Tag Archives: Rise

The effects of sea-level rise on communities are complex and unpredictable, says a new study

Climate change stands poised to melt the planet’s ice caps and raise sea levels worldwide, with dramatic effects for human society. But these effects won’t be felt all at once, a new study suggests.

Image credits Makoto Seimori.

The research, led by the University of Exeter in partnership with Cornwall Archaeological Unit, Cardiff University and 14 other institutes, focused on the Isles of Scilly, a group of islands of the UK’s south-west coast. The 140 islands of today are the remnants of a single large island which was gobbled up by the seas less than 1,000 years ago, the team reports. But the changes in land area and the shifts in human cultures associated with them took place at variable rates, they add, and were often ‘out of step’ with the average rate of sea-level rise.

Such findings showcase that the effects of rising seas are more complex and unpredictable than we assume, and will be much further reaching than simply forcing coastal communities to relocate.

Rising seas flood all boats

“When we’re thinking about future sea-level rise, we need to consider the complexity of the systems involved, in terms of both the physical geography and the human response” said lead author Dr. Robert Barnett, of the University of Exeter. “The speed at which land disappears is not only a function of sea-level rise, it depends on specific local geography, landforms, and geology.”

“Human responses are likely to be equally localized. For example, communities may have powerful reasons for refusing to abandon a particular place.”

The team studied the process through which the old island turned into the current cluster of 140 islands, which overall lasted some 12,000 years. They first developed a sea-level curve for the Isles over this time (a chart that shows sea level over time). Then, the team analyzed how these changes influenced the landscape, vegetation, and human populations from archaeological evidence as well as samples of pollen and charcoal collected by the Lyonesse Project (2009 to 2013).

The findings suggest that between 4,000 and 5,000 years ago, the island was rapidly becoming submerged. The inhabitants were seemingly trying to adapt to the changes in their landscape rather than abandoning the area altogether. Around 4,400 years ago, during the Bronze Age, the island had a permanent population that showed “a significant acceleration of activity”.

Land losses during this time were quite quick despite sea levels rising quite slowly, because a large part of Scilly at this point was relatively flat and close to sea level. According to the team, land here was being lost at a rate of around 10,000 sq. meters per year (a 100 by 100 meter square), roughly equivalent to a large rugby stadium. Exactly why these early inhabitants weren’t scared by higher seas is unclear; however, the team believes that they created more opportunities for fishing, the collection of shellfish, or the hunting of marine bird species. It’s possible that much of this lost land developed into intertidal habitats (exposed at low tide and submerged at high tide), which were still useful and traversable to coastal communities.

After around 4,000 years ago, the island was progressively submerged, even during times with lower rates of sea-level rise (around 1 mm per year).

“It is clear that rapid coastal change can happen even during relatively small and gradual sea-level rise,” said Dr. Barnett.”The current rate of mean global sea-level rise (around 3.6 mm per year) is already far greater than the local rate at the Isles of Scilly (1 to 2 mm per year) that caused widespread coastal reorganization between 5,000 and 4,000 years ago.”

“It is even more important to consider the human responses to these physical changes, which may be unpredictable. As can be seen today across island nations, cultural practices define the response of coastal communities, which can result in polarised agenda, such as the planned relocation programs in Fiji versus the climate-migration resistance seen in Tuvalu.”

Sea level rise led to new marine resources becoming available for communities on the island of Scilly, but the team believes it is “unlikely” that this mechanism will prove enough to support today’s communities as they become affected or displaced by rising sea levels.

“More certain though, is that societal and cultural perspectives from coastal populations will be critical for responding successfully to future climate change,” says Dr. Barnett.

The study “Nonlinear landscape and cultural response to sea-level rise,” has been published in the journal Science Advances.

We could see up to 1.3m of sea-level rise by 2100 if we don’t take action now

A new study says we should be expecting an average sea-level rise in excess of 1 meter by 2100 and 5 meters by 2300 if we don’t meet current targets for the reduction of greenhouse gas emissions.

Image via Pixabay.

The analysis used projections compiled by over 100 international experts to estimate changes in sea levels under low- and high-emission scenarios, the team explains, in order to help policymakers have a better understanding of “the state of the science” on this threat.

The waters are coming

“The complexity of sea-level projections, and the sheer amount of relevant scientific publications, make it difficult for policymakers to get an overview of the state of the science,” says Professor Benjamin Horton, Acting Chair of Nanyang Technological University, Singapore (NTU Singapore) Asian School of the Environment, who led the survey.

