Climate & Climate Change

New estimate of ocean heat finds more warming

March 10, 2017 | The oceans may be storing 13 percent more heat than previously estimated, according to a new study co-authored by scientists at the National Center for Atmospheric Research (NCAR).The finding, published in the journal Science Advances, is based on a new analysis of how ocean temperatures have changed since 1960. The research team, led by Lijing Cheng of the Chinese Academy of Sciences, compared their results to estimates published in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change in 2013."In other words, the planet is warming quite a lot more than we thought," said NCAR scientist Kevin Trenberth, a study co-author.The vast majority of excess heat trapped on Earth by greenhouse gas emissions — about 90 percent — is stored in the oceans, but measuring how the heat content of the oceans has changed over time has been a challenge due to sparse observations.The deployment of an Argo float off a research vessel. Data collected from Argo floats were used to validate a new estimate of ocean heat content. (Image courtesy of the Australian Commonwealth Scientific and Industrial Research Organization.)Historically, the temperature of ocean waters was measured by a variety of ships, but this limited observations to areas where ships traveled. In more recent decades, measurements of ocean heat have increased, thanks to new observational techniques. In 2000, scientists began deploying a network of thousands of floats called Argo to profile conditions in the top layer of the ocean extending down 2,000 meters (6,562 feet). Argo achieved near global coverage in 2005, though some remote regions are still not sampled.To fill the large gaps in the historical ocean temperature record, the research team used a combination of statistical techniques and model output to determine how useful a single observation can be for inferring information about the surrounding area, as well as how the temperatures in different parts of the world's oceans relate to one another. They found that, in most regions, a single ocean observation could provide valuable information about conditions as far as 2,000 kilometers (1,243 miles) away.To check if they were correct, they used Argo observations. At first, they chose data from only a small number of floats in the network to mimic the scarcity of observations that would have been available in the mid-20th century. Then they used their new technique to create an entire ocean temperature map based on those few observations. When they checked their map against the full complement of Argo observations, they found that their reconstruction tracked closely with reality. "The results were remarkable," Trenberth said. "They give us much more confidence about what the ocean heat content was, stretching back to the late 1950s."The results allowed the team to estimate the total warming between 1960 and 2005 to be 337 zettajoules (a measure of energy). They also found that changes were small until 1980, when the amount of heat stored in the oceans began to steadily increase. Since 1990, significant amounts of heat have begun to seep deeper into the ocean layers. NCAR scientist and co-author John Fasullo said the study also highlights the impact of improved observations and models, which are giving scientists important insights into what the world once looked like."Science not only looks toward the future, but is also continually trying to make sense of the past," he said. "This work is an example of how advances in technology have enabled an improved understanding of past changes in the ocean, where variability has always been a bit of an enigma due to its vastness and depth. The insights associated with this work change not only our understanding of past climate but also how future changes might unfold."The other co-authors are Tim Boyer, of the National Oceanic and Atmospheric Administration; John Abraham, of the University of St. Thomas; and Jiang Zhu, of the Chinese Academy of Sciences.About the articleTitle: Improved estimates of ocean heat content from 1960 to 2015Authors: Lijing Cheng, Kevin Trenberth, John Fasullo, Tim Boyer, John Abraham, and Jiang ZhuJournal: Science Advances, DOI: 10.1126/sciadv.1601545Writer/contactLaura Snider, Senior Science Writer and Public Information Officer FundersChinese Academy of SciencesNational Science Foundation of ChinaU.S. Department of EnergyNational Science FoundationNASA CollaboratorsChinese Academy of SciencesNational Oceanic and Atmospheric AdministrationUniversity of St. Thomas

