Hurricane Katrina was the costliest hurricane ever to make landfall in the U.S. Even now, seven years after the storm, many of my Louisiana friends still bear emotional and financial scars. So it’s a bit spooky to watch Hurricane Isaac take nearly the same path as Katrina over the Gulf of Mexico.

As Isaac has moved north over the Gulf’s warm waters, it has strengthened from a tropical storm to a Category 1 hurricane. The good news is that the New Orleans levees that failed so catastrophically during Katrina are now stronger and taller.

And now the bad news: Low-lying communities outside the levee system will probably flood as Isaac pushes ocean water ashore. This phenomenon, called “storm surge,” is typically more dangerous than wind or rain from a hurricane.

Unfortunately, sea level rise is increasing the flooding risk from even relatively weak storms like Isaac. This is true along the Gulf Coast, which is experiencing the highest rate of sea level rise in the U.S. It’s true in other parts of the world too, like New York City and Shanghai.

Meanwhile, climate change is expected to make the air warmer and more humid, which could increase the intensity of hurricanes. The more intense the storm, the bigger the storm surge.

With a little luck, Isaac will leave Louisiana and Mississippi residents unscathed. But as the residents of New Orleans can tell you, it only takes one intense hurricane to cause years of grief. The best evidence suggests hurricanes will get more dangerous as the world warms and sea levels rise. And the more global warming pollution we put into the atmosphere, the worse things will get.