The average global sea level has risen 8.9 inches between 1880 and 2015. That’s much faster than in the previous 2,700 years. The table below shows the specifics per decade. It shows how the pace is quickening. It added 1.84 inches between 2000 and 2010. If it adds the same amount, between 2010 and 2020, it will have risen by 9.2 inches by 2020.
|Year||Since 1880||Per Decade|
Source: "Global Average Absolute Sea Level Change, 1880-2015," Environmental Protection Agency. 2020 estimate based on the current rate of change.)
How Scientists Know the Sea Level Is Rising
Scientists accurately measure global sea level increases in three ways.
- Since 1992, NASA has collected data from satellites.
- NASA also uses tide gauges in many parts of the world to get a global average. The gauges block out the impact of waves and tides to get an accurate reading.
- The third method is reviewing rock formations. Scientists use this method to determine the sea level millions of years ago. They look for fossils of ocean organisms, sedimentary deposits, and even the actions of waves.
Effects of the Rising Seas
The rising sea level is affecting coastal areas all over the world. It increases flooding, worsens hurricane damage, and leaches saltwater into tidal areas. It increases migration, weakens military preparedness, and threatens historical sites. Local governments are spending billions to defend against these effects.
NOAA says flooding will affect eight of the world's largest coastal cities. It will impact 40% of Americans who live in coastal counties. Floods have hit U.S. coastal towns three to nine times more often than they did 50 years ago. From 2005 to 2017, sea level rises cost eight coastal states $14.1 billion.
Another study showed that the number of coastal flood days in 27 U.S. locations has increased dramatically. They flooded 2.1 days a year between 1956 and 1960. That exploded to 11.8 days annually between 2006 and 2010.
Between 1978 and 2015, at least 30,000 homes flooded multiple times. The federal government bought out fewer than 9% and only paid 75% of the home's value. Federal disaster funds help people rebuild their homes in the same spot. In 2012, Congress phased out subsidies for federal flood insurance. That makes it too expensive for many homeowners.
U.S. sea level rise affects three areas the most. Here are specifics on its impact.
- Flood-prone areas in New York, New Jersey, and Connecticut lost $6.7 billion in home values.
- Atlantic City, New Jersey, regularly floods when it rains. A four-foot storm surge would flood 50% of it.
- Boston is near the fastest warming body on Earth the Gulf of Maine. Storm damage affects the $8 billion Waterfront District.
- Annapolis, Maryland, now floods from high tide several days a week. Floor vents were installed to drain floodwaters from historic buildings. If sea waters rise 3.7 feet, the U.S. Naval Academy will be underwater.
- Charleston, S.C., floods 50 days a year, up from four days a year in the 1980s. By 2050, it will flood every third day. North Carolina is losing six feet of coastal land every year. The Outer Banks are eroding away.
Florida and Gulf States:
- In Miami, Florida, streets flood during high tide. The City of Miami Beach launched a five-year, $400 million public works program. It's raising roads, installing pumps, and redoing sewer connections. By 2070, Miami streets will flood every single day That threatens $136 billion of real estate.
- By 2048, the residents of 64,000 Florida homes will have to deal with chronic flooding.
- Home prices in lower-lying areas of Miami-Dade County and Miami Beach are being affected. Properties at risk of rising sea levels sell at a 7% discount to comparable properties. By 2030, Miami Beach homes could pay $17 million in higher property taxes due to flooding. By 2100, that could rise to $760 million.That's if property owners, many of whom are from overseas, don't abandon the market.
- In Louisiana, rising sea levels are flooding the Mississippi Delta. Louisiana is losing one acre an hour of wetlands. These areas nourish fisheries and protect New Orleans from hurricanes. They also absorb the greenhouse gases that cause global warming.
- Rising sea levels combined with sinking land will flood many areas around San Francisco by 2100. The land is sinking because of groundwater pumping. Parts of the airport, as well as large sections of Union City, Foster City, and Treasure Island would be underwater.
- San Diego County, California, is building the largest seawater desalination plant in the western hemisphere. The plant will cost $1 billion.