UCAR staff add climate storybook to Elementary GLOBE's line-up

March 2, 2017 | In a new illustrated storybook, a group of school children travel with a scientist to Greenland and the Maldives to learn about tools used to study climate change and its impacts. After seeing the challenge of melting glaciers and rising seas, the students come back with ideas on how to reduce their own greenhouse emissions.What in the World is Happening to Our Climate? introduces new material to a series of children's adventure science books published by Elementary GLOBE (part of the Global Learning and Observations to Benefit the Environment program).The newest storybook, funded by NASA Langley Research Center, is the product of a partnership between staff in two University Corporation for Atmospheric Research programs: the GLOBE Implementation Office and the UCAR Center for Science Education, or SciEd. SciEd supports the education and outreach efforts of the National Center for Atmospheric Research (NCAR), which UCAR manages with sponsorship by the National Science Foundation.The climate book is available for download at no charge:Becca Hatheway, SciEd's manager of teaching and learning, said NASA asked UCAR a couple of years ago to create educational resources for children in advance of the installation of the Sage III instrument on the International Space Station to measure ozone and aerosols in Earth’s atmosphere. (Sage III was installed last month).The result was What's Up in the Atmosphere: Exploring Colors in the Sky, a storybook featuring children who learn about the colors of the sky and their relationship to air quality through observations and photos. Hatheway and Kerry Zarlengo, a former elementary school teacher and literacy coach, wrote the book in 2015.During discussions about the air quality project, "we pitched the idea of doing a climate change book as well, and NASA was supportive," Hatheway said. "We've always wanted to do one on this topic — it's in the NCAR wheelhouse."UCAR's Elementary GLOBE's new climate storybook is geared to children in grades K-4. (©UCAR. Illustration by Lisa Gardiner. This image is freely available for media & nonprofit use.)Hatheway co-wrote the text for the climate book with Diane Stanitski, a deputy director at the National Oceanic and Atmospheric Administration's Earth System Research Laboratory in Boulder. The Elementary GLOBE series, which now numbers seven storybooks, is aimed at introducing K-4 students to Earth system science. The first five books focus on clouds, water, phenology, soils, and the Earth system. NASA is funding an update of those books, some of which are more than a decade old.Books are field tested by teachers, and the modules come with learning activities and a teacher's guide and glossary. The idea is that younger children will be guided in the reading and activities, while older children can learn more independently.Most of the storylines focus on a group of school children who go on adventures to learn and collect data about a topic.Lisa Gardiner, whose role at UCAR includes developing educational resources, has illustrated all of the books in the series. She said the climate book holds special meaning for her."It's at the root of what we do at SciEd," Gardiner said. "A lot of young kids want to know about climate change, but there aren't that many resources for their age group."Gardiner said she tries to make her illustrations as realistic as possible. To learn more about the Maldives, Gardiner asked Alison Rockwell of NCAR's Earth Observing Laboratory for photos from a field campaign several years ago. "I wanted to know what the houses looked like, what the people were wearing."The activities are realistic, too. The climate book's activities include building a model of a coastal community, predicting which features would be at risk of flooding, and then "flooding" the model to see the results.Children learning about wind energy in the new Elementary GLOBE climate storybook. (©UCAR. Illustration by Lisa Gardiner. This image is freely available for media & nonprofit use.)Julie Malmberg, a GLOBE project manager, said the storybooks and learning activities can be downloaded for free, or educators can purchase a hard copy of the entire module for the cost of the printing and binding. She has heard from school officials, such as one in a West Virginia district, using the resources for grade-school teacher training.Most educators, Malmberg said, download the materials. Between 2012-2016, GLOBE recorded 42,533 storybook downloads and 54,197 downloads of learning activities. Do You Know Clouds Have Names, co-authored with NCAR Senior Scientist Emerita Peggy LeMone, is the most popular storybook, while the most popular learning activities are connected to a book called The Scoop on Soils.Hatheway said SciEd plans to provide copies of the climate change and sky color books to teachers who attend its professional development workshops or programs at the Mesa Lab, as well as at conferences SciEd staffers attend. NOAA plans to distribute the climate book at the National Science Teachers Association conference this spring.While the storybooks were developed for the educational community in the U.S., some have been translated into other languages and distributed by GLOBE partners in other countries.The GLOBE Program is an international science and education program that provides students and the public worldwide with the opportunity to participate in the scientific process and contribute to understanding of the Earth system and global environment.Writer/contactJeff Smith, Science Writer and Public Information Officer   

Slower snowmelt in a warming world

BOULDER, Colo. — As the world warms, mountain snowpack will not only melt earlier, it will also melt more slowly, according to a new study by scientists at the National Center for Atmospheric Research (NCAR).The counterintuitive finding, published today in the journal Nature Climate Change, could have widespread implications for water supplies, ecosystem health, and flood risk."When snowmelt shifts earlier in the year, the snow is no longer melting under the high sun angles of late spring and early summer," said NCAR postdoctoral researcher Keith Musselman, lead author of the paper. "The Sun just isn't providing enough energy at that time of year to drive high snowmelt rates."Snowpack in the Colorado Rockies as seen from the NSF/NCAR C-130 research aircraft. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)The study was funded by the National Science Foundation, NCAR's sponsor.The findings could explain recent research that suggests the average streamflow in watersheds encompassing snowy mountains may decline as the climate warms — even if the total amount of precipitation in the watershed remains unchanged. That's because the snowmelt rate can directly affect streamflow. When snowpack melts more slowly, the resulting water lingers in the soil, giving plants more opportunity to take up the moisture. Water absorbed by plants is water that doesn't make it into the stream, potentially reducing flows.Musselman first became interested in how snowmelt rates might change in the future when he was doing research in the Sierra Nevada. He noticed that shallower, lower-elevation snowpack melted earlier and more slowly than thicker, higher-elevation snowpack. The snow at cooler, higher elevations tended to stick around until early summer — when the Sun was relatively high in the sky and the days had grown longer — so when it finally started to melt, the melt was rapid.Musselman wondered if the same phenomenon would unfold in a future climate, when warmer temperatures are expected to transform higher-elevation snowpack into something that looks much more like today's lower-elevation snowpack. If so, the result would be more snow melting slowly and less snow melting quickly. To investigate the question, Musselman first confirmed what he'd noticed in the Sierra by analyzing a decade's worth of snowpack observations from 979 stations in the United States and Canada. He and his co-authors — NCAR scientists Martyn Clark, Changhai Liu, Kyoko Ikeda, and Roy Rasmussen — then simulated snowpack over the same decade using the NCAR-based Weather Research and Forecasting (WRF) model.Once they determined that the output from WRF tracked with the observations, they used simulations from the model to investigate how snowmelt rates might change in North America around the end of the century if climate change continues unabated."We found a decrease in the total volume of meltwater — which makes sense given that we expect there to be less snow overall in the future," Musselman said. "But even with this decrease, we found an increase in the amount of water produced at low melt rates and, on the flip side, a decrease in the amount of water produced at high melt rates."While the study did not investigate the range of implications that could come from the findings, Musselman said the impacts could be far-reaching. For example, a reduction in high melt rates could mean fewer spring floods, which could lower the risk of infrastructure damage but also negatively affect riparian ecosystems. Changes in the timing and amount of snowmelt runoff could also cause warmer stream temperatures, which would affect trout and other fish species, and the expected decrease in streamflow could cause shortages in urban water supplies."We hope this study motivates scientists from many other disciplines to dig into our research so we can better understand the vast implications of this projected shift in hydrologic patterns," Musselman said.About the articleTitle: Slower snowmelt in a warmer worldAuthors: Keith N. Musselman, Martyn P. Clark, Changhai Liu, Kyoko Ikeda, and Roy RasmussenJournal: Nature Climate Change, DOI: 10.1038/nclimate3225WriterLaura Snider, Senior Science Writer and Public Information OfficerFunderNational Science Foundation

