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. 
 
 More at Energy & Environment: 
 
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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) ||||| The potential future effects of global climate change include more frequent wildfires, longer periods of drought in some regions and an increase in the number, duration and intensity of tropical storms. Credit: Left - Mellimage/Shutterstock.com, center - Montree Hanlue/Shutterstock.com. 
 
 Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner. 
 
 Effects that scientists had predicted in the past would result from global climate change are now occurring: loss of sea ice, accelerated sea level rise and longer, more intense heat waves. 
 
 Taken as a whole, the range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time. - Intergovernmental Panel on Climate Change 
 
 Scientists have high confidence that global temperatures will continue to rise for decades to come, largely due to greenhouse gases produced by human activities. The Intergovernmental Panel on Climate Change (IPCC), which includes more than 1,300 scientists from the United States and other countries, forecasts a temperature rise of 2.5 to 10 degrees Fahrenheit over the next century. 
 
 According to the IPCC, the extent of climate change effects on individual regions will vary over time and with the ability of different societal and environmental systems to mitigate or adapt to change. 
 
 The IPCC predicts that increases in global mean temperature of less than 1.8 to 5.4 degrees Fahrenheit (1 to 3 degrees Celsius) above 1990 levels will produce beneficial impacts in some regions and harmful ones in others. Net annual costs will increase over time as global temperatures increase. 
 
 "Taken as a whole," the IPCC states, "the range of published evidence indicates that the net damage costs of climate change are likely to be significant and to increase over time." 1-2 
 
 Future effects 
 
 Some of the long-term effects of global climate change in the United States are as follows, according to the Third and Fourth National Climate Assessment Reports: 
 
 Change will continue through this century and beyond 
 
 Global climate is projected to continue to change over this century and beyond. The magnitude of climate change beyond the next few decades depends primarily on the amount of heat-trapping gases emitted globally, and how sensitive the Earth’s climate is to those emissions. 
 
 Temperatures will continue to rise 
 
 Because human-induced warming is superimposed on a naturally varying climate, the temperature rise has not been, and will not be, uniform or smooth across the country or over time. 
 
 Frost-free season (and growing season) will lengthen 
 
 The length of the frost-free season (and the corresponding growing season) has been increasing nationally since the 1980s, with the largest increases occurring in the western United States, affecting ecosystems and agriculture. Across the United States, the growing season is projected to continue to lengthen. 
 
 
 
 In a future in which heat-trapping gas emissions continue to grow, increases of a month or more in the lengths of the frost-free and growing seasons are projected across most of the U.S. by the end of the century, with slightly smaller increases in the northern Great Plains. The largest increases in the frost-free season (more than eight weeks) are projected for the western U.S., particularly in high elevation and coastal areas. The increases will be considerably smaller if heat-trapping gas emissions are reduced. 
 
 + more Visualization comparing 1950s and 2010s This NASA visualization presents observational evidence that the growing season (climatological spring) is occurring earlier in the Northern Hemisphere. 
 
 Changes in precipitation patterns 
 
 Average U.S. precipitation has increased since 1900, but some areas have had increases greater than the national average, and some areas have had decreases. More winter and spring precipitation is projected for the northern United States, and less for the Southwest, over this century. 
 
 
 
 Projections of future climate over the U.S. suggest that the recent trend towards increased heavy precipitation events will continue. This trend is projected to occur even in regions where total precipitation is expected to decrease, such as the Southwest. 
 
 + more NASA visualizations of future precipitation scenarios These NASA visualizations show model projections of the precipitation changes from 2000 to 2100 as a percentage difference between the 30-year precipitation averages and the 1970-1999 average. 
 
 Precipitation Measurement Missions The official website for NASA's fleet of Earth science missions that study rainfall and other types precipitation around the globe. 
 
 Precipitation quiz Earth’s water is stored in ice and snow, lakes and rivers, the atmosphere and the oceans. How much do you know about Earth's water cycle and the crucial role it plays in our climate? 
 