“To obtain this overview, it is useful to survey leading experts on the expected sea-level rise, which provides a broader picture of future scenarios and informs policymakers so they can prepare necessary measures.”

The most optimistic scenario analyzed in this paper considered that global warming would only increase temperatures by 2 degrees Celsius above pre-industrial levels, which would translate to a rise of 0.5 meters (roughly 2 feet) by 2100, and 0.5 to 2 meters by 2300. The high-emission scenario would involve 4.5 degrees Celsius of warming and would cause between 0.6 to 1.3 meters (2 to 4 feet) sea rise by 2100, and 1.7 to 5.6 meters by 2300.

These estimations exceed those of the International Panel on Climate Change (IPCC), who set the current targets under the Paris Agreement. Researchers from The University of Hong Kong, Maynooth University (Ireland), Durham University (UK), Rowan University (U.S.), Tufts University (U.S.), and the Potsdam Institute for Climate Impact Research (Germany) took part in this study. They were chosen as they are some of the most active publishers or scientific studies on the topic (they all had at least six published papers pertaining to sea-level rise since 2014).

The large difference in sea level rise seen in this paper “provides a great deal of hope for the future, as well as a strong motivation to act now to avoid the more severe impacts of rising sea levels,” according to Dr. Andra Garner, Assistant Professor of Environmental Science at Rowan University and co-author of the study.

Still, the findings also underscore just how important it is for policy to be set in place in order to limit emissions and sea-level rise. How bad the outcome is depends entirely on how we act, and the decisions we make right now.

However, despite the sheer wealth of expertise that went into the study, there are still uncertainties. The team points to the Greenland and Antarctic Ice Sheets as the largest unknowns, as their behavior can have dramatic effects on how sea levels evolve in the future. Both of these ice sheets are key reference points for climate change and increases in sea levels, as they hold important quantities of water — and they’re both melting at much higher rates than they would naturally.

Yet, not all is lost. Climate systems have a great deal of inertia to them (as do all systems working on such scales) but taking proactive measures to limit greenhouse gas emissions would still have a significant effect.

So while the worst-case scenario definitely does seem bleak, it’s in no way out of our hands. We can choose to make things better, to limit the impact we have on the planet and the repercussions that will have on our society in the future.

The paper “Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey,” has been published in the journal Climate and Atmospheric Science.

Sea level rise by 2300 is unavoidable, despite the Paris agreement

We’re set on the path of rising sea levels, even if the pledges made for the Paris climate agreement are met and global temperatures stabilize, a new paper reports.

Image via Pixabay.

The Paris agreement on climate change mitigation was adopted in December 2015 and aims to limit the rise of global average temperatures to a maximum of 2°C compared to pre-industrial levels. The ideal scenario under the agreement would be to limit this figure to 1.5°C, and the countries that signed into the agreement are expected to make efforts towards this goal.

While a successful Paris agreement would do wonders for our efforts against climate heating and environmental degradation, we’re already set for rising sea levels around the world by 2300, a new study reports.

We’re already there

“Even if we were to meet these initial goals of the Paris agreement, the sea level commitment from global warming will be significant,” said Peter Clark, an Oregon State University climate scientist and a co-author of the study.

“When we pump more carbon into the atmosphere, the increase in temperature is almost immediate. But sea level rise takes a lot longer to respond to that warming. If you take an ice cube out of the freezer and put it on the sidewalk, it takes some time to melt. The bigger the ice cube, the longer it takes to melt.”

The authors say this is the first effort to quantify how sea levels will rise from carbon emissions (both past and future) released since the agreement was signed. In the first 15 years following the agreement, they report, will cause a rise of roughly 20 centimeters (7.9 in) by 2300. The estimate does not take into account the effect of irreversible melting in parts of the Antarctic ice sheet, the team adds, which is already underway.

A one-meter rise is expected by 2300, caused by emissions dating back to the year 1750. Around 20% of that rise can be traced back to emissions released since after the Paris agreement was signed. Around half of it (so 10% of the total projected rise) is attributable to the world’s top five polluters, the team found: the United States, China, India, Russia, and the European Union

Sea level rise is a huge threat to coastal ecosystems and human communities, with the potential to affect and/or displace hundreds of millions around the world (coastal areas are the most heavily-inhabited regions on Earth). Sea level rise is mostly driven by melt from glaciers and ice sheets draining into the ocean. But these are massive structures strewn all over the world, and they each respond to climate heating in their own time, ranging from decades to millennia.

