Energy & Sustainability

NCAR renewable energy prediction system wins prestigious Governor’s Award

BOULDER – A cutting-edge wind and solar energy forecasting system that has saved electricity consumers $40 million has won a prestigious 2014 Colorado Governor's Award for High-Impact Research in the Sustainability category as well as an honorable mention in Public-Private Partnerships. The advanced system, developed by the National Center for Atmospheric Research and implemented for Xcel Energy, has dramatically increased the amount of renewable energy provided to the grid. It was funded by Xcel Energy, which is a national leader on wind energy. Workers install panels being used by the U.S. Department of Energy to leverage a Power Purchase Agreement with Sun Edison and Xcel Energy. A prediction system developed at NCAR is helping Xcel Energy increase the amount of power going from renewable energy systems into the grid.  (Wikimedia Commons photo by Dennis Schroeder.) "It is very gratifying to take our scientific and technological expertise and apply it in a way that has a meaningful impact on society," said William Mahoney, deputy director of NCAR's Research Applications Lab. "We're developing systems that offer the dual benefit of saving costs and reducing emissions of pollutants that are harmful to the environment." The Governor's Award is given each year by CO-LABS, a nonprofit that works to inform the public about the breakthroughs and impacts from Colorado's 30 federally funded labs and research facilities. The CO-LABS consortium includes Colorado federal research laboratories, research universities, state and local governments, economic development organizations, private businesses, and nonprofit organizations. Ken Lund, executive director of Colorado's Office of Economic Development and International Trade, will present the awards at this year's reception on November 12 to teams from NCAR and three other Colorado-based research centers for extraordinary research in the areas of Atmospheric Science, Foundational Technology, Public Health, and Sustainability. The awards presentation will take place at the Denver Museum of Science & Nature.  The sponsor, the Alliance for Sustainable Energy, manages the National Renewable Energy Laboratory (NREL) on behalf of the Department of Energy (DOE).  NREL is the DOE's primary national laboratory for renewable energy and energy efficiency research and development. The annual reception is the major CO-LABS event to showcase Colorado's research facilities and the work of the CO-LABS organization. NCAR's energy forecasting system relies on a suite of tools, including highly detailed observations of atmospheric conditions, energy generation, an ensemble of cutting-edge computer models, and advanced statistical techniques, to issue high-resolution forecasts of wind energy generation that are updated with new information every 15 minutes. "The wind and solar forecasting system developed with NCAR has given Xcel Energy increased confidence each day in determining the amount of renewable energy we can expect, as we strive to provide reliable power at a competitive price for our Colorado customers," said David Eves, president and CEO of Public Service Co. of Colorado, an Xcel Energy company. "We believe this modeling will provide equal certainty for other U.S. utilities as they also increase the amount of renewable generation in their portfolios." "We're very pleased that this investment in an energy forecasting system has paid such significant dividends," said UCAR president Thomas Bogdan. “This work illustrates how an increasingly detailed understanding of the atmosphere leads to important advances for society." NCAR also received honorable mention in the Sustainability category this year for the Global Energy and Water Exchanges (GEWEX) Project, which focuses on developing better ways to understand global and regional climate, especially water resources. NCAR senior scientist Kevin Trenberth and the international GEWEX research team collectively studies the water cycle and how to translate research results into practical applications. Trenberth chaired the GEWEX scientific steering committee from 2010 to 2013. Other winners of this year's Governor's Award include: Atmospheric Science"Into the Air"Cooperative Institute for Research in Environmental Sciences and the National Oceanic and Atmospheric Administration Foundational Technology"Commercialization of Cold-Atom Technology"JILA, University of Colorado Boulder Public Health"An Oral Vaccine Produced in Rice Grain to Reduce the Risk of Lyme Disease" Centers for Disease Control and Prevention (CDC) "Researchers in Colorado's federal laboratories continue to lead the nation with valuable study that addresses some of today's most pressing problems," said Scott Sternberg, chair of CO-LABS. "Our annual ceremony does more than just recognize new discoveries, it also celebrates the impact research and science have on our state." The University Corporation for Atmospheric Research (UCAR) manages NCAR under sponsorship by the National Science Foundation. Any opinions, findings, conclusions, or recommendations expressed in this release do not necessarily reflect the views of the National Science Foundation.    

Will climate change shift renewable energy resources?

October 8, 2014 | Building a large-scale wind farm or solar power plant involves an enormous investment in time and money. Requirements include exploring prime sites for capturing energy from wind or sunshine, purchasing the land, undergoing a potentially lengthy permitting process, and installing costly infrastructure. Not surprisingly, utilities expect such facilities to last many decades. But what if, years from now, changes in climate caused some of the wind or sunshine to shift away from major facilities? An array of wind turbines generates power on a sunny afternoon at the Cedar Creek wind farm in northeast Colorado. New research is providing estimates of how the availability of wind and solar energy might shift as a result of climate change over the next few decades. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.) To help provide guidance to utilities, scientists at NCAR and the National Renewable Energy Laboratory have produced maps that show how wind speeds and solar irradiance may evolve by 2060 across the continental United States. The maps (see bottom of page for a sample) include projections for each season and for different times of day, while taking into account natural variability. The maps provide a first, rough sketch of how wind and solar patterns may shift with climate change. Research into regional climate change remains a challenging field because of uncertainties over how warming temperatures will affect particular parts of the country. The maps were created for the Department of Energy's Regional Energy Deployment System (ReEDS) model, which helps the Energy Department optimize and visualize the build-out of U.S. electricity generation and transmission systems. The underlying research will be submitted to a peer-reviewed publication. As this sampling of maps shows, the United States is likely to experience some noticeable changes in wind and sunshine patterns by 2060. For example, the Northeast should prepare for a slight increase in wintertime winds in the morning at the height of wind turbine hubs (about 250 feet above the ground). In summer and fall, a noticeable reduction in winds at the same time of day is likely. Parts of the Southwest, in contrast, are likely to have less wind at hub height in winter and somewhat more in summer and fall. By 2060, much of the country can expect more energy from the Sun during an average summer morning. In the winter, however, the northern tier is likely to get less energy from the Sun while the southern states receive more. The shifts are not overwhelming—generally 10 percent or less. But they can be important for energy planning. “These are subtle changes but they can make a difference in where a utility sites a wind or solar facility now,” said Sue Haupt, who oversees renewable energy research at NCAR. “Energy managers need to consider whether a resource is going to decline or become stronger in the future.” To create the maps, Haupt and her team drew on an advanced, NCAR-based database of current wind and solar resources, known as the Climate Four Dimensional Data Assimilation System. They then turned to simulations of projected future regional climate conditions that had already been generated by a number of computer models for the North American Regional Climate Change Assessment Program. By using artificial intelligence techniques, they were able to emphasize those computer models that most accurately captured current wind and sunshine conditions and apply those models to produce outlooks of future conditions. Haupt said she hopes to update the maps in a few years, drawing on more sophisticated climate models. Note - October 14, 2014 | The fourth paragraph and maps caption have been updated to clarify that this research, performed for the Department of Energy, will be submitted to a peer-reviewed journal. Writer/contactDavid Hosansky, NCAR & UCAR Communications Collaborating institutionNational Renewable Energy Laboratory FunderNational Renewable Energy Laboratory (U.S. Department of Energy) DIVE DEEPER The maps below indicate possible changes in projected solar radiation (top) and wind speed (bottom) during morning hours, averaged across each of the four seasons, for the year 2060 vs. 1995. Created for the U.S. Department of Energy, the maps provide a first, rough sketch of how wind and solar patterns may shift with climate change. The researchers also created additional maps for afternoon, evening, and overnight conditions. The underlying research will be submitted to a peer-reviewed journal. (Images courtesy Sue Haupt, NCAR.)    

