the region have formed an alliance and enlisted professors to help them figure out what to do. They are hiring “chief resilience officers,” an idea pioneered by the Rockefeller Foundation in New York, which is paying some of the salary cost.
In Miami Beach and Fort Lauderdale, as well as in older Northern cities like Boston and New York, tidal marshes and creeks were filled in a century or more ago to make new land, and it is in these areas — “back bays,” as some of these spots are called — where the flooding is happening first.
That is because they remain the lowest spots in the landscape, vulnerable to the rising water nearby. Old drain pipes empty into the tidal creeks, and at high tide the water can back up through these pipes, bubbling into the streets seemingly from nowhere.
In Miami Beach, the city engineer, Bruce A. Mowry, has come up with a plan for combating the flooding. He rips up problematic streets, raises them with extra dirt and repaves them, installing new drains and giant pumps that can push water back into the bay. The approach has already been shown to work in several neighborhoods.

A University of Florida scientific team approaching Lignumvitae Key as part of a study to determine how fast sea levels rose in the ancient past.
Credit Joshua Bright for The New York Times

A controversy has erupted about whether Miami Beach is polluting Biscayne Bay with the water, but the city is pushing ahead. Miami Beach plans to spend at least $400 million on its plan by 2018, raising the money through fees imposed on homes and businesses.
The huge county government for the region, Miami-Dade County, is developing its own resilience strategy, one likely to cost billions. It has committed to rebuilding some of its decaying infrastructure, like a sewage plant, in a way that safeguards against sea-level rise and storm surges.
“I don’t see doom and gloom here; I see opportunity,” said Harvey Ruvin, the clerk of courts for Miami-Dade County, who has been a leading voice on the environment in Florida for a half-century, and who recently led a county task force on sea-level rise. “We’re talking about the most robust possible jobs program you can think of, and one that can’t be outsourced.”
Many of the Republican mayors in the region are on the same page as Democrats in requesting national and state action on climate change, as well as pushing local steps. James C. Cason, the Republican mayor of Coral Gables, has convened informational sessions that draw hundreds of residents, and he has received no complaints for his stance.
“I hope in coming years when we have to spend a lot of money, the citizens will still support it,” Mr. Cason said in an interview.

Still, his city, and others in South Florida, have some hard decisions to make.

Some property owners cannot afford to raise their sea walls, putting their neighborhoods at increased risk of flooding. Will they be held legally responsible when floods do occur? A strict policy could force some people from their homes. Conversely, should public money be spent to do the work, even if it largely benefits private property?
Just for streets, storm drains and the like, South Florida governments will need to raise billions, and they have yet to figure out how. Moreover, if the rise of the sea accelerates as much as some scientists fear, it is doubtful the cities will be able to keep up.
The region has one mayor, Philip K. Stoddard of South Miami, who is a scientist himself — he studies animal communication at Florida International University — and has been a close reader of scientific papers about climate change since the 1990s.
“I remember lying in bed at night thinking, ‘I hope this isn’t real,’” Dr. Stoddard, a Democrat, recalled. “I hope other data comes in that contradicts it. It took me several years to get my head around it and say, ‘Oh, God, it is real.’”
Now he is focused on easing the pain for South Miami, with a $50 million system of sewer pipes to replace septic tanks threatened by the rising water table.
“You can play it really badly and let unpleasant things happen earlier,” he said. “Or you can push them off by doing some infrastructure repairs and some thoughtful planning.”
He is, though, under no illusions about the long-term fate of the region he calls home.
“We’re putting enough heat in the ocean to send water over us, no question,” Dr. Stoddard said. “Ultimately, we give up and we leave. That’s how the story ends.”

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The water levels at Broomhead reservoir in South Yorkshire have been low this summer. Photograph: Richard McCarthy/PA by   Damien Gayle The...