Who doesn’t want a home with a view of the sea? Well, unless the waves are washing around your living room.
Flooding is an intensifying problem in some parts as climate change bites down, and not only on low-lying coasts. But the coasts are a good place to start worrying because a rising sea level can no longer be prevented. The amount of carbon dioxide we have already added to the atmosphere makes more temperature increases inevitable, based on historical climate patterns, and rising temperatures in turn make a further rise in sea levels unavoidable.
The only question is how much the average sea level will rise by any given point in time. We don’t know exactly, in part due to unknowns about global energy policy and how warm the world will get this century.
Oceanographer John Englander believes that if anything, scientists are lowballing the problem. “Official” scientific estimates range from an increase between 30 and 90 centimeters (35 inches) by 2100, because those figures scientists can defend with high confidence. But those projections barely factor in melting in Antarctica.
By the end of the century (an arbitrarily chosen point), global sea levels could rise by 2 meters, possibly more, Englander says.
“The question we need to consider in terms of designing buildings and infrastructure is how bad could rising sea level and flooding become for the useful life of the structure?” he told Haaretz. “Outside of the circles of glaciologists working on the nuances of the massive ice sheets, there is little appreciation for the limits on our ability to accurately model and forecast the rate of sea-level rise this century.”
His role has largely become to explain the glaciology and oceanography related to rising sea levels to professionals like engineers, lawyers and people in the military, as well as to the general public, saying it in plain language while also publishing it in peer-reviewed journals.
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Après moi, le déluge
Over the last century, Englander explains, almost half of the roughly 20 centimeters of global sea-level rise has stemmed from warming seawater. The oceans have warmed by about 1 degree Celsius, increasing the volume of the water. Just that raised the global base sea level by about 8 to 10 centimeters. The rest of the rise has come from melting ice sheets and glaciers on land.
As Greenland and Antarctica melt faster, the effect of thermal expansion of the seawater will have less significance, Englander notes.
About 98 percent of potential sea-level rise is from melting Greenlandic and Antarctic ice. All the other glaciers around the world combine for a piddling 2 percent or so. Glaciers shrinking in the Alps and the like tend to command the news cycle because we see them, while the entire population of Greenland is just over 55,000. The entire population of Antarctica is zero, leaving aside visiting scientists and tourists.
Everyone from Pacific islanders to Middle Easterners needs to care about the state of Greenland and Antarctica. If they fully melt, the global sea level would rise more than 60 meters, though Englander qualifies that this could take centuries, even on our present trajectory.
In size, Greenland is about from Maine to Florida, and from the East Coast to the Mississippi River, covered by an ice sheet more than a mile thick. But it’s melting by leaps and bounds. “Every year I go there leading fact-finding tours, the change is unmistakable,” Englander says.
Greenland has enough ice to raise global sea levels more than 7 meters; we have no idea how much of this will melt this century.
The rate of Antarctic melting is even more uncertain, though just this weekend another gigantic iceberg, the size of Los Angeles at 1,270 square kilometers or almost 490 square miles, calved off the Brunt Ice Shelf. That said, Englander notes that, counterintuitively, melting icebergs and even the large floating ice shelves don’t directly affect sea levels.
“Any ice that is floating has already had its effect on global sea level. A glass of water with floating ice cubes teaches the lesson,” he says. “Floating ice cubes represent floating icebergs, both sticking about 10 percent above the surface. Just allowing the ice cubes to melt doesn't affect water level. To raise the water level, you have to add an ice cube or more water.”
Apropos: The Antarctic glaciers’ flow to the sea is rapidly accelerating. As the BBC puts it, “Wherever you look in West Antarctica right now, the message is the same: Its marine-terminating glaciers are being melted by warm seawater.” Also, the latest thinking published in July 2020 in Climate Dynamics is that Antarctic ice could also melt faster than expected.
Thus climatologists aren’t able to model the behavior of the Antarctic to required standards of scientific accuracy, Englander notes. For this century, the most widely accepted projections only include 15 centimeters of global sea-level rise stemming from Antarctica, when actually many experts believe a meter or more is very possible.
Garbage cans hoist anchor
So, flooding. Fortunately, Englander helps us grasp the magnitude of the problem by categorizing key sources including coastal storms, extreme rainfall and downhill runoff, extreme tides and the unstoppable rising sea levels.
The obvious problem is with coastal towns, as discovered by the earliest settlers. As the last ice age waned, sea levels rose rapidly. After the last “glacial maximum” 22,000 years ago, the global sea level rose 120 meters, leveling off about 6,000 years ago.
For context, Israeli archaeologists have found now-submerged Neolithic villages in the Mediterranean. One village more than 7,000 years old even put up a seawall to ward off the creeping waters. That wall is now underwater. At the peak rate of melting ice and rising seas, global oceans were rising by almost 5 meters a century.
At present, the global sea level is rising 5 millimeters a year, thus 50 centimeters, or 20 inches, in a hundred years if the rate doesn’t increase. But like the exponential growth with the current pandemic, it’s the acceleration and abrupt change that concerns the experts.
