(Press-News.org) The atmospheric conditions associated with the unprecedented drought currently afflicting California are "very likely" linked to human-caused climate change, Stanford scientists say.
In a new study, a team led by Stanford climate scientist Noah Diffenbaugh used a novel combination of computer simulations and statistical techniques to show that a persistent region of high atmospheric pressure hovering over the Pacific Ocean that diverted storms away from California was much more likely to form in the presence of modern greenhouse gas concentrations.
The research, published on Sept. 29 as a supplement to this month's issue of the Bulletin of the American Meteorological Society, is one of the most comprehensive studies to investigate the link between climate change and California's ongoing drought.
"Our research finds that extreme atmospheric high pressure in this region—which is strongly linked to unusually low precipitation in California—is much more likely to occur today than prior to the human emission of greenhouse gases that began during the Industrial Revolution in the 1800s," said Diffenbaugh, associate professor of Environmental Earth System Science at Stanford and a senior fellow at the Stanford Woods Institute for the Environment.
The exceptional drought currently crippling California is by some metrics the worst in state history. Combined with unusually warm temperatures and stagnant air conditions, the lack of precipitation has triggered a dangerous increase in wildfires and incidents of air pollution across the state. A recent report estimated that the water shortage would result in direct and indirect agricultural losses of at least $2.2 billion, and lead to the loss of more than 17,000 seasonal and part-time jobs in 2014 alone. Such impacts prompted California Governor Jerry Brown to declare a drought emergency, and the federal government to designate all 58 California counties as "natural disaster areas."
Scientists agree that the immediate cause of the drought is a particularly stubborn "blocking ridge" over the northeastern Pacific –popularly known as the Ridiculously Resilient Ridge, or "Triple R"–that prevented winter storms from reaching California during the 2013 and 2014 rainy seasons.
Blocking ridges are regions of high atmospheric pressure that disrupt typical wind patterns in the atmosphere. "Winds respond to the spatial distribution of atmospheric pressure," said Daniel Swain, a graduate student in Diffenbaugh's lab and lead author of the study. "We have seen this amazingly persistent region of high pressure over the northeastern Pacific for many months now, which has substantially altered atmospheric flow and kept California largely dry."
Blocking ridges occur periodically at temperature latitudes, but the Triple R was exceptional for both its size and longevity. While it dissipated briefly during the summer months of 2013, it returned even stronger by fall 2013 and persisted through much of the winter, which is normally California's "wet season." "At its peak in January 2014, the Triple R extended from the subtropical Pacific between California and Hawaii to the coast of the Arctic Ocean north of Alaska," said Swain, who coined the term "ridiculously resilient ridge" last fall to highlight the unusually persistent nature of the offshore blocking ridge.
Like a large boulder that has tumbled into a narrow stream, the Triple R diverted the flow of high-speed air currents known as the jet stream far to the north, causing Pacific storms to bypass not only California, but also Oregon and Washington. As a result, rain and snow that would normally fall on the West Coast were instead re-routed to Alaska and as far north as the Arctic Circle.
An important question for scientists and decision-makers has been whether human-caused climate change has influenced the conditions responsible for California's drought. Given the important role of the Triple R, Diffenbaugh's team set out to measure the probability of such extreme ridging events. The team first assessed the rarity of the Triple R in the context of the 20th century historical record. They found that the combined persistence and intensity of the Triple R in 2013 was unrivaled by any event since 1948, which is when comprehensive information about the circulation of the atmosphere is first available.
To more directly address the question of whether climate change played a role in the probability of the 2013 event, the team collaborated with Bala Rajaratnam, assistant professor of Statistics and of Environmental Earth System Science, and an affiliated faculty of the Woods Institute for the Environment. Rajaratnam and his graduate students Michael Tsiang and Matz Haugen applied advanced statistical techniques to a large suite of climate model simulations. Using the Triple R as a benchmark, the group compared geopotential heights–an atmospheric property related to pressure– between two sets of climate model experiments. One set mirrored the present climate, in which the atmosphere is growing increasingly warm due to human emissions of carbon dioxide and other greenhouse gases. In the other set of experiments, greenhouse gases were kept at a level similar to those that existed just prior to the Industrial Revolution.
The interdisciplinary research team found that the extreme geopotential heights associated with the Triple R in 2013 were at least three times as likely to occur in the present climate as in the preindustrial climate. They also found that such extreme values are consistently tied to unusually low precipitation in California, and the formation of atmospheric ridges over the northeastern Pacific.
"We've demonstrated with high statistical confidence that the large-scale atmospheric conditions, similar to those associated with the Triple R, are far more likely to occur now than in the climate before we emitted large amounts of greenhouse gases," Rajaratnam said.
"In using these advanced statistical techniques to combine climate observations with model simulations, we've been able to better understand the ongoing drought in California," Diffenbaugh added. "This isn't a projection of 100 years in the future. This is an event that is more extreme than any in the observed record, and our research suggests that global warming is playing a role right now."
INFORMATION:
View video, "Stanford scientists explain the state of California's drought": https://www.youtube.com/watch?v=GEd8h79mUSs
This article was written by Ker Than, associate director of communications, the School of Earth Sciences at Stanford University.
Causes of California drought linked to climate change
2014-09-29
ELSE PRESS RELEASES FROM THIS DATE:
Decision to reintroduce aprotinin in cardiac surgery may put patients at risk
2014-09-29
Cardiac surgery patients may be at risk because of the decision by Health Canada and the European Medicines Agency to reintroduce the use of aprotinin after its withdrawal from the worldwide market in 2007, assert the authors of a previous major trial that found a substantially increased risk of death associated with the drug. In an analysis in CMAJ (Canadian Medical Association Journal), the authors refute three major criticisms of the trial made by the regulatory bodies.
