Tag Archives: sea level rise

Satellite data shows that the Earth’s glaciers are melting faster than ever before

The rate at which glaciers are melting has been steadily picking up according to a new study, based on satellite data. They’re now losing 31% more mass every year than they were just 15 years ago. The cause is anthropogenic climate change, the authors explain.

Mountain glacier in Argentina. Image credits Adam Derewecki.

The study is based on 20 years’ worth of declassified three-dimensional satellite data. Based on these measurements, the authors estimated that mountain glaciers worldwide have been losing in excess of 328 billion tons (298 billion metric tons) of snow and ice per year every year since 2015. This is 78 billion tons (71 billion metric tons) a year more than the average between 2000 and 2004.

Half of the world’s glacial loss today is coming from the United States and Canada, the paper adds.


In addition to more ice being lost per year, global glacial thinning rates (another important indicator of glacier health) have also doubled in the last 20 years.

Virtually all of the world’s glaciers are affected, the team explains, even ones that were traditionally considered stable, such as those in Tibet. The precious few exceptions to this rule include a couple of glaciers in Iceland and Scandinavia, kept stable by increased levels of precipitation. But overall, global melt rates have been and still are accelerating. Alaska has the single highest overall melt rate seen in the study.

Melting rates are increasing quite uniformly across the world, a process that “mirrors the global increase in temperature” says Romain Hugonnet, a glaciologist at ETH Zurich and the University of Toulouse in France, who led the study. The cause, ultimately, is our growing use of fossil fuels such as coal, oil, and gas, which release greenhouse gases in the atmosphere.

The study’s findings are particularly worrying as this is the first paper to use 3D satellite imagery to examine all of Earth’s glaciers, not just those that are part of the Greenland or Antarctic ice sheets.

Not only are such results a chilling account of how deeply climate change is impacting glaciers and the world as a whole, but it also points to massive problems-to-be. Glaciers supply millions of people with their daily water needs, and them shrinking so quickly means that a lot of people will soon be in need to secure new sources of water. On the other end of the spectrum, rapid glacier shrinking increases the risk of events such as outburst floods from glacial lakes.

And, ultimately, all these glaciers melting around us have to flow somewhere — which is the ocean. Sea level rise is a very real problem that’s poised to cause us some massive issues in the future. Sea levels are already rising today, partially because of melting in glaciers and ice sheets, partially because higher mean temperatures make water expand in volume. Even so, today, glacier melt is responsible for an estimated 21% of the overall sea-level change we’ve recorded. Although the ice sheets hold overall more water and are thus the greater long-term threat, mountain glaciers hold a respectable amount of water and should not be overlooked in this regard.

Shrinking glaciers are a problem for millions of people who rely on seasonal glacial melt for daily water and rapid melting can cause deadly outbursts from glacial lakes in places like India, Hugonnet said.

But the largest threat is sea level rise. The world’s oceans are already rising because warm water expands and because of melting ice sheets in Greenland and Antarctica, but glaciers are responsible for 21% of sea level rise, more than the ice sheets, the study said. The ice sheets are larger longer term threats for sea level rise.

“It’s becoming increasingly clear that sea level rise is going to be a bigger and bigger problem as we move through the 21st century,” said National Snow and Ice Data Center Director Mark Serreze.

The paper “Accelerated global glacier mass loss in the early twenty-first century” has been published in the journal Nature.

Climate change is causing sea levels to rise faster than previously thought

Sea levels are rising much faster than previously thought. According to a new study, 40% of the world’s population living in coastal regions is at high risk. The findings reaffirm the importance of tackling greenhouse gas emissions to avoid catastrophic climate damage such as floods or tidal surges.

Image credit: Flickr / Apasciuto

The Intergovernmental Panel on Climate Change (IPCC), the world’s leading group of climate experts, said in its most recent assessment that the sea level was unlikely to rise beyond 1.1 meters by 2100. But they were too optimistic. According to a group of researchers at the University of Copenhagen’s Niels Bohr Institute, things are way worse.

Using historical data on the sea-level rise to validate models relied on by the IPCC to make its assessment, they found that sea levels could rise as much as 1.35 meters by 2100 –– 25 centimeters more than the IPCC’s most dire prediction. It might not seem like a lot, but for cities living right near the sea and small island states, it could actually spell disaster, displacing millions of people from their coastal cities and villages.

“It’s not great news that we believe the former predictions are too low,” Aslak Grinsted, a co-author of the study, told The Guardian. “The models used to base predictions of sea-level rise on presently are not sensitive enough. They don’t hit the mark when we compare them to the rate of sea-level rise we see when comparing future scenarios with observations going back in time.”

Grinsted and his team used a linear regression model to connect the rise in average temperatures to sea level rise, focusing on measuring their results against preexisting estimates. They analyzed historical data to factor in how the dynamic nature of the environment can accelerate or decelerate rising sea levels.

The results from their regression model showed that the projected global sea-level rise by the end of the 21st century by the IPCC is “at best conservative.” The world would need to emit 200 gigatons to 300 gigatons less carbon dioxide, and cool the Earth by about 0.6° Celsius, for sea-level rise to correlate with previous models, they added.

“The scenarios we see before us now regarding sea-level rise are too conservative – the sea looks, using our method, to raise more than what is believed using the present method,” Grinsted told Bloomberg. Following their results, the researchers are already in touch with the IPCC about incorporating its results in next year’s assessment.

Benjamin Horton, a professor at Singapore’s Nanyang Technological University, who wasn’t involved in the study, told Mongabay that the research is important since computer models aren’t always accurate at predicting the future. “The methodology suggests that there’s a real risk of very substantial sea-level rise,” he said.

Rising sea levels are one of the major results of the climate crisis, causing flooding and threatening coastal habitats. They are caused by melting of land-based ice such as glaciers and thermal expansion from ocean warming. Oceans absorb more than 90% of the increased atmospheric heat linked to emissions from human activity.

Just in the United States, almost 40% of the population lives in densely-populated coastal areas, where sea level plays a role in flooding, shoreline erosion, and hazards from storms, according to US National Ocean Service. On a global scale, eight of the 10 largest cities are near a coast, according to the UN Atlas of the Oceans.

The study was published in the journal Ocean Science.

Climate change could flood thousands of affordable houses in the US by 2050

As the world gets warmer, the sea level rises — it’s one of the many consequences of climate change. But sea level rise isn’t always straightforward: tides and storms also threaten homes along the coast, in addition to the direct sea level rise.

But not everyone is exposed in the same way, according to a new study. As it is so often the case, it’s the low-income Americans that will be most affected.

Estimate of affordable housing units in New Jersey at risk by 2050. Image credit Climate Central.

Climate Central, a nonprofit that analyzes and promotes climate science, showed that the number of affordable housing in the US exposed to flooding would triple over the next 30 years if emissions aren’t drastically reduced. This would mean moving from the current 7,668 units across the US expected to flood in a typical year to 24,519 units by 2050.

“The combination of physical vulnerability of affordable housing, socioeconomic vulnerability, and more frequent flooding due to sea-level rise presents a triple threat within the next 30 years to residents and owners of the country’s already scarce affordable housing,” the authors of the study wrote.