 More droughts and heat waves 
 
 Droughts in the Southwest and heat waves (periods of abnormally hot weather lasting days to weeks) everywhere are projected to become more intense, and cold waves less intense everywhere. 
 
 
 
 Summer temperatures are projected to continue rising, and a reduction of soil moisture, which exacerbates heat waves, is projected for much of the western and central U.S. in summer. By the end of this century, what have been once-in-20-year extreme heat days (one-day events) are projected to occur every two or three years over most of the nation. 
 
 + more NASA visualizations of future precipitation scenarios These NASA visualizations show model projections of the precipitation changes from 2000 to 2100 as a percentage difference between the 30-year precipitation averages and the 1970-1999 average. 
 
 NASA: Megadroughts in U.S. West projected to be worst of millennium Droughts in the Southwest and Central Plains of the United States in the second half of the 21st century could be drier and longer than anything humans have seen in those regions in the last 1,000 years, according to a NASA study published in Science Advances on February 12, 2015. 
 
 Hurricanes will become stronger and more intense 
 
 The intensity, frequency and duration of North Atlantic hurricanes, as well as the frequency of the strongest (Category 4 and 5) hurricanes, have all increased since the early 1980s. The relative contributions of human and natural causes to these increases are still uncertain. Hurricane-associated storm intensity and rainfall rates are projected to increase as the climate continues to warm. 
 
 + more NASA: What are the chances of another Hurricane Katrina? According to a new NASA study, a string of nine years without a major hurricane landfall in the U.S. is Iikely to come along only once every 177 years. This video explains the findings of this study. 
 
 Sea level will rise 1-4 feet by 2100 
 
 Global sea level has risen by about 8 inches since reliable record keeping began in 1880. It is projected to rise another 1 to 4 feet by 2100. This is the result of added water from melting land ice and the expansion of seawater as it warms. 
 
 
 
 In the next several decades, storm surges and high tides could combine with sea level rise and land subsidence to further increase flooding in many regions. Sea level rise will continue past 2100 because the oceans take a very long time to respond to warmer conditions at the Earth’s surface. Ocean waters will therefore continue to warm and sea level will continue to rise for many centuries at rates equal to or higher than those of the current century. 
 
 Arctic likely to become ice-free 
 
 The Arctic Ocean is expected to become essentially ice free in summer before mid-century. 
 
 + more Earth’s vital signs: Sea ice An indicator of changes in the Arctic sea ice minimum over time. Arctic sea ice extent both affects and is affected by global climate change. 
 
 Global Ice Viewer An interactive exploration of how global warming is affecting sea ice, glaciers and continental ice sheets worldwide. 
 
 U.S. regional effects 
 
 Below are some of the impacts that are currently visible throughout the U.S. and will continue to affect these regions, according to the Third3 and Fourth4 National Climate Assessment Reports, released by the U.S. Global Change Research Program: 
 
 Northeast. Heat waves, heavy downpours and sea level rise pose growing challenges to many aspects of life in the Northeast. Infrastructure, agriculture, fisheries and ecosystems will be increasingly compromised. Many states and cities are beginning to incorporate climate change into their planning. 
 
 Northwest. Changes in the timing of streamflow reduce water supplies for competing demands. Sea level rise, erosion, inundation, risks to infrastructure and increasing ocean acidity pose major threats. Increasing wildfire, insect outbreaks and tree diseases are causing widespread tree die-off. 
 
 Southeast. Sea level rise poses widespread and continuing threats to the region’s economy and environment. Extreme heat will affect health, energy, agriculture and more. Decreased water availability will have economic and environmental impacts. 
 
 Midwest. Extreme heat, heavy downpours and flooding will affect infrastructure, health, agriculture, forestry, transportation, air and water quality, and more. Climate change will also exacerbate a range of risks to the Great Lakes. 
 