High-resolution regional modeling (no supercomputer needed)

Annual precipitation over Colorado as modeled by the low-resolution, global Community Earth System Model (top) compared to the high-resolution, regional Weather Research and Forecasting model (below). (Images courtesy Ethan Gutmann, NCAR.) February 13, 2017 | In global climate models, the hulking, jagged Rocky Mountains are often reduced to smooth, blurry bumps. It's a practical reality that these models, which depict the entire planet, typically need to be run at a relatively low resolution due to constraints on supercomputing resources. But the result, a virtual morphing of peaks into hills, affects the ability of climate models to accurately project how precipitation in mountainous regions may change in the future — information that is critically important to water managers.To address the problem, hydrologists have typically relied on two methods to "downscale" climate model data to make them more useful. The first, which uses statistical techniques, is fast and doesn't require a supercomputer, but it makes many unrealistic assumptions. The second, which uses a high-resolution weather model like the Weather Research and Forecasting model (WRF), is much more realistic but requires vast amounts of computing resources.Now hydrologists at the National Center for Atmospheric Research (NCAR) are developing an in-between option: The Intermediate Complexity Atmospheric Research Model (ICAR) gives researchers increased accuracy using only a tiny fraction of the computing resources."ICAR is about 80 percent as accurate as WRF in the mountainous areas we studied," said NCAR scientist Ethan Gutmann, who is leading the development of ICAR. "But it only uses 1 percent of the computing resources. I can run it on my laptop."Drier mountains, wetter plainsHow much precipitation falls in the mountains — and when — is vitally important for communities in the American West and elsewhere that rely on snowpack to act as a frozen reservoir of sorts. Water managers in these areas are extremely interested in how a changing climate might affect snowfall and temperature, and therefore snowpack, in these regions.But since global climate models with low resolution are not able to accurately represent the complex topography of mountain ranges, they are unsuited for answering these questions.For example, as air flows into Colorado from the west, the Rocky Mountains force that air to rise, cooling it and causing moisture to condense and fall to the ground as snow or rain. Once these air masses clear the mountains, they are drier than they otherwise would have been, so there is less moisture available to fall across Colorado's eastern plains.Low-resolution climate models are not able to capture this mechanism — the lifting of air over the mountains — and so in Colorado, for example, they often simulate mountains that are drier than they should be and plains that are wetter. For a regional water manger, these small shifts could mean the difference between full reservoirs and water shortages."Climate models are useful for predicting large-scale circulation patterns around the whole globe, not for predicting precipitation in the mountains or in your backyard," Gutmann said.Precipitation in millimeters over Colorado between Oct. 1 and May 1 as simulated by the Weather Research and Forecasting model (WRF), the Intermediate Complexity Atmospheric Research model (ICAR), and the observation-based Parameter-Elevation Regressions on Independent Slopes Model. (Images courtesy Ethan Gutmann.)A modeling middle groundA simple statistical fix for these known problems may include adjusting precipitation data to dry out areas known to be too wet and moisten areas known to be too dry. The problem is that these statistical downscaling adjustments don't capture the physical mechanisms responsible for the errors. This means that any impact of a warming climate on the mechanisms themselves would not be accurately portrayed using a statistical technique.That's why using a model like WRF to dynamically downscale the climate data produces more reliable results — the model is actually solving the complex mathematical equations that describe the dynamics of the atmosphere. But all those incredibly detailed calculations also take an incredible amount of computing.A few years ago, Gutmann began to wonder if there was a middle ground. Could he make a model that would solve the equations for just a small portion of the atmospheric dynamics that are important to hydrologists — in this case, the lifting of air masses over the mountains — but not others that are less relevant?"I was studying statistical downscaling techniques, which are widely used in hydrology, and I thought, 'We should be able to do better than this,'" he said. "'We know what happens when you lift air up over a mountain range, so why don’t we just do that?'"Gutmann wrote the original code for the model that would become ICAR in just a few months, but he spent the next four years refining it, a process that's still ongoing.100 times as fastLast year, Gutmann and his colleagues — Martyn Clark and Roy Rasmussen, also of NCAR; Idar Barstad, of Uni Research Computing in Bergen, Norway; and Jeffrey Arnold, of the U.S. Army Corps of Engineers — published a study comparing simulations of Colorado created by ICAR and WRF against observations.The authors found that ICAR and WRF results were generally in good agreement with the observations, especially in the mountains and during the winter. One of ICAR's weaknesses, however, is in simulating storms that build over the plains in the summertime. Unlike WRF, which actually allows storms to form and build in the model, ICAR estimates the number of storms likely to form, given the atmospheric conditions, a method called parameterization.Even so, ICAR, which is freely available to anyone who wants to use it, is already being run by teams in Norway, Austria, France, Chile, and New Zealand."ICAR is not perfect; it's a simple model," Gutmann said. "But in the mountains, ICAR can get you 80 to 90 percent of the way there at 100 times the speed of WRF. And if you choose to simplify some of the physics in ICAR, you can get it close to 1,000 times faster."About the articleTitle: The Intermediate Complexity Atmospheric Research Model (ICAR)Authors: Ethan Gutmann, Idar Barstad, Martyn Clark, Jeffrey Arnold, and Roy RasmussenJournal: Journal of Hydrometeorology, DOI: 10.1175/JHM-D-15-0155.1Funders:U.S. Army Corps of EngineersU.S. Bureau of ReclamationCollaborators:Uni Research Computing in NorwayU.S. Army Corps of EngineersWriter/contact: Laura Snider, Senior Science Writer

