Projected California megastorm given added edge by climate change

By Martin Leggett - 08 Mar 2011 12:0:0 GMT
Projected California megastorm given added edge by climate change

Recurring mega-storms hit California every 200 years, and the impact of the next one could be huge, according to a USC economist. At $1 trillion in economic loss, a potential megastorm could easily exceed the damage from the projected San Andreas earthquake - and climate change is boosting their destructive potential.

Californians have long gotten used to living in the shadow of 'The Big One', a magnitude 7.0 earthquake that is predicted to hit the SoCal region hard, at some point in the future. But with an extra ratchet or two from climate change, a projected winter mega-storm, which hits California every 200 years, could, in fact be the 'Biggest One'.

University of Southern California (USC) economist has taken the data from a mega-storm simulation, run by scientists from U.S. Geological Survey (USGS) , to project an economic loss of close to $1 trillion. That is three times more than estimated loss from a major slip along the San Andreas Fault.

And the threat is every bit as real as the earthquake one. The last mega-storm to hit California was in 1861-2, and its consequences were of biblical proportions. 45 days of storm, wind and rain lashed the state, deluging both the Sacramento and San Joaquin Valleys - turning them into a 300 mile long inland sea. Communities were obliterated, and a third of taxable land devastated, leaving California bankrupt.

This was not an unprecedented event - geologists have found a regular punctuation mark, every 200 years, of thick deluge deposits, in Santa Barbara's offshore sediments. Some of these exceeded the scale of the 1861-2 disaster. In order to raise public awareness, and to help plan for the impact of such a storm, two years ago the USGS developed a simulation of a hypothetical mega-storm, known as the ARkStorm 1000.

It is the modeled flood and wind-blast damage from this simulation that USC research professor, Adam Rose, took to project the total economic loss. As well as severe damage to infrastructure and property, such a storm would see a loss in production amounting to $627 billion , over five years - enough to add 6% to the unemployment rate.

The destructive potential of these 'winter super-hurricanes' comes from the development of so-called 'atmospheric rivers' – belts of intensely water-saturated air from across the Pacific. When these run into the Sierra Nevada mountain range, and get fixed into place, they can unleash a persistent torrent of rain and wind. Climate change is already a factor in the development of these.

Mark Bernstein, USC Energy Institute managing director said "Storms form based on how warm the oceans are and how the jet stream changes." Such factors are themselves influenced by rising global temperatures. "Climate change affects how the whole ecosystem works" Bernstein concludes, "the consequence is [the rain] will come in shorter and more intense bursts."