“Much of the carbon dioxide we’ve emitted into the atmosphere will stay up there for thousands of years,” said Clark, who is on the faculty of OSU’s College of Earth, Ocean, and Atmospheric Sciences.

“So our carbon emissions this century are not only committing our planet to a warmer climate, but also to higher sea levels that will also persist for thousands of years.”

The paper “Attributing long-term sea-level rise to Paris Agreement emission pledges” has been published in the journal Proceedings of the National Academy of Sciences.


Our emissions could melt all the ice in Greenland by the year 3000 — and raise sea levels by 24 ft

Greenland may actually be green by the end of the millennium if greenhouse emissions continue unabated.


Image credits Marcel Prueske.

New research shows that, if greenhouse gas emissions continue on their current trajectory, Greenland could lose 4.5% of its ice by the end of the century, and all of it by the year 3000. That 4.5% loss of ice is equivalent to roughly 13 inches of sea level rise, the team explains.

Actually Green land

“How Greenland will look in the future — in a couple of hundred years or in 1,000 years — whether there will be Greenland, or at least a Greenland similar to today, it’s up to us,” said first author Andy Aschwanden, a research associate professor at the University of Alaska Fairbanks Geophysical Institute.

Greenland houses a lot of ice — around 660,000 square miles of solid ice sheet, which contains around 8% of all the planet’s fresh water. Between 1991 and 2015, melting here has added about 0.02 inches per year to the sea level. Needless to say, we need to know how all that ice is faring and whether there’s any cause for concern. Turns out that there is.

The team used recent topography (landscape) data of Greenland’s terrain today to model how its ice sheets will evolve in the future. This data was recorded by a NASA airborne science campaign (Operation IceBridge) during which aircraft fitted with a full suite of scientific instruments scanned Greenland’s ice sheets recording its surface, the individual layers within, and the shape of the bedrock. On average, Greenland’s ice sheet is 1.6 miles thick, but there was a lot of variation.

A wide range of scenarios concerning ice loss and changes in sea level are possible based on how greenhouse gas concentrations and atmospheric conditions evolve. The team ran 500 simulations for each emission scenario using the Parallel Ice Sheet Model, developed at the Geophysical Institute, to create a picture of how Greenland’s ice would respond to different climate conditions. The model included parameters on ocean and atmospheric conditions as well as ice geometry, flow, and thickness.

Under a business as usual scenario, we could see around 24 feet to global sea level rise by the year 3000 due to melting in Greenland alone — which would put much of San Francisco, Los Angeles, New Orleans and other cities under water. However, if we do manage to slash greenhouse gas emissions significantly, the prospects improve. Reduced emission scenarios showed between 8% to 25% melting of Greenland’s ice, which would lead to approximately 6.5 feet of sea level rise

Projections for both the end of the century and 2200 tell a similar story. A wide range of outcomes are possible, including saving the ice sheet, but it all depends on emission levels, the team explains.

The team explains that modeling ice sheet behavior is tricky because ice loss is primarily driven by the retreat of outlet glaciers. These are the glaciers at the margin of the ice sheets, and they ‘drain’ ice from deeper in the sheets through through-like structures in the bedrock. This study was the first to include these outlet glaciers in its modeling and found that their discharge could contribute as much as 45% of the total mass of ice loss in Greenland by 2200. Outlet glaciers come into contact with water, the team explains, which makes ice melt much faster than air. The more ice that comes into contact with water, the faster the rate of melting — which creates a feedback loop that dramatically affects the ice sheet’s stability.

Previous research lacked data as comprehensive as that recorded by IceBridge, so it couldn’t simulate the ice sheets’ evolution in such detail.

“Ice is in very remote locations,” says Mark Fahnestock, a researcher at the University of Alaska Fairbanks Geophysical Institute and paper co-author. “You can go there and make localized measurements. But the view from space and the view from airborne campaigns, like IceBridge, has just fundamentally transformed our ability to make a model to mimic those changes.”

“What we know from the last two decades of just watching Greenland is not because we were geniuses and figured it out, but because we just saw it happen,” he adds. As for what we will see in the future, “it depends on what we are going to do next.”

