Rising Sea Levels and Their Impact on the Economy and You
How Rising Sea Levels Are Changing Your World
Since 1880, sea levels have risen 8.9 inches on average. That doesn't sound like much, but they’re rising much faster than in the previous 2,700 years. One quarter of the 8.9-inch rise change occurred since 2000.
The rate of change is also increasing. As the table below shows, seas levels rose almost 1 1/4 of an inch between 2000 and 2010. They rose another 7/8 of an inch between 2010 and 2015. At this most recent rate, by 2020 they'll have increased by 1 3/4 inch in just five years.
|Year||Cumulative Increase (Inches)||Increase per Decade (Inches)|
|1950||3.6||Almost one inch|
|1960||4.5||Almost one inch|
|1980||5.6||Almost one inch|
|2015||8.9||7/8 in five years|
How Scientists Know Sea Levels Are 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 levels millions of years ago. They look for fossils of ocean organisms, sedimentary deposits, and even the actions of waves.
Rising sea levels affect the 40 percent of Americans who live in coastal counties.
Saltwater leaches into underground aquifers and into the soil. It disrupts the chemical balance of estuaries. Saltier water destroys oyster beds and bird habitats.
Increased salinity in Bangladesh, Vietnam, and other South Asian coastal countries threatens rice production.
Rising sea levels worsen flooding in low-lying towns. Floods have hit U.S. coastal towns three to nine times more often than they did 50 years ago.
In Miami, Florida, high sea levels flood the streets during high tide. To cope, the City of Miami Beach launched a five-year, $500 million public works program. The city must raise roads, install pumps, and redo sewer connections to keep the ocean from flooding the streets.
Atlantic City, New Jersey, is vulnerable because it is on a barrier island with low, flat terrain. The town regularly floods when it rains. Since it's so low, a four-foot storm surge would flood 50 percent of it. A similar surge in a higher city, such as Boston, would only flood 7 percent.
Annapolis, Maryland, also experiences flooding from high tide. The city is putting vents in floors to drain floodwaters from historic buildings. If sea waters rise 3.7 feet, the U.S. Naval Academy will be underwater.
Rising sea levels worsen damage from hurricanes. Seventeen of the 20 most destructive U.S. storms in history occurred after 2000. Three of them occurred in 2017.
Hurricane Harvey was a Category 4 storm that hit Texas on August 25, 2017. Damage was $125 billion. It affected 13 million people in Texas, Louisiana, Mississippi, Tennessee, and Kentucky. Eighty-eight people died from the storm.
Hurricane Irma was the most powerful Atlantic hurricane in recorded history. Damage was $50 billion. AccuWeather estimated total cost to the economy at $100 billion. It was a Category 4 storm that hit Florida on September 10, 2017. That was the first time in 100 years that two storms Category 4 or larger hit the U.S. mainland in the same year. Hurricane Irma was sustained longer than usual by ocean temperatures of 86 degrees Fahrenheit.
Hurricane Maria was a Category 4 storm when it devastated Puerto Rico on September 20. It cost $90 billion in damage. The official government death toll was 64, but a New York Times analysis said it could actually be 1,052.
Hurricane Sandy was a tropical storm that hit New York and New Jersey in 2010. Storm surges were 8 1/2 feet higher than normal at Sandy Hook, New Jersey, and 12 1/2 feet higher at Kings Point, Long Island. The storm damaged 650,000 homes, and 8 million people lost power. It forced the New York Stock Exchange to close for two days, the first such closure due to weather since 1888.
Hurricane Katrina was a Category 5 storm that flooded New Orleans in 2008. It cost $108 billion and killed 1,836 people. Its storm surge crested at 27 feet. The city lost half of its population of 450,000 and has not fully recovered.
The future impact from hurricanes could be worse. The Congressional Budget Office estimates that 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 percent of U.S. interstates, including 57 percent of arterial highways. Such a massive surge would cover almost half of rail miles, 29 airports, and almost all ports in the Gulf Coast area.
Local governments are making costly investments in an effort to prepare. San Diego County in drought-stricken California is building the largest seawater desalination plant in the western hemisphere. The MIT Technology Review reports that the plant will cost about $1 billion.
In September 2016, the Center for Climate and Security released a report warning of the impact of sea level rise on military preparedness.
Rising sea levels will increase migration. Residents from coastal areas in emerging market countries will have to move. They don't have the ability to erect barriers or install pumps. Some atoll island nations, such as the Maldives and Seychelles, will be completely underwater. Their residents will have to migrate to other countries.
Rising sea levels are Americans' second-biggest worry when it comes to climate change. A Pew Research Study found that 17 percent of Americans said rising sea levels are the effect that concerns them most.
