Huge sea-level rises caused by climate change will last far longer than the entire history of human civilization to date, according to new research, unless the brief window of opportunity of the next few decades is used to cut carbon emissions drastically.
Even if global warming is capped at governments' target of 2C - which is already seen as difficult - 20% of the world's population will eventually have to migrate away from coasts swamped by rising oceans. Cities including New York, London, Rio de Janeiro, Cairo, Calcutta, Jakarta and Shanghai would all be submerged.
"Much of the carbon we are putting in the air from burning fossil fuels will stay there for thousands of years," said Prof Peter Clark, at Oregon State University in the US and who led the new work. "People need to understand that the effects of climate change won't go away, at least not for thousands of generations."
"The long-term view sends the chilling message of what the real risks and consequences are of the fossil fuel era," said Prof Thomas Stocker, at the University of Bern, Switzerland and also part of the research team. "It will commit us to massive adaptation efforts so that for many, dislocation and migration becomes the only option."
The report, published in the journal Nature Climate Change, notes most research looks at the impacts of global warming by 2100 and so misses one of the biggest consequences for civilisation - the long-term melting of polar ice caps and sea-level rise.
This is because the great ice sheets take thousand of years to react fully to higher temperatures. The researchers say this long-term view raises moral questions about the kind of environment being passed down to future generations.
The research shows that even with climate change limited to 2C by tough emissions cuts, sea level would rise by 25 metres over the next 2,000 years or so and remain there for at least 10,000 years - twice as long as human history. If today's burning of coal, oil and gas is not curbed, the sea would rise by 50m, completely changing the map of the world.
"We can't keep building seawalls that are 25m high," said Clark. "Entire populations of cities will eventually have to move."
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All along Antarctica's coast, tongues of floating ice act as a firewall. Any major breaks in the firewall could send inland ice flowing faster to the sea, raising ocean levels and threatening coastal communities around the globe.
In some ways, it's a process already seen in some areas of Antarctica and it's concerning enough that scientists have undertaken new research to identify where the weakest links in the firewall are.
The findings, published in Nature Climate Change on Monday, show that West Antarctica - long an area of scientific concern when it comes to sea level rise - has some of the weakest areas of defense protecting its ice.
Researchers analyzed the tongues of ice - known as ice shelves - to see how much ground each ice shelf could lose before processes began to speed up, sending more inland ice to the sea.
"When they break-up, it is like pulling the plug in the bathtub for the adjacent tributary glaciers," Johannes Fürst, an ice expert at University of Erlangen-Nuremberg and leader of the new study, said. "For our article, we just wondered how far we can cut into the existing ice-shelf geometries before a notable and instant dynamic effect becomes apparent."
The cause of the cutting could be any number of factors, according to Fürst, ranging from ice shelf shape to warming seas driven by climate change. This research didn't focus on the specific causes of ice loss in the region, just how much ice could be lost until major changes occurred.
"We have known for a while now that ice shelves are important plugs for the glaciers that flow in from behind," Martin Truffer, an ice shelf researcher at the University of Alaska, said. "(This research uses) an innovative method and it shows some interesting results."
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HOBOKEN, N.J. - Every time a powerful nor'easter or tropical storm threatens New York, residents of this small city on the New Jersey bank of the Hudson River start having flashbacks to the devastating inundation they endured when Hurricane Sandy hit in 2012.
Hundreds of millions of gallons of water poured in from the river and left most of Hoboken underwater and many of its residents without power for a week. Almost immediately, city leaders decided that Hoboken had to be fortified against future floods.
A solution seemed imminent in 2014. At a celebratory announcement, Gov. Chris Christie joined federal officials to herald the city's winning a $230 million grant to finance a plan by Dutch architects to hold back the Hudson.
But more than three years after the hurricane, Hoboken is just as vulnerable to a deluge and the plan to defend it is mired in controversy. Furious residents have sounded off to city and state officials, opposing any remedy that might diminish the city's character or its biggest selling point: the dazzling views of Manhattan.
The backlash could cost the city the money Washington has offered. Some residents have even endorsed that outcome.
"Please do not destroy the one valuable asset this city has, which is its view and the charm of tree-lined streets," one resident, Suzanne Collins, wrote to state officials, saying Hoboken should "reject these funds."
The plan would inevitably involve erecting sea walls between the river and the low-lying parts of the city, possibly over 12 feet high in places. And, as Dawn Zimmer, the mayor of Hoboken, has learned, "wall" is a fighting word.
"This is a historic opportunity for our city, an opportunity that no other city in the country has," Ms. Zimmer, a Democrat, said in an interview in her City Hall office, a few blocks from where the surging river rushed in.
But irate residents, including Natalie Morales, a news anchor on the NBC "Today" show, have confronted Ms. Zimmer with their objections and directed their outrage to state officials. The mayor said she feared the public discord would cause Hoboken to lose out on its best chance to get help from the state and federal governments.
