Cutting greenhouse gas emissions would help spare cities worldwide from rising seas

BOULDER, Colo. — Coastal cities worldwide would face a reduced threat from sea level rise if society reduced greenhouse gas emissions, with especially significant benefits for New York and other U.S. East Coast cities, new research indicates.The study, by scientists at the National Center for Atmospheric Research (NCAR), used a powerful computer model to tease out the ways that winds and currents in a warming world push ocean water around, lifting it in some regions and lowering it in others. The scientists examined how these variations in sea level rise would change under two conditions: if emissions continue on their current trajectory, or if they are sharply reduced.The results showed that, if society can implement cuts soon on emissions of carbon dioxide and other heat-trapping gases, the projected increases in sea level around the globe would be significantly less toward the end of the century. This would help coastal cities in much of the world as they try to fend off rising waters, with the benefits most pronounced for cities on parts of the Atlantic and Indian oceans.Projected sea level rise for major cities worldwide will vary significantly later this century, depending on whether society continues to increase emissions of greenhouse gases at the current rate (a scenario known as RCP 8.5) or begins to sharply reduce them (RCP 4.5). Some cities, such as New York and London, would see particularly pronounced benefits if society cuts emissions. For more details on the range of projected sea level rise for major cities, click on the graphic or see table below. (Graphic by Simmi Sinha, ©UCAR. Click to enlarge. This graphic is freely available for media & nonprofit use.)  "Mitigating greenhouse gases will reduce sea level rise later this century, with some regions seeing especially significant benefits," said NCAR scientist Aixue Hu, the lead author of the new study. "As city officials prepare for sea level rise, they can factor in the compounding effect of local conditions, which are due to the winds and currents that cause internal variability in the oceans."Hu and his co-author, NCAR scientist Susan Bates, caution that the modeling study presents an incomplete picture, because it does not include runoff from melting ice sheets and glaciers — two factors that scientists are just now incorporating into computer models. Instead, it simulates the influence of climate change on variations in sea level worldwide to reveal which coastlines will benefit most from emission reductions associated with the additional heat absorbed by the ocean.The study, published this month in the journal Nature Communications, was funded by the U.S. Department of Energy and by the National Science Foundation, which is NCAR's sponsor.Global changes with local impactsSea level rise is one of the most consequential impacts of climate change, threatening to swamp low-lying islands and major coastal cities. Sea levels in some regions are expected to rise by several feet by the end of this century, due to a combination of melting ice sheets and glaciers (which account for about two-thirds of sea level rise) along with thermal expansion, or ocean waters expanding as they warm (which accounts for the remaining one-third).To study how changes in emissions would affect global sea level rise and local variations, Hu and Bates used two sets of computer simulations that are based on two different greenhouse gas scenarios.In the business-as-usual scenario, with emissions from human activity continuing to increase at current rates, global temperatures by late this century would rise by about 5.4 degrees Fahrenheit (3 degrees Celsius) over late 20th century levels. In the moderate mitigation scenario, with society taking steps to reduce greenhouse gases, warming would be held to about 3.2 degrees F (1.8 degrees C).The scientists found that reducing greenhouse gas emissions would not significantly restrain sea level rise for the next two decades. The reason, in part, has to do with the inertia of the climate system (once heat enters the oceans, it is retained for a period of time). In addition, winds and currents are naturally variable from year to year, pushing ocean water in different directions and making it hard to discern the full impact of planet-scale warming over the span of a decade or two.But the scientists found that later in the century, from 2061 to 2080, reduced emissions would have a significant impact across almost the entire world. The simulations showed that the extent of mean global sea level rise from thermal heat expansion (but not runoff from melting ice) was reduced by about 25 percent, from about 17.8 centimeters (7 inches) in the business-as-usual scenario to 13.2 centimeters (5.2 inches) in the moderate mitigation scenario.Locally, winds and currents make a differenceFor some cities, the benefits of the lower-emission scenario would be especially significant. New York City, where sea levels this century are expected to rise more than almost anywhere else in the world, would see a difference of 9.8 centimeters (3.9 inches). Other cities that would see a greater-than-average reduction include Boston (9.3 cm/3.7 in), London (8.3 cm/3.3 in), Dar es Salaam (6.8 cm/2.7 in), Miami (6.5 cm/2.6 in), and Mumbai (5.8 cm/2.3 in).On the other hand, some cities in South America (such as Buenos Aires), Asia (such as Bangkok and Jakarta), Australia (such as Melbourne), and the west coast of North America (such as Vancouver and San Francisco) would see lower-than-average benefits. And reducing greenhouse gases would have no statistically significant effect on sea level rise along the western coasts of Australia and the Philippines.The reason for the local differences in sea level rise has to do with the influence (or lack thereof) of a changing climate on major currents and on atmosphere-ocean interactions around the globe.In the northern Atlantic, for example, warming temperatures are expected to weaken the Gulf Stream that transports warmer water from the subtropics to the Arctic. The powerful current draws water away from much of the east coast of the United States, and scientists have warned that a weakening current would send those waters back toward the coastline and significantly raise sea levels. If actions taken by society resulted in reduced emissions, the Gulf Stream would be less affected and, therefore, sea level rise in the north Atlantic would be less substantial.In contrast, the currents in some other ocean basins appear to be less sensitive to climate change. Across much of the Pacific, for example, sea levels are influenced by the Pacific Decadal Oscillation, a phenomenon related to winds and sea surface temperatures. Although climate change is affecting winds and causing sea surface temperatures to rise in the Pacific, it is not disrupting currents there as much as it is in the northern Atlantic. As a result, climate change mitigation that reduces thermal expansion would generally have a less significant effect on Pacific sea levels.The study also found greater variations in future sea level rise in different regions, including some cities where local sea levels are influenced by the Pacific Decadal Oscillation or by an Atlantic climate pattern known as the North Atlantic Oscillation. As a result, the projected sea level rise in the model varied more for London and Tokyo than for New York."City planners in some places will be able to make decisions based on more certain sea level projections, but for other places it's going to be more difficult to know what the sea levels will be," Bates said.About the paperTitle: Internal climate variability and projected future regional steric and dynamic sea level rise
Authors: Aixue Hu and Susan BatesJournal: Nature CommunicationsNew research estimates the extent to which sea level rise would be reduced for major cities worldwide by later this century if society cuts emissions of greenhouse gas emissions. These tables incorporates projections based on the thermal expansion of ocean water as well as on the localized impacts of winds and currents, but they do not include additional sea level rise caused by the melting of ice sheets and glaciers. (Data produced by Aixue Hu and Susan Bates, NCAR. Graphic by Simmi Sinha, UCAR. Click to enlarge. This graphic is freely available for media & nonprofit use.)