A mother lode of wind power

May 28, 2014 | What if all the energy needed by society existed just a mile or two above our heads? That’s the question raised by researchers in an emerging field known as airborne wind energy, which envisions using devices that might look like parachutes or gliders to capture electricity from the strong, steady winds that blow well above the surface in certain regions. While logistical challenges and environmental questions remain, scientists at NCAR, the University of Delaware, and the energy firm DNV GL have begun examining where the strongest winds are and how much electricity they might be able to generate. This forecast-model depiction of winds at the 850-millibar level (about a mile above the surface) above the United States on January 30, 2013, shows a strong southerly low-level jet stream (red shading) across the Mississippi Valley, with speeds exceeding 60 knots (69 mph). Reliably strong winds at this height could serve as a valuable source of energy. (Image courtesy Weather Underground and Pennsylvania State University.) Their key finding: winds that blow from the surface to a height of 3,000 meters (nearly 10,000 feet) appear to offer the potential to generate more than 7.5 terawatts—more than triple the average global electricity demand of 2.4 terawatts (as of 2012, according to the study). Among the areas where such winds are strongest: the U.S. Great Plains, coastal regions along the Horn of Africa, and large stretches of the tropical oceans. This type of research could prove critical if airborne wind energy takes off. The growing industry now includes more than 20 startups worldwide, exploring various designs for devices that could be tethered to ground stations and then raised or lowered to capture the most suitable winds at any point in time. “From an engineering point of view, this is really complicated,” said NCAR scientist Luca Delle Monache, a co-author of a new study examining these issues. “But it could greatly increase the use of renewable energy and move the U.S. toward the goal of energy independence." To estimate the potential of airborne wind energy, Delle Monache, with Cristina Archer at the University of Delaware and Daran Rife at DNV GL, turned to an NCAR data set known as Climate Four Dimensional Data Assimilation. It blends computer modeling and measurements to create a retrospective analysis of the hourly, three-dimensional global atmosphere for the years 1985–2005. The research team looked for various types of wind speed maxima, including recurring features known as low-level jets. Such jets can be ideal for energy because their speed and density is as high or higher than jets at higher elevations that would be beyond the reach of tethered wind devices. They also blow more steadily than winds captured by conventional wind turbines near the surface, potentially offering a more reliable source of energy. Low-level jets blowing at 30-50 miles per hour or more can be found at several locations worldwide, often close to mountainous terrain or to persistent atmospheric features that help focus and channel wind. One of the strongest low-level jets on Earth flows from the Gulf of Mexico north across the Great Plains. A study by the scientists, published last month in Renewable Energy, focused on winds in January and July. The team is now looking for additional funding to provide a more complete picture of the potential of higher-level winds. Their main goals are to estimate the strength of the winds year round and to build an interface that would enable users to explore the strength of the winds over specific regions. “It’s important to understand the magnitude of this resource and what might be possible,” Delle Monache said. Writer/contactDavid Hosansky, NCAR & UCAR Communications Lead researchersCristina Archer, University of DelawareLuca Delle Monache, NCARDaran Rife, Garrad Hassan FundersNational Science FoundationDefense Threat Reduction Agency Dive deeper Christina L. Archer, Luca Delle Monache, and Daran L. Rife, "Airborne wind energy: Optimal locations and variability," Renewable Energy 64 (2014), 180–186 "High-Altitude Wind Energy: Huge Potential—And Hurdles." Environment 360 (Yale University), September 2012 In Graphic Terms During the month of July (shown above), wind speed maxima through the lowest several miles of the atmosphere exceed 15 meters per second (34 mph) in several locations around the world, including areas in the central United States and off the U.S. West Coast. The world's strongest low-level winds at that time of year are found east of Somalia. (Image reproduced from Archer et al., 2014.)

California dryin’

Bob Henson • January 13, 2014 | The first precipitation measurements in what’s now downtown San Francisco began in July 1849, a year before statehood. Now extending almost 165 years, the local rainfall database is one of the nation’s longest—and never has it shown a year as dry as 2013. From the Mexican border to the Pacific Northwest, the past 12 months have left records lying in the dust. It’s been the most parched calendar year in the weather annals of two state capitals (Salem, OR, and Sacramento, CA) as well as Los Angeles and other locations in between. The table below shows how far the new records dipped not only below average but below the prior records.   City             New record     Old record      Average     Records begin   Los Angeles, CA     3.60”       4.08” (1953)     14.93”     1877  San Francisco, CA   5.59”       9.00” (1917)     23.65”     1849  Shasta Dam, CA     16.61”      27.99” (1976)     62.72”     1943  Eugene, OR         21.19”      23.56” (1944)     46.10”     1890 San Francisco’s rainfall is prone to sharp swings from one calendar year to the next, but the dry conditions of 2013 are well below anything experienced since precipitation records began there in 1849. The recording site has moved several times within the downtown area during this period (see history). Golden Gate Weather Services maintains a comprehensive website with various San Francisco rainfall statistics. (Graphic ©UCAR, data courtesy Jan Null. This image is freely available for media & nonprofit use.)   Given this magnitude, it’s impressive how little everyday life in California has been affected by the growing drought. Despite pleas from lawmakers, the state has yet to declare a drought emergency, and Angelenos aren’t yet being asked to take any special measures. That’s largely due to the peculiarities of water supply and delivery across the Southwest. It’s a complex system involving both water and energy, and NCAR scientists are working to unravel how its future may evolve in a climate where rainfall trends are uncertain. Update – January 17: California governor Jerry Brown officially declared a drought emergency today. Two kinds of years As impressive as the 2013 rainfall records are, those who watch California weather will be even more focused on what happens over the next several months. Most of the state’s rainfall comes in the winter—roughly a third of the water used in California is drawn from the Sierra Nevada’s vast snowpack—so it’s the fall-through-spring totals that make or break things in the dry heat of summer. That’s why experts look to the water year (July–June), rather than the calendar year, as the crucial index of California precipitation. That said, the 2013–14 water year is off to a rotten start. It’s telling that a 900-acre fire destroyed dozens of homes in the Big Sur area only a few days before Christmas. The Sierra’s snowpack water content was 84 percent below average as of January 10. This week appears likely to bring record warmth to much of California, along with strong, dry winds and high fire danger in some areas. Rather than bringing wet storms from the Pacific into California, the jet stream at the 500-millibar level (about 18,000 feet) arced far to the north during most of December 2013, as shown in this map of conditions averaged for the month. (Original graphic by NOAA/ESRL Physical Sciences Division, courtesy John Monteverdi, San Francisco State University.) The culprit: a powerful, persistent ridge of upper-level high pressure has prevailed off the U.S. West Coast for more than a year now. This pattern—the strongest and longest-lasting of its type in decades, according to meteorologist/blogger Daniel Swain—tends to steer wet, mild Pacific storms far to the north. Fairbanks, Alaska, got its third freezing rain event of the autumn in early December, a time when the average low temperature there is around –12°F. East of this high pressure zone, which Swain has dubbed "The Ridiculously Resilient Ridge," the jet stream has dipped well south into the central and eastern U.S., bringing some of the most intense winter chill that's been observed in recent years (including the subzero air mass that invaded the region last week). Right now, both the short-range and seasonal outlooks remain worrisome. The most recent model guidance from the National Weather Service's Global Forecast System (GFS), which looks ahead 16 days, suggests little if any rain for much of California into the last week of January. And the latest seasonal outlook from NOAA indicates that the drought is likely to persist throughout most of the Southwest through March. As Swain puts it, "each day that passes without meaningful precipitation is another day when our long-term deficits grow measurably larger." A rainless ridge dominates the southwest United States, including California, in the 384-hour forecast produced by the NWS Global Forecast System at 06Z (1:00 a.m. EST) on January 13. The graphic above shows cumulative precipitation in inches predicted by the model for the entire 16-day period ending on January 29. (Image courtesy NOAA/NWS National Centers for Environmental Prediction.) Still, things can change quickly this time of year, notes Jan Null (Golden Gate Weather Services). Now a consulting meteorologist, Null is a former lead forecaster at the Bay Area’s National Weather Service office. He’s followed regional rainfall for a long time, having completed his master’s thesis at San José State University on San Francisco’s precipitation climatology. Null points out that, as opposed to the frequent but lighter rains of a Seattle winter, California tends to gain most of its precipitation in a few big events, which often occur from midwinter to early spring. “We still have almost six months to go,” says Null. “There are terms in the water community such as Fabulous February, Miracle March, and Awesome April. All of these have been used when we’ve turned things around after the first half of the water year.” Focusing too much on the calendar year data, Null adds, “is like taking the last half of one 49ers game, combining it with the first half of the next game, and saying, ‘We won!’ ” A nexus of moisture and power Water and energy are intertwined in many ways across the U.S. Southwest, including California. Some of those connections stand out more clearly in the harsh light of a drought. Yet there’s been little quantitative study of the interplay between the two variables as climate change unfolds. Using the Southwest as a first case study, NCAR’s David Yates and colleagues have developed a modeling system that takes on this challenge. It tracks how energy and water resources interact as population and water demands grow and as climate swings in and out of periods of drought. The "bathtub ring" around Lake Mead (top, photographed in 2007), an important water source for California, reveals the effect of low levels since the early 2000s. After reaching a record low in 2010–11, the reservoir made a brief recovery before dipping back down over the last two years. As of January 13,  the reservoir's water level was at 48% of capacity ("full pool"). (Wikimedia Commons photo by Waycool27; chart courtesy Lake Mead Water Database.) Yates and NCAR colleague Kathleen Miller recently published a summary of the project, which is supported by the NOAA Sectoral Applications Research Program. It incorporates two models, both developed for resource managers by the Stockholm Environment Institute in collaboration with NCAR: The Water Evaluation and Planning (WEAP) system The Long-range Energy Alternatives Planning (LEAP) system There’s no shortage of complexity when trying to accurately represent and predict the flows and interrelationships of water and energy across the Southwest. California's vast cities and farms draw most of their water from the yearly Sierra snowpack and the Colorado River system, including Lake Mead (pictured at right). It takes a lot of energy to move water hundreds of miles from those locations to where it’s needed. In fact, an estimated 19% of California’s electricity use and 32% of its natural gas consumption are related to water use. And there are complex regulations dictating who gets first rights to each drop. Yates and colleagues are now analyzing results from a WEAP-LEAP integration that examines how a ten-year-long drought—similar to the driest decade in a paleoclimatic simulation of the period 1456 to 1500—might affect the California of the 2020s. Among other things, a drop in available hydropower could force the state to consume more fossil fuel, which could butt up against increasingly strict guidelines for greenhouse gas emissions. Reduced hydropower would also cut into the very energy that’s used to pump water from distant reservoirs to farms and cities. Desalination is drawing interest as a way to wring potable water from the oceans that lie next door to California’s biggest cities. However, it also requires major power. A WEAP-LEAP analysis of this topic assumes that about 5% of Southern California’s water could be produced by desalination by the year 2049. In that scenario, greenhouse gas emissions are slightly higher than for “business as usual,” and the region would still need to import large amounts of water due to growing demands on top of increased year-to-year variability. Long-term outlooks, short-term implications Climate models for the 21st century continue to disagree on whether total precipitation will increase or decrease this century across the Southwest, as noted in a 2013 regional report serving as input for this year’s pending U.S. National Climate Assessment.  The risk of long-term precipitation decline appears greater the further south you go in the region, and short-term variability is expected to remain larger than any longer-term shift. In the most recent weekly U.S. Drought Monitor, based on data through January 7, 2013, about 28% of California is categorized as being in "extreme drought," and more than 98% of the state is experiencing some level of drought. (Analysis by Matthew Rosencrans, NOAA Climate Prediction Center.) There’s higher confidence that rising temperatures will tend to pull more moisture out of the system when drought happens to strike. Warmer conditions will tend to reduce the average snowpack and advance the timing of spring melt across the Sierras. Similar effects are expected in the snowy, high-altitude origins of the Colorado River. The NCAR-led Colorado Headwaters project has been working to simulate how water supplies downstream might change as the century unfolds.  As for the current drought, Yates is watching it closely. After two consecutive water years on the dry side, a severe drought this year could bring increasing trouble. Los Angeles is high on the hydrological pecking order, so the city is projecting ample water supply into at least 2015, but some Central Valley farmers may have to let fields go fallow this summer. Many other complications could ensue if the drought extends into midyear, including an increased risk of major wildland fires. Groundwater often serves as a backup during California drought, but increased pumping is making that resource more scarce over time—and the pumping itself uses energy. “It’ll be interesting to see how agricultural irrigators turn to groundwater and what kind of impact that has on electricity use in California,” says Yates. “If there’s a hot summer,I wouldn’t be surprised to see strains on the electrical system.”