- Most of the property in these cities are financed by municipal bonds or mortgages. Their destruction will hurt the investors and depress the bond market. Real estate markets could collapse in these regions, especially after severe storms.
Rising sea levels worsen damage from hurricanes. The 17 most destructive U.S. storms in history occurred after 2000, with three in 2017. Their damage cost the economy $700 billion.
About 1.2 million Americans live in coastal areas at risk of “substantial damage” from hurricanes. Most of this densely populated area lies less than 10 feet above sea level, according to the National Hurricane Center. A 23-foot storm surge would flood 67% of U.S. interstates, including 57% of arterial highways. It would cover almost half of the rail miles, 29 airports, and almost all ports in the Gulf Coast area.
Hurricane storm surges threaten 12 of the world's busiest airports. Hurricane Sandy inundated all three New York City airports. As a result, La Guardia Airport is using a $28 million federal grant to build a flood wall, rainwater pumps, and a new drainage system.
- Saltwater leaches into underground aquifers and the soil. It disrupts the chemical balance of estuaries, destroying oyster beds and bird habitats. Increased salinity in Bangladesh, Vietnam, and other South Asian coastal countries threatens rice production. In Egypt, up to 12.5 miles inland from the shoreline have become saline, threatening billions of dollars in farming losses.
- U.S. military preparedness is being compromised. There are 1,774 military sites on 95,471 miles of coastline at risk of flooding from sea level rise. More than 30 sites are already impacted. Extreme weather affects all bases, but especially those in the Pacific region. They are hubs for disaster relief efforts. There is also a huge nuclear fallout container on the Marshall Islands. Rising sea levels and storms could easily damage the dome, releasing nuclear debris into the ocean.
- Migration is increased as residents flee from flooding coastal areas. Low-lying island nations, such as the Maldives and Seychelles, will soon be underwater. By 2050, 17% of Bangladesh would be flooded, displacing 18 million people. Forty percent of Jakarta, Indonesia, home to 30 million people, lies below sea level.
- Tourism and historical sites are threatened. On Easter Island, the famous Moai statues will be destroyed if the sea rises six feet. The Marshall Islands are disappearing already. They are less than six feet above sea level, but changing sea winds have raised sea levels a foot over the past 30 years. The nation's 70,000 residents will probably emigrate to the United States, thanks to a 1986 agreement.
Causes Behind the Rising Seas
Global warming causes rising sea levels in two ways. First, as the ocean warms, it takes up more space. That alone has caused half of the sea level rise in the past century.
Second, a warmer temperature melts Greenland's ice sheets and the polar ice caps. Between 2002 and 2016, Antarctica lost 125 gigatons of ice annually. It contributed 0.013 inches of sea level rise per year. Most of this loss occurred in the West Antarctic Ice Sheet. Antarctica holds 90% of the world's ice. If it all melted, sea levels would rise 200 feet.
The rate of ice sheet melting is accelerating. Between 1992 and 2017, Antarctica shed 3 trillion tons of ice. It increased sea levels by three-tenths of an inch. But 40% of that occurred during the last five years, from 2012 to 2017.
Looked at another way, Antarctic melting has tripled since 2007. At that rate, it will increase sea levels another six inches, or 15 centimeters, by 2100. Andrew Shepherd, a professor of earth observation at the University of Leeds, said that translates into flooding in Brooklyn around 20 times a year.
Even more recently, an additional concern has been added. Between 2010 and 2016, the Antarctic grounding line has receded 600 feet per year. The grounding line is the last place where the ice meets bedrock. A receding line means warmer ocean water is melting the underside of the glacier while a warmer air temperature attacks the top layers. It creates a river under the glaciers that ferries them more quickly into the ocean.
That could raise sea level another 10 feet by 2100. It's enough to put FDR Drive and 1st Avenue on the Upper East Side in Manhattan underwater.
During the same period, Greenland lost 280 gigatons of ice per year. It's melting at the fastest rate in the past 450 years. The melting ice added 0.03 inches each year to rising sea levels. The worst losses occurred along the West Greenland coast. If the Greenland ice sheet melts completely, it would raise sea levels by 16 feet to 23 feet. That's enough to put New Orleans, Miami, and Amsterdam underwater.