UCAR statement on President Trump's budget proposal

Antonio Busalacchi, the president of the University Corporation for Atmospheric Research (UCAR), issued the following statement about the administration's budget proposal for fiscal year 2019:Today's budget proposal marks the formal starting point of a months-long process by the Trump administration and Congress to determine spending for the 2019 fiscal year that begins Oct. 1. UCAR will work with its member universities and other partners in the Earth system science community to ensure that the government continues to invest in crucial research that saves lives and property, fosters economic growth, and strengthens our national security.Although Congress agreed last week to increase spending levels for this fiscal year and next, today's budget proposal from the administration contains significantly lower spending levels in some areas. While it is not yet clear what the government’s investment in science will be, UCAR’s message will not change. We believe it is essential that cuts do not occur in important research areas that could put U.S. scientific leadership at risk. The budget should also support the goals of the Weather Research and Forecasting Improvement Act, which the president signed into law last year to improve forecasts for business and public safety officials as well as the general public. As we saw last year, improved understanding of the atmosphere is crucial for our nation's resilience. The United States endured 16 weather and climate disasters in 2017 that each cost $1 billion or more in damages, including Hurricanes Harvey, Irma, and Maria, as well as devastating California wildfires, major tornado outbreaks, and floods. These events, which left hundreds dead, cost a combined total of more than $300 billion — setting a grim new annual record for the nation. Even routine weather events have an annual economic impact of hundreds of billions of dollars, affecting food production, transportation, supply chain management, consumer purchasing, and virtually every other economic sector. High in our atmosphere, space weather disturbances pose an ongoing threat to GPS systems, communications networks, power grids, and other technologies that are essential for U.S. military readiness and the everyday functioning of our society.Responding to these risks, scientists at government agencies, universities, and the multibillion-dollar private weather industry are successfully developing a new generation of observing instruments and computer models. We are gaining the ability to predict major atmospheric and related hazards weeks, months, or even more than a year in advance, providing needed intelligence to public safety, business, and military leaders. As rival nations make major investments into better understanding the Earth system, it is more imperative than ever to focus on this work and maintain U.S. preeminence.UCAR is extremely grateful to the bipartisan majorities in the House and Senate who voted for the Weather Research and Forecasting Improvement Act and who continue to support investments into research funding. We look forward to working with Congress and the administration over the coming months as they negotiate the details of next year’s budget. 