NCAR powers up renewable energy forecasts

BOULDER—The National Center for Atmospheric Research (NCAR), building on a pioneering wind energy forecasting system that saved millions of dollars for Xcel Energy ratepayers in eight states, has entered into a new agreement with the utility for even more sophisticated weather forecasts. Wind turbines in northeast Colorado. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.) In the next two years, NCAR scientists and engineers will develop custom forecasting systems to predict sudden changes in wind, shut down turbines ahead of potentially damaging icing events, and even predict the amount of energy generated by private solar panels. The systems will be used by Xcel Energy control centers in Denver; Minneapolis; and Amarillo, Texas. The cutting-edge forecasts will help Xcel Energy, and potentially other utilities, to provide reliable power to their customers and reduce costs while moving to greater use of wind and solar. “This is pushing the state-of-the-art still further, using the latest science to enable Xcel Energy to generate energy from the atmosphere more effectively,” says NCAR program director Sue Ellen Haupt, who is overseeing the new project. “Every improvement to the forecasts results in additional savings.” Xcel Energy officials say the more accurate forecasts are critical as they increase their use of renewable energy. “The importance and value of accurate renewable energy generation forecasts increases with the size of our renewable energy generation portfolio,” says Ben Fowke, chairman, president, and CEO of Xcel Energy. “Xcel Energy has been the largest utility provider of wind energy for the last nine years and we are continuing to grow our renewable energy portfolio.” The new project represents the latest venture by NCAR into renewable energy. In addition to the lab’s earlier work with Xcel, it is also spearheading a three-year, nationwide project to create unprecedented, 36-hour forecasts of incoming energy from the Sun for solar energy power plants. “By creating more detailed and accurate forecasts of wind and Sun, we can produce a major return on investment for utilities,” says Thomas Bogdan, president of the University Corporation for Atmospheric Research, which manages NCAR on behalf of the National Science Foundation. “This type of cutting-edge research helps make renewable energy more cost competitive.” Reliable forecasts needed Xcel Energy has been utilizing increasing amounts of energy from renewable sources, especially wind. But this shift means relying on resources that are challenging to predict and manage. Changes in weather can have significant impacts on wind energy production. This graphic shows how passing thunderstorms and a cold front generated an 800-megawatt jump in energy production over the course of just four hours. (Image courtesy Sue Ellen Haupt, NCAR. This image is freely available for nonprofit and media use.) Energy generated by a wind turbine, solar panel, or any other source must be promptly consumed because large amounts of electricity cannot be stored in a cost-effective manner. If an electric utility powers down a coal or natural gas facility in anticipation of wind-driven energy, those plants may not be able to power up fast enough should the winds fail to blow. The only option in such a scenario is to buy energy on the spot market, which can be very costly. In order to help utility managers anticipate wind energy more reliably, NCAR began designing a wind energy prediction system for Xcel Energy in 2009 that saved the utility’s customers over $6 million in 2010 alone. The specialized system relies on a suite of tools, including highly detailed observations of atmospheric conditions, an ensemble of powerful computer models, and artificial intelligence techniques to issue high-resolution forecasts for wind farm sites. Following up on that work, NCAR has entered into a two-year agreement with Xcel Energy to focus on the following areas: Forecasting “ramp” events. A new system under development at NCAR can provide utility managers with advance notice of a major change in wind energy over a few hours due to a passing front or another atmospheric event. The system, known as VDRAS (Variational Doppler Radar Analysis System) relies on techniques that combine observations from radars and other tools with computer simulations to create more accurate forecasts for particular wind farms. Predicting ice and extreme temperatures. To keep aircraft safe from potentially lethal icing conditions while aloft, NCAR has created state-of-the-art ice forecasting systems that use computer models and specialized algorithms. Applying similar technology, researchers at NCAR and Pennsylvania State University will develop a 48-hour forecasting system at designated wind farms to predict the impacts of freezing rain and fog on wind turbines, which cannot operate when coated in ice. The team also will forecast extreme low and high temperatures, which can cause wind farms to temporarily shut down. Generating solar forecasts. Xcel Energy customers who have their own solar panels draw far less energy from the grid while the sun is out, and can even sell excess energy back to the utility. To help Xcel Energy better anticipate when their customers are getting power from their own panels, NCAR will create a solar energy forecasting system, using a combination of computer models and specialized cloud observing tools. Some of these new systems will provide “probabilistic forecasts,” estimating the chances that a particular weather event will occur. This means that utility managers will be able to make decisions based on whether there is an 80 percent chance of certain weather events at a wind farm the next day, or a 20 percent chance. “We’re taking our expertise in critical areas, such as keeping airplanes safe from icing, and applying it to obtaining as much energy as possible from the atmosphere,” says NCAR program manager Marcia Politovich, who is overseeing the development of icing and extreme temperature forecasts. “This is cutting-edge science.” Once the systems are finalized, they will be turned over to Xcel Energy or a utility contractor for ongoing operation. NCAR researchers will publish the results in peer-reviewed journals, enabling other utilities and forecast providers to learn about the technologies. “Xcel Energy is recognized by the energy industry as a national leader in proactively moving forward with the utilization of renewable energy,” says William Mahoney, deputy director of NCAR's Research Applications Laboratory. "This new project is an example of how improved understanding of the atmosphere can provide significant benefits to society."  

Solar energy to get boost from cutting-edge forecasts

BOULDER—Applying its atmospheric expertise to solar energy, the National Center for Atmospheric Research (NCAR) is spearheading a three-year, nationwide project to create unprecedented, 36-hour forecasts of incoming energy from the Sun for solar energy power plants. A new research initiative is designed to lead to unprecedented 36-hour forecasts of incoming energy from the Sun, thereby helping utilities obtain energy more efficiently from solar energy power plants. (Wikimedia Commons photo by Thomas R. Machnitzki.) The research team is designing a prototype system to forecast sunlight and resulting power every 15 minutes over specific solar facilities, thereby enabling utilities to continuously anticipate the amount of available solar energy. The work, funded primarily with a $4.1 million U.S. Department of Energy grant, will draw on cutting-edge research techniques at leading government labs and universities across the country, in partnership with utilities, other energy companies, and commercial forecast providers. Much of the focus will be on generating detailed predictions of clouds and atmospheric particles that can reduce incoming energy from the Sun. “It’s critical for utility managers to know how much sunlight will be reaching solar energy plants in order to have confidence that they can supply sufficient power when their customers need it,” says Sue Ellen Haupt, director of NCAR’s Weather Systems and Assessment Program and the lead researcher on the solar energy project. “These detailed cloud and irradiance forecasts are a vital step in using more energy from the Sun.” The project takes aim at one of the greatest challenges in meteorology: accurately predicting cloud cover over specific areas. In addition to helping utilities tap solar energy more effectively, detailed cloud predictions can also improve the accuracy of shorter-term weather forecasts. The project expands NCAR’s focus on renewable energy. NCAR designed a highly detailed wind energy forecasting system with Xcel Energy that saved Xcel ratepayers an estimated $6 million in a single year. The center is also creating advanced prediction capabilities to enable wind farm developers to anticipate wind energy potential anywhere in the world. “Improving forecasts for renewable energy from the Sun produces a major return on investment for society,” says Thomas Bogdan, president of the University Corporation for Atmospheric Research, which manages NCAR on behalf of the National Science Foundation. “By helping utilities produce energy more efficiently from the Sun, we can make this market more cost competitive.” Clouded forecasts More than half of all states in the U.S. have mandated that utilities increase their use of renewable energy as a way to reduce dependence on fossil fuels such as coal, oil, and natural gas, which affect air quality and release greenhouse gases associated with climate change. But the shift to energy sources such as solar or wind means relying on resources that are difficult to predict. Because large amounts of electricity cannot be stored in a cost-effective manner, power generated by a solar panel or any other source must be promptly consumed. If an electric utility powers down a coal- or natural gas-fired facility in anticipation of solar energy, those plants may not be able to power up fast enough if clouds roll in. The only option in such a scenario is to buy energy on the spot market, which can be very costly. Conversely, if more sunshine reaches a solar farm than expected, the extra energy can go to waste. But predicting clouds, which form out of microscopic droplets of water or ice, is also notoriously difficult. Clouds are affected by a myriad of factors, including winds, humidity, sunlight, surface heat, and tiny airborne particles, as well as chemicals and gases in the atmosphere. Solar energy output is affected not just by when and where clouds form, but also by the types of clouds present. The thickness and elevation of clouds have greatly differing effects on the amount of sunlight reaching the ground. Wispy cirrus clouds several miles above the surface, for example, block far less sunlight than thick, low-lying stratus clouds. To design a system that can generate such detailed forecasts, NCAR and its partners will marshal an array of observing instruments, including lidars (which use laser-based technology to take measurements in the atmosphere); specialized computer models; and mathematical and artificial intelligence techniques. Central to the effort will be three total sky imagers in each of several locations, which will observe the entire sky, triangulate the height and depth of clouds, and trace their paths across the sky. The team will test these advanced capabilities during different seasons in several geographically diverse U.S. locations: the Northeast, Florida, Colorado/New Mexico, and California. The goal is to ensure that the system works year round in different types of weather patterns. Not just for solar energy Once the system is tested, the techniques will be widely disseminated for use by the energy industry and meteorologists. “This will raise the bar for providing timely forecasts for solar power, ” Haupt says. “It also represents a great opportunity for providing far more detail about clouds in the everyday weather forecasts that we all rely on.” One application for such detailed forecasts could be short-term predictions of pavement temperatures. Such information would be useful to airport managers, road crews, and professional race car drivers. “Pavement temperatures make quite a bit of difference in how tires grip the surface,” says Sheldon Drobot, deputy director of NCAR’s Weather Systems and Assessment Program. “This has substantial safety implications.” NCAR is launching the solar project with numerous partners in the public and private sectors. These include: Government labs: National Renewable Energy Laboratory, Brookhaven National Laboratory, the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory and other NOAA facilities; Universities: The Pennsylvania State University, Colorado State University, University of Hawaii, and University of Washington; Utilities: Long Island Power Authority, New York Power Authority, Public Service Company of Colorado, Sacramento Municipal Utility District (SMUD), Southern California Edison, and the Hawaiian Electric Company; Independent system operators: New York ISO, Xcel Energy, SMUD, California ISO, and Hawaiian Electric; and Commercial forecast providers: Schneider Electric, Atmospheric and Environmental Research, Global Weather Corporation, and MDA Information Systems. Computing time will be provided by the New York State Department of Economic Development's Division of Science, Technology and Innovation on an IBM Blue Gene supercomputer at Brookhaven National Laboratory.

