For decades, environmental advocates have urged governments, companies, and individuals to take drastic actions to limit climate change and prevent the Earth’s average temperature from exceeding 1.5 degrees Celsius (2.7 degrees Fahrenheit) over pre-industrial times.
Now, some climate experts are advocating for a different target: They want to create limits for rising seas instead, setting the upper limit at about two feet or slightly higher, depending on the location. Relative sea levels along the U.S. coast have already climbed about a foot and could swell up to six more by 2100 if greenhouse gas emissions from fossil fuels and methane are not significantly curbed.
“Sea-level rise is an easily understood impact of climate change since it’s direct, visible, and growing,” says Rafe Pomerance, a former environmental expert in the federal government who coauthored an opinion article on this topic and has been urging policymakers to recognize the salience of rising seas, especially in Florida, which is particularly vulnerable.
Why is sea level rise dangerous?
Earth’s rising temperatures expand ocean molecules and melt land glaciers across the world, elevating water levels. Shifting the focus to the damage this water produces locally makes sense, Pomerance says, because it “directly describes people’s lives and property that are at stake.”
While the coast of the U.S. accounts for only 10 percent of the continental land mass, some 40 percent of the population currently lives near there. Rising oceans are also important globally, since low-lying countries like Bangladesh and the Netherlands face “a death sentence” as water infiltrates vast areas if the current trajectory isn’t altered, according to the United Nations Secretary-General.
The 1.5-degree Celsius warming target is “meaningless to most Americans,” agrees Anthony Leiserowitz, director of Yale University’s Program on Climate Change Communication. People often mistakenly think such a small number is inconsequential, because they don’t know that average temperatures have been so stable during the past 10,000 years that a single degree change has “led to the rise and fall of empires,” he says. Plus, there’s confusion in the U.S. about a goal not rendered in Fahrenheit.
Rising seas are among the most consequential effects of climate change, says Alice C. Hill, an expert on energy and the environment at the nonprofit Council on Foreign Relations in Washington, D.C., who coauthored the opinion piece. Higher coastal levels don’t only damage homes near the ocean, but also impact communities even miles inland, she says. Roads, public transportation, sanitation systems, water treatment plants and drinking wells, electrical grids, and agricultural fields can all be damaged. Moreover, during hurricanes, storm surges that start from a higher ocean level can greatly increase destruction.
(Learn more about how rising temperatures will impact life on Earth.)
Communicating these impacts is important for encouraging the quicker adoption of climate solutions like renewable energy, Pomerance says. Focusing on temperature hasn’t sufficiently motivated change, which is why last year was the hottest on record, with global temperatures nearing the 1.5-degree Celsius limit.
Individuals can use websites from the National Oceanic and Atmospheric Administration and the nonprofit Climate Central to determine how much the rising ocean will affect their specific coastline, which is influenced by numerous factors including topography and ocean currents. The free sites allow users to digitally raise the local water level one foot at a time to observe the flooding effects.
Using federal government flood maps is a less accurate predictor, Hill says, because “the maps are old and not updated and they do not typically reflect climate risk.”
Understanding what will be lost
Scientists are increasingly documenting how communities are being damaged by rising seas. University of Washington scientists who combined sea-level projections with topographies along Washington’s coast found some parts of Seattle and other areas will be permanently underwater if worst-case projections are realized. Even at lower levels, certain drinking water wells and agricultural fields will be impacted.
“There could be places where agriculture is no longer viable,” says Guillaume Mauger, a scientist in the university’s Climate Impacts Group who worked on the projections.
The Florida Keys, a low-lying chain of islands south of Miami, has estimated that nearly half the roads in the county will be at least occasionally impassible in fewer than 25 years under moderate estimates of ocean increases. Certain parts of New York City are also threatened by a rise experts have called the fastest in the area in 1,500 years.
These changes will trigger a five to 18-fold increase in the number of Americans moving away from affected communities, researchers at Florida State University recently calculated. Experts are already mapping out “managed retreat” options for parts of Louisiana’s Gulf Coast, Houston, and other U.S. communities when the water becomes untenable.
People may decide to leave communities well before they’re permanently under water, Hill says, due to periodic nuisance flooding, like that already seen in Miami, which makes everyday activities difficult. She worries this could sink property values in many areas.
How to communicate a global crisis
Not everyone agrees that rising oceans make for an ideal climate communications message.
“There’s no silver bullets” when it comes to getting people to recognize the impending effects and the urgency of action, Leiserowitz says. People in the middle of the U.S. and other countries are not directly affected and those even a few miles from the coast may not realize they’ll be impacted. “Climate change is difficult to communicate… [A person’s] ability to understand what’s going on, on this planet at all times is incredibly constrained,” Leiserowitz says.
Unpublished recent research by Matto Mildenberger at the University of California, Santa Barbara and others confirms this challenge. Showing people maps of local sea-level rise projections for the year 2100 produced mixed results. Concern was actually reduced in households most likely to be flooded, but it rose—along with support for costly climate reduction policies—when people were told traffic and commute times would soar from roads damaged by rising waters.
This follows a prior study by Mildenberger that found people shown information that their own home is at high risk for flooding nonetheless think it will be other, more geographically-distant people who will be harmed by climate change.
Still, focusing on water damage instead of temperature rise is worthwhile, Hill says. Communities will be vastly altered or damaged beyond repair by coastal flooding, but many residents aren’t paying sufficient attention.
This rise will inevitably lead to loss of land and services; the higher the rise, the more loss there will be.
“How much loss is too much for communities to accept, and what’s required to keep sea-level rise below that?” Pomerance says. “That question has never been asked explicitly before.”