Sea levels are rising several times faster than in the past 2,800 years and are accelerating because of man-made global warming, according to new studies.
An international team of scientists dug into two dozen locations across the globe to chart gently rising and falling seas over centuries and millennia. Until the 1880s and the world’s industrialisation, the fastest rise in sea levels was about 3cm to 4cm a century, plus or minus a bit.
During that time the global sea level really did not get much higher or lower than 7.62cm above or below the 2,000-year average. But in the 20th century the world’s seas rose 14cm.
Since 1993 the rate has soared to 30cm and two different studies, published on Monday in the journal Proceedings of the National Academy of Sciences, said that by 2100 the world’s oceans would rise between 28 and 131cm, depending on how much heat-trapping gas Earth’s industries and vehicles expel.
“There’s no question that the 20th century is the fastest,” said Bob Kopp, Rutgers earth and planetary sciences professor and the lead author of the study that looked back at sea levels over the past three millennia.
“It’s because of the temperature increase in the 20th century, which has been driven by fossil fuel use.”
If seas continue to rise as projected, another 45cm of sea-level rise will cause lots of problems and expense, especially with surge during storms, said study co-author Stefan Rahmstorf, of the Potsdam Institute for Climate Impact Research in Germany.
The link to temperature is basic science, the study’s authors say. Warm water expands. Cold water contracts. The scientists pointed to specific past eras when temperatures and sea rose and fell together.
Both studies project increases of about 57 to 131cm if greenhouse gas pollution continues at the current rate. If countries fulfill the treaty agreed last year in Paris and limit further warming to another two degrees Fahrenheit, the rise in sea levels would be in the 28cm to 56cm range.