The Attacking Ocean (35 page)

Epilogue

The Attacking Ocean
has taken us on a journey back to the Ice Age, to a time when sea levels were as much as 122 meters lower than today. We’ve traveled through the subsequent nine thousand years of warming that brought global shorelines to their near-modern configurations about a millennium before the first civilizations developed in Mesopotamia and along the Nile. For the next six millennia, the climb was effectively minimal, as the Egyptian pharaohs built the pyramids, complex states developed in South Asia and China, and Rome dominated much of the Western world. The geology may have been relatively quiescent, but human vulnerability to the attacking sea increased dramatically. Coastal populations in low-lying environments like the Nile delta and the great estuaries of what are now Bangladesh, China, and Vietnam rose dramatically from a few tens of thousands to millions. Mushrooming cities acquired a growing vulnerability to natural cataclysms and extreme weather events like tropical cyclones with their ferocious storm surges. The major threats from the ocean were not those of rising shorelines, but from earthquake-caused tsunamis and violent storms, phenomena whose potential for damage ashore increased significantly if local sea levels rose even slightly or subsidence allowed the ocean to surge inshore, contaminating water supplies and flooding agricultural land. There were certainly casualties and suffering, but nothing on the scale that lurks in the foreseeable future, thanks to the sustained warming that began during the height of the Industrial Revolution around 1860. Since
then, sea levels have resumed an inexorable climb, which now seems to be accelerating, whence the thoughtless media hysteria that focuses, laser-like, on perceived imminent catastrophe, on a world of rapidly melting ice sheets smothered by seawater. Reality is, of course, much more complex.

History allows us to take a more measured look at the intricate relationship between warming temperatures and rising sea levels. The rapid warm-up immediately after the Ice Age far exceeded the pace of today’s changes. But even then sea level rise, while faster than today, was
cumulative
, a matter of fractions of a centimeter, or at the most a centimeter or so a year, sometimes not even that. Sea level rise is a seemingly long-term problem, which is why many people discount the threat. One could do this with some impunity in earlier times, but not today, when tens of millions of us live a few meters above sea level, even below it. In the short term, the greatest threat comes not from cumulative sea level change but from extreme natural events, whether earthquakes, tsunamis, or tropical storms, which spread water
horizontally
over low-lying coastal landscapes and river deltas, some of the most densely inhabited environments on earth. Combine this with tiny annual sea level rises and you have a volatile and growing recipe for long- and short-term disaster; the former is global, the later predominantly local.

MUCH OF THIS book is a litany of destruction wrought by what are, by historical standards, transitory events. But how do these past catastrophes stack up against the challenges of the longer-term future, the next century or so? There are, of course, some low-lying settlements and island populations that are already being forced to move, but such relatively small-scale shifts pale beside the decade- and century-long disruptions that lie ahead in densely populated nations like China, Europe, and the United States.

At a general level, the figures are daunting. Roughly two hundred million people globally live along coastlines less than five meters above today’s sea level. By the end of the twenty-first century, this figure is
projected to increase to four hundred million to five hundred million. At the same time, coastal megacities will continue their breakneck growth. In Europe, a sea level rise of about a meter will threaten thirteen million people. A billion people live within twenty meters of mean sea level on land measuring only some eight million square kilometers, an area roughly equivalent to that of Brazil. The land loss will affect the gross national product of flooded areas, impinge on expanding urban settlement, inundate agricultural land, reduce job opportunities, and eradicate coastal wetlands that offer a measure of protection against flooding.

Which nations are most vulnerable? Bangladesh is close to the top of any list, as are the Pacific Islands described in
chapter 12
, and also the Bahamas. Vietnam with its Mekong delta is under threat. More than a third of the river’s delta will vanish underwater with a one-meter sea level rise. In a perhaps prophetic event, the Vietnamese government evacuated 350,000 people in the face of Tropical Storm Ketsana in September 2009. The same storm left 80 percent of Manila in the Philippines underwater. Shanghai with its estuary and dense urban population is also high on the list. In Europe, the Low Countries and the southern Baltic coast, including the Oder and Vistula estuaries, are potential victims, as is eastern England. In the Mediterranean, densely populated flatlands such as the Nile delta, and, of course, the Po delta and Venice, are under attack. Without sea level defenses already in place, constructed at vast cost, some of these areas would already be underwater.