 Southwest. Increased heat, drought and insect outbreaks, all linked to climate change, have increased wildfires. Declining water supplies, reduced agricultural yields, health impacts in cities due to heat, and flooding and erosion in coastal areas are additional concerns. 
 
 References ||||| Lewis Crawford (R) gets some help from wrecker driver Terrance Lezama after his vehicle was stranded by freeway flooding as heavy rains hit Houston, Texas January 9, 2012. 
 
 WASHINGTON For the nearly 5 million people who live along the U.S. coasts from Maine to the Gulf of Mexico and the West Coast, rising seas fueled by global warming have doubled the risk of so-called once-a-century floods, according to a trio of environmental reports released on Wednesday. 
 
 These new reports - one from the non-profit group Climate Central and two others published in the peer-reviewed journal Environmental Research Letters - offer a detailed picture of where the most severe risks are along coastlines of the contiguous 48 states. 
 
 Based on 2010 U.S. Census population data and a fresh analysis of high tide lines by the National Oceanic and Atmospheric Administration, the Climate Central report's findings can be seen online at surgingseas.org 
 
 South Florida may be "indefensible" against floods caused by higher seas and the bigger storm surges that are expected to result, said Ben Strauss, an expert on ecology and evolutionary biology who is chief operating officer of Climate Central. He co-authored the two journal reports and the online report. 
 
 An estimated $30 billion in taxable property is vulnerable in southeast Florida alone, according to a preliminary independent analysis cited in the report. 
 
 In California, some places that have never seen severe floods could be vulnerable to them in the next decade or two, Strauss said. 
 
 Climate scientists maintain that people, businesses and infrastructure in low-lying coastal areas of the contiguous 48 U.S. states are vulnerable to sea level rise, and world sea levels have risen by 8 inches since 1880. 
 
 This rise in the world's seas is caused by the expansion of ocean waters as they warm and by the melting of glaciers and ice sheets, Strauss said. This is due to global warming fueled by the emission of heat-trapping greenhouse gases, he and other climate scientists have said. 
 
 Forecasts for sea level rise this century range from 2 to 7 feet, with most estimates centering around 3 to 4 feet, given a projected rise in global temperature of at least 2 to 3 degrees F (1.1 to 1.6 degrees C), Strauss said. 
 
 VULNERABLE ZONES 
 
 As seas rise, they amplify storm surges, the reports said. 
 
 Global warming will more than double the odds of once-a-century floods by 2030 for more than two-thirds of the 55 coastal locations considered in the analysis, the Climate Central report said. For a majority of the locations, warming triples the odds of century floods. 
 
 By 2030, storm surges combined with rising seas could raise waters to 4 feet or more above high tide lines at many locations, the reports said, noting that 4.9 million people live in 2.6 million homes in this vulnerable zone between the observed high tide and the top of expected flood waters. 
 
 Cities are likely to be hit hardest, Strauss said, with 90 percent of the impact projected to come in areas with extremely dense population. 
 
 In 285 coastal cities and towns, more than half the population lives below the 4-foot mark, the Climate Central report found. Florida has 106 of these at-risk municipalities; Louisiana has 65, New Jersey and North Carolina have 22 each, Maryland has 14, New York has 13 and Virginia has 10. 
 
 Florida is a special case because in addition to rising seas and storm surges, its geology and system of drainage canals pose complex problems. "Basically, south Florida in the long term is indefensible," Strauss said. 
 
 "A lot of the state is built on porous bedrock, bedrock that's like Swiss cheese," he said. "You can't practically build a wall to keep the sea out. The water will come up through the ground." 
 
 To prepare for the future, he said, researchers looked to the past, and compared current flooding patterns to what occurred before sea levels rose 8 inches, starting in 1880. 
 
 "Today's century storm would be a once-in-200- or 300-year event, or rarer if there had been no sea level rise from global warming over the last century," Strauss said. "The point is, we're already in the teeth of this." 
 
 (Editing by Eric Beech)
– 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.)