The climate secrets of southern clouds

BOULDER, Colo. — This month, an international team of scientists will head to the remote Southern Ocean for six weeks to tackle one of the region's many persistent mysteries: its clouds.What they discover will be used to improve climate models, which routinely underestimate the amount of solar radiation reflected back into space by clouds in the region. Accurately simulating the amount of radiation that is absorbed or reflected on Earth is key to calculating how much the globe is warming.The field campaign, called the Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study, or SOCRATES, could also help scientists understand the very nature of how clouds interact with aerosols — particles suspended in the atmosphere that can be from either natural or human-made sources. Aerosols can spur cloud formation, change cloud structure, and affect precipitation, all of which affect the amount of solar radiation that is reflected.During the mission, which will run from mid-January through February, the scientists will collect data from a bevy of advanced instruments packed onboard an aircraft and a ship, both of which are specially designed for scientific missions."SOCRATES will allow for some of the best observations of clouds, aerosols, radiation, and precipitation that have ever been collected over the Southern Ocean," said Greg McFarquhar, a principal investigator and the director of the University of Oklahoma Cooperative Institute for Mesoscale Meteorological Studies (CIMMS). "These data will provide us with critical insight into the physics of cloud formation in the region, information we can use to improve global climate models."The U.S. portion of SOCRATES is largely funded by the National Science Foundation (NSF).“The Southern Ocean is famously remote and stormy and it's hard to imagine a worse place to do a field campaign. But a vast, stormy ocean is a great laboratory for studying clouds, and it's clear from our models that we have a lot to learn about them,” said Eric DeWeaver, program director for Climate and Large-Scale Dynamics in NSF’s Geoscience directorate."I'm excited about this campaign because I think it will answer some fundamental questions about clouds and their dependence on atmospheric conditions," DeWeaver said. "We'll be able to use this information to understand cloud behavior closer to home and how clouds are likely to adjust to changing climatic conditions."Critical observing and logistical support for SOCRATES is being provided by the Earth Observing Laboratory (EOL) at the National Center for Atmospheric Research (NCAR). Other U.S. principal investigators are based at the University of Washington.The Australian portion of SOCRATES is largely funded by the country's government through the Australian Marine National Facility, which is owned and operated by CSIRO.A supercooled mysteryMcFarquhar and his colleagues think the reason that climate models are not accurately capturing the amount of radiation reflected by clouds above the Southern Ocean is because they may not be correctly predicting the composition of the clouds. In particular, the models may not be producing enough supercooled water — droplets that stay liquid even when the temperature is below freezing.One possible explanation for the problem is the way models represent how clouds interact with aerosols, a process that affects the amount of supercooled water in a cloud. These representations were developed from atmospheric observations, largely in the Northern Hemisphere, where most of the world's population lives.But the atmosphere over the Northern Hemisphere — even over the Arctic — contains many more pollutants, including aerosols, than the atmosphere over the Southern Ocean, which is relatively pristine."We don't know how appropriate the representations of these processes are for the Southern Hemisphere," McFarquhar said. "SOCRATES will give us an opportunity to observe these cloud-aerosol interactions and see how much they differ, if at all, from those in the Northern Hemisphere."Flying through hazardous cloudsThe NSF/NCAR HIAPER Gulfstream V has been modified to serve as a flying laboratory. (©UCAR. This figure is freely available for media & nonprofit use.)For the SOCRATES field campaign, observations will be taken from the NSF/NCAR High-performance Instrumented Airborne Platform for Environmental Research, or HIAPER, a highly modified Gulfstream V aircraft, and the R/V Investigator, an Australian deep-ocean research vessel."Much of what we currently know about Southern Ocean cloud, aerosol, and precipitation properties comes from satellite-based estimates, which are uncertain and have undergone few comparisons against independent data," said co-investigator Roger Marchand, a scientist at the University of Washington. "The data collected during SOCRATES will also enable us to evaluate current satellite data over the Southern Ocean, as well as potentially help in the design of better satellite-based techniques."The research aircraft will be based out of Hobart, Tasmania, and will make about 16 flights over the Southern Ocean during the course of the campaign. The many high-tech instruments on board will measure the size and distribution of cloud droplets, ice crystals, and aerosols, as well as record the temperature, winds, air pressure, and other standard atmospheric variables.The instruments include NCAR's HIAPER Cloud Radar (HCR) and High Spectral Resolution Lidar (HSRL). The wing-mounted HCR is able to "see" inside clouds and characterize the droplets within, while the HSRL can measure air molecules and aerosols. Together, the two highly advanced instruments will give scientists a more complete picture of the wide range of particles in the atmosphere above the Southern Ocean.The nature of the research — flying a plane in search of supercooled water —presents some challenges with aircraft icing."Oftentimes, the cleaner the air, the more probable large drops and severe icing conditions become," said Cory Wolff, the NCAR project manager who is overseeing aircraft operations for SOCRATES. "We have a number of precautions we're taking to mitigate that risk."First, a mission coordinator whose sole job is to monitor icing conditions will join each flight. Second, the design of the flights themselves will help the crew anticipate icing conditions before they have to fly through them. On the flight south from Tasmania, the HIAPER GV will fly high above the clouds — and the icing danger. During that leg of the flight, the scientists will collect information about the clouds below, both with onboard radar and lidar as well as with dropsondes — small instrument packages released from the aircraft.With that information, the scientists can determine whether it's safe to pilot the aircraft through the clouds on the return trip, collecting detailed information about the cloud composition.Sailing the stormiest seasThe Australian R/V Investigator will take measurements of the atmosphere and ocean during its six-week voyage. (Image courtesy CSIRO.)The measurements taken from the sky will be complemented by data collected from instruments on board the Australian R/V Investigator, including the NCAR Integrated Sounding System. The ISS gathers extensive data by using a radar wind profiler, surface meteorology sensors, and a balloon-borne radiosonde sounding system. The team will launch soundings every six hours, and sometimes more often, throughout the campaign."Observations from the ship will help us understand the background state of the atmosphere — how it's behaving," said NCAR scientist Bill Brown, who traveled to Australia in late November to prepare the ISS for the voyage.The ship will be deployed for the entire six weeks and will face its own challenges, notably the notorious roughness of the Southern Ocean, sometimes called the stormiest place on Earth."There are no land masses to break up the winds down there," Brown said. "So the ocean can be quite rough."SOCRATES investigators will also draw on measurements from another Australian ship as it travels between Tasmania and Antarctica on resupply missions, the R/V Aurora Australis, as well as observations from buoys and some land-based instruments on Macquarie Island."I am excited that we will have such a comprehensive suite of observations," McFarquhar said. "If we just had the cloud observations we wouldn’t have the appropriate context. If we just had the aerosols and measurements below the clouds, we wouldn't be able to understand the complete picture."For more about the SOCRATES campaign, visit the project website.Collaborating institutions:Australian Antarctic DivisionAustralian Bureau of MeteorologyAustralian Department of Environment and EnergyColorado State UniversityCooperative Institute for Mesoscale Meteorological StudiesCSIROKarlsruhe Institute of TechnologyMonash UniversityNational Center for Atmospheric ResearchNational Science FoundationNorthWest Research AssociatesQueensland University of TechnologyUniversity of California San DiegoUniversity of Colorado BoulderUniversity of Illinois at Urbana-ChampaignUniversity of MelbourneUniversity of OklahomaUniversity of Washington

