The findings show that some 150 million people are now living on land that will be below the high-tide line by midcentury.

What changed: The standard way of calculating land elevation is based on satellite readings, but they often don’t differentiate true ground level from the tops of trees or buildings. The researchers used artificial intelligence to determine the error rate and correct for it.

Hope: The new data shows that 110 million people already live in places that are below the high-tide line, demonstrating the effectiveness of protective measures like sea walls and other barriers.

Impeachment inquiry hears from first current White House official

Lt. Col. Alexander Vindman, a Ukraine expert on the National Security Council, on Tuesday told House impeachment investigators that he heard President Trump appeal to Ukraine’s president to investigate former Vice President Joe Biden during their July 25 phone call.

He is the only witness so far who listened in on the phone call, which is central to the inquiry, and he told officials that he had reported his concerns about the exchange to a White House lawyer.

Mr. Trump attempted to undercut Colonel Vindman’s credibility, accusing him on Twitter of being a political opponent.