California, break out the waders

Warming planet could make big floods more likely

Minnesota Public Radio
Edited transcript, 9:50 AM, February 5, 2013

Every Thursday, MPR meteorologist Paul Huttner joins The Daily Circuit to talk about the latest research on our changing climate and the consequences we're seeing here in Minnesota and worldwide.

This week on Climate Cast, meteorologist Paul Huttner joined us to examine how a warming planet could make "megafloods" more likely. We also took a look at FEMA's new flood maps that significantly expand flood zones.

Kerri Miller: I spotted this interesting article in Scientific American about how atmospheric rivers are driving more intense rainstorms and they predict that our changing climate will bring more flooding because of it. Make the connection for us.

Paul Huttner: It fits with the overall pattern of climate change. First of all, these atmospheric rivers -- or what we might call the Pineapple Express, you can think of it as a fire hose -- these moisture plumes that plow into the west coast of the United States bring heavy rainfall to California. We know that. Here's the good part of it: they produce 50 percent of California's annual rainfall. That's a good thing.

But what's not such a good thing is that every once in a while these atmospheric rivers, which are like a fire hose that kind of snakes around, it becomes stationary and it just blasts California with what we call a megaflood. These events have happened historically. In fact, there was a huge megaflood in 1861-1862, 43 days of rain that flooded the entire Central Valley in California. It killed thousands of people. The concern is that it's due to happen again. They seem to happen every couple hundred of years.

Here's the connection with climate change: more water vapor in the atmosphere (about 4 percent increase) may make these storms a little more frequent. We're due for another one. The concern is this could happen in the near future in California.

(Full transcript here. Original article below:)

Megastorms Could Drown Massive Portions of California

Huge flows of vapor in the atmosphere, dubbed "atmospheric rivers," have unleashed massive floods every 200 years, and climate change could bring more of them

By Michael D. Dettinger and B. Lynn Ingram | Scientific American

The intense rainstorms sweeping in from the Pacific Ocean began to pound central California on Christmas Eve in 1861 and continued virtually unabated for 43 days. The deluges quickly transformed rivers running down from the Sierra Nevada mountains along the state’s eastern border into raging torrents that swept away entire communities and mining settlements. The rivers and rains poured into the state’s vast Central Valley, turning it into an inland sea 300 miles long and 20 miles wide. Thousands of people died, and one quarter of the state’s estimated 800,000 cattle drowned. Downtown Sacramento was submerged under 10 feet of brown water filled with debris from countless mudslides on the region’s steep slopes. California’s legislature, unable to function, moved to San Francisco until Sacramento dried out—six months later. By then, the state was bankrupt.

(Article here.)