UCAR names inaugural Next Generation Fellows

BOULDER, Colo. — The University Corporation for Atmospheric Research has announced winners of the inaugural UCAR Next Generation Fellowships. The first cohort of three graduate students was selected from a highly competitive field. The fellowships are intended for graduate students from underrepresented communities who hold an undergraduate degree in atmospheric or related Earth system science and are attending a North American university for graduate work. Successful candidates receive financial support for two years of graduate school and two summer internships.The program offers three distinct tracks: Earth system science, diversity and inclusion in the Earth system sciences, and public policy."I am excited to welcome this talented inaugural cohort," said Antonio Busalacchi, UCAR president. "We created the Next Generation Fellowships because we recognize the value and importance of fostering greater diversity in Earth system science. I look forward to the mutual benefits that interaction with our new fellows will bring and welcome them to the UCAR community."The 2017 UCAR Next Generation Fellows(*indicates a UCAR Member Institution)Tania Lopez - Earth System Science FellowCarnegie Mellon UniversityUCAR Fellow Tania Lopez At Carnegie Mellon University, Tania Lopez is studying civil and environmental engineering as a first-year Ph.D. student. Her examination of engineering design standards and of changes in observed extreme precipitation are the first phases in her research on the impact of climate change on precipitation patterns for stormwater infrastructure design decisions, performance, and resilience. Lopez is interested in developing more expertise in computational and statistical tools for analyzing precipitation data and understanding changes in current and projected future patterns. These interests will bring her to Boulder to strengthen collaboration with NCAR scientists during her summer internships in 2018 and 2019.Lopez received a B.S. in engineering physics from Mexico's Monterrey Institute of Technology and Higher Education (ITESM). She credits her family’s encouragement for her persistence pursuing and achieving her goals. "Despite the difficulties I came across pursuing higher education, I was not discouraged," she said. "My desire grew stronger and I could envision a clearer goal." That included a master’s in civil and environmental engineering at Carnegie Mellon, which she earned on the way to her current doctoral studies. "I have always felt passionate about my field, my decisions, and speaking up for minority inclusion," she said. Lopez sums up her career ambitions this way: "to serve as an effective intermediary between climate science and decision making concerned with engineered systems, where human needs and climate interact."Aara’L Yarber - Diversity and Inclusion FellowPennsylvania State University*UCAR Fellow Aara'L Yarber First-year doctoral student Aara’L Yarber is in the meteorology program at Pennsylvania State University. She is studying atmospheric and climate dynamics and their societal impacts, with particular interest in Africa and the Caribbean. Yarber is planning research using WRF, the Weather Research and Forecasting model, along with its dust module, with the goals of developing an observation network in West Africa and of improving understanding of dust transport and its linkage to respiratory disease. She will continue focusing on her dual interests in environmental science and environmental justice during her 2018 and 2019 summer internships in Boulder with the UCAR Office of Diversity and Inclusion.Yarber began her undergraduate studies at Howard University* with a focus on physics and astronomy. With several undergraduate courses in weather and climate under her belt, she then participated in an atmospheric field campaign in Sal, Cape Verde. It was the summer before her senior year, and during the campaign she "became fascinated with weather, climate, and air quality, and the effects of these phenomena on underrepresented groups." In pursuit of atmospheric science, she hopes "to contribute not only to scientific advancement but also positively influence social and environmental change." Her career goals include advocating for diversity in atmospheric science "not only for the sole purpose of scientific advancement but to provide voices for communities that have long faced environmental inequity."Linh Anh Cat - Public Policy FellowUniversity of California, Irvine*UCAR Fellow Linh Anh CatLinh Anh Cat is in the fourth year of the doctoral program in ecology at the University of California, Irvine. In addition to her dissertation work on patterns of fungal disease dispersal and climate change, she has written a science policy review linking that research to her public policy focus. The review examines valley fever, a fungal disease prevalent in the U.S. Southwest, and calls for binational cooperation with Mexico to study the negative impact of climate change on exposure. She will explore her policy interests during her summer 2018 and 2019 internships with UCAR’s Washington, D.C., office.For her undergraduate work at the University of Central Florida, Cat earned dual bachelor of science degrees in environmental studies (policy track) and in biology. She has contributed to an array of activities during her academic career that reflect her interest in working at the intersections of diversity, equity, inclusion, and science policy. In addition to her studies, these activities have ranged from organizing local science outreach events to serving on the American Association of University Women’s National Student Advisory Council to tackle women and minority representation in STEM. "My goal is to be a leader in science policy," Cat said. "I want to work on enacting innovative policies at the intersection between climate change, air quality, human health, and the disproportionate impact on women and minorities."