A splash of reality

August 13, 2012 | When it's clean, plentiful, accessible, and controllable, water is easy to take for granted. Things are different when the supply becomes a torrent—or a trickle. For much of the United States, the summer of 2012 has been one of those times. The most extensive U.S. drought in almost 60 years has enveloped some of the nation’s most productive farmland. The impacts go well beyond agriculture: in parts of the Midwest, shifting soils are cracking building foundations and prompting water restrictions more familiar in California than Indiana. In this image, the large bubble atop the central United States represents the volume of all of Earth's water, including oceans and groundwater. The smaller bubble atop Kentucky denotes the volume of Earth's freshwater (groundwater, lakes, swamp water, and rivers), while the tiny bubble over Georgia represents lakes and rivers alone. (Image courtesy USGS Water Science Photo Gallery.) Even as public attention comes and goes, water is consistently Topic A for a wide-ranging group of researchers. Hydrologists have teamed with meteorologists, climate scientists, and engineers to analyze flood, drought, and water storage. The last decade has seen breakthroughs in the mapping of glaciers and aquifers, plus a steadily improving picture of how water flows into and out of the atmosphere. In the United States, there’s a growing network of drought specialists and an enhanced warning system for regional drought. These advances are running neck and neck with ominous trends. Earth’s warming climate threatens to shunt precipitation toward polar regions and the tropics, with an increased risk of drought at latitudes where billions of people live. Higher temperatures will tend to pull more water out of soils. Even without climatic change, the global demand for water continues to grow hand in hand with population. Water access already varies hugely among countries, and major U.S. aquifers are being depleted at a worrisome pace. As portrayed by the National Drought Mitigation Center, the “hydro-illogical cycle” describes how drought, as a slow-moving natural disaster, tends to emerge under the radar screen, then intensify until people can no longer ignore it or wish it away—until it rains again. (Illustration ©National Drought Mitigation Center.) As they work to understand the hydrologic cycle that sustains our water supply, and the evolution of climate factors that may change it, scientists and policy experts at NCAR and elsewhere bemoan what’s been dubbed the “hydro-illogical cycle,” where pulses of public concern triggered by drought evaporate as soon as the rains return. “We ignore drought until the situation is dire, lament the impacts, justifiably call for help, and clamor for emergency funding,” said J.D. Strong, executive director of the Oklahoma Water Resources Board, in written testimony before Congress on July 25 (see PDF). “But invariably it rains, at which point we forget there was ever a problem and go back to business as usual. We must break this cycle.” In this special report, we take a closer look at water availability and the science that's under way at NCAR, UCAR member universities, and a variety of other partners to help us predict its course. Less water than it seems With more than 70% of Earth covered by oceans, it’s impressive how small the supply of freshwater is by comparison—only about 2 to 3% of the planet’s total water (see graphic). More than two-thirds of that freshwater is locked up in polar ice sheets. Much smaller amounts lie in ice caps and glaciers at lower latitudes, where people can access meltwater. Most of the world’s remaining freshwater is held in deep, inaccessible underground aquifers and within the soil itself. Less than 1% of all global freshwater is readily available in rivers, reservoirs, lakes and shallow aquifers, according to a University of Michigan report. As for the atmosphere, it’s not so much a home for water as a highway for it, according to NCAR's Kevin Trenberth, who heads the scientific steering committee for a major international effort to map the world's energy and water cycles (see sidebar at bottom). According to Trenberth, a typical molecule of water vapor enters the atmosphere from the ocean and spends 8 to 9 days in the air before it returns earthward as rain or snow and flows toward the ocean. At that point, the molecule is usually hundreds or even thousands of miles from the place where it evaporated. Earth’s water is perpetually in motion through the global hydrological cycle, which involves ocean, land, clouds, lakes and rivers, plants, snow, and ice. (© UCAR. UCAR Digital Image Library.) It’s a major task for scientists simply to map out how much water exists at each point in this hydrologic cycle. River flows and reservoir levels are monitored around the world, but many nations are hesitant to release the data for research. Moreover, experts have warned for years that the longstanding network of river gauges in many areas, including the United States, is deteriorating. Measuring evapotranspiration (ET)—the process of water transpiring from plants and evaporating from soil, pavement, and other surfaces into the air—is a challenge of its own. About two-thirds of all rain and snow that falls on land areas ends up entering the atmosphere this way. But there’s not yet a gold-standard measurement technique for ET, and variations in space and time remain poorly mapped. There’s been some promise in combining land-based measurements of ET at specially equipped sites with satellite-based estimates over broader regions. More than a dozen institutions from eight nations have been working over the last several years to evaluate such ET datasets in a project called LandFLux-EVAL. And a team led by NASA’s Matthew Rodell used new ET data to balance the water budgets for seven river basins in Africa, Europe, and North and South America. Evapotranspiration (ET)—the amount of water vapor entering the air from sources other than oceans—varies dramatically across the United States, as shown in this map of total ET for the 2007 growing season (May 1–September 30). In parts of the Deep South, ET averaged as much as 15 mm (0.6 inches) per week. The map was prepared by Baburao Kamble as part of a project to assess ET on a weekly basis using data from NASA’s MODIS satellite. (Image courtesy Baburao Kamble, University of Nebraska Lincoln.) Trenberth and colleagues are using a variety of datasets to put together energy and moisture budgets­ on a continent-by-continent basis, depicting flows in and out of each part of the Earth system over the lifecycle of various ingredients. “We’re trying to see how well we can complete the budget not only for the average but for each month,” says Trenberth, who plans to report on the work in December at the annual meeting of the American Geophysical Union. “I think we may be closer than anyone has been so far.”  Computers and water It’s not only long-term budgets that pose challenges when it comes to modeling the flow of water. For short-term weather models, the emphasis is on correctly depicting the timing and location of rain and snow. This depends on a variety of model aspects, including how observations are assimilated in the model and how well the land surface is depicted, according to NCAR’s Jimy Dudhia. He’s one of the lead developers of ARW, the advanced research version of the multiagency Weather Research and Forecasting model. During 2012 hurricane modeling exercises, researchers used the advanced research version of the Weather Research and Forecasting model (NCAR WRF-ARW) to track Hurricane Ernesto as it weakened and moved inland across southern Mexico. This forecast, issued for 0900 UTC on August 14, projected that more than 204 millimeters (8 inches) of rainfall would fall across some areas (shown in white) over the preceding 111 hours. In this version of the model, the spacing between grid points is 4 kilometers (2.5 miles). Click to enlarge. (Image courtesy NCAR/NESL/MMM.) Dudhia adds that short-term models serve as a critical tool in predicting the risk of flash floods. “This is a challenge because the river flow depends so critically on the position, timing, and intensity of rainfall from thunderstorms, especially over complex terrain,” says Dudhia. Climate models have a different assignment—depicting the trends in water behavior over larger areas and longer periods—so they typically include more aspects of the water cycle, including those that play out gradually. The NCAR-based Community Land Model (CLM), one component of the NSF- and DOE-funded Community Earth System Model (CESM), tracks moisture as it evaporates and transpires, falls as rain or snow, enters river channels, and infiltrates the soil. The CLM also depicts accumulating snowfall and includes a reservoir that simulates the water table. Because of perennial limits on computing power, models like the CLM have often specified glaciers, wetlands, and lakes as elements that remain fixed as the climate evolves. Now, says NCAR land modeler Samuel Levis, “we’re beginning to simulate how some of these water bodies may change in response to simulated changes in the climate.” Another branch of models looks more specifically at where water is headed across and below the land surface, with an eye toward helping water planners. Reed Maxwell (Colorado School of Mines) heads up the ParFlow project, an open-source model of watershed flow that draws on CLM and other components developed at NCAR, Los Alamos National Laboratory, the University of Bonn, and the University of Colorado Boulder. A similar effort in Canada, Hydrogeosphere, was developed at the universities of Laval and Waterloo. At Michigan State University, David Hyndman and colleagues are using integrated hydrologic models to examine how precipitation and temperature may shift as climate change affects the water cycle. (Photo by Kurt