Two NCAR scientists honored by American Geophysical Union

BOULDER, Colo. — Martyn Clark, senior scientist at the National Center for Atmospheric Research (NCAR), will be honored next week as a Fellow of the American Geophysical Union (AGU) for his exceptional contribution to Earth science.Clark is an expert in the numerical modeling and prediction of hydrologic processes. His current research includes developing new modeling methods to improve streamflow forecasts and better understand climate change impacts on regional water resources. Clark, who grew up in Christchurch, New Zealand, has authored or co-authored 135 journal articles since receiving his Ph.D. from the University of Colorado in 1998.NCAR Senior Scientist Martyn Clark (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)"This well-deserved honor reflects Martyn's eminent work in the increasingly critical area of water-resource prediction and management," said NCAR Director James W. Hurrell.Clark said he was delighted to see NCAR's hydrologic modeling recognized. "Hydrology is beginning to play a much stronger role in addressing important interdisciplinary science questions about Earth System change, such as how changes in the terrestrial water cycle affect biological productivity and how groundwater can buffer water stress in ecosystems and human societies. It's exciting to advance modeling capabilities in these areas."NCAR Senior Scientist Bette Otto-Bliesner. (©UCAR. Photo by Carlye Calvin. This image is freely available for media & nonprofit use.)Clark is among 60 individuals from eight countries recognized as Fellows this year; only one in one thousand AGU members receive this recognition in any given year. Nearly 40 percent of this year's fellows are from the 110 member colleges and universities of the University Corporation for Atmospheric Research (UCAR), which manages NCAR. This year's class will be honored next Wednesday at the 2016 AGU Fall Meeting in San Francisco.NCAR Senior Scientist Bette Otto-Bliesner, who was named an AGU Fellow last year, is being honored by her peers in the Paleoceanography and Paleoclimatology Focus Group and Ocean Sciences Section by being asked to give the 2016 Emiliani Lecture. She will give the lecture next Wednesday at the AGU Fall Meeting on the topic of "Resolving Some Puzzles of Climate Evolution Since the Last Glacial Maximum: A Melding of Paleoclimate Modeling and Data."The AGU, dedicated to advancing Earth and space sciences for the benefit of society, is a not-for-profit, professional organization representing 60,000 members in more than 140 countries. 

Extreme downpours could increase fivefold across parts of the U.S.

