Image: Michel_r/Wikimedia Commons
SHANGHAI -- Some 1,000 years ago, the Chinese named this city "Shanghai" based on its location. It literally means "above the sea." Those pioneers probably never imagined the situation that confronts this city today: Shanghai is on its way to being below the sea.
Climate change is pushing up the sea level globally. While in Shanghai, such rise is roughly the length of a rice grain in each of recent years, the low-lying city with a population of more than 20 million has had to pour billions of dollars into rebuilding infrastructure to protect against potential floods. It is also revising its growth plans, hoping to reduce its vulnerabilities.
It has used its perch on the Yangtze River Delta to become one of the world's prime financial and shipping centers, but now it also finds itself being menaced by other hazards rooted in climate change. During the past years, the city has suffered more extreme weather, missed rain during the normal wet season and seen a temperature hike almost four times higher than the global level.
Climate change threatens Shanghai's economy in various ways. Because global warming is heating up the sea, local fisheries are expected to see their business drop. Scientists have discovered that fish here do not flourish in hotter water. Typhoons and other forms of extreme weather are scaring away tourists and giving large cargo ships reasons to seek other ports.
But the city's biggest concern remains the slow, steadily mounting threat that comes from sea level rise. Higher tides are washing away the precious delta soil upon which the city's foundations are built, and water supplies are becoming more tainted as seawater intrudes more deeply into the fresh water of the Yangtze.
What stands between Shanghai and drowning is an average 13 feet of land. Construction of thousands of high-rise buildings, combined with the pumping of groundwater, is making the soil subside. The removal of groundwater is now under tighter controls, and water is actually being pumped back to wells, a move that has slowed the city's slump into the East China Sea.
Build a floodgate on the Yangtze?
But that won't save it from another danger. Meteorologists warn of more floods, as giant storm surges can ride in on higher tides to invade the city. To defend Shanghai, engineers have stretched hundreds of miles of levees along its rivers. The lowest of those levees were built to withstand a one-in-1,000-year tidal surge.
Along some major waterways, including by the landmark Bund financial center, where century-old architecture and some ultra-modern glass and steel buildings stand on its two sides, river dikes were built even higher.
Such ambitious infrastructure has already defended Shanghai against the highest tidal surge in modern times, which came during a 1997 typhoon. Experts think it might be able to handle the incremental sea level rise as far out as 2100. But this city was not built on hope; it wants more guarantees.
Zhang Zhenyu, spokesman of Shanghai Flood Control Headquarters, said that the city is considering building a floodgate near the Yangtze estuary. The gate could be raised and lowered in accordance with tide and weather, controlling water flowing in and out of the river.
Although the plan is still under discussion, mainly for its possible negative impacts on ships and nature, it is most likely to get a go-ahead, disclosed Zhang.
"After all, building of such gate would be more effective and less costly [than raising and re-enforcing levees]," Zhang explained, adding that more than $6 billion has already been poured into flood control infrastructure over the last decade.
Destroying natural sea barriers
Shanghai keeps reinforcing riverside barriers, but sometimes it has also been the effort's worst enemy. To catch up with its population boom and support an economy that grows at a double-digit rate almost every year, the land-scarce city has dried up coastal wetlands and filled them with new factories and apartments in its never-ending hunt for more space.
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Reply | Report Abuse | Link to thisWell I guess that one didn't work. What I meant to say is "good luck" to Shanghai.
Reply | Report Abuse | Link to thisOf course building a giant city on the soft soil of a river delta, pumping out groundwater and etc... has absolutely no effect.
Reply | Report Abuse | Link to thisAnd no fish exist in any water warmer than 60 degrees.
At least they are doing something to mitigate the possible effects natural global warming.
"... in Shanghai, such rise is roughly the length of a rice grain in each of recent years"
Reply | Report Abuse | Link to thisI'm a bit confused. The rice in my bowl mesures over a centimeter, the rice in my neighbor's bowl mesures about a third of a centimeter.
Q83256
Sea levels increase when glaciers recede. This is why glacier-fed rivers need careful flow measurements.
Reply | Report Abuse | Link to thisYet standard physics defines sublimation as the evaporation of ice without passing through the liquid stage. To my knowledge, nobody is monitoring worldwide sublimation, so if glaciers are evaporating we have no evidence of this. Sublimation can be monitored by weighing samples of ice together with any meltwater from it.