‘A hot drought’: Warming is driving much of the Colorado River’s decline, scientists say

‘A hot drought’: Warming is driving much of the Colorado River’s decline, scientists say

SOURCE: AZ Central (USA Today) DATE: September 7, 2018 SNIP: Since 2000, the amount of water flowing in the Colorado River has dropped 19 percent below the average of the past century, a decline that has left the Southwest on the brink of a water shortage. Now, new research indicates that a large portion of that decline isn’t due to less rain and snow falling from the sky, but to warmer temperatures brought on by climate change. Scientists from the University of California-Los Angeles and Colorado State University found that about half the trend of decreasing runoff from 2000-2014 in the Upper Colorado River Basin was the result of unprecedented warming across the region. “A good chunk of the decline we’re seeing right now is temperature-related. And as the Earth continues to warm, we’re going to see less flow in the river,” said Brad Udall, a water and climate scientist at Colorado State University who co-authored the research. “We need to prepare for a river that has significantly less water in it.” [The researchers] calculated that 53 percent of the trend was linked to warming, which has shrunk the average snowpack in the mountains, boosted the uptake of water by plants and increased the amount of water that evaporates off the landscape. The researchers attributed the remaining 47 percent of the decrease in the river’s flow to shifts in precipitation patterns, with less rain and snow falling in four areas of Colorado that tend to be especially productive in feeding tributaries in the Rocky Mountains. The study, which was published Aug. 30 in the journal Water Resources Research, is...
Immense rains are causing more flash flooding, and experts say it’s getting worse

Immense rains are causing more flash flooding, and experts say it’s getting worse

SOURCE: Washington Post DATE: June 24, 2018 SNIP: Torrential rain events across the United States are becoming more frequent and more intense, leading to record rainfall, rare extreme flooding and perilous infrastructure failures. Experts say the immense rains — some spawned by tropical ocean waters, others by once-routine thunderstorms — are the product of long-rising air temperatures and an increase in the sheer size of the storms. Because warmer air can hold more water, large storms are dropping far more rain at a faster clip. “Things are definitely getting more extreme,” said Andreas ­Prein, an atmospheric scientist at the National Center for Atmospheric Research in Boulder, Colo. “You just have to look at the records. All areas of the continental U.S. have seen increases in peak rainfall rates in the past 50 years. . . . And there is a chance that we are underestimating the risk, actually.” Since 1880, global temperature has risen just more than 0.13 degrees per decade, for a total of 1.8 degrees Fahrenheit (1 degree Celsius). The amount of water air can hold is based on temperature — put very simply, the warmer the air is, the more water it can hold. Theoretically, experts say, an additional 1.8 degrees would amount to about 7 percent more water in the air, resulting in a similar increase in extreme rainfall. But what Prein and other researchers have found is much higher across a vast portion of the United States. According to the 2014 National Climate Assessment, the eastern half of the continental United States has seen the most dramatic change in extreme rainfall. The amount of rain during...
Changes in nonextreme precipitation may have not-so-subtle consequences

Changes in nonextreme precipitation may have not-so-subtle consequences

SOURCE: Illinois News Bureau DATE: September 18, 2017 SNIP: Major floods and droughts receive a lot of attention in the context of climate change, but University of Illinois researchers analyzed over five decades of precipitation data from North America to find that changes in nonextreme precipitation are more significant than previously realized and larger than those in extreme precipitation. These changes can have a strong effect on ecosystems, agriculture, infrastructure design and resource management, and point to a need to examine precipitation in a more nuanced, multifaceted way. “This study articulates how everyday precipitation events – not just the extremes that have been the focus of most studies – are changing,” said Illinois civil and environmental engineering professor and lead author Praveen Kumar. “It’s not just the amount of rainfall that is important; it’s the duration of that rainfall and the amount of time between rainfalls and dry...
Stunning new analysis reveals just how unprecedented Harvey was

Stunning new analysis reveals just how unprecedented Harvey was

SOURCE: Think Progress DATE: September 14, 2017 SNIP: Hurricane Harvey’s landfall in Texas was “unprecedented” and “beyond anything experienced,” as the National Weather Service described it late last month. Now scientists are beginning to quantify just how unprecedented it was. A study released Friday by Metstat, a weather-analysis company specializing in “detailed precipitation analysis” and “weather frequency analysis,” found that Harvey delivered a stunning once-in-25,000-year deluge over much of southeast Texas. Some places saw an unimaginable once-in-500,000-year deluge, which translates to a 0.0002 percent chance of this deluge occurring in any given year. Since global warming has been making extreme precipitation events more likely, however, the U.S. won’t have to wait 25,000 years to witness the next event of Harvey’s proportion. As climatologist Michael Mann explained during the storm, “the kind of stalled weather pattern that is drenching Houston is precisely the sort of pattern we expect because of climate change.” Climate science predicted a weaker jet stream, and Harvey stalled because of a weakened jet...
Extreme rainfall risks could triple in the U.S. under climate change, scientists warn

Extreme rainfall risks could triple in the U.S. under climate change, scientists warn

SOURCE: Washington Post, Nature DATE: December 5, 2016 SNIP: U.S. residents may want to start preparing for a stormier future, scientists say. According to a new study, future climate change could cause an increase in extreme precipitation events throughout much of the country — in fact, these events could become up to five times more frequent in some areas. It’s an outcome many climate scientists have already predicted for the planet as a whole, according to Andreas Prein, a scientist at the National Center for Atmospheric Research and the new study’s lead author. “We expect that intense rainfall extremes will get more frequent and more intense in the future climate because if we warm up the atmosphere, air can hold more moisture,” he said. In fact, he added, records from the past few decades indicate that we’re already seeing this effect in the warming United...