Sea Level Rising, A Few Millimeters At A Time
Wetlands south of New Orleans. Photo by Brett Duke
As with most people who lived it, the Great Depression left my mother with an unshakeable belief in the value of small change. If she found a product for sale just a penny-a-pound less than at the nearby store she would drag her (loudly) complaining children to that location.
Her standard explanation: “Pennies make nickels, nickels make quarters, and quarters make dollars. All those pennies can add up to something big.”
I couldn’t help thinking about mom as Rick Leuttich, one of the world’s experts on hurricane storm surge, explained the very big importance of today’s very small increases in global sea level rise.
Last century sea level rise averaged 1.4 millimeters per year, but more than doubled between 2006 and 2015 to 3.6 mm and now is pushing past 3.8 mm per year.
Those small but rising figures have climate scientists shouting the alarm not just because that accelerating trend could add a foot or more to the height of the Gulf of Mexico by the end of this century, but for the dangers tiny increases represent right now.
Yet when the average person pulls up a metric conversion table, the reaction is: Get a grip, scientists!
That’s hardly a quarter of an inch.
But Leuttich, a former member of our regional levee authority, says those small changes are adding up to some big numbers people are already beginning to see — especially for those living behind flood walls and levees build decades ago.
“Those small increases in sea level are happening every year but we don’t notice them because we haven’t had a major storm, and the level of protection we had for that decade has never been tested,” he said.
“Well, eventually you have a storm and now surge waves are coming over the top of that levee when they never did before in storms of the same size and magnitude.
“That’s because storm surge comes on top of the current sea level — which is now higher than it was before. And those few inches can change everything.”
And, of course, our subsidence problems only add to the significance of every millimeter of sea level rise here.
There are plenty of examples in our recent history of how this change is already costing us serious money. Until the 1990s, north shore real estate was considered a safe haven from storm surge. But now tropical storms and minor hurricanes routinely push water over the sea wall in Mandeville and soak neighborhoods in LaPlace and other River Parishes communities.
