Smaller Colorado River projected for coming decades, study says

EurekAlert via the Earth Institute at Columbia University: Some 40 million people depend on the Colorado River Basin for water but warmer weather from rising greenhouse gas levels and a growing population may signal water shortages ahead. In a new study in Nature Climate Change, climate modelers at Columbia University's Lamont-Doherty Earth Observatory predict a 10 percent drop in the Colorado River's flow in the next few decades, enough to disrupt longtime water-sharing agreements between farms and cities across the American Southwest, from Denver to Los Angeles to Tucson, and through California's Imperial Valley.

"It may not sound like a phenomenally large amount except the water and the river is already over-allocated," said Richard Seager, a climate scientist at Columbia University's Lamont-Doherty Earth Observatory and lead author of the new study.

The study expands on findings published in 2007 in the journal Science that the American Southwest is becoming more arid as temperatures rise and rainfall patterns shift from human-caused climate change. It also comes on the heels of a major study of the Colorado River Basin by the U.S. Department of Interior that projected longer and more severe droughts by 2060, and a 9 percent decline in the Colorado's flows.

"The projections are spot on," said Bradley Udall, an expert on hydrology and policy of the American West, at the University of Colorado, Boulder. "Everyone wondered what the next generation of models would say. Now we have a study that suggests we better take seriously the drying projections ahead."

The present study narrows in on three key regions for water managers—the Colorado River headwaters, the greater California-Nevada region and Texas, which gets nearly all of its water from within state borders. The study makes use of the latest models (those used by the Intergovernmental Panel on Climate Change in its Fifth Assessment Report due out next fall), to estimate seasonal changes in precipitation, evaporation, water runoff and soil moisture in the near future, 2021-2040. "It's a much finer grain picture than the one we had in 2007," said Seager....

The Colorado River, near Page, Arizona, shot by Adrille, Wikimedia Commons,  under the Creative Commons Attribution-Share Alike 3.0 Unported license

More potent than carbon dioxide, nitrous oxide levels in California may be nearly three times higher than previously thought

Lawrence Berkeley National Laboratory News Center: Using a new method for estimating greenhouse gases that combines atmospheric measurements with model predictions, Lawrence Berkeley National Laboratory (Berkeley Lab) researchers have found that the level of nitrous oxide, a potent greenhouse gas, in California may be 2.5 to 3 times greater than the current inventory.

At that level, total N2O emissions—which are believed to come primarily from nitrogen fertilizers used in agricultural production—would account for about 8 percent of California’s total greenhouse gas emissions. The findings were recently published in a paper titled “Seasonal variations in N2O emissions from central California” in Geophysical Research Letters. Earlier this year, using the same methodology, the researchers found that levels of methane, another potent greenhouse gas, in California may be up to 1.8 times greater than previous estimates.

“If our results are accurate, then it suggests that N2O makes up not 3 percent of California’s total effective greenhouse gases but closer to 10 percent,” said Marc Fischer, lead researcher on both studies. “And taken together with our previous estimates of methane emissions, that suggests those two gases may make up 20 to 25 percent of California’s total emissions. That’s starting to become roughly comparable to emissions from fossil fuel CO2.”

Accurate estimates of the California’s greenhouse gas emissions are important as the state works to reduce emissions to 1990 levels by 2020, as mandated by a law known as AB 32. The vast majority of the reduction efforts have been focused on CO2….

This map shows the amount of nitrous oxide emissions in California (in nanomoles per square meter per second). The "x" represents the location of the measurement tower in Walnut Grove, CA. From the LBNL website

  

California confronts a sea change

David Helvarg in the Los Angeles Times: Governors Andrew Cuomo of New York and Chris Christie of New Jersey don't need to wait on gridlocked Washington to confront future risks from climate-change intensified storms. They can instead look at how California is already moving forward on common-sense adaptations, and do it themselves. With 3.5 million Californians living within three feet of sea level, and the best available science projecting a 3- to 5-foot rise in sea level for the state by 2100, doing nothing would be irresponsible.

In Northern California, rising sea levels are projected to affect more than a quarter of a million people and threaten more than $60 billion in infrastructure in the San Francisco Bay/Delta region, putting power stations, water-treatment plants, roads, buildings and the San Francisco and Oakland airports (both built on filled wetlands) at risk. In Southern California, scientists point to the loss of 3,000 beachfront homes to major El Niño winter storms in the 1980s as suggestive of what climate change has in store.

...For starters, California is ahead of most states in its attempts to address the problem at its source by reducing greenhouse gas emissions. ... But climate change is happening, so adaptation, as well as prevention, is going to be essential.

A number of local and state efforts are underway. This year, the San Francisco Bay Conservation and Development Commission, the state's original coastal protection group, amended its long-standing San Francisco Bay Plan to make sure projected sea-level rise is taken into account by any new project, such as a planned $1.5-billion development on Treasure Island in the middle of the bay.

After repeated flooding from winter storms in 2009-10 shut down the Great Highway along the city's share of the Pacific coast, the Army Corps of Engineers proposed pumping dredged sand onto the beach to shore it up and a city think tank suggested "planned retreat" — shrinking and rerouting the highway at a cost of $343 million — as the best long-term solution. While the options are reviewed, city workers continue armoring the southbound lanes with boulders....

The Newport Pier in Newport Beach, California, shot by Alienburrito, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license