Stepnitz, courtesy Michigan State University.) At Michigan State University, a team led by David Hyndman is looking at future changes in the water cycle using MSU’s large-scale, high-resolution Integrated Landscape Hydrology Model. “It’s taking the what-if scenario of projected changes in temperature and precipitation and putting that into something that people understand and relate to,” says Hyndman. Of course, human interventions into the hydrologic cycle can be profound, as people dam rivers, tunnel through mountains, and construct canals to move water from its origins to where it is needed. NCAR scientist David Yates and colleagues at the Stockholm Environment Institute have been developing the Water Evaluation and Planning (WEAP) systems model to help water managers and planners understand the implication of climate on our coupled natural and managed water systems. (See "Who needs glaciers?") Where the moisture is moving As greenhouse gases continue to pile up in a warming atmosphere, the job of tracking and projecting Earth's freshwater gets even more complex. But there’s already a good deal of clarity about the direction of some key water trends. For one thing, higher temperatures are expected to rev up the hydrologic cycle. Warmer air allows more water to evaporate from both land and sea, and that added moisture will tend to intensify rain and snow when and where they form, a trend already being observed in the United States and many other places. On the flip side, the dry spells in between precipitation events will tend to grow longer. Combined with the increased ET from soils, this means an enhanced risk of drought in much of the globe, even where total precipitation may not be changing. New work by NCAR’s Aiguo Dai confirms this outlook.  It’s also become more evident that climate change won’t treat all latitudes equally. Climate models still disagree on how precipitation will change in some regions. However, they concur on the big picture: the dry-leaning zones of the subtropics, centered around latitudes 30°N and 30°S, will tend to expand into the midlatitudes and dry out even further, putting intensified pressure on regional water supplies. For example, the dry, sunny climates found in the southwestern United States and the Middle East have fostered irrigation-dependent agriculture and drawn ever-increasing numbers of residents. Meanwhile, precipitation is expected to increase on average closer to the poles and in the belt of heavy rainfall near the equator that shifts north and south with the seasons. The growth of hydrophilanthropy (Photo courtesy David Kreamer.) Hydrologist David Kreamer (University of Nevada, Las Vegas) is encouraging his peers to look at society’s access to water in the broadest possible terms. At a July 2012 meeting in Boulder, Kreamer pointed out that roughly a billion people lack access to clean drinking water and about 5 million die each year from water-related illnesses. To address these issues, Kreamer and other water experts, including Michael Campana (Oregon State University) and his WaterWired blog, are putting energy toward what Kreamer has dubbed hydrophilanthropy. (See PDF of Kraemer’s 2010 article in the Journal of Contemporary Water Research and Education.) “Solutions to global clean water problems are achievable,” said Kreamer. “I think people who are involved in water have a natural proclivity to be philanthropic.” Kraemer reached out to colleagues at the biennial meeting of a unique group fostering collaborative work on water issues. The NSF-sponsored Consortium of Universities for the Advancement of Hydrologic Science (CUAHSI) includes more than 100 colleges, universities, and other institutions. Its major products include online data catalogs, open source software, and the biennial meeting, which is hosted by UCAR every other summer in Boulder. Dozens of researchers gave talks and presented posters in July at this year’s meeting. Keynote speakers included Roger Pielke Jr. (University of Colorado Boulder), Soroosh Sorooshian (University of California, Irvine), and Tom Dunne (University of California, Santa Barbara). “At the high latitudes and the low latitudes, we’re actually seeing increasing water tables,” says Jay Famiglietti, who directs the Hydrology & Climate Research Group at the University of California, Irvine. At the same time, he adds, “Most of the aquifers in midlatitudes are under huge stress.” (See “Reservoirs beneath our feet.”) Glaciers will also feel the pinch of a warming climate, although there are many questions about how quickly an increase in glacial melt might segue into eventual depletion for the millions who rely on glaciers as a primary or supplemental water source. (See “Who needs glaciers?”) How will we manage? As water managers contemplate the future, they’re paying close attention to where efficiency and conservation can make the biggest gains. A new global outlook by the National Intelligence Council predicts that nearly half of humanity will live in water-stressed regions by 2030. Globally and nationally, agriculture gulps more water than any other part of society, making up roughly 80% of water consumption. A single farmer atop the Ogallala Aquifer of the High Plains may draw on as much water as a good-sized city. The ongoing global rise in meat eating is expected to put additional strain on water resources, since it typically takes more water to produce a calorie of meat versus one of grain. The energy sector accounts for an estimated 27% of nonagricultural U.S. water use, as noted in a 2010 Harvard report. Aside from the large amounts of water required to grow corn for ethanol, water is pumped through coal plants and nuclear reactors to keep them cool. Much of that water returns to source streams, albeit at higher temperatures than before. Large amounts of water are also pumped into the ground to squeeze out oil and natural gas, through the technique known as fracking (hydraulic fracturing). This year’s drought is already putting a crimp on the hydrocarbon boom in some U.S. states. For the public, water utilities are the most familiar part of the supply chain, especially when customers are asked or required to restrict water use during dry periods. Through his work with a variety of clients from Florida to California, NCAR’s Yates has seen what happens when finite supplies go head to head with development pressures. “It’s hotly political. People want to build,” he says. However, he believes the intensity of recent droughts, together with rising demand, is starting to engender more caution: “I think the utilities are questioning their assumptions.” David Yates (©UCAR. Photo by Carlye Calvin.) A utility-based alliance is now helping bring water providers into the loop on climate research. (See ”Keeping the tap flowing.”) Yates and NCAR economist Kathleen Miller published a guide (see PDF) to help drinking water utilities anticipate how climate change might affect supply and demand. And Yates collaborated with Denver Water and consulting firm Riverside Technology on a report released in March by the Water Research Foundation. It examines the potential impacts of climate change on water supplies in Colorado’s populous Front Range region, using two different hydrology models. The NCAR-based Colorado Headwaters project is also producing new detail on how precipitation may evolve in the high mountains that feed the Colorado River. (See ”Three state of water.”) Colorado offers a useful window into the complexities of water projections, according to Brad Udall. He directs the Western Water Assessment, one of NOAA’s seven Regional Integrated Science and Assessment groups. “We get affected by weather from all points on the compass,” says Udall. “We’ve got these big mountains and summer monsoonal flow. All of these things are difficult to resolve in our current models.” Stir in climate change, and this detailed portrait morphs into a motion picture. “When a lot of people talk about climate change adaptation, they say, Give me a target and I’ll plan for it. That doesn’t appreciate the fact that the target is going to move throughout the 21st century.” As a rule, says Udall, “We don’t deal very well with moving targets.” Kevin Trenberth (©UCAR. Photo by Carlye Calvin.) A global eye on energy and water cycles The world’s most comprehensive program to outline the flow of heat and moisture through Earth’s atmosphere is heading in new directions. Formerly the Global Energy and Water Cycle Experiment, GEWEX is now Global Energy and Water Exchanges. Adopted in July, the new name reflects the broadening nature of the group’s work. “We recognized that the old name was obsolete—we are no longer an experiment,” says NCAR’s Kevin Trenberth, who chairs the GEWEX scientific steering group. GEWEX is in its 25th year as part of the World Climate Research Programme, with an international project office supported by NASA and located in Silver Spring, MD. Drawing on support from a variety of participating nations, GEWEX fosters collaborative field projects, workshops, dataset development and assessment, and other activities to bolster research on water and energy cycles, with the ultimate goal of reproducing and predicting global hydrologic processes and their effects. As part of an overall revamp of the parent program toward research that supports climate services, GEWEX has adopted a new set of seven imperatives, as well as four grand science questions: How can we better understand and predict precipitation variability and changes?  How do changes in land surface and hydrology influence past and future changes in water availability and security? How does a warming world affect climate extremes, especially droughts, floods, and heat waves, and how do land area processes, in particular, contribute?  How can understanding of the effects and uncertainties of water and energy exchanges in the current and changing climate be improved and conveyed?  