The paper “Contribution of the Greenland Ice Sheet to sea level over the next millennium” has been published in the journal Science Advances.


Sea level change isn’t constant across the East Coast — because of long-past glaciers

A new study explains why different areas along the U.S. East Coast see significantly more sea level change than others.


Image credits Dimitris Vetsikas.

Seas and oceans across the globe are creeping ever so slowly upwards as climate change warms them up and melts glaciers big and small. However, local sea levels aren’t (surprisingly) the same everywhere — and this holds true for the U.S. East Coast as well. A new study published by researchers from the Woods Hole Oceanographic Institution (WHOI) comes to explain why.

Been under a lot of pressure lately

Over the last century, coastal communities near Cape Hatteras (North Carolina) and the Chesapeake Bay (Virginia) have seen about a foot and a half of sea level rise.  New York City and Miami, in contrast, have only seen roughly two-thirds of that rise (i.e. one foot) over the same period. Farther north in Portland, Maine, for example, sea levels only rose only about half a foot.

Which is weird, right? I mean, all the Earth’s oceans are linked together so, their water should be level, right? Not if you’re on a period of post-glacial rebound, says lead author Chris Piecuch.

Vast areas of land in the Northern Hemisphere, including Canada and parts of the Northeast U.S, were covered in massive glaciers during the last Ice Age, he explains. This effectively squashed the lands, pushing them down into the mantle (the crust is essentially a jigsaw puzzle of solid pieces floating on molten rock — see here). These ice sheets peaked in size and mass during the Last Glacial Maximum some 26,500 years ago, and then started melting to the state we see today. As they did so, the pressure they exerted on the ground also disappeared — and these areas started to rebound. Neighboring lands, meanwhile, started sinking, creating sort of a seesaw effect.

That effect continues to this day, Piecuch explains.

For the study, Piecuch and his team gathered tidal gauge measurements of sea levels in areas such as Norfolk Naval Station in Virginia and the Outer Banks in North Carolina. They also drew on GPS satellite data to see how much local landmasses had moved up and down over time, and looked to fossils recovered from salt marshes (which are a good indicator of past coastal sea levels). They combined all of this observational data with complex geophysical models to produce a more complete view of sea level changes since 1900 than ever before.

Post-glacial rebound, they found, accounted for most of the variation in sea level rise along the East Coast. Interestingly, however, when that factor was removed from the dataset, the team found that “sea level trends increased steadily from Maine all the way down to Florida.”

“The cause for that could involve more recent melting of glaciers and ice sheets, groundwater extraction and damming over the last century,” Piecuch says. “Those effects move ice and water mass around at Earth’s surface, and can impact the planet’s crust, gravity field and sea level.”

“Post-glacial rebound is definitely the most important process causing spatial differences in sea level rise on the U.S. East Coast over the last century. And since that process plays out over millennia, we’re confident projecting its influence centuries into the future. But regarding the mass redistribution piece of the puzzle, we’re less certain how that’s going to evolve into the future, which makes it much more difficult to predict sea level rise and its impact on coastal communities.”

The paper “Origin of spatial variation in US East Coast sea-level trends during 1900–2017” has been published in the journal Nature.


Rising seas, rising costs: some $14 trillion worldwide per year by 2100

Sea level change won’t just displace millions from their homes — but also drain our coffers.


Image via Pixabay.

If we fail to contain climate change as per the United Nations’ 2ºC limit, we’d better be ready to cough up some dough. The change in sea level will have dramatic economic consequences, potentially costing us some $14 trillion worldwide annually by 2100, according to new research led by the UK National Oceanographic Centre (NOC).

Show me the money

“More than 600 million people live in low-elevation coastal areas, less than 10 meters above sea level,” says lead author Dr. Svetlana Jevrejeva, from the NOC. “In a warming climate, global sea level will rise due to melting of land-based glaciers and ice sheets, and from the thermal expansion of ocean waters. So, sea level rise is one of the most damaging aspects of our warming climate.”

The research stemmed from the lack of any sea level projections covering scenarios of warming below the 2°C and 1.5°C targets during the entire 21st century and beyond, the team writes. It might sound like some obscure, overly-technical tidbit of science, but such projections are actually invaluable to us today — they’re the closest thing we have to scrying the future in a crystal ball. With the added benefit that they actually work, unlike said balls.

Armed with such projections, we can make an informed decision on our actions today.

Sea Change.

