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UN report forecasts rising seas, temperatures threatening coastal cities

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A new IPCC report on our oceans finds a troubling brew of higher temperatures, melting ice, and more violent storms

A woman stands on a seawall on Majuro Atoll.
Without serious efforts to mitigate carbon emissions, the oceans could rise an average of 1.1 meters by 2100, which would completely reshape coastlines, plunge major cities underwater, and displace millions
Genevieve French / Greenpeace

Today’s release of the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC), focused on our seas and frozen lands, underscores the accelerating risks to our planet, especially to coastal cities. Scientists found that low-lying coastal zones, home to 680 million people, or 10 percent of the world’s 2010 population, are under extreme risk of a combination of increased sea level rise, more extreme weather, and more frequent and strong storms.

Without serious efforts to mitigate carbon emissions, the oceans could rise an average of 1.1 meters by 2100, according to the Intergovernmental Panel on Climate Change, or IPCC, which would completely reshape coastlines, plunge major cities underwater, and displace millions. And that’s what scientists can predict; according to Regine Hock of the University of Alaska Fairbanks, a coauthor of the report and a glacier expert, “the sea level rise can go way beyond [that] because of this potential instability of the West Antarctic ice sheet.”

Paris Mayor Anne Hidalgo, chair of C40, an alliance of international cities fighting climate change, said the report makes for “shocking reading,” offering more evidence that we’re in a climate emergency city leaders must respond to immediately.

“The world’s coasts provide a home to around 1.9 billion people and over half of the world’s megacities, all of which are in grave danger if we don’t act immediately to prevent rising temperatures and sea levels,” she said in a statement. “Extreme high temperatures, coastal flooding, and more frequent natural disasters are becoming the new normal. Several cities, home to hundreds of thousands of people, are already disappearing underwater. This is what the climate crisis looks like now.”

A For Sale sign pokes out above floodwaters in a Florida street.
An apartment for rent sign is seen in a flooded street in Fort Lauderdale, Florida, on September 30, 2015.
Getty Images

Rising coastlines and rougher weather

The report, drawn from almost 7,000 papers by over 100 leading climate scientists, expresses virtual certainty that the global ocean has warmed unabated since 1970, soaking up more than 90 percent of the excess heat in the climate system. The rate of warming has doubled since 1993, leading to ocean acidification, deoxygenation, decreased populations of fish and marine life, and a sharp increase in marine heatwaves.

Increased global temperatures have melted polar ice, as well as glaciers around the world; in the western U.S., many small glaciers will disappear in the coming decades, the report notes, impacting agricultural practices and hydroelectric power generation. The Greenland ice sheet is shrinking three times faster than it was a decade ago, and the Antarctic ice sheet is thawing at a rapidly increasing rate; the ice loss between 2007 and 2016 is triple that recorded between 1997 and 2006.

Hotter temperatures and higher oceans mean more and stronger storms, and increasing storm surges and flooding. During a call with press yesterday to discuss the report’s conclusions, IPCC Vice Chair Ko Barrett said the impacts delivered by tropical cyclones and hurricanes have become “significantly worse” due to climate change, in part because these storms are loaded with more rainfall and the resulting storm surge is riding higher due to rising seas. There’s also increasing evidence these storms are stronger and more frequent. Extreme El Niño and La Niña events, which can cause dramatic swings in global weather patterns, are projected to become twice as frequent.

This more extreme weather means that extreme sea level events—historically rare storms that caused extensive flooding once per century—are expected to happen much more frequently, and in some places annually, by 2050.

These accelerating shifts spell increasing risk for those living on or near the ocean. A report last year by the Union for Concerned Scientists, “Underwater: Rising Seas, Chronic Floods, and the Implications for U.S. Coastal Real Estate,” predicted that 300,000 residential and commercial properties will likely face chronic and disruptive flooding by 2045, threatening $135 billion in property damage and forcing 280,000 Americans to adapt or relocate. The U.S has already experienced a significant rise in billion-dollar weather and climate disasters over the last few years. The SROCC report suggests the number of unprecedented monster storms—Harvey in Houston, Florence in the Carolinas, Michael on the Panhandle, and Maria in Puerto Rico—will become even more frighteningly commonplace.

People rush to find safety and higher ground as floodwaters rush in and inundate a neighborhood.
The more extreme weather predicted in the latest IPCC report means that extreme sea level events—historically rare storms that caused extensive flooding once per century—are expected to happen much more frequently, and in some places, annually by 2050.
© Greenpeace / Jeremy Sutton-Hi

What can be done?

The report details different emissions scenarios, or “representative concentration pathways,” with the RCP 2.6—an aggressive response to climate change and meeting emissions targets—resulting in less drastic sea level rise than RCP 8.5, a future where no serious mitigation or action is undertaken.

But in addition to immediately adopting emergency measures to reduce carbon emissions, the report recommends that countries prepare today for the physical impact of rising waters: We have to adapt to and manage the changes to the ocean and environment that we can no longer avoid, an effort that will require tens to several hundreds of billions of dollars in investment per year. This includes “hard protection,” such as sea walls and other infrastructure, which the authors suggest can be a cost-efficient response, though one that may not be affordable to many resource-limited areas.

The U.S could do quite a few things to begin addressing the scope of the climate challenge, especially when it comes to coastal flooding and rising sea levels. Our leaders could discuss whether or not to retreat from threatened areas (and make the program to buy-back property in low-lying areas speedier and more efficient), or invest in a massive plan for resilient infrastructure. The nation could strengthen building codes. It could also reform the series of programs, including the National Flood Insurance, FEMA flood mapping, and community development block grants, for rebuilding after storms, which form the backbone of the nation’s response to hurricanes.

But so far, the nation hasn’t engaged in such a serious dialogue. This summer, the National Flood Insurance Program, set to expire September 30, was the subject of competing bills in Congress and a genuine effort to reform. But nothing was passed, and the program is only set to be solvent next month due to a continuing resolution that keeps government programs operating as they were before. With so much residential and commercial property at risk, not to mention neighborhoods and cities, it seems well past time to take action.

The SROCC notes that, while completely accurate projections about sea level rise post 2050 depend on the dynamics of our collective response to climate change, important decisions now around critical infrastructure, coastal protection, and city planning can, with foresight, prove valuable, especially if they’re made with flexible responses in mind. Politicians and planners still have time to make smart decisions to prepare for a future shaped by rougher waters.

“The scientific evidence of the damage that fossil fuel powered societies are wreaking on the natural world is now unequivocal and impossible to ignore,” says Hidalgo. “Fortunately, we also know what needs to be done to prevent complete climate breakdown. Emissions must peak by 2020, and halve by 2030. At least 27 of the world’s largest cities are already on this trajectory, with more than 100 committed to similar levels of ambition.”