The frequency of coastal floods has already risen sharply in recent decades due to global warming, and this trend will not slow down as long as emissions don’t also slow down. Tidal flooding that now occurs once a year may occur on a weekly basis in some coastal communities, according to previous estimations.

This is particularly concerning for affordable housing and low-income households. The US has an estimated 35 affordable rental units available for every 100 extremely low-income renters. These homes are even more vulnerable to flooding, as they are older and not equipped with resilience features.

Researchers at Climate Central wanted to quantify the current and future coastal flood risk to the affordable housing inventory so stakeholders could understand the overall exposure of this already scarce resource. They focused on the year 2050 as an objective to highlight the threats for residents and find plans for resilience.

They first gathered data from the National Housing Preservation Database’s dataset to find affordable housing in the US and map it. They used this information combined with climate models to create an interactive map, through which people can see how their hometown might be affected due to sea-level rise. The timeline of the map can be switched from 2030 to 2100.

A screenshot from the map. Credits: Climate Central

New Jersey has the highest percentage of its affordable housing stock currently exposed to sea-level rise, followed by New York and Massachusetts. Fewer units are at risk in California, but these units face a high risk of repetitive flooding, as in Maryland, Alabama, and Texas.

But the risk becomes much more significant by 2050 if emissions keep growing. New Jersey could see nearly 7,000 units exposed, a four-fold increase; and New York and Massachusetts would continue to rank among the top three states for the absolute and relative number of units exposed, the study showed.

The researchers also ranked the top 20 cities in terms of annual numbers of units exposed by 2050. Cities in the Northeast and California are the most vulnerable, with New York City remaining the most exposed, with over 4,000 units at risk per year by 2050. Five cities in New Jersey also ranked in the top 20.

“I hope this can guide policy that will help the people who are most vulnerable to coastal flooding, which is low-income people in affordable housing. We feel like we’ve really pinpointed that problem with this study,” said in a statement Benjamin Strauss, a co-author of the study who is also chief at Climate Central.

Having a better understanding of the exposure of affordable housing to flood-risk events is of vital importance to support strategic resilience planning, the researchers argued. They suggested implementing flood-threat reduction measures and land-regulatory policies to protect the lives of those who live there.

The good news is that 75% of the affordable housing stock vulnerable to future floods is concentrated in just 20 cities, which means that targeted impacts could make a big difference.

The findings follow previous studies that have warned over the impact of sea-level rise in the US. Earlier this year, a study from the University of Southern California found 13 million people would be displaced across the country by 2100, placing extreme strain on several cities throughout the country.

The study was published in the journal Environmental Research Letters.

Melting ice sheets could add 40cm to global sea level rise

The ice sheets of Greenland and Antarctica could together contribute nearly 40 centimeters to global sea-level rise by 2100, if greenhouse gas emissions continue at their current growing levels, according to a new study led by NASA. The findings are in line with previous projections and highlight the effects of climate change.

Credit NASA

More than 60 scientists from three dozen international institutions generated new estimates of how much of an impact Earth’s melting ice sheets could have on global sea levels. The ice caps have enough frozen waters to lift oceans 65 meters, according to previous estimates.

The Intergovernmental Panel on Climate Change (IPCC), which groups leading climate researchers, said in a report last year that Greenland would contribute 8 to 27 cm to global sea-level rise between 2000-2100, while Antarctica could contribute 3 to 28 cm. Meltwater from ice sheets contribute to a third of global sea-level rise, it said.

“One of the biggest uncertainties when it comes to how much sea level will rise in the future is how much the ice sheets will contribute,” said project leader and ice scientist Sophie Nowicki, now at the University at Buffalo, in a statement. “And how much the ice sheets contribute is really dependent on what the climate will do.”

The researchers used two climate scenarios, one in which emissions continue at their current level and one in which they are drastically reduced by 2100. Under a high emissions scenario ice loss in Antarctica would cause sea levels to rise 30 centimeters by the end of the century, with Greenland contributing an extra nine centimeters, they found.

Such a sea-level rise would have severe consequences around the world, increasing the power of storm surges and exposing coastal regions to flooding. Even in the lower emissions scenario, the melt of the Greenland sheet would cause ocean levels to rise three centimeters by 2100.

“The strength of the report was to bring together most of the ice sheet modeling groups around the world, and then connect with other communities of the ocean and atmospheric modelers as well, to better understand what could happen to the ice sheets,” said Heiko Goelzer, a co-author from Utrecht University, in a statement.

Until the 21st century, the West Antarctic and Greenland ice sheets generally accumulated as much mass as they shed. Runoff was compensated by fresh snowfall. But over the last two decades, the growing pace of climate change has upended this balance. Last year, Greenland lost a record of 532 billion tons of ice—the equivalent of six Olympic pools flowing into the Atlantic every second.

The study was published in the journal The Cryosphere.

The planet has lost 28 trillion tons of ice in less than 30 years, study finds

The Earth has lost 28 trillion tons of ice between 1994 and 2017, a group of United Kingdom researchers found based on satellite surveys of glaciers, mountains, and ice sheets. This could cause sea levels rise to steeply increase, possibly reaching a meter (three feet) by the end of the century.

Ívar Atli Sigurjónsson. Flickr (CC BY-NC-ND 2.0)

Based at Leeds and Edinburgh universities and University College London, the researchers described the level of ice loss as “staggering” and warned that the melting of the ice is reducing the planet’s ability to reflect solar radiation back into space (albedo). As ice disappears, the soil is absorbing more heat and warming the planet.

But that’s not it. Ecosystems in the Arctic and Antarctic waters are being disrupted by cold freshwater pouring from glaciers and ice sheets. Meanwhile, the loss of glaciers located in mountain ranges could mean the loss of fresh water sources on which many communities rely on across the world.

“In the past researchers have studied individual areas – such as the Antarctic or Greenland – where ice is melting. But this is the first time anyone has looked at all the ice that is disappearing from the entire planet,” co-author Andrew Shepherd told The Guardian.

“What we have found has stunned us.”

Arctic sea ice (7.6 trillion tons), Antarctic ice shelves (6.5 trillion tons), mountain glaciers (6.2 trillion tons), the Greenland ice sheet (3.8 trillion tons), the Antarctic ice sheet (2.5 trillion tonnes), and Southern Ocean sea ice (0.9 trillion tons) have all decreased in mass, the study found.

Up to 60% of the ice loss was from the northern hemisphere, and the remainder was from the southern hemisphere. The rate of ice loss has risen by 57% since the 1990s – from 0.8 to 1.2 trillion tones per year – owing to increased losses from mountain glaciers, Antarctica, Greenland, and from Antarctic ice shelves.

The majority of all ice loss was driven by atmospheric melting (68% from Arctic sea ice, mountain glaciers ice shelf calving, and ice sheet surface mass balance), with the remaining losses (32% from ice sheet discharge and ice shelf thinning) being driven by oceanic melting.