A corollary of creeping sea level is higher tides, and higher “king tides” when the gravitational forces of the Sun, Moon and Earth align, Englander notes. The higher the base sea level, the worse the extreme high tides will be.
King tides aren’t a problem in the Mediterranean, at least so far. The Mediterranean has tides of course, but the average height in the Mediterranean is only a few centimeters largely due to the restricted opening at the Strait of Gibraltar. Compare that with the typical meter in the Atlantic Ocean.
Nobody ever came to Tel Aviv for its surfing, though in 2010 a big wave, maybe even a rogue one, struck a ship off Spain’s Mediterranean coast, killing two.
A different flooding factor that very much affects Israel is extreme weather. Storms are already intensifying and staying longer thanks to climate change, and can be expected to erode the beaches and the kurkar cliffs of the Levant coast. Much of the Israeli coastline is protected, to some degree, by these cliffs but they crumble easily, for one thing. Also, any levee – and the kurkar cliffs are a sort of natural seawall – are only as good as their weakest or lowest point. As seas rise, water will encroach inland through the Hula Valley in the north, for instance.
Regarding global warming and Israel, the long-term forecast is for aridification, but because of extreme weather in recent years, the inland Lake Kinneret, the Sea of Galilee, has risen to levels not seen for decades. Meanwhile, heavy rains have been overwhelming drainage systems in low-lying cities, turning roads into rivers and sending plastic garbage bins sailing down the streets. After a downpour in early 2020, two people in Tel Aviv were trapped in an elevator and drowned.
Apropos extreme weather, some regions are expected to experience less precipitation in total, but when it rains, it pours. Extreme rain (and snow) aren’t related to rising sea levels. But some major cities around the world are all the more vulnerable to rising sea levels because they’re on the coast – and they’re sinking.
Mardi Gras in boats
Whole neighborhoods are subsiding – sinking – because underground aquifers are being overexploited to supply burgeoning populations, industry and agriculture. On top of that, as it were, where cities are built skyward, the sheer weight of human construction can cause subsiding, too.
“Dried-up lands compress under their own weight …. In China more than 50 cities have subsided because of heedless pumping,” The Economist reported in 2017.
Even if the aquifers were left pristine, high-rise areas weighing down on relatively small areas can do enough to deform the Earth’s outer crust. That’s if the underlying ground is rock. If the underlying ground is soil, it will be compressed, explains seismologist Tom Parsons of the U.S. Geological Survey.
He conservatively estimates that San Francisco’s buildings alone weigh 1.6 trillion kilograms (3.5 trillion pounds), which may have caused Bay Area land to sink by as much as 8 centimeters. Lagos, Nigeria sits on islands, sandbars and lagoons; its highest point is just 7 meters above sea level and it’s subsiding at “between 2 and 87 millimeters” a year, Parsons writes, illustrating the diversity of the sinking rates and how local views can be misleading at a global level. Venice and New Orleans are also sinking fast and are extremely vulnerable, so vast efforts are being made to save them – probably futile efforts, Englander says.
Even worse, many of the slowly subsiding coastal cities are expected to keep growing. The United Nations predicts that by 2050, about 70 percent of the world’s population will live in cities.
So what do we have here? Around the world, many coastal cities are already sinking, are expected to grow further and will be facing seas that will inevitably rise; we just don’t know by how much and when. Many will get slammed by foul weather and flooding that they’re not equipped to handle – Tel Aviv’s heavy rain and Texas’ snow are just two of a great many examples.
Humankind has apparently managed to decouple Earth’s climate from its long-term patterns. Predicting mega-drought in the Mediterranean and Levant as a result of climate change, scientists note that prehistorically, the reprieve from droughts came from the changing orbital position of the Earth around the Sun. “Now humanity is responsible, and humanity has yet to find a way to alleviate the situation,” Yochanan Kushnir of the Lamont-Doherty Earth Observatory at Columbia University told Haaretz in 2018.
Englander, on the other hand, notes that there is something we can do, and the sooner the better: Prepare for the sea-level rise and other flooding to come, including where relevant by planning to move to higher ground, as explained in his book due out on April 6, “Moving to Higher Ground.”
Again, not all flooding is sea-level-related. In February, northern India was slammed by flooding originating in the Himalayas, which was blamed on climate change.
“It seems that the rock mass got weakened due to freezing and thawing process due to the climate change phenomenon and crashed down along with a glacier hanging on it,” Kalachand Sain, head of the Wadia Institute of Himalayan Geology, told Voice of America. This week we also learned that the Gulf Stream has reached its weakest point in over a thousand years, portending weather that may be even more extreme.
Apropos of which, an online NASA tool helps you discover which melting glacier may accelerate the rise of the global sea level, and indirectly coastal flooding.
Sometimes there are no solutions. As climate change writer Linda Poon wrote on Bloomberg last month, “In developed cities, there isn’t much that can be done to reverse the effect of urbanization,” which is one reason why Indonesia has decided to move its capital out of rapidly-sinking megacity Jakarta. That town is sinking the fastest: more than 3 meters in the last three decades.
In any case, we must find the courage to identify and acknowledge the problems and make plans before sharks swim into our living rooms or glacial dams burst and flood our mountain valley refuge – and the insurance company refuses to pay.