Three states of water

August 13, 2012 | From ocean to ocean, the relationships between individual states and their water supplies are changing. Climate scientists have projected serious regional changes over the next 50 years, but many states are already having to make tough decisions regarding their water use and their interaction with water. Among them are Colorado, Louisiana, and Oklahoma. NCAR scientists are involved in collaborative projects in all three states to evaluate the long-term effects of today’s decisions. Along the Colorado From its high-altitude origins just west of the Continental Divide in the Colorado Rockies, the Colorado River flows onward, providing water for cities and farms throughout much of the southwestern United States. (Photo by Bonnie Carol.) Recent statewide fires have moved Colorado residents to ask hard questions about the future of water and drought in the state. Models project that the warming atmosphere will change the character of winter storms in the Rocky Mountains, affecting residents and farmers across the Southwest who rely on the storms as their primary water source. Snowmelt from the high peaks of the Rockies provides more than 80 percent of the water flowing downstream to major cities, including Phoenix and Las Vegas. To better understand how winter storms will be affected by changes in climate, scientists at NCAR’s Research Applications Laboratory are working to perfect the modeling of precipitation, snowpack, snowmelt, runoff, and other variables in the high-altitude basins where the Colorado River begins its southwestward trek to the Pacific. NCAR's Roy Rasmussen heads the interdisciplinary team behind the Colorado Headwaters Project. (© UCAR. Photo by Carlye Calvin.) Dubbed the Colorado Headwaters Project, this team of 15 people led by Roy Rasmussen is made up of atmospheric and social scientists and engineers. It also collaborates with researchers at the University of Colorado Boulder, the University of Washington, and the University of Texas at Austin. The goal is to better understand how the complex terrain of the Rockies affects rain and snow on the small scale, and to incorporate that knowledge into larger-scale projections from climate models going decades into the future. The team used the advanced research version of the Weather Research and Forecasting model (ARW), which reproduced snowfall and other weather variables for four winters from the last decade with high accuracy at points separated by as little as 5 kilometers (about 3 miles). They also drew on results from the NCAR-based Community Climate System Model (which is supported by NSF and the U.S. Department of Energy). Those results indicated that the region’s climate would see a 3.6ºF (2ºC) increase in temperature and a 15% increase in precipitation over recent conditions by 2045–55 if global emissions of greenhouse gases continue to increase at a moderate pace. The group then used the CESM estimates with ARW to determine what would happen on a finer scale. Colorado’s famed terrain produces wide variations in rain and snow across small areas. To better reproduce these patterns in weather and climate projections, the Colorado Headwaters effort is employing high-resolution models that depict major peaks, ridges, and valleys across the state. (Image courtesy Colorado Headwaters project.) The results showed that snowfall increased overall by 12% at midcentury compared to the past decade. However, the results varied by altitude: snowpack increased at the highest elevations and decreased at lower elevations. "Our results show islands of enhanced snow in the highest Colorado peaks, surrounded by areas with more rain and melting," says Rasmussen. Spring melt occurred three weeks earlier than today, and the snowline elevation increased by an average of 660 feet (200 meters). Shifts in runoff and evaporation were also projected. Future studies will consider changes in storm tracks. These findings suggest that different cities will be affected different ways. In states such as Arizona, the changes could mean severe drops in water access; in Colorado, the results suggest a shorter snow season and a snowpack that melts and evaporates more quickly, even with the potential for heavier snow at the highest elevations. David Gochis, an NCAR scientist who works on the project, puts things into perspective from a water-management point of view: “We will still face significant challenges in water management. There will be more evaporation and more pressure on water supplies, particularly in the summertime,” he adds. Coastal concerns At the northern end of Isle de Jean Charles, 30 families of the Biloxi-Chitimacha-Choctaw tribe hold on to land threatened by environmental and commercial pressures. Extending from the top right of the photo is Island Road, the only means of getting to the island from the mainland. (©UCAR. Photo by Monika Wnuk.) On the other side of the Continental Divide, waters from eastern Colorado and many other states flow into the mighty Mississippi, eventually spilling into its famed delta in far southeast Louisiana. Here, the rapidly changing coast tells a complex water story pertinent to coasts everywhere. Hurricanes Katrina and Rita brought attention to the delta’s vulnerability to natural forces, but the daily vulnerability of the coast to geologic and human activity is talked about less often. Natural buffers against storm surge have long been a function of barrier islands, healthy marshes, natural ridges adjacent to bayous, and cypress swamps. In combination with artificial levees, these landscape features have allowed humans to live and work in an otherwise flood-prone area. However, society has also jeopardized the ability of the landscape to repair itself. Land subsidence (sinking) coupled with a rise in sea level have exacerbated erosion and allowed destructive storm surges to penetrate the coast and move further inland. When humans are not affecting the landscape, then river deltas can work to both erode and replenish barrier islands in a cyclic fashion. However, levees built to divert sediments away from Louisiana’s coast haven’t allowed for this cycle to unfold. Moreover, decades of oil drilling have left open pipelines underwater that encourage the flow of salt water into delicate wetland ecosystems. Unaccustomed to saltwater, entire cypress swamps decay along the coast, further contributing to flooding and erosion. NCAR’s SOARS program (Significant Opportunities in Atmospheric Research and Science) sent two students to Louisiana this summer to investigate this multifaceted water issue. See the sidebar at the bottom to dive deeper into the specifics of their community-based research. Drought in a boom-and-bust water regime Only months after heavy winter rains erased a severe drought, Oklahoma returned to record heat and bone-dry conditions in the summer of 2012, paving the way for destructive wildland fires. A fire just east of Norman on August 3 spawned this pyrocumulus cloud, photographed from the roof of the National Weather Center. (Photo courtesy James LaDue, NOAA.) Where Louisiana looks to mitigate the effects of too much water, Oklahoma struggles to make sense of year-to-year variability in precipitation. “There is nothing steady about rain in Oklahoma,” says Jeffrey Basara, director of research at the Oklahoma Climatological Survey. Basara recalls periods of significant drought in 2000, 2006, 2011, and 2012 and how sharply they contrasted with extreme rainfall events like the record-breaking flash flood in Oklahoma City in 2010. Such variability on short time scales calls attention to future water sustainability in the state.  In Oklahoma, aquifers provide most of the water distributed to homes and businesses. The Arbuckle Simpson Aquifer, located in the south-central part of the state, is the only source of water that supports the various streams, rivers, and lakes in a 500-square-mile area, supplying a total of 39,000 users. Ownership and limits to use of the aquifer are now being disputed by a mix of parties, including landowners who wish to sell the water to neighboring states, a group of citizens concerned about preservation and sustainability of Oklahoma’s water supply, and members of the Chickasaw Nation who claim original rights to the source. Since 2003 the aquifer has been studied more intensively than any other in the state. Shown here in light brown, the Arbuckle-Simpson Aquifer is located in south-central Oklahoma. (Map courtesy U.S. Geological Survey.) Scientists in NCAR’s Earth System Laboratory (NESL) are using an interdisciplinary approach to chart how people value water and perceive drought risk in south-central Oklahoma and whether this lines up with climate projections for future water availability. Environmental anthropologist Heather Lazrus is teaming with climatologist Debasish PaiMazumder and ecosystem scientist Erin Towler on the project. NCAR's Heather Lazrus brings an anthropological perspective to an interdisciplinary study of water use in Oklahoma. (©UCAR. Photo by Carlye Calvin.) Based on a foundation of anthropological theory, Lazrus is conducting and analyzing interviews in hopes of illuminating the cultural mechanisms through which people understand water-related risk. PaiMazumder is using NCAR’s Nested Regional Climate Model to develop plausible drought scenarios in Oklahoma’s current and future climates through an exploration of drought impact indices (mainly precipitation, temperature, and soil moisture). And Towler is analyzing stream flow patterns in wet and dry years to understand the impact of drought. Using Lazrus’s findings on how people view water availability and drought risk, PaiMazumder will develop a new index for assessing the damage caused by droughts. The results will be made available to water planners and the public. Also, Towler will identify impacts to drinking water, fishing, and other ecosystem components that rely on water availability. “Our hope is to communicate the potential of drought in a way that parallels how people understand it,” says Lazrus. Monika Wnuk, a recent graduate of the University of Chicago, was an intern with NCAR & UCAR Communications in the summer of 2012. SOARS protégés lead research in the bayou A human issue accompanies the changes in land and water use in coastal Louisiana, where economically vulnerable populations live For her 2012 research as a UCAR SOARS protégé, Sandra Maina (Florida International University) worked with residents of far southeast Louisiana and conceptualized a smartphone application to depict the science and the human stories behind their sinking landscape. (©UCAR. Photo by Monika Wnuk.) on land that is in immediate danger. Among these groups is the Biloxi-Chitimacha-Choctaw Native American tribe residing on the island of Isle de Jean Charles. Forced by westward expansion in the 1800s onto the southernmost part of the Mississippi Delta, this tribe struggles to hold onto the land that has long sustained it. Out of a population of 80 families a decade ago, the remaining 30 families of Native American descent live on a two-mile strip of land on either side of one road, surrounded by land that has become too soggy for use. Residents can only point to where their family’s cow pastures, forests, and cemeteries used to be. A four-foot dirt levee separates their homes from the Gulf of Mexico. Residents drive almost daily to the mainland on a low-lying road that tends to flood. But relocation would be expensive, and there are other factors keeping the remaining families in place. For example, the region is considered a fishing paradise, and tribal members are constantly at odds with fishermen who set up camps on the island. Through UCAR’s SOARS program (Significant Opportunities in Atmospheric Research and Science), Sandra Maina, a graduate student in environmental studies at Florida International University, and Frances Roberts-Gregory, a senior in environmental science and anthropology at Spelman College, spent the summer of 2012 conducting interdisciplinary research in this vulnerable community. Maina and Roberts-Gregory were introduced to local issues by their community mentor, Kristina Peterson, a research associate at the University of New Orleans Center for Hazards Assessment, Response and Technology. Peterson is deeply invested in the community, serving as a pastor at the local Bayou Blue Presbyterian Church and as an activist for the region at conferences across the nation. Following the guidelines of participatory action research, Maina and Roberts-Gregory asked members of the community to express their needs, then designed their projects accordingly. Maina met with community members on the five most vulnerable strips of land along the coast—Chauvin, Dulac, Dularge, Montegut, and Pointe au Chien—in order to identify points of cultural interest that are at risk of flooding and erosion. Following her summer of fieldwork, she hopes to direct the creation of a smartphone application that would map these places and include a history of each one, along with a video message from a community member. The app would also keep users updated on ongoing restoration projects in the area. Even some homes and business that were built on stilts to accommodate flooding are now difficult to access at any time. (©UCAR. Photo by Monika Wnuk.) “Lots of big organizations want to exclude the community,” says Maina. “This smartphone app seeks to include and empower it.” Roberts-Gregory applied tools from ethnobotany and anthropology to determine which culturally significant plants are threatened by ecosystem changes. Her procedure started with documents from the 1930s that details curatives used by Native Americans in the area, supplemented with conversations with community members who work with the same plants. Roberts-Gregory describes her experience with participatory action research as “just as complex as the water situation in Louisiana.” Every week brought new conversations, focus groups, content analysis, and new angles to the issues at hand. Although the process took time, she sees community input as essential to community-relevant results. Both students hope that future scientists continue community-based interdisciplinary projects in the region. From what they’ve seen, residents know the issues and are eager to continue the conversation—and move into action.