“To put the losses we’ve already experienced into context, 28 trillion tonnes of ice would cover the entire surface of the UK with a sheet of frozen water that is 100 metres thick,” group member Tom Slater from Leeds University told The Guardian. “It’s just mind-blowing.”

The researchers argued there’s “little doubt” that climate change is behind the staggering losses. They note that the planetary surface temperature has already grown by 0.85ºC since 1880 and that this has been amplified in the polar regions. Sea and atmospheric temperatures have risen as a result, triggering the ice losses.

The findings come a week after researchers found in another study that Greenland’s ice sheet, the world’s second-largest ice body, might have passed a point of no return. The snowfall that replenishes the country’s glaciers every year can’t keep up with the pace of the ice melt, meaning the ice sheet will lose ice even if temperatures stop rising.

The study was published in the journal Cryosphere Discussions.

Dams have helped to limit sea-level rise, study finds

While melting glaciers and thermal expansion are driving up ocean levels, the construction of large-scale dams is helping to limit that increase. A new study argues that dams prevented water from entering the oceans and stalled the rising seas.

Credit Astrid Westvang Flickr (CC BY-NC-ND 2.0)

The rate of global sea-level rise since 1900 has varied over time, but the contributing factors are still poorly understood. Previous studies found that the summed contributions of ice-mass loss, terrestrial water storage, and thermal expansion of the ocean could not be reconciled with observed changes in the mean sea level.

In this new study, researchers looked at information about sources and measurements to come up with a new and more accurate estimation. They argued that dams and reservoirs had a big impact on sea levels over the past 100 years, as well as thermal expansion of the seas and the melting of glaciers.

The world now has about 58,000 large dams, many of them built over the last 60 years. There was a construction boom between the 1950s and 1970s, leading to many large-scale dams being completed. The researchers argued that the ability of dams to block water from flowing into the sea has slowed sea level rise.

“A large part of this dip is because sea level [rise] was almost brought to a halt because of the amount of water stored in dams,” lead author Dr. Thomas Frederikse, from Nasa’s Jet Propulsion Laboratory in Pasadena, California, told BBC. “So by building dams, we almost stopped sea level rise for a decade or so.”

The study found sea level has increased by approximately 1.5 mm per year over the twentieth century, with fluctuations stretching over several decades. Changes in the sea level were the net result of many geophysical and climatological processes, with some of the largest contributions coming from ice-mass loss and thermal expansion.

Without dams and reservoirs, the sea level would have been around 12% higher, according to the researchers. Nevertheless, the influence of dams started to fade away in the 1990s, as fewer dams were built due to growing concerns about their environmental impact.

The lack of new dams plus the growing influence of climate change and the greater thermal expansion of waters has led to sea levels rising more quickly over the past 30 years, the researchers argued, now running at about 3.35mm per year.

This prompts the question of whether new dams could help deliver the world from rising waters. Frederiske says that adding new extra barriers wouldn’t necessarily work now, suggesting instead to cut greenhouse gas emissions.

“At the height of the dam-building, we were able to slow sea-level rise by about 0.8mm per year. And now we’re seeing sea levels rising in the last 10 years by about four millimeters per year,” he said.

“So it means that you have to build five times the number of dams that we built in that period to stop the current rate of sea-level rise.”

The study was published in the journal Nature.

Mangrove forests could be gone by 2050 if sea levels continue to rise

If climate action doesn’t scale up soon, mangrove forests could drown under rising seas by 2050, according to a new study, which looked at mangrove ecosystems from around the world. This would be bad news for the whole planet, as trees store carbon dioxide and protect communities from storms and coastal erosion.

Credit Flickr

Researchers from Rutgers University argued that mangrove forests would be in danger if the sea level rises by more than six millimeters per year. Despite the fact that it might seem like a lot, the threshold could actually be reached in just 30 years if the world doesn’t reduce its greenhouse gas emissions.

The planet has already warmed over one degree Celsius, leading to a wide array of consequences. Sea levels are already growing globally three millimeters per year, although in some parts of the world there has been a more drastic change. Island states like Tuvalu are especially under risk.

The mangrove ecosystems can adapt to a certain level of sea-level rise by migrating inland and building up sediment. But their defense mechanisms are only effective until a certain point, after which they simply can’t keep up. That’s what the authors wanted to determine by looking at their ancient history.

The researchers looked at sediment data from 78 mangrove ecosystems from the past ten millennia. They were able to determine that the mangroves are more likely to die when sea level rise rates exceed 0.23 inches (6 millimeters). The problem is that we’ll exceed that by 2050 if climate action doesn’t increase.

The consequences of that would be massive. Mangrove ecosystems, found in many places in the world from Africa to Argentina, store more carbon dioxide than rainforests, so if they die it would be very bad news for the planet. Mangroves are also very rich in biodiversity as they provide habitat to many species, in which fishermen rely upon their livelihood.

“If they disappear, there’s going to be imbalances in the number of fish and other species that rely on them,” co-author Erica Ashe, a postdoctoral scientist at Rutgers University, told Earther. “And that could have effects on other species, even ones that actually aren’t sheltered by these mangroves because when the levels of different species change, that can affect the entire system.”

But we can still prevent this from happening. Governments need to find solutions to keep sea-level rise below that threshold “to mitigate climate change and to protect millions of people who depend on mangroves for shelter, flood protection, food, and fiber,” University of Queensland professor Catherine Lovelock wrote in an article commenting the study.

Countries committed to limit global warming to two degrees Celsius by signing the Paris Agreement in 2015. Nevertheless, their current climate pledges put us in a world of up to four degrees Celsius by 2010. This year new pledges have to be presented by countries to increase ambition levels.

The study was published in the journal Science.

As sea level rises in Europe, setting up defenses would save money in the long-run

Sea level rise is one of the many threats that a warmer planet will cast upon us, and people in many regions of the world are already dealing with this in different ways.

From being displaced from their homes to setting up defenses against the water, coastal communities are adapting in different ways. But this is just the beginning, a new study warns.

Image credits: Flickr.

A new study by European Commission scientists looked at the costs of protecting coastal communities from climate change — as sea levels are predicted to rise as much as one meter by the end of the century and more intense storms.

More than 200 million European citizens live within 50 km from the coastline, stretching from the Atlantic Ocean and the Baltic Sea to the north and west, and the Mediterranean and the Black Sea in the southern and eastern parts of the continent. Furthermore, current trends indicate that migration toward coastal zones is continuing, and coastal populations are expected to grow in the coming decades, the authors argued.

Global mean sea level has increased by 13–20 cm compared to pre-industrial times, a process has accelerated since the 1990s due to global warming. This has already contributed to coastal recession and made Europe’s coasts more susceptible to coastal hazards such as floods and water surges. A continued sea-level rise could lead to widespread coastal floods in Europe.

Coastal flood losses in Europe now amount to 1.4 billion euros ($1.5 billion) per year and each year about 100,000 EU citizens are affected by coastal flooding. This, the team reports, is just the start. The annual coastal flood losses for Europe by the end of the century are projected to grow to 209.8 billion euros.

