Waves driven by a cyclone appear in the Elbe estuary near the North Sea close to northern Germany. (Christian Charisius/European Pressphoto Agency) 
 
 A group of scientists says it has now reconstructed the history of the planet’s sea levels arcing back over some 3,000 years — leading it to conclude that the rate of increase experienced in the 20th century was “extremely likely” to have been faster than during nearly the entire period. 
 
 “We can say with 95 percent probability that the 20th-century rise was faster than any of the previous 27 centuries,” said Bob Kopp, a climate scientist at Rutgers University who led the research with nine colleagues from several U.S. and global universities. Kopp said it’s not that seas rose faster before that – they probably didn’t – but merely that the ability to say as much with the same level of confidence declines. 
 
 The study was published Monday in the Proceedings of the National Academy of Sciences. 
 
 Seas rose about 14 centimeters (5.5 inches) from 1900 to 2000, the new study suggests, for a rate of 1.4 millimeters per year. The current rate, according to NASA, is 3.4 millimeters per year, suggesting that sea level rise is still accelerating. 
 
 Oceanographer Josh Willis from NASA's Jet Propulsion Laboratory explains how sea levels have changed over the last two decades. (NASA) 
 
 Unsurprisingly, the study blames the anomalous 20th-century rise on global warming — and not just that. It also calculates that, had humans not been warming the planet, there’s very little chance that seas would have risen so much during the century, finding that instead of a 14 centimeter rise, we would have seen somewhere between a 3 centimeter fall and a 7 centimeter rise. 
 
 [Why the U.S. East Coast could be a major ‘hotspot’ for rising seas] 
 
 The new work is particularly significant because, in effect, the sea level analysis produces a so-called “hockey stick” graph — showing a long and relatively flat sea level “handle” for thousands of years, followed by a “blade” that turns sharply upwards in very recent times. 
 
 The discovery of such patterns itself has a long history, going back to a 1998 study by climate researcher Michael Mann of Penn State University and two colleagues — who found a “hockey stick” graph for the planet’s temperature, rather than for its sea level. Since then the “hockey stick,” in its various incarnations, has come in for voluminous criticism from skeptics and doubters of human-caused climate change — even as multiple scientists have continued to affirm the conclusion that the last 100 years or so are way out of whack with what the planet has seen in the past thousand or more. 
 
 [Why the planet’s ancient past holds a worrying lesson about Antarctica] 
 
 The new research also forecasts that no matter how much carbon dioxide we emit, 21st-century sea level rise will still greatly outstrip what was seen in the 1900s. Nonetheless, choices made today could have a big impact. For a low emissions scenario, it finds that seas might only rise between 24 and 61 centimeters. In contrast, for a high emissions scenario — one that the recent Paris climate accord pledged the world to avert — they could rise as much as 52 to 131 centimeters, or, at the very high end, 4.29 feet. 
 
 However, Kopp notes that the methods used to project these totals may not fully capture what happens over the course of this century. “We have a model that’s calibrated against a period when a certain set of processes, largely thermal expansion and glaciers, were dominant,” he says, “and we’re looking forward to a period when other factors will be dominant.” 
 
 As Kopp’s words acknowledge, the major contributors to sea level rise in the 20th century were the melting of mountain glaciers around the globe and the natural expansion of ocean water as it warms. However, in the 21st century, researchers think that the truly major players in potential sea level rise, the huge ice sheets of Greenland and Antarctica, will come to play a larger role. (Just how large remains unclear.) 
 
 The current study was based on combining a variety of so-called “reconstructions” of past rates of sea level from 24 locations around the world with more recent measurements from 66 global tide gauges. That’s necessary because you can’t just measure sea level change in a single place and get a global picture — over long time periods, factors ranging from whether land is rising or sinking to changes in ocean currents and the gravitational pull of the planet’s ice sheets mean that different regions can see different amounts of sea level rise (or fall). 
 
 One of the sites where past sea levels were reconstructed by scientists is pictured below: 
 
 
 
 Coastal wetland in Newfoundland, Canada, that harbors a record of sea level for the past 2,000 years. (Courtesy of Ben Horton) 
 
 The new study follows in the footsteps of a 2011 study that looked at the ocean and climate records contained in salt marshes in North Carolina to infer the history of sea level rise over the past 2,100 years — research that had many of the same authors. That study, too, found that the recent sea level rise is unprecedented over that time period. 
 
 Mann of Penn State, one originator of the “hockey stick” reference and a co-author on the 2011 study (but not the current one), said by email that he thinks the current work is an “incremental advance” on that prior study, albeit one he agreed with in broad outline 
 
 Mann continued by email: 
 
 The study nonetheless reiterates the conclusion we reached [in 2011] that the acceleration in sea level rise over the past century is unprecedented over at least the past millennium, and that this acceleration is directly related to the spike in surface temperature over the past century (i.e. the “hockey stick”). 
 