Wedged into the coastline between the Lincoln and Holland Tunnels, Hoboken is one of the country's most densely populated places, with more than 50,000 people living in slightly more than a square mile. Some of the land closest to the river is elevated, but most of the city lies low and is notoriously susceptible to flooding even after just a heavy downpour.
City officials have tried to ease the flooding problem with pumps and cisterns, but stopping the river would require walls, Ms. Zimmer said. Not that she would call them that.
Instead, she is careful to use less provocative terms, such as a "flood-protection measure," and emphasizes that a wall could double as an "amenity," such as a bench or planter, that would fit into the urban landscape. But a wall by any other name has stirred indignation among prospective neighbors, who have vented in public comments sent to the New Jersey Department of Environmental Protection, which is responsible for devising a plan that will meet the federal requirements.
"No to the wall," Stacy Wallace-Albert wrote in all capital letters, succinctly summarizing the opinion of many neighbors.
There is no hard and fast plan to build a wall anywhere yet. A barrier was just one part of a plan from a team led by the Office for Metropolitan Architecture, a Dutch firm founded by the architect Rem Koolhaas. The plan was submitted to Rebuild by Design, a post-Hurricane Sandy design competition overseen by the federal Department of Housing and Urban Development.
That plan, called "Resist, Delay, Store, Discharge," involved strategies for holding rain and floodwater and slowing its release into the city's sewer system. But its fundamental purpose was to prevent a repeat of what happened in Hoboken during Hurricane Sandy.
State engineers have drawn up five configurations, including some that would place a wall on the waterfront and one that would have it wind along city streets and end on a block lined with brownstones. They are scheduled to whittle those alternatives down to three within several weeks, but the uproar from residents may have set back that schedule.
Resentment started bubbling up late last year at additional public meetings requested by Ms. Zimmer to elicit the opinions of a cross section of her constituents. She got an earful.
Some residents said that the waterfront and the front-row view of Manhattan were Hoboken's most attractive features, and that to obscure the panorama would be foolish.
But the loudest opposition came from residents along Garden Street, which runs south several blocks from the river. Once they understood that one concept involved a wall four feet high or taller dividing their narrow street, they rebelled.
"You're going to ruin the character of the neighborhood," one woman said. One of her neighbors added: "I got denied a zoning thing I wanted to do in my home, but you're going to put a four-foot wall in front of my house. No good."
Online, the reaction was even more vituperative. Some residents started a petition calling for the rejection of the Garden Street proposal, saying the plan would expose "taxpaying homeowners who were not in a flood zone to new flood risks by trapping them on the 'wet side' of the new wall."
Among the over 700 people who have supported the petition was Ms. Morales, who lives on one of the blocks that would be affected. The newscaster took a shot at Ms. Zimmer on the petition site, writing, "This is corruption at its finest!" and alleging a "kickback scheme at the highest level."
Ms. Morales did not respond to several requests for comment. A spokeswoman for the "Today" show, Megan Kopf, declined to comment about Ms. Morales's postings or whether NBC News had policies covering the involvement of its journalists in local politics.
Ms. Zimmer seemed mystified by Ms. Morales's statements, saying she had met her only once before the newscaster showed up at a meeting about the Rebuild by Design process and challenged the engineers. "Did any of you guys walk the streets before you did the plans?" Ms. Morales asked them.
The mayor shrugged off the personal attacks, but she and other residents said they were troubled by the idea that Hoboken should pass up the $230 million.
Sitting in his home-furnishings store that was flooded by Hurricane Sandy, Brian Battaglia shook his head at the thought. "To walk away from doing anything in Hoboken that stops the water from coming in seems unbelievable," he said, recalling how the rising water burst through the back door and shoved everything to the front wall.
"If you didn't drive down the back side of town and see people's lives thrown out in the street, you might feel that way," Mr. Battaglia said.
LaTrenda Ross, a 27-year resident of public housing in Hoboken, said she had not forgotten what Hurricane Sandy wrought. "To go through that for two weeks with no heat, no lights, no nothing, no food, it was a disaster," she said.
Ms. Zimmer said she would be happy if a way could be found to resist a rising Hudson without limiting access to the waterfront or disrupting residential blocks. The Department of Environmental Protection said it would consider altering the proposed configurations to placate residents.
In the meantime, Ms. Zimmer has met with small groups of residents to try to assuage their fears. She said a friend recounted how her young daughter came home and explained that "they're going to build a wall 12 feet high" that would block a schoolmate's bedroom window.
Ms. Zimmer told her friend, "That's not going to happen."
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New research published Monday adds to a body of evidence suggesting that a warming climate may have particularly marked effects for some citizens of the country most responsible for global warming in the first place - namely, U.S. East Coasters.
