New insights into predicting future droughts in California: Natural cycles, sea surface temperatures found to be main drivers in ongoing event

According to a new NOAA-sponsored study, natural oceanic and atmospheric patterns are the primary drivers behind California's ongoing drought. A high pressure ridge off the West Coast (typical of historic droughts) prevailed for three winters, blocking important wet season storms, with ocean surface temperature patterns making such a ridge much more likely. Typically, the winter season in California provides the state with a majority of its annual snow and rainfall that replenish water supplies for communities and ecosystems.

Further studies on these oceanic conditions and their effect on California's climate may lead to advances in drought early warning that can help water managers and major industries better prepare for lengthy dry spells in the future.

"It's important to note that California's drought, while extreme, is not an uncommon occurrence for the state. In fact, multi-year droughts appear regularly in the state's climate record, and it's a safe bet that a similar event will happen again. Thus, preparedness is key," said Richard Seager, report lead author and professor with Columbia University's Lamont Doherty Earth Observatory.

This report builds on earlier studies, published in September in the Bulletin of the American Meteorological Society, which found no conclusive evidence linking human-caused climate change and the California drought. The current study notes that the atmospheric ridge over the North Pacific, which has resulted in decreased rain and snowfall since 2011, is almost opposite to what models project to result from human-induced climate change. The report illustrates that mid-winter precipitation is actually projected to increase due to human-induced climate change over most of the state, though warming temperatures may sap much of those benefits for water resources overall, while only spring precipitation is projected to decrease.

The report makes clear that to provide improved drought forecasts for California, scientists will need to fully understand the links between sea surface temperature variations and winter precipitation over the state, discover how these ocean variations are generated, and better characterize their predictability.

This report contributes to a growing field of science-climate attribution-where teams of scientists aim to identify the sources of observed climate and weather patterns.

"There is immense value in examining the causes of this drought from multiple scientific viewpoints," said Marty Hoerling, report co-author and researcher with NOAA's Earth System Research Laboratory. "It's paramount that we use our collective ability to provide communities and businesses with the environmental intelligence they need to make decisions concerning water resources, which are becoming increasingly strained."

To view the report, visit:?http://cpo.noaa.gov/MAPP/californiadroughtreport.

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Terrestrial ecosystems at risk of major shifts as temperatures increase

Over 80% of the world's ice-free land is at risk of profound ecosystem transformation by 2100, a new study reveals. "Essentially, we would be leaving the world as we know it," says Sebastian Ostberg of the Potsdam Institute for Climate Impact Research, Germany. Ostberg and collaborators studied the critical impacts of climate change on landscapes and have now published their results in Earth System Dynamics, an open access journal of the European Geosciences Union (EGU).

The researchers state in the article that "nearly no area of the world is free" from the risk of climate change transforming landscapes substantially, unless mitigation limits warming to around 2 degrees Celsius above preindustrial levels.

Ecosystem changes could include boreal forests being transformed into temperate savannas, trees growing in the freezing Arctic tundra or even a dieback of some of the world's rainforests. Such profound transformations of land ecosystems have the potential to affect food and water security, and hence impact human well-being just like sea level rise and direct damage from extreme weather events.

The new Earth System Dynamics study indicates that up to 86% of the remaining natural land ecosystems worldwide could be at risk of major change in a business-as-usual scenario (see note). This assumes that the global mean temperature will be 4 to 5 degrees warmer at the end of this century than in pre-industrial times -- given many countries' reluctance to commit to binding emissions cuts, such warming is not out of the question by 2100.

"The research shows there is a large difference in the risk of major ecosystem change depending on whether humankind continues with business as usual or if we opt for effective climate change mitigation," Ostberg points out.

But even if the warming is limited to 2 degrees, some 20% of land ecosystems -- particularly those at high altitudes and high latitudes -- are at risk of moderate or major transformation, the team reveals.

The researchers studied over 150 climate scenarios, looking at ecosystem changes in nearly 20 different climate models for various degrees of global warming. "Our study is the most comprehensive and internally consistent analysis of the risk of major ecosystem change from climate change at the global scale," says Wolfgang Lucht, also an author of the study and co-chair of the research domain Earth System Analysis at the Potsdam Institute for Climate Impact Research.