 The new paper emerges even as another study, also published Monday in the Proceedings of the National Academy of Sciences, produced very similar 21st-century projections of sea level rise. That paper, led by Matthias Mengel of the Potsdam Institute for Climate Impact Research in Germany, also calculated that with unconstrained emissions, the Earth could see a maximum of some four feet of sea level rise by 2100. But it too acknowledged that the approach “cannot cover processes” like the possible collapse of the oceanfront glaciers of the West Antarctic ice sheet, which, it said, “is hypothesized to be already underway.” 
 
 Such calculations are roughly in line with the 2013 projections of the U.N.’s Intergovernmental Panel on Climate Change for expected sea level rise by 2100, although they rely on a different, more simple type of model than that body used. However, Princeton climate scientist Michael Oppenheimer, who was not involved in the current work but collaborates with Kopp and was his postdoctoral adviser, says that this agreement between approaches still “begs the question of just how much disintegration of the polar ice sheets will contribute to sea level during the 21st century since neither type of model is adequate for capturing this growing and potentially disastrous contribution – and that is ultimately the most important unknown, both with regard to sea level and potentially with respect to the whole field of climate change.” 
 
 Capping a major day for sea level rise news, Kopp also released a report Monday along with Benjamin Strauss of Climate Central and two other researchers, using the current study’s approach to determine that thousands of coastal “nuisance” floods in the United States over the 20th century would not have happened without human-caused global warming. 
 
 Based on just four inches of sea level rise attributed to humans in the 20th century, and another two inches so far in the 21st, Strauss said he “was really surprised to see that there are human fingerprints on thousands of coastal floods that we’ve already had in the United States.” The reason is that such nuisance floods — King Tide flooding in Miami would be a good example — represent what Strauss calls a “threshold” phenomenon, which is caused after sea level rise reaches a certain level. 
 
 “I think these studies really put the human fingerprint on Miami Beach’s hundred-million-dollar saltwater flooding problem, and really a lot of what’s going on in South Florida,” Strauss said. 
 
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 For more, you can sign up for our weekly newsletter here, and follow us on Twitter here. ||||| Skip Ad x Embed x Share Sea level rise is one of the most visible ramifications of global warming and new research published on Monday now shows the startling present-day impacts of global warming-related sea level rise. 
 
 Yana Kibyakova walks through a flooded street that was caused by the combination of the lunar orbit, which caused seasonal high tides, and what many believe is the rising sea levels due to climate change on Sept. 29, 2015 in Miami Beach, Fla. (Photo: Joe Raedle, Getty Images) 
 
 Sea levels rose faster in the past century than during the previous 27 centuries due to man-made global warming, a pair of studies published Monday found. 
 
 "The 20th century rise was extraordinary in the context of the last three millennia — and the rise over the last two decades has been even faster," said Robert Kopp, study lead author and an associate professor at Rutgers University. 
 
 The study, "Temperature-driven global sea-level variability in the Common Era," was published in the peer-reviewed Proceedings of the National Academy of Sciences. 
 
 To reach their conclusions, the scientists compiled a database of geological sea-level indicators from marshes, coral atolls and archaeological sites around the world that spanned the last 3,000 years. 
 
 Global sea levels stayed fairly steady for about 3,000 years. Then, with the Industrial Revolution, global sea levels began to rise, the study said. Scientists say the seas rose 5.5 inches from 1900 to 2000, a significant increase, especially for low-lying coastal areas. 
 
 Oops! Make that 20 centuries of sea level rise in one handy chart, via @Climate Central pic.twitter.com/hmAOm4C41t — Elizabeth Kolbert (@ElizKolbert) February 22, 2016 
 
 The burning of fossil fuels for energy produces heat-trapping greenhouse gases. The warm air cause glaciers and ice sheets in Greenland and Antarctica to melt. Warm water expands, taking up more space than cooler water or ice. Global sea levels have closely mirrored temperature changes over the years. As temperatures go up, so do sea levels. 
 
 
 
 Rising sea levels have already impacted U.S. coastal cities. 
 
 What new sea-level data from the past reveal about our future: Millennia of sea-level change https://t.co/WHOvMODmBJpic.twitter.com/Ls3O1pts75 — Stefan Rahmstorf (@rahmstorf) February 22, 2016 
 
 Parts of Norfolk, Va., Charleston, S.C., and Miami flood at high tides, even when it's not raining, according to the National Oceanic and Atmospheric Administration. Floods from storm surges, magnified by the rise in the sea level, have devastated cities including New Orleans and New York. 
 
 Another study — also published Monday in the Proceedings of the National Academy of Sciences by scientists from Germany, Spain and Columbia University — found that global sea level could increase by roughly one to four feet by 2100, depending on how much carbon dioxide, methane and other gases are released into the atmosphere in the coming decades. 
 
 Fastest sea level rise in 2800 years is happening now & it'll only get worse: https://t.co/kVQyPhjIPbpic.twitter.com/1bMrdEblXu — seth borenstein (@borenbears) February 22, 2016 
 
 Read or Share this story: http://usat.ly/1XJ8cBd ||||| The Thwaites Glacier in Antarctica is seen in this undated NASA image. 
 
