Scientists Are More Confident Than Ever In Troubling Sea Level Rise Projections

The following article by Aleandro Davila Fragoso appeared on the ThinkProgress.org website Februar 23, 2016:

Charles Warsinske has a daunting and unusual task for a city planner: move a town out of the way of climate change.

“If you think about it too long it’s somewhat overwhelming,” said Warsinske, manager of the Quinault Indian Nation Community Development Planning Department. “It seems like the climate change thing is certainly on everybody’s minds right now and it’s a very, very complicated thing.”

For the Quinault Nation, which has lived next to the Quinault River and the Pacific coast just west of Seattle for generations, climate change raises more issues than for most communities. Their culture and economy depend on the bounty of the land, forests, rivers, and oceans that are behaving as differently as any tribal elder can remember. The glaciers that feed the rivers and support the salmon population — so integral to their livelihood — are disappearing. Forests on tribal lands are changing, too, as invasive species threaten critical resources.

What’s more, the waters that feed this ancient tribe have become unusually violent. In fact, intensified storms associated with human-caused climate change have brought the Pacific Ocean and the Quinault River over their seawalls recently with such force that tribe officials issued a state of emergency in March of 2014. They issued another the following January.

“With the thermal expansion of the ocean, with the warmer temperatures, and so on … we are experiencing flooding,” Warsinske told ThinkProgress. They are also “experiencing a lot of erosion along the shorelines and that hasn’t happened before,” he said.

In response to these threats, officials started reviewing earthquake, tsunami, and climate studies, including sea level rise projections. Soon after, the tribe understood that Taholah, the reservation’s main population center, didn’t stand a chance against rising waters. This is how an ambitious plan to move some 700 people half a mile up the hill in the next two decades came to be. That means moving not just homes, but also police and fire stations, a school, administrative buildings and businesses — as well as all the infrastructure that comes with it.

Moving the town was an “extremely difficult” and costly decision to make, Quinault President Fawn Sharp told ThinkProgress. But there was no other option. The signs and dangers of coastal erosion, unprecedented tidal surges, and sea level rise were on their doorsteps in the most literal way.

“We are looking at 300 to 400 million dollars for all the infrastructure and buildings,” said Warsinske, noting they are pursuing every funding stream and grant they can think off to gather the money they need.

Sea level studies informing policymakers like Sharp and city planners like Warsinske have been forecasting a rise in ocean waters for years. The Intergovernmental Panel on Climate Change — and most of the scientific community for that matter — have long said a warmer ocean, a loss of glaciers and ice sheets, and a reduction of liquid water storage, are together increasing ocean volume worldwide. “It is virtually certain that global mean sea level rise will continue for many centuries beyond 2100, with the amount of rise dependent on future emissions,” the IPCCsaid in a 2013 report.

For years, however, there has been a discrepancy between two different ways of doing sea level rise projections. Research using the so-called semi-empirical model exploiting statistical relationships between sea level and climate forces didn’t match those using the process-based models that employ complex physics of separate elements. This meant that the scientific community — along with the IPCC — has been wary on the level of certainty reached in some of the projections.

That’s not to say the scientific community was unsure sea level rise is happening, and that greenhouse gases are behind it. It means that the certainty surrounding sea level rise projections needed to improve, according to the IPCC. Now, however, two separate studies developed by the Potsdam Institute for Climate Impact Research in Germany, andRutgers University in the United States, say modeling techniques are agreeing like never before in their conclusions.

Most importantly, while the Potsdam study found that sea level rise will likely be as much as 50 inches by the end of the century unless greenhouse gas emissions are rapidly reduced, the Rutgers study found that global sea levels rose faster in the last century than in the last 3,000 years. Both studies were published Monday in the Proceedings of the National Academy of Sciences.

Researchers reached by ThinkProgress said that together, these studies are important tools for policymakers and stress the high stakes of inaction. They also show how much models have evolved and that certainty behind sea level rise projections is equally growing. “One important thing that this paper shows us is a maturation of the modeling techniques being used,” said Andrea Dutton, assistant professor of geology at the University of Florida, while referring to the Rutgers study. In an email to ThinkProgress, Dutton also noted the study gives robust confidence on future sea level projections.

Anders Levermann, a co-chair for adaptation at the Potsdam Institute for Climate Impact Research, said the study he coauthored finds with a 90 percentile confidence level that future sea level rise will be between 20 to about 50 inches. This high level of confidence come as scientists have made significant progress in modeling how mountain glaciers and ice sheet loss affect the environment, he said.

“I think now we can give a relatively confident statement with respect to the sea level rise that we have to expect if we don’t avoid greenhouse gas emissions,” said Levermann, who went on to add that to keep sea level rise at a manageable level within this century “we need to do what was agreed upon in Paris and that is to reduce emissions.”

The Rutgers study, meanwhile, puts the role of humans in sea level rise within an unprecedented historical context, researchers said. “Scientists are never 100 percent sure but we are very sure about this,” said Benjamin Horton, a researcher of marine sciences at Rutgers University. “We are in the statistical significance of 95 percent that the rates we are experiencing now are faster than anything in the prior 27 centuries.”

To reconstruct past sea level trends scientists analyzed more than a decade’s worth of data found in salt marshes from around the globe, looked at the microfossils found in sediments, and applied radiocarbon dating. Researchers said they observed a relationship between sea level changes and temperature more than once.

“One of the novel things that we have is that there are two intervals where there is a clear relationship between temperature and sea level,” said Robert Kopp, a climate scientist at Rutgers University. Sea levels dropped about 8 centimeters — roughly 3 inches — during a global cooling period that took place between 1000 and 1400 CE. This cooling likely happened as the planet’s orbit changed and volcanic activity increased releasing aerosols. But then sea level trends did the opposite during the warming that began around the 19th century, Kopp said.

Using the statistical relationship between temperature and rate of sea level change, researchers then calculated how much sea level rise would have happened in the 20th century without global warming. “We can say with 95 percent probability that [sea level rise] would have been less than half of what we actually saw,” said Kopp, noting “it is very likely that sea level [trends] would have been somewhere between a fall of about 3 centimeters and a rise of about 7 centimeters.”

Last century’s average global sea level rose about 14 centimeters, or five inches, he said.

Most scientists reached by ThinkProgress said they hope new research will narrow down into what sea level rise will be like at the local level. The idea is that coastal city planners and policymakers will be better equipped to mitigate and adapt to a warming world of higher sea levels. In fact, Potsdam researchers are making their tools available online so other experts can look into the data.

Some scientists, however, warn that even projected sea level rise trends proposed in Monday’s research should be used with caution. “I think the most important point to take away from this is not the agreement between the different modeling techniques,” said Dutton, “but that both of these approaches to modeling future sea level rise are probably underestimating the rate of sea level rise.”

Meanwhile, residents and officials in Taholah said they are concerned about what the future of sea level rise and climate change holds for them as they get ready to evacuate. Kathy Rosenmeyer, 58, lives three blocks away from the coast and said she’s already instructed her daughter who lives next door to not wait for her, and instead “just drive away” if the seawall that protects their area breaches.

“I guess we’ve pretty much figured if anything disastrous happens we are gone,” she said. “I know it’s not safe where I live.”

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