What about the United States, where millions of people live at, or close to, today’s sea level? Using government elevation databases, researchers at the University of Arizona have analyzed the vulnerability of every coastal city in the lower forty-eight states with a population of over 50,000 people.
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The results provide sobering food for thought. Coastal cities along the Gulf and southern Atlantic coasts will be especially hard hit. Miami, New Orleans, Tampa, and Virginia Beach, Virginia, could lose more than 10 percent of their land areas by 2100. An average of 9 percent of land within 180 US coastal cities could be threatened within the same time frame. Collectively 40.5 million people live in
these cities, twenty of which have populations of over 200,000. This is apart from erosion and resulting temporary flooding as well as storm damage in a future of more extreme events.

Global warming has raised sea levels about 20 centimeters since 1880 and the rate of rise is accelerating. Many scientists expect a rise of 20 to 203 centimeters this century, depending on the release of greenhouse gases and other pollutants into the atmosphere. More specifically, the Arizona study projects a 2.5- to 20-centimeter climb by 2030 and a 10-to 49-centimeter rise by 2050, the amount varying considerably from one location to another. If current rates of greenhouse gas emissions continue, global temperatures will rise to an average of thirteen degrees Celsius warmer than today by 2100. According to Jeremy Weiss of the University of Arizona, this would lock us into at least 4 to 6 meters of sea level rise in subsequent centuries, as parts of the Greenland and Antarctic ice sheets dissolve.
²
With an almost 3-meter rise, nine large cities, including Boston and New York, will have lost 10 percent of their current land areas. With a near 6-meter rise, about a third of the land area within US coastal cities will have vanished.

Apart from sea level rises flooding urban acreage, there is the additional issue of vulnerability to so-called hundred-year storms. More than two thirds of the studied locations now have a more than doubled risk of a hundred-year tempest within the next eighteen years. The figure is even higher for areas outside the Gulf of Mexico. These flood levels are often 1.2 meters above average high tide levels, yet across the country nearly five million people live in houses less than 1.2 meters above high tide. In 285 cities and towns, more than half the population lives on land below this line. Nearly four million people dwell less than a meter above high tide. About half of them reside in Florida, where eight out of ten of the most threatened cities lie. About thirty billion dollars in taxable property is vulnerable below the 1.2-meter line in just three coastal counties in southeastern Florida alone—quite apart from Miami-Dade, the most threatened county in the state.

None of these figures take into consideration the potential damage that could be caused by a mere 1.2 meters of flooding to dry land devoid of housing, including 7,770,00 hectares of roads, bridges, commercial
buildings, military bases, airports, and agricultural land—and the list goes on and on.

INEVITABLY, THERE ARE those who argue that the risks are negligible at this stage, that we shouldn’t concern ourselves with such long-term threats. They accuse the experts of relying on inadequate data, on faulty computer models and too few observation points along the coast. One can only point out that the data is improving literally monthly and is the best available. Science is, after all, a cumulative progress. Those who deny the reality of global warming and accompanying sea level rises are flogging a dead horse. Many of them have well-scripted agendas or a blind faith in some form of usually outdated political ideology. We’re now at a point where we can no longer behave like ostriches with our heads in the sand.

Consider the climatic projections for California, produced by an impressive army of highly qualified experts.
³
Thoroughly researched projections speak of a 60 percent reduction in mountain snowpack by the year 2100, the snowfall that yields much of the state’s water supplies. Heat waves and severe storms will become more commonplace and the Pacific along the California shoreline may rise as much as 122 centimeters within a century. Future sea levels will be higher here than in Oregon or Washington, for the movements of tectonic plates are causing the coast to sink as higher temperatures and melting ice contribute simultaneously to a rising Pacific.

The effects of this climb are already with us. Reliable measurements from the Golden Gate document a rise of eighteen centimeters over the past century. The projected sea level rise above this eighteen centimeters may seem like an academic figure, but most emphatically not for an enclosed bay, where much of the surrounding shoreline lies only a few meters above sea level and intensive groundwater pumping has caused widespread subsidence. At issue here is not so much the actual higher water level, but a future in which a higher incidence of major winter storms will coincide with high tides, causing the sea to cascade much farther inshore and to remain longer on the flooded land. Imagine a future
when the runways at Oakland and San Francisco Airports remain partially underwater for weeks, even months, or when storm surges inundate freeways close to high tide level. The disruptions would be enormous, to say nothing of the flooding and destruction of buildings close to sea level. This future is reality, not science fiction.

