A Sentinel-2 satellite image from May 20 shows the Dutch province of Zeeland, including the port of Rotterdam, Europe’s largest seaport in the top right corner. Much of the region is below sea level and depends on a complex system of dikes, canals and dams for survival.
Credit: European Space Agency
Credit: European Space Agency
Climate change is causing oceans to rise faster than scientists’ most pessimistic predictions, resulting in past flood risks for coastal economies that are already struggling to adapt.
The revised estimates were published in Tuesday Ocean Science affects two fifths of the world’s population living near coasts. Trillion-dollar insured properties can be even more at risk from floods, superstorms, and tidal waves. The research suggests that countries will have to curb their greenhouse gas emissions even more than expected to keep sea levels under control.
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“It means our carbon budget is going to be depleted even further,” said Aslak Grinsted, a geophysicist at the University of Copenhagen who co-authored the study. Economies must cut 200 billion tons of additional carbon – equivalent to about five years of global emissions – to stay within the thresholds set by previous forecasts, he said.
The warmer it gets, the faster the sea level will rise. The sensitivity models of the future seem to conflict with historical data.
Credit: Aslak Grinsted
The researchers built on the models of the United Nations Intergovernmental Panel on Climate Change, many of which only consider the last 150 years, by including data going back several centuries. The new observations show that a sea rise of about half a meter can be expected by the end of the century with a temperature rise of only 0.5 degrees Celsius. Oceans can rise more than 1 meter at 2 degrees Celsius, a trajectory that is easy to pass under current climate policy.
“The models on which we base our sea level rise forecasts are not sensitive enough at the moment,” said Grinsted. “To put it plainly, they don’t hit right when we compare them to the rate of sea level rise that we see when we compare future scenarios with observations going back in time.”
The conclusions follow last month’s warning that rising temperatures have melted 28 trillion tons of ice – equivalent to a 100m thick layer of ice covering the entire UK – making the most adverse climate scenarios more likely. The new methodology for tracking sea level change could help insurance companies, real estate developers and urban planners set up tidal defense systems.
“The scenarios we’re seeing now regarding sea level rise are too conservative – the sea looks to rise more by our method than is assumed by the current method,” said Grinsted, adding that his team at the Niels Bohr Institute is in contact with the IPCC about processing the results in next year’s sixth edition Evaluation report.