Writing in Nature Geoscience, John Krasting and three colleagues from the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration find that "Atlantic coastal areas may be particularly vulnerable to near-future sea-level rise from present-day high greenhouse gas emission rates." The research adds to recent studies that have found strong warming of ocean waters in the U.S. Gulf of Maine, a phenomenon that is not only upending fisheries but could be worsening the risk of extreme weather in storms like Winter Storm Jonas.
"When carbon emission rates are at present day levels and higher, we see greater basin average sea level rise in the Atlantic relative to the Pacific," says Krasting. "This also means that single global average measures of sea level rise become less representative of the regional scale changes that we show in the study."
In the new research, the scientists used a high powered climate change model based at the Geophysical Fluid Dynamics Laboratory in Princeton, N.J., that simulates the ocean, the atmosphere and the cycling of carbon throughout the Earth system. The goal was to determine how much sea level rise would occur in the Atlantic, versus the Pacific, under a variety of global carbon emissions scenarios.
And the simulation found that at high emissions scenarios similar to current rates, the Atlantic sea levels rise considerably faster than the Pacific, with particularly noteworthy impacts for the U.S. East Coast. (Other recent research by scientists with the U.S. Geological Survey has suggested this increased rate of sea level rise is already happening - finding sea level rise rates "~ 3-4 times higher than the global average" along a large stretch of the U.S. East Coast, which the researchers dubbed a sea level rise "hotspot.")
The reason for the difference, the researchers say, is that the Atlantic, more than the Pacific, is characterized by a strong "overturning" ocean circulation - technically known as the Atlantic Meridional Overturning Circulation, or AMOC - that spans the north-south length of the globe and ultimately connects waters off New York with those at the tip of Antarctica. This means that waters circulate through the entire Atlantic much faster than they do throughout the Pacific: A "parcel" of water that sinks beneath the surface in the Atlantic will generally make it back to the surface again in 200 to 300 years, versus about three times as long for the Pacific, Krasting explains.
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Four winters ago, as worried rescuers watched the quickly rising waters of a Peninsula creek and tried to decide whether to alert local residents, they turned to a small green plant for guidance.
"You see that shrub?" one public safety official said. "When it's under water, we're going to start evacuating."
Today, that sentinel shrub has been replaced by a sophisticated network of gauges, sensors and computers that can save lives and property -- not only in flood-prone Menlo Park, Palo Alto and East Palo Alto, but also in vulnerable South Bay and East Bay communities.
Counting El Niño's raindrops in distant mountains, the new flood-prediction systems are for the first time allowing the Bay Area to anticipate disasters, not merely respond to them.
"We can ramp up, adding resources and personnel," said Menlo Park Fire Chief Harold Schapelhouman. "It becomes part of normal planning."
A revolution in technology allows for the highly automated and near-instantaneous analysis of enormous volumes of digital information about water flow.
It works like this: Separate streams of data -- collected from mountain peaks and rushing creeks -- are integrated into huge databases. Computers then track rising waters and predict flood risk, based on creekbed capacity and the surrounding landscape.
As waters run high, the computers can issue an electronic flood alert to local residents downstream. For instance, mid-Peninsula residents who are registered to get an alert -- by text or email -- are kept informed about four different flood-prone locations along San Francisquito Creek. They will be notified nearly two hours in advance of the water overflowing its banks.
"We know what is coming down the system," said Len Materman of San Francisquito Creek's Joint Powers Authority, which has a newly expanded system of automated rain and creek gauges perched 2,000 feet above the vulnerable mid-Peninsula cities. "We can give people solid information for decision-making" about such things as when to sandbag, get electronics and antiques off the floor or seek higher ground.
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The amount of sea level rise that comes from the oceans warming and expanding has been underestimated, and could be about twice as much as previously calculated, German researchers have said.
The findings in the Proceedings of the National Academy of Sciences, a peer-reviewed US journal, suggest that increasingly severe storm surges could be anticipated as a result.
Sea level can mount due to two factors - melting ice and the thermal expansion of water as it warms.
Until now, researchers have believed the oceans rose between 0.7 to 1mm per year due to thermal expansion.
But a fresh look at the latest satellite data from 2002 to 2014 shows the seas are expanding about 1.4mm a year, said the study.
"To date, we have underestimated how much the heat-related expansion of the water mass in the oceans contributes to a global rise in sea level," said co-author Jurgen Kusche, a professor at the University of Bonn.
The overall sea level rise rate is about 2.74mm per year, combining both thermal expansion and melting ice.
Sea level rise was also found to vary substantially from place to place, with the rate around the Philippines "five times the global rate."
Meanwhile, sea level on the US west coast is largely stable because there is hardly any ocean warming in that area, said the findings.