Among the many options at our disposal to adapt to this new scenario, the authors focused on building protective structures. Specifically, they explored the costs and benefits of dike improvements along the European coastline, concluding that setting up sea defenses would save money in the long run in the region.

The benefit to cost ratio (BCR) of increased protection, however, varies strongly across Europe, the study found. Costs outweigh the benefits for 76% of the European coastline. Low BCR can be related to several factors, like sparsely populated coastlines, such as in Greece and Malta. Also, long and complex coastlines imply higher dike construction costs, hence lower BCR, such as in many parts of Finland and Sweden.

Benefits tend to outweigh costs in areas where population density is larger than 500 people per km2, the researchers argued. In urbanized areas, the benefits tend to exceed the costs. As a result, when benefits and costs are aggregated at the regional level, the total benefits are dominated by those in urban centers and this compensates for the low BCR in less densely populated and rural coastal stretches.

At the country level, Belgium is the country with the highest percentage of coastline where benefits exceed costs, followed by France and Italy. These are also the countries with some of the highest expected BCRs. On the lower end of the analysis is Malta, for which the expected country-level BCR is the lowest in Europe.

“Our results highlight potential savings in terms of avoided damages that can be obtained through strategies that increase structural flood protection at the subnational scale,” the authors wrote. “Sea levels are projected to increase long after 2100 and very likely this will happen at an accelerating rate.”

For Hannan Cloke, a hydrology professor at Reading University, who did not participate in the study, setting up coastal protection isn’t necessarily the only way of protecting against sea-level rise. Nature-based solutions such as recreating dunes or marshland or retreating from coastal zones should also be considered, she argued.

These solutions work with natural processes and have many other benefits for wildlife and humans, Cloke said, as well as removing some of the worst issues of coastal defenses such as the way concrete walls can simply displace erosion further along the coast to places which are not defended.

“Do we really want to live in a world in which we all live behind huge walls? Is this the only way to adapt? Many of us have trapped ourselves in places that will no longer be safe, and in some places building large defenses is the only option. Certainly, London will not survive without the next-generation Thames barrier,” Cloke wrote.

The study was published in the journal Nature Communications.

Worse than expected

According to recent a global survey with 100 leading experts, oceans are likely to rise as much as 1.3 meters by 2100 if Earth’s surface warms another 3.5 degrees Celsius. By 2300, when ice sheets covering West Antarctica and Greenland will have shed trillions of tonnes in mass, sea levels could go up by more than five meters under that temperature scenario, redrawing the planet’s coastlines, they reported.

The new projections for both the 2100 and 2300 horizons are significantly higher than those from the UN Intergovernmental Panel on Climate Change (IPCC), including a special report on oceans it released in September.

“It is clear now that previous sea-level rise estimates have been too low,” co-author Stefan Rahmstorf, head of Earth system analysis at the Potsdam Institute for Climate Impact Research (PIK), told AFP.

The study was published in the journal Climate Atmospheric Science.

Sea level rise could endanger three times more people than previously expected

Sea level rise could be much more difficult and expensive to deal with than previously thought, new research found, not because of faster changes in sea levels but because of an increase in estimates of the number of people living on low ground.

Credit Wikipedia Commons

The study, published in Nature Communications, argued 110 million people worldwide live below the high-tide level, including many partly protected by sea walls or other infrastructure. Even under a scenario of very modest climate change, that number will rise to 150 million in 2050 and 190 million by 2100.

An even worse scenario of climate change and sea-level rise would mean that as many as 340 million people living below the high-tide level could be in peril, researchers concluded. Such figures are three times — or more — higher than earlier estimates.

“We’ve had a huge blind spot as to the degree of danger, and that’s what we’ve been striving to improve,” Benjamin Strauss of Climate Central, who wrote the new study with colleague Scott Kulp, told the Washington Post.

Prior research relied on data about coastal elevations that come from radar measurements from the 2000 space shuttle Endeavor mission. But that dataset has problems. The instrument detected the height not only of the coastal land surface but anything else that was on it, such as houses and trees.

This introduced errors in land-elevation estimates averaging about 6½ feet globally, the new study said. “For all of the resources we have rightly invested in improving our sea-level projections, we didn’t know the height of the ground beneath our feet,” Strauss said.

Some wealthy countries, such as the United States, have used laser-based coastal measurements to gain more accuracy, but most other countries have not been able to do so. The new study used the more accurate U.S. measurements as a guide, training an algorithm to apply similar adjustments to the global dataset from the space shuttle.

This is where the much higher numbers for exposed populations come from, with the biggest changes in exposure coming to countries in Asia. The study estimates that 110 million people live below the current high-tide level vs. an estimated 28 million for the older data set.

“In terms of global estimates, I think the analysis convincingly shows that the situation is probably even worse than previous studies suggested,” Stéphane Hallegatte, an economist at the World Bank who studies climate change, told The Washington Post. “We are talking about hundreds of millions of people who will be directly exposed.”

The study considers a scenario that would lead to 2 degrees Celsius, or 3.6 degrees Fahrenheit, of global warming by 2100, the temperature rises that world leaders have set as an absolute limit. The study projects that 150 million would live below the high tide line by 2050 and 200 million by 2100. Those exposed to an annual flood in that year would be 360 million.

The world is on course to warm considerably more than 2 degrees Celsius, however, so there are more dire scenarios. If key instabilities kick in in Antarctica, 480 million people would be exposed to an annual flood in 2100. The findings are worst for Asia, notably in China, Bangladesh, and India.

Sea level rise could threaten 300,000 US coastal homes, in the “business-as-usual” scenario

Within the next 30 years, sea level rise could have dramatic consequences for US coastal communities, threatening over 300,000 homes with regular flooding.

Image via Wikipedia.

As temperatures continue to rise, icesheets continue to melt and sea levels continue to rise. Sea levels also rise directly due to the thermal expansion of the water. The relationship isn’t exactly linear, but there is a clear cause-effect relationship. However, many people seem to think that there will be no tangible consequences close to home — but that couldn’t be further from the truth.

“The impact could well be staggering,” said Kristina Dahl, a senior climate scientist at the Union of Concerned Scientists (UCS) to The Guardian. “This level of flooding would be a tipping point where people in these communities would think it’s unsustainable.

“Even homes along the Gulf coast that are elevated would be affected, as they’d have to drive through salt water to get to work or face their kids’ school being cut off. You can imagine people walking away from mortgages, away from their homes.”

Along with colleagues, Dahl assessed this impact using data from the National Oceanic and Atmospheric Administration (NOAA) and real estate company Zillow. They present the results in the form of an interactive map which you can check out here.

Image credits: UCS.

When working on this type of predictions, researchers opt for one of several scenarios. Here, they chose a high sea level rise scenario, where planet-warming emissions are barely constrained and the seas rise by 2 meters (6.5ft) globally by the end of the century.

If this is the case, then 310,000 US homes would be threatened by 2045, flooding as often as once every other week. By the end of the century, there would be as many as 2.4m threatened homes, worth around a trillion dollars.