 OSLO, Vast glaciers in West Antarctica seem to be locked in an irreversible thaw linked to global warming that may push up sea levels for centuries, scientists said on Monday. 
 
 Six glaciers, eaten away from below by a warming of sea waters around the frozen continent, were flowing fast into the Amundsen Sea, according to the report based partly on satellite radar measurements from 1992 to 2011. 
 
 Evidence shows "a large sector of the West Antarctic ice sheet has gone into a state of irreversible retreat", said lead author Eric Rignot of the University of California, Irvine, and NASA's Jet Propulsion Laboratory in Pasadena, California. 
 
 The coastal ends of the glaciers rest on bedrock below sea level, holding back a vast weight of ice and making them vulnerable to melt, he said. He likened the process to uncorking a full bottle of wine while it was lying on its side. 
 
 This part of Antarctica would be a major contributor to sea level rise in coming decades and centuries since the glaciers hold enough ice to raise sea levels by 1.2 meters (4 feet). 
 
 "It's passed the point of no return," he told a telephone news conference. 
 
 Ice-penetrating radars showed no mountain ranges entombed under the ice, for instance, that could halt the flow. The fastest retreat was 34-37 km (21-23 miles) over the period in the Smith/Kohler glacier. 
 
 Even so, cuts in greenhouse gas emissions, part of efforts to rein in global warming, could at least slow the slide of the Pine Island, Thwaites, Haynes, Pope, Smith and Kohler glaciers. 
 
 "We do think this is related to climate warming," Rignot said. The scientists believed that a build-up of man-made greenhouse gases in the atmosphere was affecting wind patterns around Antarctica, driving warmer waters towards the continent. 
 
 Almost 200 nations have agreed to work out a U.N. pact by the end of 2015 to combat global warming, which the U.N. Intergovernmental Panel on Climate Change (IPCC) says will cause more floods, droughts, heat waves and higher seas. 
 
 SEA LEVELS 
 
 Monday's findings may also mean that scenarios by the IPCC for sea level rise are too low. The IPCC said last year that sea levels are likely to rise by between 26 and 82 cm (10 and 32 inches) by the late 21st century, after a 19 cm (7 inch) rise since 1900. 
 
 "The major ice sheets of this planet will have a larger and larger role in sea level rise in the decades ahead," said Sridhar Anandakrishnan, professor of geosciences at Pennsylvania State University, who was not involved in the study. 
 
 Last week, another study also suggested a part of the far bigger ice sheet in East Antarctica may also be more vulnerable than expected to thaw. The IPCC says it is at least 95 percent probable that warming is caused by human activities, led by the burning of fossil fuels. 
 
 Monday's study, to be published in the journal Geophysical Research Letters, adds to signs of climate change under way. 
 
 On May 6, the Obama administration issued a study saying that warming "once considered an issue for a distant future has moved firmly into the present." 
 
 And the IPCC said in March there were signs of irreversible changes to tropical coral reefs and to the Arctic. 
 
 A separate study of the Thwaites glacier by the University of Washington in the journal Science also said it may have begun an unstoppable collapse that could last from 200 to 1,000 years. 
 
 A disappearance of the Thwaites alone would raise world sea levels by 60 cm (1.96 feet) but the "glacier also acts as a linchpin on the rest of the ice sheet, which contains enough ice to cause another three to four meters of sea level rise", it said. 
 
 The findings contrast with a paradoxical expansion of the extent of ice floating on the sea around Antarctica in recent winters that the scientists said may be part of natural variations. "The changes in the glacier reflect much longer-term processes," Tom Wagner, a scientist with NASA's Science Mission Directorate in Washington, said in the telephone briefing. 
 
 (Editing by Mark Heinrich)
– It's "extremely likely" that sea levels rose faster in the 20th century than at any other time in the previous 2,700 years "and the rise over the last two decades has been even faster," scientists say. A new study—based on "reconstructions" of past sea levels from 24 areas around the world, plus tide gauges—finds global sea levels were steady for almost three millennia before they began to rise with the Industrial Revolution, reports USA Today. "We can say with 95% probability that the 20th-century rise was faster than any of the previous 27 centuries," the lead author tells the Washington Post. Sea levels rose 5.5 inches from 1900 to 2000, or about 1.4 millimeters per year. NASA puts the current rate at 3.4 millimeters per year. Scientists expect sea levels to rise between 9.5 inches and 2 feet by 2100—if we stick to the climate treaty agreed upon in Paris. But a high emissions scenario could see seas rise by more than 4 feet. Another study in Proceedings of the National Academy of Sciences seconds that finding but notes researchers didn't consider the collapse of glaciers of the West Antarctic ice sheet, which "is hypothesized to be already underway." There's no surprise why: Humans burned fossil fuels, which produced greenhouse gases, which melted glaciers and warmed ocean waters, scientists say. If not for humans, sea levels might not have risen at all and thousands of coastal "nuisance" floods in the US would have been avoided, according to Climate Central. (Some 316 US cities may be partially submerged by 2100.)