North American storm clusters could produce 80 percent more rain

BOULDER, Colo. — Major clusters of summertime thunderstorms in North America will grow larger, more intense, and more frequent later this century in a changing climate, unleashing far more rain and posing a greater threat of flooding across wide areas, new research concludes.The study, by scientists at the National Center for Atmospheric Research (NCAR), builds on previous work showing that storms are becoming more intense as the atmosphere is warming. In addition to higher rainfall rates, the new research finds that the volume of rainfall from damaging storms known as mesoscale convective systems (MCSs) will increase by as much as 80 percent across the continent by the end of this century, deluging entire metropolitan areas or sizable portions of states."The combination of more intense rainfall and the spreading of heavy rainfall over larger areas means that we will face a higher flood risk than previously predicted," said NCAR scientist Andreas Prein, the study's lead author. "If a whole catchment area gets hammered by high rain rates, that creates a much more serious situation than a thunderstorm dropping intense rain over parts of the catchment.""This implies that the flood guidelines which are used in planning and building infrastructure are probably too conservative," he added.The research team drew on extensive computer modeling that realistically simulates MCSs and thunderstorms across North America to examine what will happen if emissions of greenhouse gases continue unabated.The study will be published Nov. 20 in the journal Nature Climate Change. It was funded by the National Science Foundation, which is NCAR's sponsor, and by the U.S. Army Corps of Engineers. Hourly rain rate averages for the 40 most extreme summertime mesoscale convective systems (MCSs) in the current (left) and future climate of the mid-Atlantic region. New research shows that MSCs will generate substantially higher maximum rain rates over larger areas by the end of the century if society continues a "business as usual" approach of emitting greenhouse gases . (©UCAR, Image by Andreas Prein, NCAR. This image is freely available for media & nonprofit use.)A warning signalThunderstorms and other heavy rainfall events are estimated to cause more than $20 billion of economic losses annually in the United States, the study notes. Particularly damaging, and often deadly, are MSCs: clusters of thunderstorms that can extend for many dozens of miles and last for hours, producing flash floods, debris flows, landslides, high winds, and/or hail. The persistent storms over Houston in the wake of Hurricane Harvey were an example of an unusually powerful and long-lived MCS.Storms have become more intense in recent decades, and a number of scientific studies have shown that this trend is likely to continue as temperatures continue to warm. The reason, in large part, is that the atmosphere can hold more water as it gets warmer, thereby generating heavier rain.A study by Prein and co-authors last year used high-resolution computer simulations of current and future weather, finding that the number of summertime storms that produce extreme downpours could increase by five times across parts of the United States by the end of the century. In the new study, Prein and his co-authors focused on MCSs, which are responsible for much of the major summertime flooding east of the Continental Divide. They investigated not only how their rainfall intensity will change in future climates, but also how their size, movement, and rainfall volume may evolve.Analyzing the same dataset of computer simulations and applying a special storm-tracking algorithm, they found that the number of severe MCSs in North America more than tripled by the end of the century. Moreover, maximum rainfall rates became 15 to 40 percent heavier, and intense rainfall reached farther from the storm's center. As a result, severe MCSs increased throughout North America, particularly in the northeastern and mid-Atlantic states, as well as parts of Canada, where they are currently uncommon.The research team also looked at the potential effect of particularly powerful MCSs on the densely populated Eastern Seaboard. They found, for example, that at the end of the century, intense MCSs over an area the size of New York City could drop 60 percent more rain than a severe present-day system. That amount is equivalent to adding six times the annual discharge of the Hudson River on top of a current extreme MCS in that area."This is a warning signal that says the floods of the future are likely to be much greater than what our current infrastructure is designed for," Prein said. "If you have a slow-moving storm system that aligns over a densely populated area, the result can be devastating, as could be seen in the impact of Hurricane Harvey on Houston."This satellite image loop shows an MCS developing over West Virginia on June 23, 2016. The resulting floods caused widespread flooding, killing more than 20 people.  MCSs are responsible for much of the major flooding east of the Continental Divide during warm weather months. (Image by NOAA National Weather Service, Aviation Weather Center.) Intensive modelingAdvances in computer modeling and more powerful supercomputing facilities are enabling climate scientists to begin examining the potential influence of a changing climate on convective storms such as thunderstorms, building on previous studies that looked more generally at regional precipitation trends.For the new study, Prein and his co-authors turned to a dataset created by running the NCAR-based Weather and Research Forecasting (WRF) model over North America at a resolution of 4 kilometers (about 2.5 miles). That is sufficiently fine-scale resolution to simulate MCSs. The intensive modeling, by NCAR scientists and study co-authors Roy Rasmussen, Changhai Liu, and Kyoko Ikeda, required a year to run on the Yellowstone system at the NCAR-Wyoming Supercomputing Center.The team used an algorithm developed at NCAR to identify and track simulated MCSs. They compared simulations of the storms at the beginning of the century, from 2000 to 2013, with observations of actual MCSs during the same period and showed that the modeled storms are statistically identical to real MCSs.The scientists then used the dataset and algorithm to examine how MCSs may change by the end of the century in a climate that is approximately 5 degrees Celsius (9 degrees Fahrenheit) warmer than in the pre-industrial era — the temperature increase expected if greenhouse gas emissions continue unabated.About the paperTitle: Increased rainfall volume from future convective storms in the USAuthors: Andreas F Prein, Changhai Liu, Kyoko Ikeda, Stanley B Trier, Roy M Rasmussen, Greg J Holland, Martyn P ClarkJournal: Nature Climate Change  

UCAR Congressional Briefing: Moving research to industry

WASHINGTON — Federally funded scientific advances are enabling the multibillion-dollar weather industry to deliver increasingly targeted forecasts to consumers and businesses, strengthening the economy and providing the nation with greater resilience to natural disasters, experts said today at a congressional briefing.The panel of experts, representing universities, federally funded labs, and the private sector, said continued government investment in advanced computer modeling, observing tools, and other basic research provides the foundation for improved forecasts.The nonprofit University Corporation for Atmospheric Research (UCAR) sponsored the briefing."Thanks to a quiet revolution in modern weather prediction, we can all use forecasts to make decisions in ways that wouldn't have been possible just 10 years ago," said Rebecca Morss, a senior scientist with the National Center for Atmospheric Research (NCAR) and deputy director of the center's Mesoscale and Microscale Meteorology Lab. "Now we are looking to the next revolution, which includes giving people longer lead times and communicating risk as effectively as possible."Fuqing Zhang, a professor of meteorology and statistics at Pennsylvania State University, highlighted the ways that scientists are advancing their understanding of hurricanes and other storms with increasingly detailed observations and computer modeling. Researchers at Penn State, for example, fed data from the new National Oceanic and Atmospheric Administration GOES-R satellite into NOAA's powerful FV3 model to generate an experimental forecast of Hurricane Harvey that simulated its track and intensity."The future of weather forecasting is very promising," said Zhang, who is also the director of the Penn State Center for Advanced Data Assimilation and Predictability Techniques.  "With strategic investments in observations, modeling, data assimilation, and supercomputing, we will see some remarkable achievements."Mary Glackin, director of science and forecast operations for The Weather Company, an IBM business, said the goal of the weather industry is to help consumers and businesses make better decisions, both by providing its own forecasts and by forwarding alerts from the National Weather Service. The Weather Company currently is adapting a powerful research weather model based at NCAR, the Model for Prediction Across Scales (MPAS), for use in worldwide, real-time forecasts.The NCAR-based Model for Prediction Across Scales simulates the entire globe while enabling scientists to zoom in on areas of interest. It is one of the key tools for improving forecasts in the future. (©UCAR. This image is freely available for media & nonprofit use.) "We have a weather and climate enterprise that we can be extremely proud of as a nation, but it's not where it should be," Glackin said. "Weather affects every consumer and business, and the public-private partnership can play a pivotal role in providing better weather information that is critically needed."Antonio Busalacchi, president of UCAR, emphasized the benefits of partnerships across the academic, public, and private sectors. He said that research investments by the National Science Foundation, NOAA, and other federal agencies are critical for improving forecasts that will better protect vulnerable communities and strengthen the economy."These essential collaborations between government agencies, universities, and private companies are driving landmark advances in weather forecasting," Busalacchi said. "The investments that taxpayers are making in basic research are paying off many times over by keeping our nation safer and more prosperous."The briefing was the latest in a series of UCAR Congressional Briefings that draw on expertise from UCAR's university consortium and public-private partnerships to provide insights into critical topics in the Earth system sciences. Past briefings have focused on wildfires, predicting space weather, aviation weather safety, the state of the Arctic, hurricane prediction, potential impacts of El Niño, and new advances in water forecasting.