How much has it warmed? Over the past century, the earth's air temperature has warmed by 1.00 degrees Fahrenheit. Researchers found that 2017 was the warmest year on record. As a result, the upper 2,300 feet of ocean warmed by 0.18 degrees Fahrenheit. Like your swimming pool, the water in the ocean warms more slowly than the air.
A warmer ocean causes sea level rise in two ways. First, warm water takes up more space. About half of the sea level rise in the past century is because of this effect.
Second, warmer temperatures melt the ice sheets covering Greenland and the polar ice caps. Over the winter, snowfall rebuilds the ice. But shorter winters mean less time for water to evaporate and turn into snow. As a result, more water stays in the ocean and the glaciers aren’t rebuilt. At the same time, more water enters the ocean from the melting ice.
Melted water combines with seawater below the ice sheets, creating a river under the glaciers that ferries them more quickly into the ocean. Higher sea temperatures combine with higher air temperatures to melt the ice sheets from the top and the bottom.
Between 2002 and 2016, Antarctica lost 125 gigatons of ice each year. 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 percent of the world's ice. If it all melted, sea levels would rise 200 feet.
During the same period, Greenland lost 280 gigatons of ice per year. It added 0.03 inches per 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 16-23 feet. That's enough to put New Orleans, Miami, and Amsterdam underwater.
Sea Level Rise Predictions
Scientists estimate that, if climate change isn't arrested, average sea levels will rise between one and two feet by 2100. The Intergovernmental Panel on Climate Change is an international group of hundreds of climate experts. They don't make recommendations or policies. They simply state observations about the facts they find. The Panel published this forecast in 2007.
A two-foot rise would flood tens of millions of people living in low-lying areas. It's enough to swamp many U.S. East Coast cities.
A 2010 North Carolina study predicted 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 expensive beach-front properties.
In 2017, researchers led by the University of Melbourne, Australia, found new data. It suggested that sea levels could rise as much as six feet by 2100. It found that larger ice sheets collapse more rapidly because their weight. As Antarctica melts, it will reach larger sheets that are more inland. When they melt, they'll do so at a faster pace than smaller ice sheets have in the recent past. A six-foot rise would put Atlantic City underwater. The National Oceanic and Atmospheric Administration provides an interactive viewer that shows this and other impacts of sea level rise on coastlines.
The Speed of Today's Sea Level Rise Is Unprecedented
How do recent sea level increases compare to the past? During the last Ice Age, the sea level was 400 feet lower than it is today. That was about 26,500 years ago, after the Neanderthals went extinct (40,000 years ago) but before Homo sapiens learned how to farm (12,000 years ago). Massive ice sheets extended as far south as New York and the Rockies. Great Britain, Germany, and Poland were also covered in ice. Lower sea levels exposed the Bering land bridge from Siberia to Alaska, allowing the ancestors of Native Americans to migrate to the Americas.
The Ice Age ended when the earth's orbit wobbled closer to the sun. Sunlight hit the northern ice masses, which had grown so large they had become unstable. When they melted, fresh water poured into the ocean, reversing the ocean currents that carry warm water north from the equator. Warm water flowed south, melting the Antarctic and changing the polar winds. This chain reaction released carbon dioxide from the Southern Ocean by 100 parts per million over thousands of years. It's about the same amount that's been released in the last 200 years.
The last time the oceans were this warm was 100,000 years ago. Neanderthals lived in Europe. Homo Sapiens lived in Africa, where droughts reduced them to no more than 10,000 adults. But sea levels were 20 to 30 feet higher. Why were sea levels higher, when carbon dioxide wasn’t warming the climate? The earth had shifted on its axis closer to the sun. Higher levels of radiation had been heating the earth's atmosphere and oceans over the past 4,000 years.
Recent greenhouse gas emissions have heated the earth the same amount in only 150 years. The earth is as hot as it was 100,000 years ago. But it's happened so fast that the ice hasn't melted yet. It's like putting an ice cube in hot coffee. Once the hotter temperatures from the earth's atmosphere have had time to melt the polar ice caps, sea levels could rise another 20 to 30 feet.
Governments have begun addressing the immediate impacts of sea level rise. 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.
The only permanent solution is to slow or reverse global warming. The amount of greenhouse gases emitted into the earth's atmosphere need to be reduced or eliminated. Those gases act like a blanket over the earth's atmosphere. They prevent the earth's natural heat from radiating out into space. Instead, the blanket sends it back to Earth. The oceans can absorb the heat without much rise in their temperature. Instead, they expand. But when they've absorbed all they can, their temperatures rise. That began to happen in the beginning of the 20th century.