An alarming, just published, report from Climate Central warns that flooding projected across the globe by 2050 will be far worse than previously thought. The areas affected are mostly in Asia, where millions live on or near the coast. Flooding by seawater implies not only inundation of homes, but the salting of cultivated fields. Worldwide, chronic floods will endanger 300 million people. By the end of this century, the high tide line will be permanently higher than the land where 200 million people now work, farm, and call home.
These dire predictions result from the discovery that coastal elevations are actually lower than previously estimated; hence more vulnerable to flooding, inundation and the contamination of freshwater. In fact, the incursions of saltwater could make the land uninhabitable even before it disappears under the sea.
The previous estimates of land elevation were calculated using data produced by satellite photography, which sees the tops of trees and buildings, thus overestimating the elevation of the land. The problem is particularly acute in areas of dense forest and close clusters of buildings. More accurate means of measurement, using lasers and overflights, are expensive and consequently not widely used.
Cities on the world’s coasts are the most densely populated areas on the planet, and most of them have low elevations. The older elevation estimates have been found to be too high on an average of approximately six to eight feet, which is the same as or even more than the highest sea level rise projections for all of the 21st century. The elevations of some American cities, including New York, Miami and Boston, were overestimated by an average of 15.5 feet.
As we now know, the rise in sea level occurs when the combustion of fossil fuels and other emissions caused by human activity pollute the atmosphere. The planet grows warmer, causing glaciers and ice sheets to melt and flow into the oceans. The increased volume of water raises the level of the sea.
The estimates of the number of people who will lose their farms and homes to floods of saltwater are based on moderate emissions cuts mandated by the Paris climate accords. (We are not currently meeting those goals.) If pollution and the subsequent greenhouse gases continue to increase, by the end of the century chronic flooding and permanent inundation will imperil the land that shelters and feeds 640 million people living now (actually more; based on 2010 data), close to 10 percent of the global population. Ironically, the people most likely to suffer are the ones least responsible for polluting emissions.
The United States is already experiencing the predicted effects of global warming. Hurricane Harvey caused epic flooding in Houston; diseases once confined to the tropics are increasingly occurring in the temperate zone; extreme heat is responsible for a sharp increase in deaths in Nevada and Arizona; wildfires are consuming California . . .
The loss of land and the resulting migration of climate refugees will surely give rise to humanitarian crises of unprecedented severity and have devastating effects on the world economy. Other aspects of global warming like drought and extreme heat will also have catastrophic consequences. All living creatures, from plants to insects, fish, birds and humans will have to flee their habitats and invade others. Some will survive; many won’t.