A flood like the one that ravaged Louisiana over the past few days has a 0.2 percent chance of occurring any given year and should only occur once every 500 to 1,000 years, according to scientists at the National Oceanic and Atmospheric Administration (NOAA).
But there have been eight such storms in the United States alone since May 2015.
Since Friday, when the flooding in Louisiana began, an estimated 40,000 homes were damaged and 30,000 people were rescued from the historic levels of flooding after the state saw two feet of rain in less than two days.
And Louisiana is not alone. In the last 15 months, Oklahoma, Texas, South Carolina, Maryland and West Virginia all experienced devastating floods – resulting in widespread injury, property damage, economic loss, and death – that give insight into what climate change looks like in action.
“This is an unprecedented event here,” Barry Keim, the state climatologist, told the Seattle Times. “There is nothing in the recent past that even comes close.”
The US has been hit particularly hard in the last year and half, but the problem is occurring all over the world.
“While Louisiana was flooding, there were also huge flood events under way in Moscow (biggest rains in 129 years of record-keeping), the Sudan, Manila, and probably plenty of other places,” climate activist Bill McKibben told the Seattle Times.
The global south in particular is both more vulnerable to the effects of climate change and less equipped to deal with those effects, The Washington Post reports, pointing to the increasingly violent monsoons in southeast Asia and droughts in the Sahara as places where the impacts of climate change are felt first and worst.
“There’s definitely an increase in heavy rainfall due to climate change,” John Nielsen-Gammon, the state climatologist in Texas, told The New York Times. “The actual increase from place to place is going to be variable because of the randomness of the weather. Some places will see a dramatic change.”
Scientists are often hesitant to attribute that dramatic change entirely to climate change, since storms have always been a part of the planet's weather, but there is no doubt that weather patterns are getting more extreme and that human behavior such as air pollution and unsustainable water and land management strategies have contributed.
Storms like the one in Louisiana occur, say climatologists, when heat-trapping gases are released into the air from fossil fuels used in electricity generation, motor vehicles, and industrial processes. Other greenhouse gases are produced by livestock raising practices, irrigation, and fertilizers. These gases are capable of trapping excess water vapor in the air, which gives the atmosphere more heat-trapping ability and fuel storms that drop the hurricane-levels of rain that Louisiana experienced this week.
“We’re in a system inherently capable of producing more floods,” Kenneth Kunkel, of the Cooperative Institute for Climate and Satellites, told the Guardian. “Assuming we don’t change our ways, warming is a virtual certainty and increased water vapor is virtual certainty. That means increases in heavy rainfall is virtual certainty.”
These storms are able to do so much damage in part because the current infrastructure was built for the pre-climate change environment.
“It’s prudent to consider that if you’re building something with a 100-year lifetime, it’s virtually certain that it will experience an increase in extreme rainfall,” Dr. Kunkel told the Guardian. “We either pay now or pay later. If we build resilience into infrastructure, we can protect life and property.”