In the San Francisco Bay area and elsewhere, sea level changes over the past century, and especially over the past two decades, have created what can be called a launchpad for storms and exceptionally high tides, somewhat akin to the effects of water overflowing from a shallow lake in flat terrain that spreads over surprisingly long distances. History tells us that even modest sea level climbs increase such storm-related flooding dramatically. Even many centuries ago with many fewer people around, these events led to thousands of casualties, famine, and even the collapse of royal dynasties. The threat is infinitely higher and more urgent today, not only because of storms and warming, but also because of a second reality: the enormous numbers of people at risk along the world’s coasts—at least two hundred million of us and climbing.

With more severe storms and extreme weather events projected for the future, even a few centimeters make a profound difference between the once-a-decade flood and a hundred-year storm surge. Of course, flood levels will reach different levels in individual locations and on diverse timelines. For example, the US Gulf Coast experiences more major storms and accompanying storm surges than other portions of the North American shoreline. Hurricane Isaac came ashore near New Orleans in August 2012 and brought widespread flooding. Katrina destroyed levees and caused catastrophic loss of life. A recent national study of flood-threatened areas found that over half the sites examined had a one-in-two chance of water reaching a level 1.2 meters higher than the average local high tide by 2030.
⁴
By 2050, many locations should experience 1.5-meter or higher floods above high tide on a regular basis. Beach homes and mansions line kilometer after kilometer of low-lying coastline, inviting destruction. Perhaps it’s also worth mentioning that current sea level studies assume that recent historical storm patterns won’t change. However, in a warming future, the frequency of
storm surges and other extreme weather events could affect the extent of coastal flooding in dramatic ways.

WHAT’S TO BE DONE? No one has entirely satisfying or utterly realistic solutions. The options are limited and almost invariably dauntingly expensive. Do we build enormous sea defenses and wall off the ocean, as the Netherlands have been doing for centuries? Over many centuries, the Dutch have created formidable armor designed to combat the kinds of storms and sea surges that blow ashore perhaps only once in a millennium or perhaps only every hundred thousand years—but no one knows when the epochal storm surge will come. There are numerous other examples. Saint Petersburg in Russia was built on a swamp, fed by the Neva River and the Baltic Sea. Twenty-six kilometers of levees and gates shield the city from floodwater. A massive seawall erected at vast expense with Japanese funding protects Malé, the capital of the Maldive Islands in the Indian Ocean, which is only a few meters above the ocean.

Could one develop a sea defense system to protect the New York harbor region and the extremely valuable real estate surrounding it? (It’s worth noting that the original Dutch settlers built their tiny community in south Manhattan on higher ground, safe from flooding. Only much later, after the British takeover in 1664, and as New York became an increasingly important shipping center, did settlement expand into lower-lying areas. Perhaps the Dutch remembered their experience at home.) The cost of building New York a sea defense system would be at least $15 billion. And then, as many experts have pointed out, you have to maintain and upgrade them over the long term, and that is very expensive as well. The city has already taken modest steps such as installing floodgates at sewage plants and raising the ground level while developing low-lying areas in Queens. At the same time, subway design and other infrastructure projects incorporate the best guesses and estimates of the time as to what would be the worst that nature could throw at the city as 100- or 500-year events, but the increasing frequency of severe storms on an almost annual basis creates a new dynamic.
“Anyone who says there’s not a dramatic change in weather patterns, I think is denying reality,” said New York governor Andrew Cuomo at a press conference on October 30, 2012. New York mayor Mike Bloomberg agreed, adding, “What is clear is that the storms that we’ve experienced in the last year or so, around this country and around the world, are much more severe than before.”
⁵
The levee solution has been widely used in the New Orleans region, but as experience has shown, such barriers are fallible unless properly built and, again, that is expensive. Levees are in place around Hoboken, New Jersey, but the Hudson River rose when Sandy came and swept over the levees at both ends of the city, flooding some lower-lying neighborhoods and turning others into islands. Over twenty thousand people had to be rescued from their homes. The waters were a brew of rainwater, river water, and sewage, ponded like water in a bathtub inside the levees. There was only a single pumping station to drain the streets.