WASHINGTON (AFP) - Just as an oil tanker steaming ahead at full speed cannot stop immediately, so the dramatic rise in sea levels will continue even if the world manages to slash greenhouse gas emissions to zero by 2030, experts warned in a study published on Monday (Nov 4).
Emissions between 2015, when the Paris climate change accord was thrashed out, and 2030 would be enough to raise levels by 8cm by 2100, according to research by experts based in Germany.
They would rise by 20cm by 2300 in comparison with the reference period of 1986-2005, according to the study published in the Proceedings of the National Academy of Sciences (PNAS).
In total, sea levels can be expected to rise by at least a metre by 2300 in the extremely unlikely event that greenhouse gas emissions fall to zero in the next 11 years.
And that may be a conservative estimate: United Nations-backed scientists are already predicting an increase in water levels of between 26cm and 77cm by the end of this century alone.
A full quarter of that 1m rise by 2030 will be due to emissions from China, the United States, the European Union, Russia and India in the preceding 40 years, the authors of the latest report concluded.
By comparison, oceans rose by around 20cm in the 20th century.
The goal of the study, co-author Alexander Nauels of the Climate Analytics institute in Berlin told AFP, was to show that current emissions will have a clear effect on rising sea levels that will be felt over the next 200 years.
"We all focus on the 21st century," he said, warning that "sometimes that can create the false impression that after the 21st century, nothing else will happen".
Sea level rise is due to a number of complex phenomena that can play out over extremely long time scales, making its study difficult. It is still unclear why Antarctic ice is melting more slowly than in Greenland.
"When you're looking into the sea level rise problem, it's a very slow and responding system," said Dr Nauels.
"A centimetre doesn't sound like much but it's actually a lot," he added.
In a report published last year, experts from the Intergovernmental Panel on Climate Change said reducing the rise in sea level by 10cm would save 10 million people in coastal areas from being exposed to flooding, storm surges and other risks.