Los Angeles underwaterMarch 24, 2011
There is good news and bad news coming out of California. The bad news is that the Chicken Littles are clucking about sea level rise. The good news is that at least some coastal communities are acting sensibly instead of panicking.
The Bad News
We live in trying times. As our greatest minds peer into the future through their climate models we are only now beginning to understand the appalling fate that awaits us in an overheated, over-carbonized world. Los Angeles is the latest city to be warned of its frightful destiny.
According to the Los Angeles Times
Sea levels have risen about 8 inches in the last century, and scientists expect them to rise several feet by the end of this century as climate change warms the ocean.
The hardest hit area of Los Angeles would be the Harbor/San Pedro/Long Beach region. As the LA Times notes, global seas rose by about 8 inches during the last century. Let’s see what impact this rise has had along the Harbor area of Los Angeles. The following animation was made from a detail of a 1912 T. Newman map of Los Angeles county and from a 2011 Google Earth image. The top half is photoshopped to clearly demarcate the land and water.
I can just hear the Chicken Littles clucking “Sure, the Los Angeles harbor region gained ground during the 20th century. But that was with only 8 inches of sea level rise. And everybody knows that the sea level rise rate along the california coast is rapidly increasing due to global warming.”
Not so fast, Mr Little. Here is the relative sea level at Los Angeles for the last 85 years from the National Oceanic and Atmospheric Administration (NOAA). Click to see the graph in context at the NOAA website.
Wait a minute, only 0.83 mm per year? That’s only 83 mm (or 3.5 inches) per century. And there is no acceleration that I can see. It is kind of hard to believe there will be “several feet by the end of this century.”
What would be the consequences of “several feet [of sea level rise] by the end of this century?” The bad news for Los Angeles and California was first revealed in the Pacific Institute’s “The Impacts of Sea-Level Rise on the California Coast.” They considered the devastation that will be wrought by a 1.4 meter (4.6 feet) sea level rise (based on the seminal work of Stefan Rahmstorf) during the 21st century.
The Pacific Institute created Hazard Maps of sections of the California coast that would be inundated by a 100 year flood event with sea levels at their current level and with sea levels 1.4 meters higher. I have stitched together several of those maps to show the region from the Los Angeles Harbor over to the Seal Beach area. The light blue areas show the places that the Pacific institute figures would be inundated in a 100 year flood with year 2000 sea levels. The dark blue areas show the places that they think would be flooded with the same 100 year event and an additional 1.4 meters of sea level.
But with the present, nearly steady, sea level rise rate the sea level will only go up by 0.083 meters (about 3.5 inches) in 100 years. Roughly speaking, if there is no acceleration in sea level rise rate near Los Angeles, then only about 6% of the dark blue areas would actually flood.
Sea level rise rates would have to increase unrealistically to get to an extras 1.4 meters in the 21st century. We are 10 years into the century so far, and the sea level near Los Angeles has gone up only about 8 millimeters. That leaves 1,392 millimeters to go in the next 90 years. Here are a few hypothetical of sea level rise rate scenarios for the 21st century that would get us those 1392 millimeters…
These scenarios don’t look very promising, do they? If we could somehow increase the sea level rise rate in Los Angeles harbor from its present value of 0.83 milimeters per year up to about 15 mm/year (a minor 18 fold increase) overnight, and keep it there for the next 90 years we could reach that target of 1.4 meters of sea level rise for the century. Or we could try a linearly increasing sea level rise rate that gets to about 30 mm/year by 2100. That’s a whopping 36 fold increase from today’s rate by 2100.
Here’s the deal: The sea level at Los Angeles has an acceleration 0.0019 mm/year/year. Unless there is a gigantic increase in that rise rate, then the seas will rise by only about 12 cm in this century. And there is zero indication that the sea level rise rate in Los Angeles has increased a whit in the last 85 years.
The good news
Although the Los Angeles Times article tries to impart a notion of acquiesence to the sea level rise scare by the “conservative city” of Newport Beach, they go on to say…
“…city planners are looking at raising seawalls by a foot or more to hold back the ocean.”
Wow, a whole one foot to protect from 1.4 meters (4.5 feet) of sea level rise. Seems like the city planners in Newport Beach agree with my assesment more than with the 1.4 meter scare predicted by Mr. Rahmstorf.