6. Sea levels could rise another 1.3 meters (4.3 feet) in the next 80 years.

This map shows areas that would flood (marked in red) due to 1-meter sea-level rise. (Photo: NASA)

In another study published this month, scientists report that global sea levels will likely rise 0.5 to 1.3 meters (1.6 to 4.3 feet) by the end of this century if greenhouse gas emissions aren’t rapidly reduced. Even if last year’s Paris Agreement does spur ambitious climate policy, sea levels are still projected to rise 20 to 60 cm (7.8 to 23.6 inches) by 2100. Taken with the longer-term effects from melting ice sheets in Greenland and Antarctica, that means any strategy to endure sea-level rise must involve adaptation plans as well as efforts to slow the trend.

7. Up to 216 million people currently live on land that will be below sea level or regular flood levels by 2100.

Higher sea levels can exacerbate storm surges, like this 2013 flood in Wenzhou, China. (Photo: STR/AFP/Getty Images)

Of the estimated 147 million to 216 million people in harm’s way, between 41 million and 63 million live in China. Twelve nations have more than 10 million people living on land at risk from sea-level rise, including China as well as India, Bangladesh, Vietnam, Indonesia and Japan. Bangladesh is especially vulnerable, identified by the U.N. as the country most in danger from rising seas. Once the ocean rises by 1.5 meters (4.9 feet) next century, it will affect 16 percent of Bangladesh’s land area and 15 percent of its population — that’s 22,000 km² (8,500 mi²) and 17 million people.

The situation is also urgent for low-lying island nations like Kiribati, the Maldives, the Marshall Islands and the Solomon Islands, where land is already so close to sea level that a few inches make a world of difference. Some are even mulling mass relocations — the government of Kiribati, for one, has a web page outlining its strategy for “migration with dignity.” A town on Taro Island, the capital of Choiseul Province in the Solomon Islands, is also planning to move its entire population in response to rising seas. The small community of Newtok, Alaska, has already begun the difficult process of transplanting itself away from the encroaching coast.

8. Sea-level rise can contaminate water used for drinking and irrigation.

Sea-level rise can aid saltwater intrusion of freshwater aquifers, as seen in this schematic illustration. (Image: NRC.gov)

In addition to surface flooding, sea-level rise can both push up the freshwater table and contaminate it with seawater, a phenomenon known as saltwater intrusion. Many coastal areas rely on aquifers for drinking water and irrigation, and once they’re tainted by saltwater they may be unsafe for humans as well as crops.

It is possible to remove salt from water, but the process is complex and costly. San Diego County recently opened the Western Hemisphere’s largest desalination plant, for example, and several other sites are proposed in the state. Yet that may not be practical for many coastal communities, especially in less wealthy nations.

9. It can also threaten coastal plant and animal life.

Floods fueled by rising seas may harm baby sea turtles, like these South African loggerheads. (Photo: Jeroen Looyé/Flickr)

Humans aren’t the only ones who’ll suffer as sea levels rise. Any coastal plants or animals that can’t quickly move to new, less flood-prone habitats could face dire consequences. As one 2015 study noted, sea turtles have a long-established habit of laying eggs on beaches, which need to stay relatively dry for their babies to hatch.

Inundation for one to three hours reduced egg viability by less than 10 percent, the study’s authors found, but six hours underwater cut viability by about 30 percent. “All embryonic developmental stages were vulnerable to mortality from saltwater inundation,” the researchers write. Even for hatchlings that do survive, being starved of oxygen in the egg could lead to developmental problems later in life, they add.

Other beach life may also be at risk, including plants. A recent study found that some salt marshes can adapt, both by growing vertically and by moving inland, but not all flora will be so fortunate. “Trees have to work harder to pull water out of salty soil; as a result, their growth can be stunted — and if the soil is salty enough, they will die, a common sign of sea-level rise,” Climate Central explains. “Even trees that are especially suited to salty soil can’t survive repeated flooding by seawater.”

10. Global flood damage for large coastal cities could cost $1 trillion a year if cities don’t take steps to adapt.

This Google Earth simulation shows a Tokyo neighborhood with 1.3-meter sea-level rise. (Image: Google Earth)

The average global losses from flooding in 2005 were about $6 billion, but the World Bank estimates they’ll rise to $52 billion per year by 2050 based on socioeconomic changes alone. (That means things like increasing coastal populations and property value). If you add the effects of sea-level rise and sinking land — which is happening even faster in some places — the cost could surge to $1 trillion per year.

11. It’s too late to stop sea-level rise — but not too late to save lives from it.

A full moon shines over an iceberg that broke off Greenland’s Jakobshavn Glacier. If the entire Greenland ice sheet melted, sea levels would rise about 6 meters, or 20 feet. (Photo: Joe Raedle/Getty Images)

Unfortunately, CO2 emissions linger in the atmosphere for centuries, and today’s CO2 levels have already committed Earth to dangerous sea-level rise. About 99 percent of all freshwater ice resides in two ice sheets: one in Antarctica and one in Greenland. Both are expected to melt if humanity’s CO2 output isn’t curbed quickly, but the question is when — and how much damage we still have time to prevent.

The Greenland ice sheet is smaller and melting more quickly. If it completely melted, sea levels would rise by about 6 meters (20 feet). The Antarctic ice sheet has been more buffered from warming so far, but it’s hardly immune, and would raise the ocean by 60 meters (200 feet) if it melted. (Estimates vary widely on how long these ice sheets might survive — while most expect they’ll take centuries or millennia to melt, a controversial 2015 paper suggested it could happen much more quickly.)

Sea levels have naturally risen and receded for billions of years, but they’ve never risen this quickly in modern history — and they’ve never had so much human help. It’s unclear what effect they’ll have on our species, but what is clear is that our descendants will still be dealing with this problem long after we’re all gone. Giving them a head start on a solution is the least we can do.

“With all the greenhouse gases we already emitted, we cannot stop the seas from rising altogether, but we can substantially limit the rate of the rise by ending the use of fossil fuels,” says Anders Levermann, a climate scientist at Columbia University and co-author of the new study on future sea-level rise. “We try to give coastal planners what they need for adaptation planning, be it building dikes, designing insurance schemes for flooding or mapping long-term settlement retreat.”

As another recent study pointed out, any policy decisions made in the next few years and decades “will have profound impacts on global climate, ecosystems and human societies — not just for this century, but for the next ten millennia and beyond.”

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Tomorrow, in the final part of this three-part posting I will look at some positive things that we can all be doing now.

But let me leave you with a rather beautiful consequence of these changing times. As seen over on Grist:

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Incredible glacier art pays homage to our disappearing ice