Image credits S. Jevrejeva et al., 2018, Environmental Research Letters.

For the study, the team estimated the pace and consequences of sea level rise (on both a local and global level) in scenarios where warming was restricted to 1.5 ºC and 2 ºC. Then, they compared these projections to those of scenarios that assume unmitigated warming — emissions scenario Representative Concentration Pathway (RCP) 8.5.

Finally, drawing on country income groups as detailed by the World Bank (high, upper middle, lower middle, and low-income countries), the team assessed what bill these sea level changes will entail for us. These cost estimations focused mostly on costs associated with coastal areas both from a global perspective and on the level of a few individual countries, using the Dynamic Interactive Vulnerability Assessment (DIVA) framework. DIVA is a global model of coastal systems used to asses the consequences of sea-level rise on human communities and wild species based on parameters such as coastal erosion (both direct and indirect), coastal flooding (including rivers), wetland surface change, and salinity intrusion into deltas and estuaries.

“We found that with a temperature rise trajectory of 1.5°C, by 2100 the median sea level will have risen by 0.52m (1.7ft),” Dr Jevrejeva explained. “But, if the 2°C target is missed, we will see a median sea level rise of 0.86m (2.8ft), and a worst-case rise of 1.8m (5.9ft).”

“If warming is not mitigated and follows the RCP8.5 sea level rise projections, the global annual flood costs without adaptation will increase to $14 trillion per year for a median sea level rise of 0.86m, and up to $27 trillion per year for 1.8m. This would account for 2.8 per cent of global GDP in 2100.”

The team also adds that upper-middle income countries (such as China, for example) would see the largest increase in flood costs. While sea level rise will affect everyone roughly equally, richer countries will feel the effects the least — mostly due to their current infrastructure providing better protection than those of poorer countries.

Country costs.

Image credits S. Jevrejeva et al., 2018, Environmental Research Letters.

Tropical areas, however, will see extreme sea levels more often than the rest of the world. The changes will have a severe and negative effect on the economies of developing coastal nations and the habitability of low-lying coastlines.

“Small, low-lying island nations such as the Maldives will be very easily affected,” Dr Jevrejeva concludes, “and the pressures on their natural resources and environmental will become even greater. These results place further emphasis on putting even greater efforts into mitigating rising global temperatures.”

The paper “Flood damage costs under the sea level rise with warming of 1.5 °C and 2 °C” has been published in the journal Environmental Research Letters.


Half a degree (C) more global warming would leave 5 million people homeless

The seemingly inconsequential jump from 1.5 degrees to 2.0 degrees Celsius of global warming is anything but — that half of a degree would mean 5 million people across the world will need to move, or find a way to live in flooded areas.


Image credits George Hodan.

The 2015 Paris climate agreement seeks to stabilize global temperatures to less than 2 degrees Celsius above pre-industrial levels, with efforts made to ensure we never go more than 1.5 degrees Celsius above pre-industrial levels. And that sounds like a reasonable, safe goal. An international team from the Princeton, Rutgers, and Tufts Universities, alongside researchers from Climate Central and ICF International, however, wanted to find out what such a scenario would entail for people living in the most at-risk areas — coastal areas.

Still underwater

They drew on a global network of tide gauges and a framework of local sea-level projections to estimate how the frequency of storm surges and other extreme sea-level events would fare under three scenarios: global temperature increases of 1.5°, 2.0°, and 2.5°C.

Their results suggest that by 2150, the minute difference between an increase of 1.5° and 2.0°C would equate to the permanent inundation of areas that currently house 5 million people, including 60,000 who live in small island nations.

“People think the Paris Agreement is going to save us from harm from climate change, but we show that even under the best-case climate policy being considered today, many places will still have to deal with rising seas and more frequent coastal floods,” said first author DJ Rasmussen.

Unsurprisingly, the team reports that higher temperatures will make extreme sea level events much more common than they are today. Based on long-term hourly tide gauge records, they estimated current and future return periods of such events throughout the 22nd century. Under the 1.5°C scenario, this value is still expected to increase. For example, New York City is expected to see one Hurricane Sandy-like flood event every five years by the end of the 21st century under these conditions.

Extreme sea levels can be borne of high tides, storm surges, or a combination of these two — sometimes referred to as a storm tide. When whipped by hurricanes or other large storms, such events can flood into coastal areas, threatening life and property alike. A background of rising average sea levels will only compound the destructiveness and frequency of such events.