AGU, AMS honor NCAR scientists

BOULDER, Colo. — Three senior scientists from the National Center for Atmospheric Research (NCAR) have been recognized by professional organizations for their exceptional contributions in the atmospheric and climate sciences. NCAR Distinguished Senior Scientist Kevin Trenberth is being awarded the Roger Revelle Medal by the American Geophysical Union (AGU). The honor, named after a renowned oceanographer, is given annually to recognize “outstanding contributions in atmospheric sciences, atmosphere-ocean coupling, atmosphere-land coupling, biogeochemical cycles, climate or related aspects of the Earth system.”Trenberth is an expert in climate variability and climate change, and he has pioneered research into the interactions between the atmosphere and the oceans, especially the El Niño and La Niño cycle. Trenberth will receive the medal at the AGU annual meeting in December, held this year in New Orleans.NCAR Senior Scientist Clara Deser has been chosen by the American Meteorological Society (AMS) to be the 2018 Walter Orr Roberts Lecturer at the organization's annual meeting, to be held in January in Austin, Texas. The appointment, named after NCAR's founding director, is conferred in "recognition of significant contributions to the understanding of atmospheric processes derived from multidisciplinary research activities."Deser's lecture, which will be given Jan. 11, is  "New Perspectives on the Role of Internal Variability in Regional Climate Change and Climate Model Evaluation." She uses both models and observations to study climate variability and climate change.NCAR Senior Scientist Gordon Bonan has been named a fellow of the AMS. Fellows are elected for making "outstanding contributions to the atmospheric or related oceanic or hydrologic sciences or their applications during a substantial period of years."Bonan's research examines the interactions of terrestrial ecosystems with climate. He specializes in the development of, and experimentation with, models of the Earth's biosphere, atmosphere, hydrosphere, and geosphere systems.Kevin TrenberthClara DeserGordon Bonan