BOULDER, Colo. — At century's end, the number of summertime storms that produce extreme downpours could increase by more than 400 percent across parts of the United States — including sections of the Gulf Coast, Atlantic Coast, and the Southwest — according to a new study by scientists at the National Center for Atmospheric Research (NCAR).The study, published today in the journal Nature Climate Change, also finds that the intensity of individual extreme rainfall events could increase by as much as 70 percent in some areas. That would mean that a storm that drops about 2 inches of rainfall today would be likely to drop nearly 3.5 inches in the future."These are huge increases," said NCAR scientist Andreas Prein, lead author of the study. "Imagine the most intense thunderstorm you typically experience in a single season. Our study finds that, in the future, parts of the U.S. could expect to experience five of those storms in a season, each with an intensity as strong or stronger than current storms."The study was funded by the National Science Foundation (NSF), NCAR's sponsor, and the Research Partnership to Secure Energy for America.“Extreme precipitation events affect our infrastructure through flooding, landslides and debris flows,” said Anjuli Bamzai, program director in NSF’s Directorate for Geosciences, which funded the research.  “We need to better understand how these extreme events are changing. By supporting this research, NSF is working to foster a safer environment for all of us.”The figure shows the expected increase in the number of summertime storms that produce extreme precipitation at century's end compared to the period 2000 - 2013. (©UCAR. Courtesy Andreas Prein, NCAR. This image is freely available for media & nonprofit use.)A year of supercomputing timeAn increase in extreme precipitation is one of the expected impacts of climate change because scientists know that as the atmosphere warms, it can hold more water, and a wetter atmosphere can produce heavier rain. In fact, an increase in precipitation intensity has already been measured across all regions of the U.S. However, climate models are generally not able to simulate these downpours because of their coarse resolution, which has made it difficult for researchers to assess future changes in storm frequency and intensity.For the new study, the research team used a new dataset that was created when NCAR scientists and study co-authors Roy Rasmussen, Changhai Liu, and Kyoko Ikeda ran the NCAR-based Weather Research and Forecasting (WRF) model at a resolution of 4 kilometers, fine enough to simulate individual storms. The simulations, which required a year to run, were performed on the Yellowstone system at the NCAR-Wyoming Supercomputing Center.Prein and his co-authors used the new dataset to investigate changes in downpours over North America in detail. The researchers looked at how storms that occurred between 2000 and 2013 might change if they occurred instead in a climate that was 5 degrees Celsius (9 degrees Fahrenheit) warmer — the temperature increase expected by the end of the century if greenhouse gas emissions continue unabated.Prein cautioned that this approach is a simplified way of comparing present and future climate. It doesn't reflect possible changes to storm tracks or weather systems associated with climate change. The advantage, however, is that scientists can more easily isolate the impact of additional heat and associated moisture on future storm formation."The ability to simulate realistic downpours is a quantum leap in climate modeling. This enables us to investigate changes in hourly rainfall extremes that are related to flash flooding for the very first time," Prein said. "To do this took a tremendous amount of computational resources."Impacts vary across the U.S.The study found that the number of summertime storms producing extreme precipitation is expected to increase across the entire country, though the amount varies by region. The Midwest, for example, sees an increase of zero to about 100 percent across swaths of Nebraska, the Dakotas, Minnesota, and Iowa. But the Gulf Coast, Alabama, Louisiana, Texas, New Mexico, Arizona, and Mexico all see increases ranging from 200 percent to more than 400 percent.The study also found that the intensity of extreme rainfall events in the summer could increase across nearly the entire country, with some regions, including the Northeast and parts of the Southwest, seeing particularly large increases, in some cases of more than 70 percent.A surprising result of the study is that extreme downpours will also increase in areas that are getting drier on average, especially in the Midwest. This is because moderate rainfall events that are the major source of moisture in this region during the summertime are expected to decrease significantly while extreme events increase in frequency and intensity. This shift from moderate to intense rainfall increases the potential for flash floods and mudslides, and can have negative impacts on agriculture.The study also investigated how the environmental conditions that produce the most severe downpours might change in the future. In today's climate, the storms with the highest hourly rainfall intensities form when the daily average temperature is somewhere between 20 and 25 degrees C (68 to 77 degrees F) and with high atmospheric moisture. When the temperature gets too hot, rainstorms become weaker or don't occur at all because the increase in atmospheric moisture cannot keep pace with the increase in temperature. This relative drying of the air robs the atmosphere of one of the essential ingredients needed to form a storm.In the new study, the NCAR scientists found that storms may continue to intensify up to temperatures of 30 degrees C because of a more humid atmosphere. The result would be much more intense storms."Understanding how climate change may affect the environments that produce the most intense storms is essential because of the significant impacts that these kinds of storms have on society," Prein said.About the articleTitle: The future intensification of hourly precipitation extremesAuthors: Andreas F. Prein, Roy M. Rasmussen, Kyoko Ikeda, Changhai Liu, Martyn P. Clark, and Greg J. HollandJournal: Nature Climate Change, DOI: 10.1038/NCLIMATE3168Writer:Laura Snider, Senior Science Writer and Public Information Officer

