Rising Seas From Fossil Fuels Threaten Inland Migration 'Never Witnessed in Modern Civilization'

Less than six months away from the next United Nations summit for parties to the Paris climate agreement, scientists on Tuesday released a study showing that even meeting the deal's 1.5°C temperature target could lead to significant sea-level rise that drives seriously disruptive migration inland.

Governments that signed on to the 2015 treaty aim to take action to limit global temperature rise by 2100 to 1.5°C beyond preindustrial levels. Last year was not only the hottest in human history but also the first in which the average global temperature exceeded 1.5°C. Multiple studies have warned of major impacts from even temporarily overshooting the target, bolstering demands for policymakers to dramatically rein in planet-heating fossil fuels.

The study published Tuesday in the journal Nature Communications Earth and Environment warns that 1.5°C "is too high" and even the current 1.2°C, "if sustained, is likely to generate several meters of sea-level rise over the coming centuries, causing extensive loss and damage to coastal populations and challenging the implementation of adaptation measures."

"To avoid this requires a global mean temperature that is cooler than present and which we hypothesize to be closer to +1°C above preindustrial, possibly even lower, but further work is urgently required to more precisely determine a 'safe limit' for ice sheets," the paper states, referring to Antarctica and Greenland's continental glaciers.

Co-author Jonathan Bamber told journalists that "what we mean by safe limit is one which allows some level of adaptation, rather than catastrophic inland migration and forced migration, and the safe limit is roughly 1 centimeter a year of sea-level rise."

"If you get to that, then it becomes extremely challenging for any kind of adaptation, and you're going to see massive land migration on scales that we've never witnessed in modern civilization," said the University of Bristol professor.

In terms of timing, study lead author Chris Stokes, from the United Kingdom's Durham University, said in a statement that "rates of 1 centimeter per year are not out of the question within the lifetime of our young people."

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There are currently around 8.18 billion people on the planet. The study—funded by the United Kingdom's Natural Environment Research Council—says that "continued mass loss from ice sheets poses an existential threat to the world's coastal populations, with an estimated 1 billion people inhabiting land less than 10 meters above sea level and around 230 million living within 1 meter."

"Without adaptation, conservative estimates suggest that 20 centimeters of [sea-level rise] by 2050 would lead to average global flood losses of $1 trillion or more per year for the world's 136 largest coastal cities," says the study, also co-authored by University of Wisconsin-Madison professor Andrea Dutton and University of Massachusetts Amherst's Rob DeConto in the United States.

DeConto said Tuesday that "it is important to stress that these accelerating changes in the ice sheets and their contributions to sea level should be considered permanent on multigenerational timescales."

"Even if the Earth returns to its preindustrial temperature, it will still take hundreds to perhaps thousands of years for the ice sheets to recover," the professor explained. "If too much ice is lost, parts of these ice sheets may not recover until the Earth enters the next ice age. In other words, land lost to sea-level rise from melting ice sheets will be lost for a very, very long time. That's why it is so critical to limit warming in the first place."

While the paper sparked some international alarm, Stokes highlighted what he called "a reason for hope," which is that "we only have to go back to the early 1990s to find a time when the ice sheets looked far healthier."

"Global temperatures were around 1°C above preindustrial back then, and carbon dioxide concentrations were 350 parts per million, which others have suggested is a much safer limit for planet Earth," he said. "Carbon dioxide concentrations are currently around 424 parts per million and continue to increase."

The new paper continues an intense stream of bleak studies on the worsening climate emergency, and specifically, looming sea-level rise. Another, published by the journal Nature in February, shows that glaciers have lost an average of 273 billion metric tons of ice annually since 2000.

Despite scientists' warnings, the government whose country is responsible for the largest share of historical planet-heating emissions, the United States, is actually working to boost the fossil fuel industry. Upon returning to office in January, U.S. President Donald Trump declared an "energy emergency" and ditched the Paris agreement.

Responding to the new study on social media, Scottish ecologist Alan Watson Featherstone called out both the U.S. and U.K. governments. He said that with many countries "scaling back their already meager and [totally] inadequate actions to address climate breakdown, our present-day human culture is on a suicide course."