‘Unique and alarming’: Engineers to be tested as rain events intensify

‘Unique and alarming’: Engineers to be tested as rain events intensify

SOURCE: The Sydney Morning Herald and Nature Climate Change DATE: July 30, 2018 SNIP: Australia’s rainfall events are already becoming more intense with climate change, raising the risks of flashflooding and potentially exceeding the nation’s engineering codes, a new study finds. While it’s long been understood the atmosphere holds about 6.5 per cent more moisture per degree of warming, climate models have largely not captured the impact on individual storms, said Seth Westra, an associate professor at the University of Adelaide’s engineering school. “It’s much more, two or three times the rate of that simple rule of thumb,” said Professor Westra, who is one of the authors of the paper appearing in Nature Climate Change on Tuesday. “It’s a really unique and alarming aspect of our conclusions.” The study examined rainfall records across Australia from 1966 to 2013 and identified an increase in the intensity of short-duration rain events “well outside the natural year-to-year variability you’d expect”, he said. “In fact, they are more severe than climate models have been suggesting.” “The sorts of rates that engineers have been using [for these events] are lower than the historical changes that we’re observing in this study,” Professor Westra said, adding that engineering codes may need to be updated to recognise “more radical rainfall” events in the future. From Nature Climate Change: “Our results indicate that CC scaling on temperature provides a severe underestimate of observed changes in hourly rainfall extremes in Australia, with implications for assessing the impacts of extreme...
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...
Heavy Rainfall Has Increased by Up to 70 Percent in Parts of the U.S. Since the 1950s, and It Will Only Get Worse, Experts Say

Heavy Rainfall Has Increased by Up to 70 Percent in Parts of the U.S. Since the 1950s, and It Will Only Get Worse, Experts Say

SOURCE: Weather.com DATE: June 9, 2018 SNIP: Heavy rainfall from storms has increased by up to 70 percent in some areas of the United States since the 1950s and will only get worse in the coming years, thanks to global warming, scientists say. The 2014 National Climate Assessment reported that downpours from storms are dumping more water across the nation than ever before, with the Midwest, Pacific Northwest and the Upper Plains receiving the greatest increase in heavy rainfall. The Environmental Protection Agency notes that heavy rainfall events have increased by 70 percent in the Pacific Northwest over the past six decades or so, more than any other region in the United States. Andreas Prein of the University Corporation for Atmospheric Research (UCAR) and the National Center for Atmospheric Research (NCAR) says peak rain rates, which arrive when the core of a storm is overhead, have increased across the country by 30 percent over the past 60 years. And while some areas will continue to get wetter from heavy downpours, other regions will get drier. “The combination of more intense rainfall and the spreading of heavy rainfall over larger areas means that we will face a higher flood risk than previously predicted,” Prein said in a press release. “If a whole catchment area gets hammered by high rain rates, that creates a much more serious situation than a thunderstorm dropping intense rain over parts of the...
When Tropical Cyclones Can’t Move On

When Tropical Cyclones Can’t Move On

SOURCE: National Center for Environmental Information at NOAA DATE: June 6, 2018 SNIP: Tropical cyclones—also sometimes referred to as hurricanes and typhoons—are taking substantially longer to move from place to place, according to a new study by NCEI scientist Jim Kossin. In his paper, “A Global Slowdown of Tropical Cyclone Translation Speed (link is external),” published in Nature, Kossin demonstrates that, globally, tropical cyclones slowed by 10 percent between 1949 and 2016. With additional water vapor in the atmosphere in a warming world, as little as a 10 percent slowdown could double local rainfall and flooding impacts caused by 1°C of warming. According to the study, tropical cyclones have slowed in both hemispheres and in every ocean basin except the Northern Indian Ocean. But, tropical cyclones have generally slowed more in the Northern Hemisphere, where more of these storms typically occur each year. “Of great importance to society,” says Kossin, “tropical cyclones over land have slowed down 20 percent in the Atlantic, 30 percent in the western North Pacific, and 19 percent in the Australian region. These trends are almost certainly increasing local rainfall totals and freshwater flooding, which is associated with very high mortality risk.” Hurricane Harvey in 2017 serves as a dramatic example of the consequences a slow-moving or “stalled” tropical cyclone can produce. Harvey—the hurricane that refused to leave—dumped upwards of 50 inches of rain on Houston, Texas, and the surrounding area in just five days. Some locations received two feet of rain in just two days. [Slower than expected?...
The Strange Future Hurricane Harvey Portends

The Strange Future Hurricane Harvey Portends

SOURCE: The Atlantic DATE: August 31, 2017 SNIP: Humans have begun an international project to move water around the world, far more ambitious than any network of aqueducts or hydroelectric dams ever constructed or conceived. The Earth system is getting warmer. Water is evaporating faster. There’s more of it in the air. It’s moving through the system faster. As a result, the coming centuries will play out under a new atmospheric regime, one with more extreme rain, falling in patterns unfamiliar to those around which civilization has grown. For each degree Celsius of warming the atmosphere is able to hold 6 percent more water. For a planet that’s expected to warm by 4 degrees by the end of the century, that means a transition to a profoundly different climate. “Rainfall extremes have increased in intensity I think at every latitude in the northern hemisphere,” says Massachusetts Institute of Technology climate scientist Paul O’Gorman. In 2012, a study led by Lawrence Livermore National Laboratory oceanographer Paul Durack found that the global water cycle was actually speeding up at twice the rate predicted by climate models, likely intensifying by 16 to 24 percent by the end of the...