The rising seas global warming has already locked in

While debate rages about how to fight climate change, the impacts that rising temperatures have already locked in are getting worse.

Why it matters: We’re learning more about how much of the damage is irreversible, like with rising sea levels — which means we need to think about not just stopping the problem, but also about adapting to the parts we can't stop.

Driving the news: Rising sea levels will threaten 40 million more people — three times that of previous estimates — over the next 30 years, new research says. Poorer Asian countries are most at risk.

What they’re saying: “Most sea level rise between now and 2050 is already baked in,” said Benjamin Strauss, co-author of the peer-reviewed report by science organization Climate Central.

The big picture: Most political attention focuses on how to slow climate change by cutting greenhouse gas emissions that are increasing Earth’s temperature, but an equally consequential part of this problem is adapting to a warmer world we’re already living in — and which we'll be living in no matter what in the coming decades.

What’s new: The researchers used a more sophisticated method of determining “the true ground level from the tops of trees or buildings,” co-author Scott Kulp told the NYT.

• This method has already been used in more developed parts of the world, but not Asia, which is one reason the projected impacts are newest and most dire there.
• “The numbers are biggest in Asia generally because there is such high-population density and it is so concentrated in the lowest elevations toward the coast,” Strauss said.
• The research doesn’t account for population growth, so the impact could be even greater if these countries keep growing, which they’re expected to.

How it works: The research finds that 40 million more people will live in areas below high-tide levels by 2050 — which means, Strauss said, that “either you get coastal defense or you better move.”

• This increase is on top of the 110 million people already living below high-tide levels with protection from infrastructure, like levees.
• “While levees can protect us, they may also give us a false sense of security, because when they fail the results can be catastrophic,” said Strauss, noting the challenges facing New Orleans.

What we’re watching: Strauss hopes that this research galvanizes cities to better prepare for rising seas that are inevitably coming, but also momentum to cut emissions to limit the worst impacts by the end of this century.

• His research suggests that if we continue business as usual — emissions left mostly unchecked — up to 200 million more people will be at risk by 2100.

Editor's note: The graphic in this story has been corrected to note that 760,000 people were estimated to be below high tide levels in the U.S. in 2010, not 76,000.