Of course, coastal states would be the most affected, particularly low-lying states. A million homes in Florida would be threatened by 2100, as would 250,000 homes in New Jersey and 143,000 homes in New York. Persistant flooding is only one of the problems associated with sea level rise. The most immediate problem is that people already have to pay more money for insurance — and as disasters become more and more likely, property damage also expands.

“My flood insurance bill just went up by $100 this year, it went up $100 the year before,” said Philip Stoddard, the mayor of South Miami. “People on the waterfront won’t be able to stay unless they are very wealthy. This isn’t a risk, it’s inevitable.”

It should be said that the report doesn’t factor in technological advances that might offset some of the sea level rise. However, this likely wouldn’t make much of a difference in the US, considering that the country doesn’t have a national sea level rise plan, and the current administration seems completely uninterested in anything related to protecting the environment.

Sea level rise is accelerating, could lead to twice as much sea level rise by 2100 than previously expected

A study using satellite data found that not only are sea levels rising — but the rate is accelerating.

Sea levels might be rising two times faster than we thought, a new study suggests.

Steve Nerem, a professor of aerospace engineering sciences at the University of Colorado-Boulder and lead author on the paper, analyzed 25 years of satellite data to calculate how fast sea levels are rising as a result of climate change. He found that sea levels are currently growing by 3 mm/year, but this isn’t a steady growth. The rate is accelerating by 0.08 mm/year every year. It might not seem like much, but it picks up year after year and in the long-term, it can end up making a big difference.

“This acceleration, driven mainly by accelerated melting in Greenland and Antarctica, has the potential to double the total sea level rise by 2100 as compared to projections that assume a constant rate–to more than 60 cm instead of about 30,” said Nerem.

He also says that his models are extremely conservative, as he didn’t consider any major events such as the collapse of important ice sheets or accelerating global warming. This means that in reality, we can probably expect sea levels to grow even more than his predictions.

“And this is almost certainly a conservative estimate,” he added. “Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that’s not likely.”

Climate change causes sea level rise through two mechanisms. First, warmer water expands, which accounts for about half of the sea level rise we’ve seen so far. Secondly, warmer temperatures melt land ice which then flows into the ocean, adding to the increase.

Image credits: EPA / CSIRO / NOAA.

In order to quantify this change, Nerem and his colleagues used data from satellite altimeter measurements starting in 1992, including the U.S./European TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 satellite missions. Processing and interpreting the data isn’t easy — there are several natural events (such as volcanic eruptions) which can cause variability, and it can be difficult to see the underlying trend. So, to aid their work, the team used climate models to account for such events and weed them out. They also used so-called tide gauge data to assess potential errors in the measurements. This tide gauge data is very important in limiting the uncertainty in the results.

However, researchers warn that their findings should also be taken with a grain of salt. The research has only found the initial rate of acceleration — this rate itself needn’t be static. Sea level rise isn’t a car steadily cruising on the highway. Rather, it’s a car driving through a city, going faster or slower depending on external parameters. Researchers hope to further build on this research, refining the results and building on even more data. Lastly, they hope that this global data can be used at a local level, so that satellite data can be used to predict what will happen in your backyard.

“This study highlights the important role that can be played by satellite records in validating climate model projections,” said co-author John Fasullo, a climate scientist at the National Center for Atmospheric Research. “It also demonstrates the importance of climate models in interpreting satellite records, such as in our work where they allow us to estimate the background effects of the 1991 eruption of Mount Pinatubo on global sea level.”

Journal Reference: R. S. Nerem, B. D. Beckley, J. T. Fasullo, B. D. Hamlington, D. Masters and G. T. Mitchum. Climate-change–driven accelerated sea-level rise detected in the altimeter era. https://doi.org/10.1073/pnas.1717312115

Sites under risk.

Rising seas risk washing tens of thousands archaeological sites clean off the map in the US alone

Thousands of historic and archeological sites along the southern US coast risk being engulfed by sea-level rise by the end of the century, scientists report.

Sites under risk.

The sites at risk from rising sea-levels.
Image credits David G. Anderson et al., 2017, PLOS ONE.

Climate change isn’t putting just our future at risk — it’s also engendering out past, according to new research. More than 13,000 archaeological sites, historic buildings, and cultural landscapes on the Atlantic and Gulf coasts of the southeastern United States are at risk from sea-level rise and could be submerged by 2100.

No ark for this flood

The team, led by David Anderson from the University of Tennessee, Knoxville drew on data from the Digital Index of North American Archaeology (DINAA) to estimate the risk posed by sea-level rise on archaeological sites. DINAA is a platform that aggregates archeological and historical datasets compiled over the past century and from numerous sources. Its aim is to provide researchers and the public with a comprehensive view of when and where humans settled.

Based on position and elevation data, the team warns that over 13,000 sites in the southeast alone may find themselves topped with water for a mere 1 meter (3.28 ft) rise. This includes over 1,000 sites listed on the National Register of Historic Places as having important cultural properties. But things could get much, much worse.

“These numbers increase substantially with each additional 1 m rise in sea level, with >32,000 archaeological sites and >2400 NRHP properties lost should a 5 m rise occur,” the authors warn.

“Many more unrecorded archaeological and historic sites will also be lost as large areas of the landscape are flooded. The displacement of millions of people due to rising seas will cause additional impacts where these populations resettle.”

Large linked data sets such as the DINAA, which can predict the potential impacts of phenomena across wide areas, are essential when developing procedures for sampling, triage, and mitigation efforts, the team explains. Therefore, they hold the key to planning and adaptation in the face of climate change, extreme weather events, and the displaced populations these will bring about — factors that could shape our civilization profoundly in the years to come.

“Sea level rise will thus result in the loss of much of the record of human habitation of the coastal margin in the Southeast,” the paper reads, “and the numbers indicate the magnitude of the impact on the archaeological record globally.”

The paper “Sea-level rise and archaeological site destruction: An example from the southeastern United States using DINAA (Digital Index of North American Archaeology)” has been published in the journal  PLOS ONE.

Sweden's port of Lulea risks getting too shallow for ships because sea levels around it are dropping. Credit: Wikimedia Commons.

Why sea levels around Finland and Sweden are dropping while the rest of the world is drowning

Sweden's port of Lulea risks getting too shallow for ships because sea levels around it are dropping. Credit: Wikimedia Commons.

Sweden’s port of Lulea risks getting too shallow for ships because sea levels around it are dropping. Credit: Wikimedia Commons.

One of the biggest consequences of man-made climate change is sea level rise. On average, sea levels are rising at a rate of more than 3 millimeters (mm) a year, bearing serious repercussions for human health and the economy, particularly in coastal regions which are most vulnerable. And because our planet isn’t a bathtub, in some places the sea level is rising two or three times faster than average. For instance, by 2030 sea levels could be 431 mm (17 inches) higher, with the highest rise at Mayport, Fernandina Beach, and Daytona Beach. People living around China’s Yellow River delta are swamped by sea level rise of more than 250 mm (9 inches) a year.

Sea levels aren’t rising everywhere, though. In fact, in some places like Scandinavia, they’re dropping.

