By 2050, sea levels are projected to rise by up to a foot


Los Angeles and other coastal areas of the United States will face frequent flooding, degraded infrastructure and other profound challenges if sea levels rise by as much as 1 foot by 2050, a federal study released Tuesday found.

The report outlines an alarming new future for communities, ecosystems and economies along the nation’s coast, and predicts that over the next 30 years, the US coast will see sea-level rise as sharp as it has seen in the past hundred.

“It’s telling — thirty years, 2050, is not far off,” said Ben Hamlington, a research scientist at NASA’s Jet Propulsion Laboratory in La Cañada Flintridge and one of the report’s lead authors.

Researchers found that sea level along the United States coast will rise an average of 10 to 12 inches by 2050. On the west coast, the expected rise will be as much as 8 inches.

Although a one-foot rise in sea level might not sound like much to some people, it would contribute to a significant increase in the frequency of coastal flooding — even in the absence of storms or heavy rains, researchers said.

According to the report, the two main causes of sea level rise are the expansion of ocean water with warming and the melting of ice sheets and glaciers. Both processes are driven by increased global temperatures related to fossil fuels and greenhouse gas emissions.

“One of the first ways we feel 10 inches is caused by high tide or nuisance flooding,” Hamlington said, noting that West Coast communities that already see occasional flooding during King Floods will soon experience a new breed of “Flooding regimes” where even small tides send seawater ashore.

Even regular El Niño events off the west coast, already associated with higher sea levels, are being piled onto this higher foundation.

“As elsewhere on the West Coast, our sea level rise is very closely linked to global warming,” Hamlington said.

The prospect of sea-level rise in California meeting western mega-drought conditions only adds to the region’s uniquely precarious position.

Although the drought and sea-level rise are not directly linked, “they are both consequences and negative impacts that we expect with global warming,” he said.

The report, which updates the 2017 federal sea level projections, was led by researchers from the National Oceanic and Atmospheric Administration, NASA, the US Geological Survey and other government agencies. Together, they stressed that sea-level rise caused by global climate change is already a “clear and present risk” for the nation and will continue to worsen in the coming decades and centuries without immediate action.

The researchers used tide gauges, satellite observations and computer models to narrow predictions of sea level rise with increasing precision, they said.

“This report is a wake-up call for the United States,” NOAA Administrator Rick Spinrad told reporters. “It’s a wake-up call with a silver lining: it gives us the information we need to act now and position ourselves optimally for the future.”

Tens of millions of people in the United States and hundreds of millions of people worldwide live in areas at risk of coastal flooding.

The East Coast could see sea-level rises of up to 14 inches and the Gulf Coast up to 18 inches by 2050, according to the report, with regional variations mainly due to changes in land elevation.

In addition, “sea-level rise is not acting alone,” the researchers said. Sinking land, storm surges, wave action and other coastal flooding factors combine to significantly increase the vulnerability of communities along the coast.

Moderate flooding, which can already be damaging and disruptive by today’s standards, is projected to be 10 times more common by 2050 than it is today, according to Nicole LeBoeuf, director of the NOAA National Ocean Service.

Rising sea levels also pose a critical risk to infrastructure such as roads, water supplies, power plants, oil and gas wells and wastewater treatment systems, as well as almost “everything we use, eat and wear” that comes and arrives through the supply chain, coastal ports said LeBoeuf during the press conference.

“The magnitude of these direct and cascading impacts will be high,” she said, noting that 40% of the US population lives within 60 miles of the coast. “There will be very different impacts along those shores, but there’s no denying that a large part of our economy and our revenue and tax base is paramount right there.”

In California, the impact could be acute: Daily flooding over land a foot above sea level puts about $15 billion worth of real estate at risk and would affect about 38,000 people, according to Patrick Barnard, a USGS research geologist who also worked on the project Report.

The daily emergence of groundwater, pushed up by rising sea levels, could also expose another 350,000 people and $100 billion worth of property, he said.

“There are definitely many low-lying communities that are experiencing seasonal or annual flooding today,” Barnard said. Venice, Seal Beach, Newport and parts of Huntington Beach are examples. “They are already on a razor’s edge, and another one foot rise in sea level will increase the frequency of flooding in these communities.”

Coastal erosion — already a problem in California, Louisiana, and South Florida — will also worsen as the waters rise, eroding oceanfront cliffs, threatening local real estate, and changing ecosystems and shorelines forever.

Barnard said it’s hard to imagine coastal urban areas like Los Angeles retreating completely, but “it’s definitely getting more costly to defend the coast and more costly to conserve beaches.”

And while some residents may choose to relocate, many of the communities most vulnerable to coastal flooding and other climate change hazards are low-income communities with restricted mobility, according to a separate Los Angeles County report released late last year .

The response to sea-level rise increasingly includes adaptation and mitigation in addition to prevention. Sea levels will continue to rise in the coming decades and centuries, even as global emissions and temperatures fall, the latest report says. This is largely due to the ocean’s ongoing response to the warming that has already occurred.

But that doesn’t mean all hope is lost. While projections for 2050 are more certain, the researchers said reductions in current and future emissions could still change the rate of sea-level rise in the future.

“Failing to curb future emissions could have an even bigger impact on Americans,” Spinrad told reporters.

Specifically, according to the report, failure to curb future emissions could result in an additional increase of 1.5 to 5 feet by 2100.

Even greater sea level rise is possible if global warming exceeds 5.5 degrees due to rapid melting of the ice sheets. NOAA found last year that the planet’s average land and ocean surface temperature was 1.51 degrees higher than the 20th-century average.

“It is important to emphasize that this report supports previous studies and confirms what we have known all along, which is that sea levels continue to rise at a very alarming rate, endangering communities around the world,” NASA Administrator said Bill Nelson.

The researchers hoped their findings would provide a basis for an urgent and appropriate response.

USGS’ Barnard said California is in many ways ahead of the curve when it comes to considering the projections and developing policy guidance, while JPL’s Hamlington said some policymakers and related groups in the state have already come forward about the inclusion her work.

“This underscores the immediacy of the problem,” Hamlington said, “both in terms of the sea level rise that we expect and the flooding that we expect.” By 2050, sea levels are projected to rise by up to a foot

Tom Vazquez

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