Days of record-breaking heat ahead

BOULDER, Colo. — If society continues to pump greenhouse gases into the atmosphere at the current rate, Americans later this century will have to endure, on average, about 15 daily maximum temperature records for every time that the mercury notches a record low, new research indicates.That ratio of record highs to record lows could also turn out to be much higher if the pace of emissions increases and produces even more warming, according to the study led by scientists at the National Center for Atmospheric Research (NCAR).Over the last decade, in contrast, the ratio of record high temperatures to record lows has averaged about two to one."More and more frequently, climate change will affect Americans with record-setting heat," said NCAR senior scientist Gerald Meehl, lead author of the new paper. "An increase in average temperatures of a few degrees may not seem like much, but it correlates with a noticeable increase in days that are hotter than any in the record, and nights that will remain warmer than we've ever experienced in the past." The United States has experienced unusual warmth lately, as indicated by this July 22, 2016, weather map showing much of the country facing highs in the 90s and 100s and lows in the 70s. New research indicates that more record high temperatures may be in store. (Weather map by the National Oceanic and Atmospheric Administration's Weather Prediction Center.)The 15-to-1 ratio of record highs to lows is based on temperatures across the continental United States increasing by slightly more than 3 degrees Celsius (5.4 degrees Fahrenheit) above recent years, which is about the amount of warming expected to occur with the current pace of greenhouse gas emissions.The new research appears this week in the "Proceedings of the National Academy of Sciences." It was funded by the Department of Energy (DOE) and the National Science Foundation (NSF), which is NCAR's sponsor. The study was coauthored by NCAR scientist Claudia Tebaldi and by Dennis Adams-Smith, a scientist previously at Climate Central and now at the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory.Hotter days  In a 2009 study, Meehl and colleagues found that the ratio of record daily high temperatures to record daily low temperatures has steadily increased since the 1970s as average temperatures over the United States have warmed. Computer models at that time indicated that the ratio could continue to increase during this century, although the research team looked into just one scenario of future emissions. The scientists also found that the models were overstating the ratio of record highs to record lows in recent years, compared to observations.By digging further into the issue and analyzing why the models differed from observations, Meehl and his co-authors have now produced a better calibrated projection of future record-breaking daily highs across the U.S. They based their projections on the average temperature increase over the continental United States, rather than on a particular scenario of future emissions.By about 2065, for example, U.S. temperatures will rise by an average of slightly more than 3 degrees C (5.4 degrees F) if society maintains a “business as usual” increase in the emission of greenhouse gases. Under such a scenario, the ratio of record daily high temperatures to record daily lows will likely be about 15 to 1, although it could range anywhere from 7 to 1 up to 22 to 1, the study found.If temperatures increase even more this century, the ratio of record highs to record lows will jump substantially. For example, if temperatures climb more than 4 degrees C (7.2 degrees F), Americans could experience about 38 record highs for every record low. Such an outcome could occur if society does not make any efforts to mitigate the production of greenhouse gases."Every degree of warming makes a substantial amount of difference, with the ratio of record highs to record lows becoming much greater," Meehl said. "Even with much warmer temperatures on average, we will still have winter and we will still get record cold temperatures, but the numbers of those will be really small compared to record high maximums."If temperatures were not warming, Meehl said, the ratio of record highs to record lows would average out to about one to one.Instead, record high temperatures have already become a common occurrence in much of the country. The ratio of record highs to lows has averaged about 2 to 1 over the first decade of the 21st century, but there is considerable year-to-year variation. The ratio was about 5 to 1 in 2012, dropping to about 1 to 1 in 2013 and 2014, then almost 3 to 1 in 2015. The unusual warmth of 2016, resulting from both climate change and natural patterns such as El Niño, has led to 24,519 record daily maximums vs. 3,970 record daily minimums—a ratio of about 6 to 1.Precipitation and the warm 1930sA key part of the study involved pinpointing why the models in the 2009 study were simulating somewhat more daily record high maximum temperatures compared with recent observations, while there was good agreement between the models and the observed decreases in record low minimums. The authors focused on two sets of simulations conducted on the NCAR-based Community Climate System Model (version 4), which is funded by DOE and NSF and developed by climate scientists across the country.Their analysis uncovered two reasons for the disparity between the computer models and observations.First, the models tended to underestimate precipitation. Because the air is cooled by precipitation and resulting evapotranspiration — the release of moisture from the land and plants back to the atmosphere — the tendency of the computer models to create an overly dry environment led to more record high temperatures.Second, the original study in 2009 only went back to the 1950s. For the new study, the research team also analyzed temperatures in the 1930s and 1940s, which is as far back as accurate recordkeeping will allow. Because the Dust Bowl days of the 1930s were unusually warm, with many record-setting high temperatures, the scientists found that it was more difficult in subsequent years to break those records, even as temperatures warmed. However, even taking the warm 1930s into account, both the model-simulated and observed ratio of record highs to record lows have been increasing."The steady increase in the record ratio is an immediate and stark reminder of how our temperatures have been shifting and continue to do so, reaching unprecedented highs and fewer record lows," said Tebaldi. "These changes pose adaptation challenges to both human and natural systems. Only a substantial mitigation of greenhouse gas emissions may stop this increase, or at least slow down its pace."About the articleTitle: "US daily temperature records past, present, and future"Authors: Gerald A. Meehl, Claudia Tebaldi, and Dennis Adams-SmithJournal: Proceedings of the National Academy of Sciences