The loss of polar ice also affects the many species that live there. Polar bears are just one of the 17 species that will go extinct as a result.
Predictions for the Future
Timing is critical. A five-year delay in addressing climate change would increase sea levels by another 7.8 inches. That's almost as much as the 8.9-inch increase that's occurred since 1880. Here's a timeline of what will happen if nothing is done.
- By 2033, rising sea levels will flood 4,000 miles of fiber optic cables that deliver the internet and telephone services. Relocating the cables would be expensive and only buy a little time. At first, New York, Miami, and Seattle would be affected the most. Over time, everyone will be impacted by a disruption in these services.
- By 2038, 170 U.S. coastal cities and towns will be “chronically inundated” according to the Union of Concerned Scientists. They will see 10% of their area flooded at least twice a month. By 2100, more than half of the communities along the Eastern Seaboard and Gulf Coast will experience it.
- By 2045, another study found that 300,000 coastal properties will be flooded 26 times a year. The value of that real estate is $136 billion.
- By 2100, that number will rise to $1 trillion. At most risk are homes in Miami, New York's Long Island, and the San Francisco Bay area. For example, San Francisco would experience $62 billion in property damage by a four-foot rise in sea levels. It would also put the headquarters of Facebook and Yahoo underwater.
- The Intergovernmental Panel on Climate Change predicted sea levels will rise between one and two feet by 2100. That's 52 cm to 98 cm. The IPCC made this forecast in 2007. A two-foot rise would flood tens of millions of people living in low-lying areas. It would swamp many U.S. East Coast cities.
Other, more recent, studies have issued more dire warnings.
In February 2018, NASA found that sea levels are rising faster than the IPCC forecast. NASA predicts sea levels will be three to four feet higher by 2100. That's 91 cm to 122 cm. It based this on recent measurements of melting ice in Greenland and Antarctica. They warn this is a conservative estimate. A May 2019 study confirmed this estimate.
A 2010 North Carolina study also confirmed that ocean levels will rise three feet by 2100. That would flood 50,000 residents of the state. It would also damage tens of thousands of expensive beach-front properties. Nationally, a three-foot rise would displace 4.2 million people according to a Harvard study.
In 2017, researchers led by the University of Melbourne, Australia predicted sea levels could rise as much as six feet by 2100. That's 183 cm. As Antarctica melts, it will reach the larger sheets that are more inland. Their weight will make them melt faster than smaller ice sheets have in the recent past. A six-foot rise would put Atlantic City underwater. A six-foot rise would flood 100,000 homes in New York City, causing $39 billion in property damage. In Miami, 54,000 homes costing $14 billion would be flooded.
The worst predictions are based on what happened the last time the temperature was this high. That was 116,000 years ago, and the sea level was 20 to 30 feet higher. Why isn't the sea level that high now? Warming has happened so fast that the ice hasn't had time to fully melt yet. It's like putting an ice cube in hot coffee, it doesn't melt instantly. Over thousands of years, ice will continue to melt unless the temperature is reduced.
The worst prediction of all comes from looking at the Earth the last time greenhouse gas emissions were this high. Carbon dioxide is 411 parts per million. The last time it was this high was during the Pliocene era. Back then, the sea level was 66 feet higher. Again, it takes time for the temperature to rise in response to greenhouse gases. It's like turning on the burner to heat the coffee. Until greenhouse gases are reduced, the temperature will continue to climb.
Potential Solutions to the Problem
There are three types of solutions to sea level rise. The most widely-discussed are coping solutions. Coastal cities are installing drainage systems and building up seawalls. Island populations are moving. Tourists are flocking to visit popular vacation spots, like the Maldives before they are underwater.
In Boston, developers are planning ahead. Skanska Commercial Development constructed an elliptical office tower designed to withstand fierce wind storms. The building's electrical infrastructure is located 40 feet above the 100-year floodplain. It also has a 40,000-gallon water reclamation tank, and a raised ground floor.
But coping solutions don't address the root cause of global warming. Nations are focused on the second type of solution, reducing future greenhouse gas emissions. They are switching from fossil fuels to clean alternatives. These include solar energy, wind energy, and geothermal energy sources.They are instituting carbon taxes to raise the cost of burning carbon. Carbon emissions trading rewards businesses that adhere to carbon caps.
