Jan 4, 2013

The Coming Megafloods

by
Michael D. Dettinger and B. Lynn Ingram
,
Scientific American
  • Finds that 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
  • States that geologic evidence shows that truly massive floods, caused by rainfall alone, have occurred in California about every 200 years, with the most recent occurring in 1861
  • States that such floods were most likely caused by atmospheric rivers: narrow bands of water vapor about a mile above the ocean that extend for thousands of miles
  • States that atmospheric rivers are appearing in climate models used to predict future climate changes: scientists do not program atmospheric rivers into weather and climate models; the rivers emerge as natural consequences of the way that the atmosphere and the atmospheric water cycle work, when the models are let loose to simulate the past, present or future
  • States that in climate model projections, air temperatures get warmer by about four degrees Fahrenheit on average because of increasing greenhouse gas concentrations; because a warmer atmosphere holds more water vapor, atmospheric rivers could carry more moisture
  • States that in six of the seven climate models, the average rain and snow delivered to California by future atmospheric rivers increases by an average of about 10 percent by the year 2100