Aprotinin, used to control bleeding in cardiac surgery, was withdrawn worldwide in 2007 after the ...
Revolutionary hamstring tester will keep more players on the field
2014-09-29
Elite sporting stars can assess and reduce their risk of a hamstring injury thanks to a breakthrough made by QUT researchers.
The discovery could be worth a fortune to football codes, with hamstring strain injuries accounting for most non-contact injuries in Australian rules football, football and rugby union, as well as track events like sprinting.
Using an innovative field device, a research team led by Dr Anthony Shield, from QUT's School - Exercise and Nutrition Sciences, and former QUT PhD student, Dr David Opar, now at the Australian Catholic University, measured ...
Drug for kidney injury after cardiac surgery does not reduce need for dialysis
2014-09-29
Among patients with acute kidney injury after cardiac surgery, infusion with the antihypertensive agent fenoldopam, compared with placebo, did not reduce the need for renal replacement therapy (dialysis) or risk of death at 30 days, but was associated with an increased rate of abnormally low blood pressure, according to a study published in JAMA. The study is being posted early online to coincide with its presentation at the European Society of Intensive Care Medicine annual congress.
More than 1 million patients undergo cardiac surgery every year in the United States ...
Climate detectives reveal handprint of human caused climate change in Australia
2014-09-29
Australia's hottest year on record in 2013 along with the accompanying droughts, heat waves and record-breaking seasons of that year was virtually impossible without the influence of human-caused global warming.
New research from ARC Centre of Excellence for Climate System Science (ARCCSS) researchers and colleagues, over five different Australian papers in a special edition of the Bulletin of the American Meteorological Society (BAMS), has highlighted the powerful influence of global warming on Australia's climate.
"We often talk about the fingerprint of human-caused ...
Rising prevalence of sleep apnea in US threatens public health
2014-09-29
DARIEN, IL – Public health and safety are threatened by the increasing prevalence of obstructive sleep apnea, which now afflicts at least 25 million adults in the U.S., according to the National Healthy Sleep Awareness Project. Several new studies highlight the destructive nature of obstructive sleep apnea, a chronic disease that increases the risk of high blood pressure, heart disease, Type 2 diabetes, stroke and depression.
"Obstructive sleep apnea is destroying the health of millions of Americans, and the problem has only gotten worse over the last two decades," said ...
Targeted combination therapy halts disease, extends life in advanced melanoma patients
2014-09-29
A world-first study in today's New England Journal of Medicine heralds the efficacy of a targeted combination drug therapy after reporting major declines in the risk of disease progression and death in people with metastatic melanoma.
The multi-centre, double-blind, randomised, phase 3 trial compared oral dabrafenib (150 mg twice daily) and oral trametinib (2 mg once daily) combination therapy with oral dabrafenib (150 mg twice daily) and placebo.
All trial patients had inoperable stage 3C or 4 metastatic melanoma that had a BRAF gene mutation V600E or V600K. Among ...
Investigating the 'underground' habitat of Listeria bacteria
2014-09-29
The literature describes Listeria as ubiquitous bacteria with widespread occurrence. Yet they only become a problem for humans and animals when they contaminate food processing facilities, multiply, and enter the food chain in high concentrations. An infection with Listeria monocytogenes can even be fatal for humans or animals with weakened immune systems.
Listeria in soil or water are not dangerous
"Listeria in soil or water represent a relatively low risk to humans," explains study director Beatrix Stessl. "The concentrations are too low. The aim of our study was ...
Trial shows trastuzumab should remain as standard of care for HER2-positive breast cancer
2014-09-29
JACKSONVILLE, Fla., Sept. 29, 2014 — Analysis of more than 8,000 women who participated in the world's largest study of two treatments for HER2-positive breast cancer reinforces other findings from the clinical trial showing that trastuzumab (Herceptin) should remain the standard of care for this cancer, says a Mayo Clinic researcher.
This study, being presented at the European Society for Medical Oncology (ESMO) 2014 Congress in Madrid, reveals that when used as a single HER2-targeted therapy in addition to standard chemotherapy, trastuzumab offers a better outcome than ...
Tooth serves as evidence of 220 million-year-old attack
2014-09-29
At the beginning of the age of dinosaurs, gigantic reptiles—distant relatives of modern crocodiles—ruled the earth. Some lived on land and others in water and it was thought they didn't much interact. But a tooth found by a University of Tennessee, Knoxville, researcher in the thigh of one of these ancient animals is challenging this belief.
Stephanie Drumheller, an earth and planetary sciences lecturer, and her Virginia Tech colleagues Michelle Stocker and Sterling Nesbitt examined 220-million-year-old bite marks in the thigh bones of an old reptile and found evidence ...
A molecular mechanism involved in cellular proliferation characterized
2014-09-29
Researchers from Guillermo Montoya's team at the Spanish National Cancer Research Centre (CNIO), in collaboration with Isabelle Vernos' Group from the Centre for Genomic Regulation (CRG), have uncovered the molecular interaction between TACC3 and chTOG, key proteins in forming the internal cellular framework that enables and sustains cell division. Published today in Nature Communications, the observations may help to optimise current oncological therapies specifically designed to fight against this framework, named by the scientific community as microtubules.
KEY MOLECULES ...