Reservoirs beneath our feet

August 13, 2012 | One of the largest bodies of water in the United States can’t be seen from the air. It stretches from Nebraska to Texas, and it helps produce $35 billion in wheat, corn, and other agricultural products each year. But the vast Ogallala Aquifer isn’t on the radar of Rand McNally or Google Maps, because it lies underground. The Gravity Recovery and Climate Experiment (GRACE) measures changes in the mass of water and other Earth-system components by tracking tiny changes in the gravitational pull exerted on its twin satellites. (Image courtesy Astrium.) The Ogallala is part of an array of aquifers around the world that help provide food, water, and energy for millions of people. Much like oil and gas reserves, the bounty of an aquifer can seem endless until its flow begins to slacken. A revolutionary satellite system is giving scientists a far better idea of where aquifers are being depleted the most quickly—vital data for helping manage these enormous but ultimately limited resources. The twin satellites known as GRACE, the Gravity Recovery and Climate Experiment, have been tracking Earth’s gravitational field in detail since 2002. Led by German science agencies, NASA’s Jet Propulsion Laboratory, and the University of Texas at Austin, GRACE measures tiny gravity-induced changes in the tracks of its satellites, which allows scientists to infer changes over time in ocean currents, glaciers, and other geophysical features.  “GRACE has shown us that the human fingerprint on the water landscape is extremely strong,” says Jay Famiglietti, who directs the Hydrology & Climate Research Group at the University of California, Irvine.  A GRACE-ful approach Famiglietti is part of a group of scientists who’ve spent years unraveling GRACE data to deduce how aquifers are changing. The only sure way to verify an aquifer’s depth at any given point is to drill into it. That’s been done courtesy of some 9,000 wells tapping into the water of the Ogallala, which is among the world’s best-characterized aquifers. The depth and volume of many other aquifers isn’t known. But GRACE can monitor changes even without knowing an aquifer's total storage. Satellite data suggests that depletion of northern India's aquifers has continued since NCAR’s Sean Swenson and colleagues published a 2009 analysis. The map above shows the change in total water storage as measured by the GRACE satellite between 2002 and 2012. The graph shows trends for the strongly depleted area in northern India within the box outlined on the map. Year-to-year changes in the monsoon play a large role in the rate of aquifer use, along with increased development and other factors. (Images by Sean Swenson, NCAR.) “We already knew that groundwater is being depleted in these aquifers,” says Famiglietti. “GRACE allows us to quantify the rates of depletion, which is very difficult to do on the ground and almost impossible to do internationally.” Sean Swenson. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.) When NCAR’s Sean Swenson was a graduate student at the University of Colorado Boulder, he developed techniques to reduce errors in GRACE data and greatly improve its spatial resolution. Swenson now focuses on development of NCAR’s Community Land Model, but he’s often asked to participate in GRACE-related research. In 2009, Swenson collaborated on a study led by V.M. Tiwari (National Geophysical Research Institute, India) concluding that groundwater in northern India had been depleted by roughly 54 cubic kilometers (13 cubic miles) per year between 2002 and 2008, perhaps the most rapid loss on Earth for an area that size. “This is probably the largest rate of groundwater loss in any comparable-sized region on Earth," the study noted. With India’s monsoon weaker than normal this year, it’s been suggested that the energy associated with aquifer pumping helped trigger power outages that affected hundreds of millions of people across northern India in late July. Swenson and Famiglietti are collaborating on another study, now in review, examining groundwater depletion in a drought-prone area spanning parts of Turkey, Iraq, and Iran. Swenson is also working with Famiglietti’s former Ph.D. student, Min-Hui Lo (National Central University, Taiwan), to develop models of aquifer loss that GRACE and other data can help verify.  Wells that won’t do so well This map shows the locations of major aquifers in the contiguous 48 states. The Ogalalla Aquifer is shown in pale blue, stretching from Nebraska south to Texas. California’s Central Valley aquifer system is shown in darker blue at far left. (U.S. National Atlas map courtesy Mission 2012: Clean Water.) Within a single aquifer, there can be enormous variation. A recent study led by Bridget Scanlon (University of Texas at Austin) analyzed depletion rates for the Ogallala and for the aquifer system that supports agriculture across California’s fertile Central Valley. The Ogallala’s situation is the more dire of the two. The north end of this aquifer, beneath western Nebraska, is replenished by water descending from the Platte River system through sandy soil. Here, irrigation demands are relatively modest. Further south, there’s very little recharge from surface water, and fine-grained soils help keep rain and snow from percolating downward. Some of the “fossil” groundwater used to irrigate crops in western Kansas and Texas may date back to the last ice age, more than 13,000 years ago. Corn stalks from the previous year’s harvest lie atop parched fields in northeast Colorado in early June 2012. Many of the crops grown in the region rely on irrigation from the vast Ogallala Aquifer. (©UCAR. Photo by Bob Henson. This image is freely available for media & nonprofit use.) Extrapolating from recent depletion rates, Scanlon and colleagues found that some parts of the southern Ogallala may essentially run dry within the next 30 years. That doesn’t necessarily doom farmers; only about 30% of the region’s crops are irrigated, and many farmers would shift to less-thirsty crops as needed. However, the overall stress on water supply would undoubtedly soar. At Michigan State University, Bruno Basso has been examining the effects of Ogallala depletion and climate change on agriculture. He is also investigating the potential impact of adaptation strategies farmers could use to improve soil quality, crop yield, and water use efficiency. The strategies studied by Basso include using water-sipping no-till techniques, optimizing the mix of plants, altering planting dates, and employing new cultivars not yet developed but simulated in crop modeling. These approaches could help keep crop yields from plummeting, says Basso, although he stresses that economic and climatic uncertainties will shape how farmers ultimately act. As opposed to the Ogallala, there's more flexibility in managing water across California’s Central Valley, where rain and snowmelt from the Sierra Nevada helps recharge the aquifer system. Since the 1960s, a set of groundwater banks built within the Tulare River basin has gathered water during wet years and sent it underground, to be pumped back up as needed during dry years. In the Central Valley, “Groundwater banking offers great promise for more sustainable management of groundwater," the study by Scanlon and colleagues concludes. Yet climate change remains a question mark for central California’s aquifers. If precipitation simply became more variable, without increasing or decreasing in the long term, then groundwater banking would be well suited for adapting to that shift. But putting water underground and pulling it back out is an energy-intensive endeavor. And it’s possible that the total amount of rain and snow might decrease, especially toward southern parts of the state. Water expert Jay Famiglietti (University of California, Irvine) is conducting a 50-lecture tour this year sponsored by the American Geophysical Union. (©UCAR. Photo by Bob Henson. This image is freely available for media & nonprofit use.) There’s no doubt that on-and-off drought since around 2000 has taken a toll on water supplies across the U.S. Southwest, including lakes Mead and Powell, which were running at 50-60% of capacity in recent weeks. In a 2011 study, Famiglietti and colleagues estimated that the aquifers beneath California’s Sacramento and San Joaquin River basins had lost nearly enough water in seven years to fill Lake Mead. Beyond the concerns in his own part of the world, Famiglietti is communicating about global pressures on water access in several ways. Later this year, he plans to publish the first GRACE-derived global map of aquifer trends. Right now Famiglietti is in the midst of a 50-week, 50-lecture global tour called Water 50/50, supported by the AGU’s Birdsal-Dreiss Distinguished Lectureship. He’s also one of the featured scientists in a major documentary on water issues, Last Call at the Oasis, released earlier this year. Among his key messages in the film is a call to map out Earth’s water resources as thoroughly as its oil and gas resources have been charted. “Nationally and internationally,” he says, “we need to push for a thorough exploration of Earth’s water environment.”

Who needs glaciers?