Applying indigenous and Western knowledge to environmental research

November 3, 2016 | Native American researchers, students, and community members will partner with Western science organizations to help shape mutually beneficial research projects as part of a two-year National Science Foundation grant awarded recently to the University Corporation for Atmospheric Research. UCAR manages the National Center for Atmospheric Research (NCAR) under sponsorship by NSF.The project marks a milestone in collaborations between NCAR|UCAR and Native American partners to increase the presence of indigenous perspectives and participants in geoscience research. It also comes at a time when indigenous people are among the hardest-hit by climate change, with several communities forming America's first wave of climate refugees.Aimed at building research partnerships between Native American and Western scientists, the NCAR|UCAR project has two supporting goals: broadening career paths for Native American students interested in Earth system science, and increasing the cultural sensitivity of Western scientists. Other partners in the project include the NCAR-based Rising Voices program, Haskell Indian Nations University, the University of Arizona's Biosphere 2, Michigan State University, and the GLOBE citizen science program conducted by the UCAR-based Global Learning and Observations to Benefit the Environment."It's an exciting opportunity for both young indigenous scientists and scientists at NCAR and Biosphere 2," said Carolyn Brinkworth, NCAR director of Diversity, Education, and Outreach, and principal investigator of the project. "It's also a very different way of thinking about the science - truly integrating indigenous and traditional Western practices to benefit all of our partners."For example, she noted, indigenous communities can contribute important information about climate change by bringing generations of knowledge and experience with resource management and environmental and ecological processes.Students attending the Rising Voices workshop in Waimea, Hawaii, in 2016, visited a food garden planted according to traditional Hawaiian techniques to learn about climate change and phenology – the study of the seasonality of plants and animals. (Photo courtesy Craig Elevitch.)The pilot project is one of 37 awarded nationwide as part of a new NSF program called INCLUDES (Inclusion across the Nation of Communities of Learners of Underrepresented Discoverers in Engineering and Science). The program aspires to make careers in science, technology, engineering, and mathematics (STEM) more accessible to underserved populations.Two students from tribal colleges and universities will be selected to become interns in UCAR's SOARS program (Significant Opportunities in Atmospheric Research and Science). The students will join research teams comprised of mentors from NCAR, Biosphere 2, and their home communities to co-develop their research projects.One of the project partners, the four-year-old Rising Voices program, has brought social and physical scientists and engineers together with Native American community members to build bonds that lead to research collaboration."The INCLUDES project will actualize many topics we've been talking about in Rising Voices," said Heather Lazrus, an NCAR environmental anthropologist and Rising Voices co-founder. "The project will create a pathway for the students to become engaged in atmospheric sciences at a young age through a citizen science component, and then help keep them engaged for the long haul.”The GLOBE citizen science component will help the SOARS students reach out to their communities through a number of activities, especially with middle- and high-school students. The project also will connect community youth with undergraduate programs at Haskell and the University of Arizona.As it does for all its interns, SOARS will provide multiple mentors to help the Native American students develop their research, computer modeling, scientific communication, and professional skills.SOARS Director Rebecca Haacker said the internship program has brought in students from Haskell before. “But this will enable us to expand our relationship with indigenous students, and it's nice to see the student internships being part of this larger effort.”The mentors will be supported with cultural training by Michigan State University professor Kyle Powys Whyte, who is also a member of Rising Voices. "We don't want a situation of Western scientists working with Native Americans without any preparation," Brinkworth said. "We want the Western scientists to be introduced to the students' culture, their ways of thinking, their ways of working."The plan is for two SOARS interns to be selected by early 2017 and participate in research projects over the summer. In a second phase, NSF plans to bring together all the pilot projects two years from now with the goal of building out a comprehensive “Alliance” program.Brinkworth said that when she saw the request for proposals, she thought NCAR was uniquely positioned, in part because of Rising Voices, which has strengthened relationships among participating scientists and Native American communities.She hopes the new pilot project and the lessons to be learned will become a template for other efforts. "We are trying to produce a model for other Western scientific organizations that want to partner with indigenous scientists and communities," she said.Writer/contactJeff Smith, Science Writer and Public Information Officer 

