What can Hurricane Isaac teach us about climate vulnerability?

As with any single event, Hurricane Isaac doesn’t tell us anything about whether hurricanes are getting worse due to climate change. But Isaac’s impacts should be examined to teach us about our vulnerabilities to the types of extreme events scientists tell us climate change will make more common.

While there is nothing unusual about a Category 1 hurricane in late August, its large size and slow speed meant that Isaac’s impacts were more characteristic of a much stronger storm. In some areas the storm surge rivaled that of Hurricane Katrina and the 20 inches of rain that fell in New Orleans (breaking a city record dating back to 1871) would qualify as a spectacularly wet month, let alone single storm. These impacts are consistent with what scientists expect in the future as rising sea level exacerbates storm surge and as hurricanes drop more rain.

The experiences of Louisiana and Mississippi communities as they cope with Isaac’s deluge can help us prepare for future disasters. For example, one legacy of Hurricane Katrina was that New Orleans’ upgraded levee system and emergency procedures were more effective with Hurricane Isaac. While other areas in Louisiana flooded, pumps in New Orleans were able to handle the rain and levees rebuffed a 12-foot storm surge.  In hard-hit Plaquemines Parish, the National Guard was confident they had safely evacuated everyone from the area.

However, there is still more work to be done, as evidenced by the overtopping of levees in Plaquemines Parish and Slidell, Louisiana; mandatory evacuations due to the risk of levee failure at Lake Tangipahoa, Mississippi; and a contaminated water system in St. John the Baptist Parish, Louisiana. As climate change increases the risk of extreme weather, it will be important to improve resilience.

The question is: How much more extreme weather can we take before adaptation efforts are simply insufficient? In the town of Jean Lafitte, Louisiana, Mayor Tim Kerner said, “We can’t do this every year.” While noting that his community was incredibly resilient, the constant flooding was taking a mental and financial toll that few could handle for long. If we are to avoid this fate in the long run, we must both adapt to changing extreme weather risk and act to reduce CO2 emissions today in order to preserve our vulnerable communities.