Seas are rising way faster than any time in past 2800 years

A new study concludes that sea levels on Earth are rising at a rate several times faster than they have risen in the past 2,800 years. However, Princeton climate scientist Michael Oppenheimer, who was not involved in the current work but collaborates with Kopp and was his postdoctoral adviser, says that this agreement between approaches still “begs the question of just how much disintegration of the polar ice sheets will contribute to sea level during the 21st century since neither type of model is adequate for capturing this growing and potentially disastrous contribution – and that is ultimately the most important unknown, both with regard to sea level and potentially with respect to the whole field of climate change”.

The PNAS team, which includes scientists from the U.S., Germany, Singapore, and the United Kingdom, built their global picture from two dozen studies of local sea-level rise going back three millennia, plus 66 tide-gauge records going back to 1700.

“The 20th century rise was extraordinary in the context of the last three millennia – and the rise over the last two decades has been even faster”, Kopp said.

Simulating sea level in the absence of global warming, the researchers estimate that the 20th century rise would have been at most 0.7 millimeters annually.

The surge in sea levels in the coming decades will continue a trend that began around 1950, when after centuries of minor fluctuations up and down, the level began to increase – and at a rapidly accelerating rate.

The lead author of the study, which was published Monday in the journal “Proceedings of the National Academy of Sciences”, was Robert E. Kopp, an associate professor in Rutgers’ Department of Earth and Planetary Sciences. “They also demonstrate that one of the most risky impacts of global warming, namely rising seas, is well underway”.

Coastal wetland in Newfoundland, Canada, that harbors a record of sea level for the past 2,000 years. According to Liu Kexiu of the National Marine Data and Information Service, “The rising temperatures from increasing greenhouse gas emissions and the land subsidence nationwide led to the high seas”. They went around the world looking at salt marshes and other coastal locations and used different clues to figure out what the sea level was at different times. They also studied the reaction of single cell organisms that are sensitive to salinity to differences in sea levels, as well as mangroves, coral, and other clues in sediment cores.

“Scenarios of future rise depend upon our understanding of the response of sea level to climate changes”, Horton said. Published in 2011, that study produced a chart of sea levels that bounced up and down over time, changing with global temperatures, and then ticked sharply upward as industrialization triggered global warming.

“I think we need a new way to think about most coastal flooding”, Benjamin H. Strauss, the primary author of one of the studies, tells the New York Times. The scientists pointed to specific past eras when temperatures and sea rose and fell together. If countries fulfil the treaty agreed upon previous year in Paris and limit further warming to another 2F, sea level rise would be in the 28 to 56cm range. Without global warming, global sea levels would have risen by less than half the observed increase and might even have fallen, according to the study.