Few previous studies have looked into the global impact of raising temperatures on ecosystems because of how complex and interlinked these systems are. "Comprehensive theories and computer models of such complex systems and their dynamics up to the global scale do not exist."

To get around this problem, the team measured simultaneous changes in the biogeochemistry of terrestrial vegetation and the relative abundance of different vegetation species. "Any significant change in the underlying biogeochemistry presents an ecological adaptation challenge, fundamentally destabilising our natural systems," explains Ostberg.

The researchers defined a parameter to measure how far apart a future ecosystem under climate change would be from the present state. The parameter encompasses changes in variables such as the vegetation structure (from trees to grass, for example), the carbon stored in the soils and vegetation, and freshwater availability. "Our indicator of ecosystem change is able to measure the combined effect of changes in many ecosystem processes, instead of looking only at a single process," says Ostberg.

He hopes the new results can help inform the ongoing negotiations on climate mitigation targets, "as well as planning adaptation to unavoidable change."

Note

Even though 86% of land ecosystems are at risk if global temperature increases by 5 degrees Celsius by 2100, it is unlikely all these areas will be affected. This would mean that the worst case scenario from each climate model comes true.

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Snow, cold temperatures hamper U.S. tornado clean-up

WEST LIBERTY, Kentucky (Reuters) - A winter snowstorm and freezing temperatures on Monday hampered clean-up efforts in Indiana and Kentucky, the states hardest hit by a wave of powerful tornadoes and storms that killed dozens of people.

Three to five inches of snow fell in southern Indiana and north-central Kentucky, where recovery efforts were underway after at least 30 tornadoes ripped through the region on Friday, the National Weather Service said.

In West Liberty, Kentucky, emergency and security personnel, insurance inspectors, business owners and their employees gathered on the main street to assess the damage amid fears heavy wet snow would cause weakened buildings to collapse.

"Anything we can do to get back to normal business, (residents) will see that as a reason to believe we can recover," said Linda Oakley, who visited the damaged flower shop where she works, accompanied by her husband and firefighters.

The storms and tornadoes that struck the Midwest and South on Friday splintered blocks of homes and tossed around vehicles like toys. They came on the heels of severe weather that killed about a dozen people earlier in the week.

Officials said at least 39 people died in the latest wave of storms - 21 in Kentucky, 13 in Indiana, three in Ohio and one in Alabama. Georgia also reported a storm-related death.

Among the dead was a 14-month-old girl who succumbed to her injuries in a hospital in Louisville, Kentucky, on Sunday, two days after she was found in a field after a tornado hit the New Pekin, Indiana, area. Nearby lay the lifeless bodies of her parents and two siblings.

Kentucky Governor Steve Beshear said on Sunday the storm had caused at least $5.8 million in property damage. He has signed an executive order barring price gouging for food and other necessities.

HARD TO FORECAST

The destruction raised fears that 2012 would be another bad tornado season in the United States. A total of 550 deaths were blamed on twisters last year, the deadliest in nearly a century, according to the National Weather Service.

Greg Carbin, a meteorologist for the National Oceanic and Atmospheric Association's storm prediction center, said tornadoes often formed in March and April but added that it was hard to predict how severe the 2012 season would be.

Tornadoes typically occur in the United States between March and July, when warm, moist air meets cooler, dry air in the atmosphere. Some parts of the country experience a late tornado season in autumn.

"There's nothing that points at something above or below normal," Carbin said.

The weather in hard-hit areas, however, was expected to begin improving on Monday. The snowstorm was moving east and expected to drop up to three inches of snow in Virginia and in West Virginia before heading out to sea by evening.

"A high-pressure system will give clean-up crews tranquil weather through at least the middle part of the week," said Andy Mussoline, a meteorologist at AccuWeather.com. "A gradual warm-up supported by plenty of sunshine will follow."

(Editing By Ellen Wulfhorst and Paul Simao)

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