New approach to geoengineering simulations is significant step forward

BOULDER, Colo. — Using a sophisticated computer model, scientists have demonstrated for the first time that a new research approach to geoengineering could potentially be used to limit Earth’s warming to a specific target while reducing some of the risks and concerns identified in past studies, including uneven cooling of the globe.The scientists developed a specialized algorithm for an Earth system model that varies the amount and location of geoengineering — in this case, injections of sulfur dioxide high into the atmosphere — that would in theory be needed, year to year, to effectively cap warming. They caution, however, that more research is needed to determine if this approach would be practical, or even possible, in the real world.The findings from the new research, led by scientists from the National Center for Atmospheric Research (NCAR), Pacific Northwest National Laboratory (PNNL), and Cornell University, represent a significant step forward in the field of geoengineering. Still, there are many questions that need to be answered about sulfur dioxide injections, including how this type of engineering might alter regional precipitation patterns and the extent to which such injections would damage the ozone layer. The possibility of a global geoengineering effort to combat warming also raises serious governance and ethical concerns."This is a major milestone and offers promise of what might be possible in the future,” said NCAR scientist Yaga Richter, one of the lead authors. “But it is just the beginning; there is a lot more research that needs to be done."Past modeling studies have typically sought to answer the question "What happens if we do geoengineering?" The results of those studies have described the outcomes — both positive and negative — of injecting a predetermined amount of sulfates into the atmosphere, often right at Earth's equator. But they did not attempt to specify the outcome they hoped to achieve at the outset.In a series of new studies, the researchers turned the question around, instead asking, "How might geoengineering be used to meet specific climate objectives?""We have really shifted the question, and by doing so, found that we can better understand what geoengineering may be able to achieve," Richter said.The research findings are detailed in a series of papers published in a special issue of the Journal of Geophysical Research – Atmospheres.Mimicking a volcanoIn theory, geoengineering — large-scale interventions designed to modify the climate — could take many forms, from launching orbiting solar mirrors to fertilizing carbon-hungry ocean algae. For this research, the team studied one much-discussed approach: injecting sulfur dioxide into the upper atmosphere, above the cloud layer.The idea of combating global warming with these injections is inspired by history's most massive volcanic eruptions. When volcanoes erupt, they loft sulfur dioxide high into the atmosphere, where it's chemically converted into light-scattering sulfate particles called aerosols. These sulfates, which can linger in the atmosphere for a few years, are spread around the Earth by stratospheric winds, forming a reflective layer that cools the planet.To mimic these effects, sulfur dioxide could be injected directly into the stratosphere, perhaps with the help of high-flying aircraft. But while the injections would counter global warming, they would not address all the problems associated with climate change, and they would likely have their own negative side effects.For example, the injections would not offset ocean acidification, which is linked directly to carbon dioxide emissions. Geoengineering also could result in significant disruptions in rainfall patterns as well as delays in healing the ozone hole. Moreover, once geoengineering began, if society wanted to avoid a rapid and drastic increase in temperature, the injections would need to continue until mitigation efforts were sufficient to cap warming on their own.There would also likely be significant international governance challenges that would have to be overcome before a geoengineering program could be implemented."For decision makers to accurately weigh the pros and cons of geoengineering against those of human-caused climate change, they need more information," said PNNL scientist Ben Kravitz, also a lead author of the studies. "Our goal is to better understand what geoengineering can do — and what it cannot."Modeling the complex chemistryFor the new studies, the scientists used the NCAR-based Community Earth System Model with its extended atmospheric component, the Whole Atmosphere Community Climate Model. WACCM includes detailed chemistry and physics of the upper atmosphere and was recently updated to simulate stratospheric aerosol evolution from source gases, including geoengineering."It was critical for this study that our model be able to accurately capture the chemistry in the atmosphere so we could understand how quickly sulfur dioxide would be converted into aerosols and how long those aerosols would stick around," said NCAR scientist Michael Mills, also a lead author. "Most global climate models do not include this interactive atmospheric chemistry.”The scientists also significantly improved how the model simulates tropical stratospheric winds, which change direction every few years. Accurately representing these winds is critical to understanding how aerosols are blown around the planet.The scientists successfully tested their model by seeing how well it could simulate the massive 1991 eruption of Mount Pinatubo, including the amount and rate of aerosol formation, as well as how those aerosols were transported around the globe and how long they stayed in the atmosphere.Then the scientists began to explore the impacts of injecting sulfur dioxide at different latitudes and altitudes. From past studies, the scientists knew that sulfates injected only at the equator affect Earth unevenly: over-cooling the tropics and under-cooling the poles. This is especially problematic since climate change is warming the Arctic at a faster rate. Climate change is also causing the Northern Hemisphere to warm more quickly than the Southern Hemisphere.The researchers used the model to study 14 possible injection sites at seven different latitudes and two different altitudes — something never before tried in geoengineering research. They found that they could spread the cooling more evenly across the globe by choosing injection sites on either side of the equator.The simulations on the left represent how global temperatures are expected to change if greenhouse gas emissions continue on a "business as usual" trajectory. The simulations on the right show how temperature could be stabilized in a model by injecting sulfur dioxide high into the atmosphere at four separate locations. Because greenhouse gases are being emitted at the same rate in the simulations on the left and the right, stopping geoengineering would result in a drastic spike in global temperatures. (©UCAR. This image is freely available for media & nonprofit use.)  Meeting multiple objectivesThe researchers then pieced together all their work into a single model simulation with specific objectives: to limit average global warming to 2020 levels through the end of the century and to minimize the difference in cooling between the equator and the poles as well as between the northern and southern hemispheres.They gave the model four choices of injection sites — at 15 degrees and 30 degrees North and South in latitude — and then implemented an algorithm that determines, for each year, the best injection sites and the quantity of sulfur dioxide needed at those sites. The model's ability to reformulate the amount of geoengineering needed each year, based on that year's conditions, also allowed the simulation to respond to natural fluctuations in the climate.The model successfully kept the surface temperatures near 2020 levels against a background of increasing greenhouse gas emissions that would be consistent with a business-as-usual scenario. The algorithm’s ability to choose injection sites cooled the Earth more evenly than in previous studies, because it could inject more sulfur dioxide in regions that were warming too quickly and less in areas that had over-cooled.However, by the end of the century, the amount of sulfur dioxide that would need to be injected each year to offset human-caused global warming would be enormous: almost five times the amount spewed into the air by Mount Pinatubo on June 15, 1991.Flipping the research question"The results demonstrate that it is possible to flip the research question that's been guiding geoengineering studies and not just explore what geoengineering does but see it as a design problem,” said Doug MacMartin, a scientist at Cornell and the California Institute of Technology. “When we see it in that light, we can then start to develop a strategy for how to meet society’s objectives."In the current series of studies, adjusting the geoengineering plan just once a year allowed the researchers to keep the average global temperature to 2020 levels in a given year, but regional temperatures — as well as seasonal temperature changes — were sometimes cooler or hotter than desired. So next steps could include exploring the possibility of making more frequent adjustments at a different choice of injection locations.The scientists are already working on a new study to help them understand the possible impacts geoengineering might have on regional phenomena, such as the Asian monsoons."We are still a long way from understanding all the interactions in the climate system that could be triggered by geoengineering, which means we don’t yet understand the full range of possible side effects," said NCAR scientist Simone Tilmes, a lead author. "But climate change also poses risks. Continuing research into geoengineering is critical to assess benefits and side effects and to inform decision makers and society."The research was funded by the Defense Advanced Research Projects Agency and the National Science Foundation, NCAR's sponsor.Any opinions, findings and conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation or the Defense Advanced Research Projects Agency.About the papers:Titles:Radiative and chemical response to interactive stratospheric sulfate aerosols in fully coupled CESM1(WACCM), DOI: 10.1002/2017JD027006Sensitivity of aerosol distribution and climate response to stratospheric SO2 injection locations, DOI: 10.1002/2017JD026888Stratospheric Dynamical Response and Ozone Feedbacks in the Presence of SO2 Injections, DOI: 10.1002/2017JD026912The climate response to stratospheric aerosol geoengineering can be tailored using multiple injection locations, DOI: 10.1002/2017JD026868First simulations of designing stratospheric sulfate aerosol geoengineering to meet multiple simultaneous climate objectives, DOI: 10.1002/2017JD026874Authors: B. Kravitz, D. MacMartin, M. J. Mills, J. H. Richter, and S. TilmesCo-authors: F. Vitt, J. J. Tribbia, J.-F. LamarqueJournal: Journal of Geophysical Research – AtmospheresData access: All the data from the experiments are available on the Earth System Gridat and or Snider, Senior Science Writer

Free family fun at Super Science Saturday: Nov. 4

BOULDER, Colo. — Come learn about our wild weather at this year’s Super Science Saturday on Nov. 4 from 10 a.m. to 4 p.m. at the National Center for Atmospheric Research (NCAR) Mesa Lab in south Boulder.The free, family-oriented event will feature weather balloon launches and a storm-chasing vehicle. Shows by NCAR wizards will include simulations of lightning and fire tornadoes, a special version of a storm surge with an intrepid reporter on the scene, and a "lightning jellyfish."Local science organizations will be on hand with special activities throughout the building."Weather can be scary, but it's also exciting and fun," said Eileen Carpenter, a science education specialist at the University Corporation for Atmospheric Research (UCAR), which manages NCAR. "The more you know about wild weather, the more you can enjoy it while staying safe."Free tickets for the scheduled shows or workshops are available at the door. Snacks and lunch items will be available for purchase in the cafe (cash only). Parking will be limited, so please consider carpooling.DetailsWhat: Super Science SaturdayWhen: Saturday, Nov. 4 from 10 a.m. to 4 p.m.Where: NCAR’s Mesa Lab, 1850 Table Mesa Drive, BoulderWho:  Activities for the entire family, with events especially focused on children ages 6 to 12.Cost:  FreeA weather balloon launch at last year's Super Science Saturday (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)