Namely, Finland and Sweden’s landmass is rising by 3 to 9 mm each year due to a geological process known as the post-glacial uplift, which started 10,000 years ago when the last Ice Age ended. And although it may look like these Scandinavian countries have nothing to worry about, sea level drop is causing all sorts of problems.

But first, a few words about what’s causing this peculiar drop in sea level while the rest of the world seems to be drowning.

A rubber mattress

Some 50 miles below our feet lies a viscous layer thousands of miles thick known as the mantle — the thickest layer of the Earth. On top of the mantle, tectonic plates float like a cake on a pudding. If you put some more sweets atop of the cake, it will start sinking into the pudding. Likewise, more weight on the crust, such as billions of tons of ice that collect during an ice age, will cause it to sink more into the mantle. Now displaced, the mantle will bulge elsewhere. When the extra weight is gone, such as in the aftermath of an ice age when all those excess glaciers melt, the mantle rebounds — it still does to this day after thousands of year. It’s much like a foam rubber mattress, in the sense that it takes a while to return to its original shape.

This post-glacial uplift is what’s overly compensating for sea level rise around the Scandinavian coastline and locals are plainly aware of this fact. “The conditions for sea transportation in the area is getting more tricky,” says Sven Knutsson, professor of soil mechanics at Lulea University of Technology, told journalist Jon Bjarki Magnusson.

For instance, the port of Lulea located in northern Sweden is getting shallower which is causing problems for larger ships attempting to enter the port, problems that were non-existing 40 years ago. Since then, the land has risen by about half a meter. In one spot, Sweden’s coastline has risen 300 meters since the Ice Age ended about 10,000 years ago. Local authorities are investing about $208 million to deepen the harbor.

The uplift is also ruining Swedish lakes. Once pristine and crystal clear, many of Sweden’s shallower lakes are now becoming murky and muddy as more and more grass grows around them. There’s not much to do in this case as any attempt to deepen the lakes simply makes no economic sense.

In Western Finland, ironically, the sea level drop is causing floods. Because the crust is rising non-uniformly, namely faster by the coastline than further east, rivers have become tilted. During the spring when Finland’s big rivers are packed with meltwater, the surroundings get flooded.

On the flipside, at least these countries are getting bigger. It’s estimated the uplift is helping Finland gain 700 hectares of land every year as its western coastline is gradually rising. Theoretically, this newly surfaced land is owned by the state but owners who have adjacent land can claim it. Already, there are feuds between residents with some ending in court.

Of course, all of these problems aren’t nearly as bad as the threats faced by people living in coastal areas all over the world.  Sea levels are rising at an increasing rate each year and as the planet heats more, as it does today, this rate will only accelerate. Sea levels are rising 50% faster than they did two decades ago, according to a recent 2017 study which attributed the acceleration to Greenland’s melting ice sheet. If this trend continues, Scandinavian countries but also other places like Scottland could actually see the sea level fall by as much as 50 meters.

Homeless man.

Society will buckle under 2 billion climate-refugees by 2100 as rising oceans displace whole cities

Immigration could become a very heated subject by the end of the century. A new paper from Cornell University estimates that some 2 billion people may be forced out of their homes by rising ocean levels by 2100, and looking for a home which populations inland may not be prepared or willing to offer.

Homeless man.

Image credits: Avi Chomotovski.

We’re already struggling to rise to the challenge of one immigration crisis caused by the civil war in Syria. And if I may get a personal opinion in, we’re not doing very well at all. The Syrian refugee exodus has divided European sentiment, more often due to propaganda and feeling than facts and figures, and has seen countries in the Middle East shun those in need and close off their borders. All of it generated huge — and for the most part avoidable — human suffering and misery.

But even it pales in comparison to what Charles Geisler, professor emeritus of development sociology at Cornell, says is in store for us by the end of the century. With Earth’s population recently breaking the 7.5 billion mark and rising rapidly, there’s a lot more people living today than there have ever before. But we’re also set to have less land than before on which those people can live.

Climate change, coastal change

“We’re going to have more people on less land and sooner that we think,” said Geisler, who was also lead author of the paper. “The future rise in global mean sea level probably won’t be gradual. Yet few policy makers are taking stock of the significant barriers to entry that coastal climate refugees, like other refugees, will encounter when they migrate to higher ground.”

The current inhabitants will be forced to seek new places to live in — according to the paper, there could be as many as 1.4 billion climate refugees by 2060 and 2 billion by 2100. And all those people won’t be competing for the same resources as are available now. Feeding and housing the 10 billion people the UN estimates will call Earth home by 2050 will take a lot of high-quality arable land and retail space, while rising ocean levels will be eating into fertile coastal zones and river deltas. Another issue is that the new low-elevation coastal areas we’ll be left with will be battered by more violent storms which will push sea water further inland, where it will disrupt agricultural activity and reduce the overall habitability of the area.

In their paper, the team gives preliminary estimates of the areas which are unlikely to support incoming climate refugees due to several factors such as “residues of war, exhausted natural resources, declining net primary productivity, desertification, urban sprawl, land concentration, ‘paving the planet’ with roads, and greenhouse gas storage zones offsetting permafrost melt.” In a worse-case scenario, the team believes that the competition over reduced space will lead to land-use trade-offs. It’s probable that we’ll see public land sold off for human settlement, and violent conflicts are also very likely to pop up.

But it also shows that there are measures we can take to alleviate both the effect of rising oceans and to ease the burden on the refugees. For example, officials in Florida, the state which can boast the USA’s second-longest coastline, have actually planned for a coastal exodus according to Geisler, in the form of the state’s Comprehensive Planning Act. China is also taking steps to prepare for an eventual flooding of its coastlines.

However, as the old adage goes, an ounce of prevention equals a pound of cure.

“The pressure is on us to contain greenhouse gas emissions at present levels. It’s the best ‘future proofing’ against climate change, sea level rise and the catastrophic consequences likely to play out on coasts, as well as inland in the future,” said Geisler.

The full paper “Impediments to inland resettlement under conditions of accelerated sea level rise” has been published in the journal Land Use Policy.


Global sea levels rose 50% faster than two decades ago because of Greenland’s melting ice sheet

The rate of global sea level rise has increased by about 50 percent in just the last two decades, according to an international team of researchers. In 1993, global sea levels increased from a rate of 2.2 millimeters/year to 3.3 millimeters/year in 2014. The dramatic increase is believed to be mostly caused by melting of Greenland’s ice sheet.


The Greenland Ice Sheet contributed 5 percent of the total sea level rise in 1993, by 2014 this figure increased to about 25 percent. Credit: Pixabay.

These findings suggest that the world’s sea levels are rising faster than thought only a couple of years ago. If this accelerated trend continues, devastating consequences might ensue. The Intergovernmental Panel on Climate Change (IPCC), which is the UN science advisory body, estimates that by the end of the century sea levels could rise by 60 to 90 centimeters (24 to 35 inches). This very conservative projection, however, assumes the rate at which sea level rises stays constant.

Sea level rise due to global warming is a serious threat, on a collision course with large and growing coastal populations. Hundreds of millions of people live in low-lying deltas around the world and only a few feet extra in sea level is enough to force them out.

