Time and tide wait for no-one. As sea levels rise, the rising tides will become more impatient. Millions of Americans will have to migrate.
Houston, Texas is about to grow in unexpected ways, thanks to the rising tides. So will Dallas. Real estate agents in Atlanta, Georgia; Denver, Colorado; Pittsburgh, Pennsylvania and Las Vegas, Nevada could expect to do roaring business.
The inland counties around Los Angeles, and close to New Orleans in Louisiana, will suddenly get a little more crowded. And from Boston in the north-east to the tip of Florida, Americans will be on the move.
An estimated 13 million US citizens could some time in this century become climate refugees, driven from their seaside homes by sea level rise of possibly 1.8 meters, according to new research.
And they will probably have to move their homes in a poorer economic climate. If governments and city authorities do not take the right steps, sea level rise could erode 4% of the global annual economy, says a separate study. That is, coast-dwellers could witness not just their towns and even cities washed away: they could see their prosperity go under as well.
California scientists report in the Public Library of Science journal PLOS One that they used machine learning techniques – in effect, artificial intelligence systems – to calculate what is most likely to happen as US citizens desert Delaware Bay, slip away from the cities of North and South Carolina, and flee Florida in the face of rising sea levels, coastal flooding and increasingly catastrophic windstorms.
In the year 2000, a third of all the planet’s urban land was in a zone vulnerable to flood. By 2040, this could rise to 40%. In 2010, in the US, more than 120m citizens – that is nearly 40% of the entire population – lived in coastal counties. In 2020, this proportion could already be higher.
She and her colleagues started from patterns of movement that began with Hurricane Katrina, in 2004, and Hurricane Rita a year later, both in Louisiana. They then let the algorithms take over the challenge of guessing what American families and businesses are most likely to do as the tides begin to flood the high streets.
“We hope this research will empower urban planners and local decision-makers to prepare to accept populations displaced by sea level rise. Our findings indicate that everybody should care about sea level rise, whether they live on the coast or not,” she said.
The California team’s worst-case forecasts are based on a premise that the world takes no real action to combat sea level rise, which is driven by global warming powered in turn by fossil fuel emissions into the atmosphere on an ever-increasing scale.
The scientists considered two scenarios, including one in which the world kept the promises made in Paris, and one in which it did not, and made no attempt to adapt to or mitigate climate change.
By 2050 losses in each scenario would be significant and much the same. But by 2100, the do-nothing option promised to hit the gross domestic product – an economist’s favourite measure of economic well-being – by 4%.
Europe and Japan would be significantly hit; China , India and Canada hardest of all. If the world’s richest nations actually worked to limit climate change and adapt to the challenges ahead, the impact on the economy could be limited to 1%.
“Macroeconomic impacts up to and beyond 2050 as a result of coastal flooding due to sea level rise – not taking into account any other climate-related impacts such as drought – are severe and increasing.
“We, as a global society, need to further co-ordinate mitigation, adaptation and climate-resilient development and consider where we build cities and situate important infrastructure.”