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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Natural variation: Warm North Atlantic Ocean promotes extreme winters in U.S. and Europe

The extreme cold weather observed across Europe and the east coast of the US in recent winters could be partly down to natural, long-term variations in sea surface temperatures, according to a new study published today.

Researchers from the University of California Irvine have shown that a phenomenon known as the Atlantic Multidecadal Oscillation (AMO) -- a natural pattern of variation in North Atlantic sea surface temperatures that switches between a positive and negative phase every 60-70 years -- can affect an atmospheric circulation pattern, known as the North Atlantic Oscillation (NAO), that influences the temperature and precipitation over the Northern Hemisphere in winter.

When the AMO is in its positive phase and the sea surface temperatures are warmer, the study has shown that the main effect in winter is to promote the negative phase of the NAO which leads to "blocking" episodes over the North Atlantic sector, allowing cold weather systems to exist over the eastern US and Europe.

The results have been published today, Wednesday 2 April, in IOP Publishing's journal Environmental Research Letters.

To arrive at their results, the researchers combined observations from the past century with climate simulations of the atmospheric response to the AMO.

According to their observations, sea surface temperatures in the Atlantic can be up to 1.5 ?C warmer in the Gulf Stream region during the positive phase of the AMO compared to the negative, colder phase. The climate simulations suggest that these specific anomalies in sea surface temperatures can play a predominant role in promoting the change in the NAO.

Lead authors of the study Yannick Peings and Gudrun Magnusdottir said: "Our results indicate that the main effect of the positive AMO in winter is to promote the occurrence of the negative phase of the NAO. A negative NAO in winter usually goes hand-in-hand with cold weather in the eastern US and north-western Europe."

The observations also suggest that it takes around 10-15 years before the positive phase of AMO has any significant effect on the NAO. The reason for this lag is unknown; however, an explanation might be that AMO phases take time to develop fully.

As the AMO has been in a positive phase since the early 1990s, it may have contributed to the extreme winters that both the US and Europe have experienced in recent years.

The researchers warn, however, that the future evolution of the AMO remains uncertain, with many factors potentially affecting how it interacts with atmospheric circulation patterns, such as Arctic sea ice loss, changes in solar radiation, volcanic eruptions and concentrations of greenhouse gases in the atmosphere.

The AMO also shows strong variability from one year to the next in addition to the changes seen every 60 - 70 years, which makes it difficult to attribute specific extreme winters to the AMO's effects.

Responding to the extreme weather that gripped the eastern coast of the US this winter, Yannick Peings continued: "Unlike the 2012/2013 winter, this winter had rather low values of the AMO index and the pattern of sea surface temperature anomalies was not consistent with the typical positive AMO pattern. Moreover, the NAO was mostly positive with a relatively mild winter over Europe."

"Therefore it is unlikely that the positive AMO played a defining role on the east coast of the US, although further work is necessary to answer this question. Such an event is consistent with the large internal variability of the atmosphere, and other external forcings may have played a role.

"Our future studies will look to compare the role of the AMO compared to Arctic sea ice anomalies, which have also been shown to affect atmospheric circulation patterns and promote colder, more extreme winters."

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Going Against the Green Grain on Natural Gas

HOUSTON—The Environmental Defense Fund is known for its willingness to work with industry on energy and climate-change policies. That inclination is on display more than ever at a major energy conference that kicked off here on Monday with a heavy focus on the development of natural gas.

More than 300 experts and executives from the global energy industry are attending the IHS Cambridge Energy Research Associates annual conference, known as CERA Week, and just a handful of them bring an environmental viewpoint to the proceedings. Among those are two experts from New York-based EDF, an influential environmental group that often deviates from its counterparts such as the Sierra Club to partner with fossil-fuel industries.

“You don’t make change by simply talking to people who agree with you,” Mark Brownstein, deputy director of the energy program at EDF, told National Journal Daily after speaking on a panel about natural gas on Monday. “You certainly don’t make change if you’re not knowledgeable about the folks that you’re trying to change.”

EDF President Fred Krupp speaks on another panel, also about natural gas, on Wednesday.

Many environmental groups are critical of natural gas, specifically the controversial method used to extract the recently discovered reserves of shale natural gas all over the country.

Hydraulic fracturing, commonly known as “fracking,” is a process in which large amounts of water, chemicals, and sand are pumped into a well at high pressures to fracture rock and allow natural gas to escape. Concerns persist about water contamination and the climate-change impact of methane, a potent greenhouse gas that escapes during the gas production process.  Natural gas burns 50 percent more cleanly than coal, but less data is available on what impact methane emissions during production are having on climate change.

“If we’re not able to do this correctly, it will fundamentally limit the supply and limit the opportunity,” Brownstein said.

Brownstein was a lone wolf on a panel of six experts; the others were all from the energy sector. Some often looked to Brownstein for the other perspective, with “other” meaning anything besides the views of an energy company or consulting firm.

The experts were discussing a new study of North America’s recently-discovered reserves of shale natural gas. Brownstein worked with industry on the report, which was led by the National Petroleum Council, a federal advisory committee made up of oil and gas executives.

“The most surprising thing to me was actually participating,” Brownstein quipped about the report.

In his closing remarks, Brownstein made a bid to win over critics of natural gas by arguing for its potential to provide the country with bountiful, and comparatively clean, energy.

“Plenty of people out there are betting that it won’t happen and preparing for the eventuality that it won’t,” Brownstein said. “I think it’s up to all of us in the room to, frankly, prove them wrong.”

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