Global warming drives sea level rise by two major mechanisms:

  • by warming ocean water; as it warms, water expands, taking up more space

  • by melting land-based ice (glaciers and ice sheets), sending more water to our oceans.

According to a new study published in Nature Climate Change, accelerating losses of mass from Greenland and Antarctica are driving up the rate of sea level rise. The researchers fixed some loose ends in satellite altimetry data, which gauges heights on the Earth’s surface from space, using satellites. Until recently, the data showed little change in sea levels over the last two decades even when other measurements like in-situ clearly showed an increase in the levels.

“We corrected for a small but significant bias in the first decade of the satellite record,” co-author Xuebin Zhang, a professor at Qingdao National Laboratory of Marine Science and Technology in China’s Shandong Province, told AFP.

While thermal expansion accounted for almost half of added sea level rise in the early 1990s, two decades later that figure was only 30 percent. Instead, contributions from ice sheets and glaciers have increased from about half of the total rise in 1993 to around 70 per cent in 2014. Most of this sharp increase can be pinned on the melting of the Greenland ice sheet which now supplies 25 percent of total sea level increase compared with just five percent 20 years earlier. Greenland contains enough frozen water to lift oceans by about seven meters (23 feet).

Even if we cease dumping greenhouse gases into the atmosphere tomorrow, sea level rise that will continue because global warming is already locked-in and by some account triggered feedback loops are accelerating warming. For instance, despite the amount of CO2 released into the atmosphere has stabilized in the last five years, CO2 levels in the atmosphere are rising — and fast. As such, these findings must serve as a wake-up call for policymakers. The cost of non-action could be dramatic by the end of the century.

The breathtaking 1991 eruption of Mt. Pinatubo in the Philippines. Credit: Wikipedia

Real extent of sea level rise obscured by 1991 massive volcano eruption

The breathtaking 1991 eruption of Mt. Pinatubo in the Philippines. Credit: Wikipedia

The breathtaking 1991 eruption of Mt. Pinatubo in the Philippines. Credit: Wikipedia

A cataclysmic 1991 eruption of  Mount Pinatubo in the Philippines caused widespread destruction of property and human lives.

The 20 million tons of sulfur dioxide and ash spewed into the atmosphere also seriously altered the planet’s climate, as these aerosols acted to cool the planet by as much as half a degree Celsius for three straight years.

Now, researchers say the Pinatubo eruption also obscured sea-level rise readings. According to the National Center for Atmospheric Research (NCAR), the rate of sea level rise is more accelerated than we were led to believe by satellite imagery, closely following what climate models predicted instead.

Satellite imaging for the purpose of assessing sea level rise around the globe first began in 1993, post-Pinatubo. Before 1993, scientists used tide gauges to measure sea level variations, but these instruments are very unreliable and their records only serve as a ballpark estimate nowadays.

Since 1993, scientists have recorded a steady sea level rise of about 3 millimeters per year, a figure which governments are currently using for their climate change mitigation process. Due to poor timing, however, the actual extent of sea level rise may have been hidden.

Sea level rises due to two primary mechanisms. On one hand, global warming raises the temperature of the water and causes it to expand. Then, rising temperature in the Arctic and Antarctica melts glaciers and ice sheets. In the past decade, we’ve seen an accelerated trend in both rising temperature and melting, yet satellite imagery did not indicate a sea level rise that would have corresponded with scientists’ expectations.

Running computer models on the Yellowstone system at the NCAR-Wyoming Supercomputing Center, scientists compared different data sets which either included or omitted volcanic aerosols. This allowed them to differentiate between Mount Pinatubo’s eruption signal and noise, like the natural variation of ocean temperature. This analysis revealed that the devasting volcanic eruption in the Philippines caused the oceans to cool and sea levels to drop by 6 millimeters, well before the TOPEX/Poseidon satellite tasked with measuring sea level rise became operational.

This higher-than-normal sea level drop means the early data the satellite recorded is not historically accurate, making it appear like the rate of sea level rise has not accelerated over time and may actually have decreased somewhat. Had the eruption never took place, a clear trend of sea level rise acceleration would have shown, according to the paper published in Scientific Reports.

“When we used climate model runs designed to remove the effect of the Pinatubo eruption, we saw the rate of sea level rise accelerating in our simulations,” said NCAR scientist John Fasullo, who led the study. “Now that the impacts of Pinatubo have faded, this acceleration should become evident in the satellite measurements in the coming decade, barring another major volcanic eruption.”

“The satellite record is unable to account for everything that happened before the first satellite was launched, ” Fasullo said. “This study is a great example of how computer models can give us the historical context that’s needed to understand some of what we’re seeing in the satellite record.”

Even a few millimeters off can have drastic consequences for climate change mitigation planning which forecasts what the sea level will look like 50 or 100 years from now.

“Sea level rise is potentially one of the most damaging impacts of climate change, so it’s critical that we understand how quickly it will rise in the future,” Fasullo said. “Measurements from Jason-3 will help us evaluate what we’ve learned in this study and help us better plan for the future.”

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.


Sea levels rise at fastest rate since the founding of Roman empire

A study ten years in the making found that sea levels are rising at the fastest rate in the last 2,800 years. The researchers say that greenhouse gas emissions that build up in the atmosphere and heat the planet, melting glaciers and ice sheets, are to blame for this sharp rise.


Image: Pixabay

Three teams of international scientists were involved in the landmark research, which assessed the relationship between “temperature and global sea-level (GSL) variability over the Common Era through a statistical metaanalysis of proxy relative sea-level reconstructions and tide-gauge data.” The work suggests with a confidence greater than 95% that half or more than 5 inches of sea level rise detected in the 20th century can be attributed to man-made global warming.

“During the past millennia, sea level has never risen nearly as fast as during the last century,” said Stefan Rahmstorf, a physics professor at Potsdam University in Germany, one of 10 authors of the paper. “That was to be expected, since global warming inevitably leads to rising seas.”

There’s a natural variability in sea levels due to ocean cycles, volcanic eruptions and other factors. Nothing other than greenhouse gases spewed by man-made activities, however, could explain the rate of sea level rise from the past century, the sharpest over the 2,800-years time frame used for the study. “Ice simply melts faster when the temperatures get higher,” Dr. Rahmstorf told the New York Times. “That’s just basic physics.”