The third solution is the most critical, but less widely discussed. Existing greenhouse gases must be removed from the atmosphere. Carbon sequestration captures and stores CO2 underground. To meet the Paris Agreement goal, 10 billion tons a year must be removed by 2050 and 100 billion tons by 2100. In 2018, only 60 million tons of carbon was sequestered according to Princeton University's Professor Steven Pacala.
One of the easiest solutions is to plant trees and other vegetation to halt deforestation. The world's 3 trillion trees store 400 gigatons of carbon. There is room to plant another 1.2 trillion trees in vacant land across the earth. That would absorb an additional 1.6 gigatons of carbon. The Nature Conservancy estimated that this would only cost $10 per ton of CO2 absorbed. California is planting trees to prevent flooding. Seattle encourages developers to add rooftop gardens or walls covered by vegetation to new building projects.
Restoring peatland and wetland areas is another low-cost carbon sequestration solution. Peatlands are the compressed remains of plants in waterlogged areas. They contain 550 gigatons of carbon. Governments must develop plans to identify, conserve, and restore the world's peatlands.
Second, farmers must manage their soil better. For example, they could reduce plowing which releases carbon into the atmosphere. Instead, they could plant carbon-absorbing plants such as daikon. The roots break up the earth and become fertilizer when they die. The government can subsidize these methods to make them cost-effective with traditional methods that rely on fertilizers.
Third, power plants can efficiently use carbon capture and storage because CO2 makes up 5% to 10% of their emissions. The government should subsidize the research as it did with solar and wind energy. It would only cost $900 million, far less than the $15 billion Congress spent on Hurricane Harvey disaster relief.
Seven Steps You Can Take Today
There are seven things you can do today to reverse sea level rise:
- First, plant trees and other vegetation to halt deforestation. You can also donate to charities that plant trees. For example, Eden Reforestation hires local residents to plant trees in Madagascar and Africa for $0.10 a tree. It also gives the very poor people an income, rehabilitates their habitat, and saves species from mass extinction.
- Second, become carbon neutral. The average American emits 16 tons of CO2 a year. According to Arbor Environmental Alliance, 100 mangrove trees can absorb 2.18 metric tons of CO2 annually. The average American would need to plant 734 mangrove trees to offset one year’s worth of CO2. At $0.10 a tree, that would cost $73.
- The United Nations program Climate Neutral Now also allows you to offset your emissions by purchasing credits. These credits fund green initiatives, such as wind or solar power plants in developing countries.
- Third, enjoy a plant-based diet with less meat. Cows create methane, a greenhouse gas. Monoculture crops to feed the cows cause deforestation. The Drawdown Coalition estimated those forests would have absorbed 39.3 gigatons of carbon dioxide. Greenpeace points out it's one of the best global warming solutions because the production of these food items creates 50% of global greenhouse gas emissions.
- Similarly, avoid products using palm oil. Most of its production comes from Malaysia and Indonesia. Tropical forests and carbon-rich swamps are cleared for its plantations. Avoid products with generic vegetable oil as an ingredient.
- Fourth, reduce food waste. The Drawdown Coalition estimated that 26.2 gigatons of CO2 emissions would be avoided if food waste was reduced by 50%.
- Fifth, cut fossil-fuel use. Where available, use more mass transit, biking, and electric vehicles. Or keep your car but maintain it. Keep the tires inflated, change the air filter, and drive under 60 miles per hour.
- Sixth, pressure corporations to disclose and act on their climate-related risks. Since 1988, 100 companies are responsible for more than 70% of greenhouse gas emissions. The worst are ExxonMobil, Shell, BP, and Chevron. These four companies contribute 6.49% alone.
- Seventh, hold the government accountable. Each year, $2 trillion is invested in building new energy infrastructure. The International Energy Administration said that governments control 70% of that.
Similarly, vote for candidates who promise a solution to global warming. The Sunrise Movement is pressuring candidates to adopt a Green New Deal. There are 500 candidates who have vowed not to accept campaign contributions from the oil industry.