Sea level rise is speeding up, scientists confirm

Climate change is making our seas rise faster and faster, confirms a new study examining 25 years of data.

Published on Monday in the journal Proceedings of the National Academy of Sciences, the study finds that sea level rise will not increase at a steady rate. Instead, the rate will accelerate by about 0.08mm each year.

While this doesn’t sound like a lot, it could lead to almost half an inch of sea level rise per year. And if this rate of acceleration continues, by the end of the century sea levels will rise by just over 2 feet. This confirms previous projections put out by the U.N. Intergovernmental Panel on Climate Change (IPCC).

This expected increase is compared to just 7 cm – or 2.7 inches – of the global average sea level rise experienced since 1993. As the study notes, one of the main causes behind the accelerating sea level rise is the melting of ice sheets in Greenland and Antarctica – and this is one of the biggest variables that will impact how quickly the seas will continue to rise.

Because of this, the researchers say their findings are a “conservative” estimate. If the climate starts to change even more rapidly, then the rate of sea level rise could increase even more.

As Steve Nerem, Associate Director of the Colorado Center for Astrodynamics Research at the University of Colorado Boulder and one of the study’s authors, told ThinkProgress, the study’s conclusions are based on the assumption that “the ice sheets [will] just continue going along at what they’ve been doing for the last 25 years.”

This isn’t likely to be the case, Nerem expects. “There may be abrupt changes in the ice sheets,” he said. “That’s why I think that this is a conservative estimate, because it doesn’t consider what if the ice sheets really start to go.”

Basically, he said, the study “has a major caveat that [it assumes that] sea level continues to change into the future at the same rate and acceleration of change as the last 25 years. Like I said, that’s probably not going to happen, [our findings are] probably on the low end.”

The researchers, however, are very confident that sea levels will continue to rise at an accelerated rate.

Commenting on the study, Andrea Dutton, an assistant professor and fellow at the Florida Climate Institute at the University of Florida who wasn’t involved in this research, said there’s an important statement included in the study that shouldn’t be ignored: “The probability that the acceleration is actually zero is less than 1 percent.”

In other words, it is more than 99 percent probable that sea level rise will accelerate. “That’s a very important statement,” Dutton said.

Often, climate models, such as those for sea level rise, include multiple curves on a graph showing the different types of scenarios – at the lowest end, the smallest rate of increase, and at the highest end a curve showing the most extreme case of global warming. When it comes to that lowest curve, said Dutton, “what this paper is saying is we know that that’s not reasonable.”

In order to reach these findings, the team of scientists from CU Boulder, the University of South Florida, NASA Goddard Space Flight Center, Old Dominion University and the National Center for Atmospheric Research studied 25 years of satellite data.

This includes data from along coastlines but also information collected over the open ocean, making it a much more comprehensive data set. It also takes into account the effects of volcanoes and changes in temperature resulting from El Nino and La Nina. The aim was to tease out the longer-term climate trends.

Effectively, the study uses this real-world data from the past few decades to produce a calculation about the rate of future sea level rise, and found that it matches the complicated climate models produced by the IPCC for a “high emissions scenario” where no action is taken to limit emissions.

The study, of course, added that more research is needed to refine the results. “As we get longer and longer time series there will be better estimates of this acceleration,” Nerem said.

“It’s really interesting,” added Dutton. “For a long time, people had been saying that the satellite data is too short for us to use and make any projections. Now it’s just starting to get long enough to do a reasonable statistical analysis of it. And they find that it has accelerated over this time period since 1993 when we first started measuring sea level using these satellites.”

Satellite data is vital to this research, said Nerem. However, last year under the Trump administration, this scientific data came under fire. Last April, President Trump’s proposed budget took aim at NASA’s climate science, a lot of which is done using satellites. Scientists feared that if a gap in data gathering were to occur due to a lack of funding or cancelling of a project, this would harm climate research. Continuous data records are critical to improving climate models and understanding how increased temperatures may be impacting the world.

“This research would not have been possible without the NASA satellite measurements,” Nerem said. “We really would be blind without those satellites. I mean, we still have other measurements but those measurements have a lot bigger errors, it’s a lot harder to tell what’s going on, and so it’s critical to have the satellite measurements and really I think everybody needs to put in a plug for the satellites so that NASA continues to give us these observations.”