If current emission trends continue unabated, the researchers confirm that the sea level will rise by as much as four feet in 2100. This would make large areas in many coastal cities around the world uninhabitable in the lack of mitigation infrastructure like dykes. The last couple of decades, flooding tides has made life miserable for residents of  Miami Beach or Norfolk, Va. These sort of events will only become more common. According to Climate Central, which also produced this great interactive map, three quarters of the coastal floods recorded in the U.S. from 2005 to 2014 can be attributed to climate change.

sea level rise

The historic Paris agreement signed by more than 190 countries last year pledged that the world will spare no effort to keep warming at no more than 2 degrees C past industrial age levels by 2100. The climate is already 1 C warmer, so this is a most ambitious goal. But even if the target is met, sea levels could rise by an additional 9 inches to 2 feet this century, the report concludes.


us sea level rise

How rising sea levels will affect US: Miami and New Orleans underwater by 2100

us sea level rise

A study assessed how sea level rise at the hand of global warming will affect coastal populations in the United States. The analysis made by Climate Central,  a nonprofit news organization that analyzes and reports on climate science, found 20 million Americans’ homes might be flooded, and more than 1,500 U.S. cities and municipalities could have at least half of their residential area under water if the world emits under a ‘business-as-usual’ scenario. Unfortunately, there’s a lot of damage that’s already been done. Carbon emitted today will continue to warm the planet for hundreds of years and its effects on the climate are already locked in. Cities like Miami and New Orleans are ‘already lost in the long run,’ said Ben Strauss, vice president for sea level and climate impacts at Climate Central.

According to Strauss, “future emissions will determine which areas we can continue to occupy or may have to abandon.” Numerous studies have been conducted by climate scientists attempting to predict sea level rise, with findings ranging from as little as 1.6 meters, to six meters, to nine meters (when adding the ice lost from the West Antarctic Ice Sheet). The extent isn’t certain, but the fact that the rise will be substantial is well agreed upon. “Just think of a pile of ice in a warm room. You know it is going to melt, but it is harder to say how quickly,” said Strauss for AFP.

After looking at studies that link carbon emissions to rising sea levels up to the year 2100, ranging from 4.3 to 9.9 m, and based on “topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emission”, the researchers made a map where they chart the populations most at risk in the United States. They found “1,185–1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents”.


According to the report, the world has already committed to  1.6 meters of long-term sea-level rise, and the damages felt extend far beyond the US – it’s a global matter with coastal areas under most serious threat, and islands more so. For the sake of simplicity and since it takes far too many resources than they can access, Strauss and colleagues settled for an US only risk assessment.

“In our analysis, a lot of cities have futures that depend on our carbon choices but some appear to be already lost,” Strauss said.

“And it is hard to imagine how we could defend Miami in the long run.”

Miami is one of these cities, under any scenario. An unabated emissions scenario sees Florida as the most vulnerable state, holding 40% or more of the population living in soon-to-be flooded areas. Next up in running order are  California, Louisiana and New York. New Orleans seems to be worse even than Miami.

sea level rise history

image: climate.org

Of course, that’s not to say that all of these cities will be lost. Most of these municipalities, along with outside help, can secure resources that they can use to build huge sea walls. That’s if conditions allow. Miami for instance, sits on a porous limestone foundation. Not even walls and levees might work. Even now the City of Miami Beach is investing hundreds of millions of dollars for a series of pumps that have already been put to work during the annual King Tide to keep the streets dry. These pumps might prove useless only a couple decades from now.

Then there’s the fact that no dike can be built to stop seawater from penetrating far inland, contaminating drinking water supplies and lifting the water table to the point of inundation along a very flat and low landscape. When this happens, a strong rainstorm would be enough to flash flood urban centers.

While much of the damage is irreversible, some of it can avoided by lowering emissions. A total of 14 cities with more than 100,000 residents could avoid locking in this century if global average emissions are set back to 1950 levels by 2050.

“Historic carbon emissions appear already to have put in motion long-term [sea-level rise] that will endanger the continuity and legacy of hundreds more municipalities,” the researchers conclude, “and so long as emissions continue, the tally will continually increase.”

An interactive two-view map lets you see how the city you live in might become affected by sea level rise under different carbon emission scenarios.

Climate change will raise sea levels by 20 feet – and this is no surprise

The media is abuzz with disturbing headlines, warning us that even reduced levels of global warming will cause massive sea level rise, up to 20 feet (6 meters). Unfortunately, that’s true. But what’s almost as worrying is that everyone is treating this as news, when in fact, we’ve known for quite a while that this is bound to happen. The study that spurred the frenzy wasn’t even a new research – it was just a review of older studies.

Image in Creative Commons, as uploaded by Mary RN on Morguefile.

According to the review, what’s strange is that sea levels aren’t higher today. As it turns out, 125,000 years ago, sea levels were about 20 feet higher, and temperatures were similar to today’s: 1 Degree Celsius higher than pre-industrial temperatures. Sea levels reached similar heights around 400,000 years ago, but temperature estimates are much less reliable for that period. But what this analysis clearly shows is that even a shift as small as one degree can have catastrophic effects, taking global climate out of balance. Sure, this has happened naturally before, but in a much longer time frame than we are doing it now (tens of thousands of years vs a hundred years).

“This evidence leads us to conclude that the polar ice sheets are out of equilibrium with the present climate,” said lead author Andrea Dutton.

The thing is, even if we magically stop all global warming tomorrow, the damage we’ve already caused will still have significant consequences; ice melting takes a lot of time, and we might have already put in motion processes which will cause massive ice melt. If we continue with the greenhouse emissions, then we’ll extend these consequences even more.

“While this amount of sea-level rise will not happen overnight, it is sobering to realize how sensitive the polar ice sheets are to temperatures that we are on path to reach within decades,” Dutton adds.

The authors analyzed three different periods:

– The first period was the Mid-Pliocene, 3 million years ago. Evidence suggests that the CO2 levels in the atmosphere were identical to today’s levels, but temperatures were between 1 and 4 degrees higher. Global sea levels were 25 meters higher (82 feet) higher. The mid Pliocene warm period is considered a potential analog of future climate because the intensity of the sunlight reaching the earth, the global geography, and carbon dioxide concentrations were similar to present.

– The second period was an unusually long interglacial period about 400,000 years ago. Greenhouse gases were at a pre-industrial level, but temperatures were similar to today’s. Sea levels were 6 meters (20 feet) higher than today – and this is the source of the headlines that made the news. The temperatures were similar to today’s, and sea levels were higher, so sea levels will get higher in time – it makes sense. Back then, much of Greenland was a spruce forest.

– The third period, 120,000 years ago, witnessed temperatures 1-2 degrees higher than today. Sea levels again reached at least six meters above present.

Knowing what the temperatures and sea levels were 125,000 years ago is no easy feat. We can’t measure that directly, so we have to use proxies. Isotopes play a key role as proxies; for example, heavier isotopes of oxygen tend to gather in ice and not in water, so we can estimate how much water vs how much ice there was on Earth at a given time. Gases trapped in ice cores are also indicative of atmospheric chemistry, which in turn governs the climate. Animals like corals and former shorelines  also provide valuable indications. If you find a coral on dry land and date it to 125,000 years, then during that period, it wasn’t dry land.

Naturally, there’s always some ambiguity when you’re working with this kind of proxies – but we have to try, and we’ve gotten much better at it in recent years. The main take-away here is that we don’t know exactly how much sea levels will rise, but they will rise; and we’re causing the rise, through greenhouse gas emissions. We’ve reached a level where we’re shaping the Earth’s climate, and we should act more responsibly.

Journal Reference: A. Dutton et al, Sea-level rise due to polar ice-sheet mass loss during past warm periods. Science 10 July 2015: Vol. 349 no. 6244 DOI: 10.1126/science.aaa4019