Future volcanic eruptions could cause more climate disruption

BOULDER, Colo. — Major volcanic eruptions in the future have the potential to affect global temperatures and precipitation more dramatically than in the past because of climate change, according to a new study led by the National Center for Atmospheric Research (NCAR). The study authors focused on the cataclysmic eruption of Indonesia's Mount Tambora in April 1815, which is thought to have triggered the so-called "year without a summer" in 1816. They found that if a similar eruption occurred in the year 2085, temperatures would plunge more deeply, although not enough to offset the future warming associated with climate change. The increased cooling after a future eruption would also disrupt the water cycle more severely, decreasing the amount of precipitation that falls globally. The reason for the difference in climate response between 1815 and 2085 is tied to the oceans, which are expected to become more stratified as the planet warms, and therefore less able to moderate the climate impacts caused by volcanic eruptions. "We discovered that the oceans play a very large role in moderating, while also lengthening, the surface cooling induced by the 1815 eruption," said NCAR scientist John Fasullo, lead author of the new study. "The volcanic kick is just that — it's a cooling kick that lasts for a year or so. But the oceans change the timescale. They act to not only dampen the initial cooling but also to spread it out over several years." The research was published today in the journal Nature Communications. The work was funded in part by the National Science Foundation, NCAR's sponsor. Other funders include NASA and the U.S. Department of Energy. The study co-authors are Robert Tomas, Samantha Stevenson, Bette Otto-Bliesner, and Esther Brady, all of NCAR, as well as Eugene Wahl, of the National Oceanic and Atmospheric Administration.An aerial view of Mount Tambora's caldera, formed during the 1815 eruption. (Image credit: Wikipedia.) A detailed look at a deadly pastMount Tambora's eruption, the largest in the past several centuries, spewed a huge amount of sulfur dioxide into the upper atmosphere, where it turned into sulfate particles called aerosols. The layer of light-reflecting aerosols cooled Earth, setting in motion a chain of reactions that led to an extremely cold summer in 1816, especially across Europe and the northeast of North America. The "year without a summer" is blamed for widespread crop failure and disease, causing more than 100,000 deaths globally. To better understand and quantify the climate effects of Mount Tambora's eruption and to explore how those effects might differ for a future eruption if climate change continues on its current trajectory, the research team turned to a sophisticated computer model developed by scientists from NCAR and the broader community. The scientists looked at two sets of simulations from the Community Earth System Model. The first was taken from the CESM Last Millennium Ensemble Project, which simulates Earth's climate from the year 850 through 2005, including volcanic eruptions in the historic record. The second set, which assumes that greenhouse gas emission continue unabated, was created by running CESM forward and repeating a hypothetical Mount Tambora eruption in 2085. The historical model simulations revealed that two countervailing processes helped regulate Earth's temperature after Tambora's eruption. As aerosols in the stratosphere began blocking some of the Sun's heat, this cooling was intensified by an increase in the amount of land covered by snow and ice, which reflected heat back to space. At the same time, the oceans served as an important counterbalance. As the surface of the oceans cooled, the colder water sank, allowing warmer water to rise and release more heat into the atmosphere. By the time the oceans themselves had cooled substantially, the aerosol layer had begun to dissipate, allowing more of the Sun's heat to again reach Earth's surface. At that point, the ocean took on the opposite role, keeping the atmosphere cooler, since the oceans take much longer to warm back up than land. "In our model runs, we found that Earth actually reached its minimum temperature the following year, when the aerosols were almost gone," Fasullo said. "It turns out the aerosols did not need to stick around for an entire year to still have a year without a summer in 1816, since by then the oceans had cooled substantially."The oceans in a changed climateWhen the scientists studied how the climate in 2085 would respond to a hypothetical eruption that mimicked Mount Tambora's, they found that Earth would experience a similar increase in land area covered by snow and ice. However, the ocean's ability to moderate the cooling would be diminished substantially in 2085. As a result, the magnitude of Earth's surface cooling could be as much as 40 percent greater in the future. The scientists caution, however, that the exact magnitude is difficult to quantify since they had only a relatively small number of simulations of the future eruption. The reason for the change has to do with a more stratified ocean. As the climate warms, sea surface temperatures increase. The warmer water at the ocean's surface is then less able to mix with the colder, denser water below. In the model runs, this increase in ocean stratification meant that the water that was cooled after the volcanic eruption became trapped at the surface instead of mixing deeper into the ocean, reducing the heat released into the atmosphere. The scientists also found that the future eruption would have a larger effect on rainfall than the historical eruption of Mount Tambora. Cooler sea surface temperatures decrease the amount of water that evaporates into the atmosphere and, therefore, also decrease global average precipitation. Though the study found that Earth's response to a Tambora-like eruption would be more acute in the future than in the past, the scientists note that the average surface cooling caused by the 2085 eruption (about 1.1 degrees Celsius) would not be nearly enough to offset the warming caused by human-induced climate change (about 4.2 degrees Celsius by 2085). Study co-author Otto-Bliesner said, "The response of the climate system to the 1815 eruption of Indonesia's Mount Tambora gives us a perspective on potential surprises for the future, but with the twist that our climate system may respond much differently."About the article:Title: The amplifying influence of increased ocean stratification on a future year without a summer Authors: J.T. Fasullo, R. Tomas, S. Stevenson, B. Otto-Bliesner, E. Brady, and E. Wahl Journal: Nature Communications, DOI: 10.1038/s41467-017-01302-z


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