August 13, 2012 | The Andean nation of Bolivia doesn’t have a very large carbon footprint. The country covers an area the size of Texas and California combined, yet. it’s home to fewer than 11 million people, most of whom are subsistence farmers. But Bolivia is already experiencing the effects of climate change as its glaciers shrink, putting water supplies at risk. Though the ski lift remains, the glacier that provided decades of skiing atop Bolivia's Chacaltaya peak disappeared in 2009, succeeded only by snowfalls such as this one in early 2011. (Wikimedia Commons image by DiverDave.) “Bolivia is a pretty dry place,” says NCAR scientist David Yates. The slow decline of the glaciers there is a concern because, as Yates points out, these storehouses of ice supply about 20 percent of the water used by major Bolivian cities such as La Paz and Santa Cruz. It’s not yet clear how Bolivia will adapt to the gradual loss of its glaciers, but Yates’ work on water planning will help that nation determine its response. Yates is part of a team based at the Stockholm Environment Institute that’s developed an interdisciplinary model called WEAP to help cities and regions evaluate their water resources and plan for the future. “By incorporating a glacier model into our water planning model,” he says, “we’re able to answer questions like, What is the reliability of these glacial resources over the next 50 to 100 years? and What kind of investments can be made now to secure the water supply in the future?” NCAR's Kathleen Miller specializes in multidisciplinary topics, including the evolving nature of water management in the context of a varying climate. (©UCAR. Photo by Carlye Calvin.) Bolivia is one of many nations around the world where people depend on glaciers for fresh water. Most of the world’s ice is locked in the vast sheets of Greenland and Antarctica; it’s the smaller glaciers in the midlatitudes and tropics that provide water for people. This is where global ice is melting the most quickly, and the situation is drawing increased concern from policymakers and researchers alike. “Everybody will need to understand what risks they face in their particular localities,” says NCAR’s Kathleen Miller, an economist who specializes in climate issues. Budgets out of balance In contrast to the vast, remote ice sheets near the poles, mountain glaciers that provide water for human populations are especially sensitive to warming temperatures. At high elevations, where the air is generally colder, glaciers gain mass from falling snow. At lower elevations, where temperatures are warmer, glaciers lose mass through melting, which provides water used by glacier-dependent areas. This balance of gain versus loss changes throughout the year, as patterns of precipitation and temperature change. However, as a rule, a glacier is stable when snow and melt are equal. A small change in temperature can easily alter this balance and push a glacier into shrinking mode. Warmer air can also turn ice directly from frozen to vapor form without melting, a process called sublimation. In line with the measured warming of the global atmosphere, most of the world’s glaciers have been losing mass on average for the last century or so, with the pace quickening over the last couple of decades.  That trend is expected to continue with increasing concentrations of greenhouse gases and continued warming. Given these trends, says glaciologist Richard Alley (Pennsylvania State University), “we have high confidence that there will be a whole lot of glacier loss.” One of the world's most prominent glaciologists is Richard Alley, based at Pennsylvania State University. (Image courtesy Oregon State University.)  But there are many unknowns when it comes to the details of glacier science. Specialists are trying to get a handle on how fast glaciers will disappear, which ones will go first, and how that will affect water supplies. It’s often not even clear exactly what fraction of the water used by societies is drawn from glaciers, both on the global and local scale, although in South America alone, millions of people are believed to rely in part on glacial water. For any given location, “glaciers aren’t the only source of water,” Miller explains. “Annual precipitation is often the primary source, while glacial melt becomes important during drought years and in late summer, after the annual snow pack has melted.” Glacier science is made even more difficult because not all glaciers act the same. They inhabit different locations, with different topographies beneath them and different climates surrounding them. And while climate change will lead to generally higher temperatures around the globe, it is far more difficult to predict the range of local temperature variability, and changes in precipitation can be even more challenging to project. Some glaciers may actually grow if they receive more snow than they do now, despite rising temperatures. That uncertainty and variation have often led to misinformation about the future of glaciers, particularly in the media. “A lot of the confusion that’s come up in the last several years is largely from generalizations,” says glaciologist Richard Armstrong (University of Colorado Boulder), who studies Himalayan glaciers. In this region alone, he points out, “there’s huge variability from east to west.” On the Tibetan plateau, for example, scientists have documented a recession of the glaciers that feed the Yangtze River in China. However, glaciers in the Karakoram Mountains along the Pakistan-China border grew slightly between 2000 and 2008. There’s a similar east-west contrast in how people use glacial water from the Himalayas, according to Armstrong. River basins in the east, such as the Ganges, are dominated by monsoons, and glaciers supply only about five percent or less of the water used there. Further west, in the mountains of Pakistan and Afghanistan, perhaps as much as half of the water supply comes from glaciers. As a whole, the Himalayas are losing ice, although not nearly as fast as stated in the Intergovernmental Panel on Climate Change’s Fourth Assessment Report in 2007. The report included a claim that failed to meet the IPCC’s requirements for scientific peer review. Based on a single magazine interview, the erroneous claim asserted that Himalayan glaciers would disappear by 2035. When the error and its source were identified, the IPCC issued a retraction. In that statement, the panel stressed that the findings in its overarching synthesis report remained valid: “Widespread mass losses from glaciers and reductions in snow cover over recent decades are projected to accelerate throughout the 21st century. . . . This conclusion is robust, appropriate, and entirely consistent with the underlying science and the broader IPCC assessment.”  Despite some decade-to-decade variation, the amount of water trapped in the world's glaciers decreased nearly every year from 1945 to 2005. (Fig. 5.9 from Chapter 5 (PDF) of Global Glacier Changes, courtesy United Nations Environment Programme.)  As Penn State’s Alley points out, “The basic picture is: warming melts ice. Is it possible to find an exception? Yes. Do you find lots and lots of exceptions? No.” Saving for a dry day The loss of glaciers will be felt particularly in river basins that depend heavily on them for meltwater. As glacial melt increases, it can release hundreds or thousands of years of locked-up water. The tap may flow more freely for a time in glacier-dependent communities. But in the longer run, glacial water will inevitably become less available, putting supplies for drinking, agriculture, and hydropower at risk and causing societies to consider water use more carefully. The Andes are home to the majority of the world’s tropical glaciers, which have been melting faster than any others, as documented by Lonnie Thompson (Ohio State University) and other pioneers of tropical glaciology. Some of these low-latitude ice stores are already completely gone. The mountain of Chacaltaya in Bolivia, for example, was home to the world’s highest ski lift for half a century. But after years of loss, the Chacaltaya glacier disappeared in 2009. According to Edson Ramírez (Universidad Mayor de San Andrés, Bolivia), it was a drop in snowfall rather than a rise in temperatures that sealed Chacaltaya’s fate. A similar process, driven by drying rather than warming, appears to be the culprit behind the loss of ice atop Mt. Kilimanjaro in Africa. Such reductions in tropical snowfall may themselves be related to large-scale warming and associated changes in atmospheric circulation, a topic of active research. La Paz, Bolivia, is among the world’s cities most dependent on water from glaciers. (Wikimedia Commons image by Wayne McLean.) More than skiing is at risk with the loss of Andean glaciers: the depletion may increase water costs and impair local economies. Hydropower, which provides 80 percent of Peru’s energy, 50 percent of Ecuador’s and nearly all of the electricity in the Bolivian capital of La Paz, could become less available, leading to higher energy prices or rationing. The full scope of the threat is not yet known, though. “One problem we have in the Andes is that the database we work with is very, very poor,” says climate scientist Mathias Vuille (University of Albany, State University of New York). “There are not enough weather stations in the region, and there has not been a good maintenance of these stations.” Andean nations tend to be poor and lack their own scientists, and many have undergone social upheaval that has interfered with glacial studies. The research now taking place in Andean nations will help to guide adaptations to the loss of glacier-based water supplies. The project that NCAR’s Yates is working on in Bolivia, for example, will inform the Inter-American Development Bank on how to invest in infrastructure projects, such as reservoirs, watershed management, and reforestation, so that money is wisely invested. “If there’s no water to fill a reservoir, you’ve just spent a bunch of money, probably had environmental impacts, and put a reservoir in a place where it won’t meet its objectives,” Yates says. A census of ice Glacier modeling, too, will aid in better assessments. The task of modeling glaciers in large numbers has been made much easier by the release earlier this year of the National Snow and Ice Data Center’s Randolph Glacier Inventory, which provides surface areas for most of the world’s estimated 160,000 glaciers as well as the locations for many of the world’s smaller glaciers and ice caps. With this in hand, scientists can compensate for many of the variations and unknowns in glacier science. For example, with a solid estimate of global glacier surface areas, scientists can estimate the volume of ice contained in these ice masses, and potentially model changes to this volume using climate models. “Glacier ice is a viscous fluid, and we know how it operates,” says Jeremy Fyke, a glacier modeler doing postdoctoral research at Los Alamos National Laboratory. “If you pour pancake batter onto a surface, you can generally figure out how thick that pancake is if you look at its area. It’s sort of the same thing with glaciers.” But modelers say they would still benefit from knowing more about the topography of the bedrock beneath glaciers and about the climate surrounding them. “A lot of these glaciers are in remote places,” Fyke notes. “They’re not cheap places to go and take measurements.” Some measurements can be taken from space—the glacier inventory, for instance, primarily used data from NASA’s Terra satellite—“but that’s sometimes inadequate,” Fyke says. “The science is improving every year, but local changes in precipitation and resulting changes in water supplies and glacier mass-balance can’t be known yet,” says NCAR’s Miller. However, she adds, that need not stop the process of preparing for a reduced water supply from glaciers. “Trying to develop a contingency planning approach will help nations respond well to any change that manifests itself.” Sarah Zielinski is a freelance writer based in Washington, D.C.


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