A man wades along a flooded street as Hurricane Irma hits the Miami area Sept. 10, 2017. (Matt McClain/The Washington Post) Rising seas will be much worse and more expensive to deal with than previously thought, new research finds, not because of faster changes in sea levels but because of an increase in estimates of the number of people living on low ground. The upshot of the study is that 110 million people worldwide live below the high-tide level — including many partly protected by sea walls or other infrastructure, as in New Orleans. Even under a scenario of very modest climate change, that number will rise to 150 million in 2050 and 190 million by 2100. If climate change and sea level rise follow a worse path, as many as 340 million people living below the high-tide level could be in peril, to say nothing of how many […]