In what may prove to be a turning point for political action on climate change, a breathtaking new study casts extreme doubt about the near-term stability of global sea levels.
The study—written by James Hansen, NASA’s former lead climate scientist, and 16 co-authors, many of whom are considered among the top in their fields—concludes that glaciers in Greenland and Antarctica will melt 10 times faster than previous consensus estimates, resulting in sea level rise of at least 10 feet in as little as 50 years. The study, which has not yet been peer reviewed, brings new importance to a feedback loop in the ocean near Antarctica that results in cooler freshwater from melting glaciers forcing warmer, saltier water underneath the ice sheets, speeding up the melting rate. Hansen, who is known for being alarmist and also right, acknowledges that his study implies change far beyond previous consensus estimates. In a conference call with reporters, he said he hoped the new findings would be “substantially more persuasive than anything previously published.” I certainly find them to be.
To come to their findings, the authors used a mixture of paleoclimate records, computer models, and observations of current rates of sea level rise, but “the real world is moving somewhat faster than the model,” Hansen says.
Hansen’s study does not attempt to predict the precise timing of the feedback loop, only that it is “likely” to occur this century. The implications are mindboggling: In the study’s likely scenario, New York City—and every other coastal city on the planet—may only have a few more decades of habitability left. That dire prediction, in Hansen’s view, requires “emergency cooperation among nations.”
We conclude that continued high emissions will make multi-meter sea level rise practically unavoidable and likely to occur this century. Social disruption and economic consequences of such large sea level rise could be devastating. It is not difficult to imagine that conflicts arising from forced migrations and economic collapse might make the planet ungovernable, threatening the fabric of civilization.
The science of ice melt rates is advancing so fast, scientists have generally been reluctant to put a number to what is essentially an unpredictable, non-linear response of ice sheets to a steadily warming ocean. With Hansen’s new study, that changes in a dramatic way. One of the study’s co-authors is Eric Rignot, whose own study last year found that glacial melt from West Antarctica now appears to be “unstoppable.” Chris Mooney, writing for Mother Jones, called that study a “holy shit” moment for the climate.
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