How much sea levels rise, on average, depends on how global mean surface temperatures evolve in the future. However, caution to the wise, the team notes that even if temperatures stabilize, sea levels are expected to continue to rise for centuries — because carbon dioxide lingers in the atmosphere for a long time and ice sheets will have inertia in responding to climate change.

Still, the researchers predict that by the end of the century, coastal flooding may be among the costliest impacts of climate change in some regions. Overall, a 1.5°C temperature increase by the end of the century (the best-case scenario under the Paris agreement) would equate to a roughly 1.6 feet (48 cm) mean sea level rise, and a 2.0°C increase to about 1.8 feet (56 cm). A 2.5°C increase would result in an estimated 1.9 feet (58 cm) increase, the team adds.

The paper “Extreme sea level implications of 1.5 °C, 2.0 °C, and 2.5 °C temperature stabilization targets in the 21st and 22nd centuries” has been published in the journal Environmental Research Letters.

More than 13 million Americans could be at risk from sea level rise by 2100

A new study analyzing sea level rise forecasts as well as population growth projections found that we’ve underestimated just how many people would be impacted by rising waters. Anywhere from 4.3 to 13.1 million people from the US alone will face the risk of inundation by 2100, according to their estimate.

Brackish sea water washes over the center line of a street in Charleston Oct. 1, 2015.
Image credits Stephen B. Morton/AP.

The team, with members from the University of Georgia and Stetson University in Florida used population trends and sea level rise estimates to establish a county-by-county risk assessment across the US. Their results suggest that previous research, based on current population numbers, underestimates the risk coastal states face.

An important implication of this is the estimated cost of adapting to sea level rise might be too low, since it doesn’t take population growth and the associated installation of more long-lasting, vulnerable infrastructure into account.

“There are 31 counties where more than 100,000 residents could be affected by 6 feet of sea level rise,” said study co-author Mathew E. Hauer, of the University of Georgia in a press release.

The southeastern U.S. coast is a hotspot for inundation risk related to sea level rise, the authors say. This is partly due to the high population growth that the area is experiencing. Over 10 percent of coastal populations in states such as Georgia and South Carolina will be affected by a global sea level increase of 1.8 meters (5.9 feet) by 2100. A similar rise would affect an estimated one million people in California and Louisiana each. Florida faces the most risk, with up to 6 million residents affected under the same scenario.

Densely populated counties in coastal areas, such as Broward or Miami-Dade Counties in Florida, San Mateo in California or Jefferson in Louisiana are expected to see more than 100,000 residents “potentially impacted” by a 0.9 meters (around 3 feet) rise in sea levels.

The study also identified three counties as having an “extreme exposure” to inundation: North Carolina’s Tyrrell and Hyde Counties, and Monroe County in Florida. Tyrell and Hyde Counties are home to abundant nature preserves on North Carolina’s Outer Banks, while Monroe County is located at the southwestern tip of Florida, encompassing a swath of Everglades National Park as well as the Florida Keys. People living in these areas will suffer “catastrophic impacts” by 2100 if steps aren’t taken to address the issue.

Image credits misterfarmer/pixabay

The authors also warn that the lack of protection for coastal residents could lead to a population migration on par with the “Great Migration” of southern African Americans after the first World War. They estimate that the cost of relocating all the people affected by sea rise by 2100 would exceed $14 trillion dollars.

“The impact projections are up to three times larger than current estimates, which significantly underestimate the effect of sea level rise in the United States,” Hauer added.

Compared to previous estimates, these are worrying numbers. The team’s estimates revolve around those 1.8 meters of sea rise used in their calculations. The study also doesn’t take factor in regional variations in the rate of sea level rise. But, while the consensus seems to be set around a 1 meter (3.6 feet) rise by 2100, there is growing concern around the stability of the Greenland and West Antarctic ice sheets in today’s warmer oceans. Faster melting of these ice sheets would rise the waterline significantly, possibly way above the 1.8 meter level the team set.

Ben Strauss told Mashable that the lack of regional variations in sea level rise would affect the results out to the year 2100, and the study also “assumes that people will be moving to the shore essentially just as briskly” in the latter half of the century as in 2020, despite the evident effects of sea level rise expected by 2070.

The full paper, titled “Millions projected to be at risk from sea-level rise in the continental United States” has been published online in the journal Nature Climate Change and can be read here.