40 Earths: NCAR's Large Ensemble reveals staggering climate variability

Sept. 29, 2016 | Over the last century, Earth's climate has had its natural ups and downs. Against the backdrop of human-caused climate change, fluctuating atmosphere and ocean circulation patterns have caused the melting of Arctic sea ice to sometimes speed up and sometimes slow down, for example. And the back-and-forth formation of El Niño and La Niña events in the Pacific has cause d some parts of the world to get wetter or drier while some parts get warmer or cooler, depending on the year.But what if the sequence of variability that actually occurred over the last century was just one way that Earth's climate story could have plausibly unfolded? What if tiny — even imperceptible — changes in Earth's atmosphere had kicked off an entirely different sequence of naturally occurring climate events?"It's the proverbial butterfly effect," said Clara Deser, a senior climate scientist at the National Center for Atmospheric Research (NCAR). "Could a butterfly flapping its wings in Mexico set off these little motions in the atmosphere that cascade into large-scale changes to atmospheric circulation?"To explore the possible impact of miniscule perturbations to the climate — and gain a fuller understanding of the range of climate variability that could occur — Deser and her colleague Jennifer Kay, an assistant professor at the University of Colorado Boulder and an NCAR visiting scientist, led a project to run the NCAR-based Community Earth System Model (CESM) 40 times from 1920 forward to 2100. With each simulation, the scientists modified the model's starting conditions ever so slightly by adjusting the global atmospheric temperature by less than one-trillionth of one degree, touching off a unique and chaotic chain of climate events.The result, called the CESM Large Ensemble, is a staggering display of Earth climates that could have been along with a rich look at future climates that could potentially be."We gave the temperature in the atmosphere the tiniest tickle in the model — you could never measure it — and the resulting diversity of climate projections is astounding," Deser said. "It's been really eye-opening for people."The dataset generated during the project, which is freely available, has already proven to be a tremendous resource for researchers across the globe who are interested in how natural climate variability and human-caused climate change interact. In a little over a year, about 100 peer-reviewed scientific journal articles have used data from the CESM Large Ensemble.Winter temperature trends (in degrees Celsius) for North America between 1963 and 2012 for each of 30 members of the CESM Large Ensemble. The variations in warming and cooling in the 30 members illustrate the far-reaching effects of natural variability superimposed on human-induced climate change. The ensemble mean (EM; bottom, second image from right) averages out the natural variability, leaving only the warming trend attributed to human-caused climate change. The image at bottom right (OBS) shows actual observations from the same time period. By comparing the ensemble mean to the observations, the science team was able to parse how much of the warming over North America was due to natural variability and how much was due to human-caused climate change. Read the full study in the American Meteorological Society's Journal of Climate. (© 2016 AMS.) A community effortRunning a complex climate model like the CESM several dozen times takes a vast amount of computing resources, which makes such projects rare and difficult to pull off. With that in mind, Deser and Kay wanted to make sure that the data resulting from the Large Ensemble were as useful as possible. To do that, they queried scientists from across the community who might make use of the project results — oceanographers, geochemists, atmospheric scientists, biologists, socioeconomic researchers — about what they really wanted."It took a village to make this ensemble happen and for it to be useful to and usable by the broad climate community," Kay said. "The result is a large number of ensemble members, in a state-of-the-art climate model, with outputs asked for by the community, that is publicly available and relatively easy to access — it's no wonder it's getting so much use."Scientists have so far relied on the CESM Large Ensemble to study everything from oxygen levels in the ocean to potential geoengineering scenarios to possible changes in the frequency of moisture-laden atmospheric rivers making landfall. In fact, so many researchers have found the Large Ensemble so useful that Kay and Deser were honored with the 2016 CESM Distinguished Achievement Award, which recognizes significant contributions to the climate modeling community.The award citation noted the pair was chosen because "the Large Ensemble represents one of NCAR's most significant contributions to the U.S. climate research community. … At a scientific level, the utility of the Large Ensemble cannot be overstated."The power of multiple runs: Looking forward — and backwardClearly, the CESM Large Ensemble is useful for looking forward: What is the range of possible futures we might expect in the face of a changing climate? How much warmer will summers become? When will summer Arctic sea ice disappear? How will climate change affect ocean life?But the Large Ensemble is also an extremely valuable tool for understanding our past. This vast storehouse of data helps scientists evaluate observations and put them in context: How unusual is a particular heat wave? Is a recent change in rainfall patterns the result of global warming or could it be from solely natural causes?With only a single model run, scientists are limited in what they can conclude when an observation doesn't match up with a model's projection. For example, if the Arctic sea ice extent were to expand, even though the model projected a decline, what would that mean? Is the physics underlying the model wrong? Or does the model incorrectly capture the natural variability? In other words, if you ran the model more times, with slightly different starting conditions, would one of the model runs correctly project the growth in sea ice?The Large Ensemble helps answer that question. Armed with 40 different simulations, scientists can characterize the range of historic natural variability. With this information, they can determine if observations fit within the envelope of natural variability outlined in the model, instead of comparing them to a single run.Creating an envelope of what can be considered natural also makes it possible to see when the signal of human-caused climate change has pushed an observation beyond the natural variability. The Large Ensemble can also clarify the climate change "signal" in the model. That's because averaging together the 40 ensemble members can effectively cancel out the natural variability — a La Niña in one model run might cancel out an El Niño in another, for example — leaving behind only changes due to climate change."This new ability to separate natural internal variability from externally driven trends is absolutely critical for moving forward our understanding of climate and climate change," said Galen McKinley, a professor of atmospheric and oceanic sciences at the University of Wisconsin–Madison.McKinley used the Large Ensemble — which she called a "transformative tool" — to study changes in the ocean's ability to take up carbon dioxide in a warming climate.The two components of the climate systemThe CESM Large Ensemble is not the first ensemble of climate simulations, though it is perhaps the most comprehensive and widely used. Scientists have long understood that it makes sense to look at more than one model run. Frequently, however, scientists have done this by comparing simulations from different climate models, collectively called a multi-model ensemble.This method gives a feel for the diversity of possible outcomes, but it doesn't allow researchers to determine why two model simulations might differ: Is it because the models themselves represent the physics of the Earth system differently? Or is it because the models have different representations of the natural variability or different sensitivities to changing carbon dioxide concentrations?The Large Ensemble helps resolve this dilemma. Because each member is run using the same model, the differences between runs can be attributed to differences in natural variability alone. The Large Ensemble also offers context for comparing simulations in a multi-model ensemble. If the simulations appear to disagree about what the future may look like—but they still fit within the envelope of natural variability characterized by the Large Ensemble—that could be a clue that the models do not actually disagree on the fundamentals. Instead, they may just be representing different sequences of natural variability.This ability to put model results in context is important, not just for scientists but for policy makers, according to Noah Diffenbaugh, a climate scientist at Stanford University who has used the Large Ensemble in several studies, including one that looks at the contribution of climate change to the recent, severe California drought.“It’s pretty common for real-world decision makers to look at the different simulations from different models, and throw up their hands and say, 'These models don't agree so I can't make decisions,'" he said. "In reality, it may not be that the models are disagreeing. Instead, we may be seeing the actual uncertainty of the climate system. There is some amount of natural uncertainty that we can't reduce — that information is really important for making robust decisions, and the Large Ensemble is giving us a window that we haven’t had before.”Deser agrees that it's important to communicate to the public that, in the climate system, there will always be this "irreducible" uncertainty."We’re always going to have these two components to the climate system: human-induced changes and natural variability. You always have to take both into account," Deser said. "In the future, it will all depend on how the human-induced component is either offset — or augmented — by the sequence of natural variability that unfolds."About the articleTitle: The Community Earth System Model (CESM) Large Ensemble Project: A Community Resource for Studying Climate Change in the Presence of Internal Climate VariabilityAuthors:  J. E. Kay, C. Deser, A. Phillips, A. Mai, C. Hannay, G. Strand, J. M. Arblaster, S. C. Bates, G. Danabasoglu, J. Edwards, M. Holland, P. Kushner, J.-F. Lamarque, D. Lawrence, K. Lindsay, A. Middleton, E. Munoz, R. Neale, K. Oleson, L. Polvani, and M. VertensteinJournal: Bulletin of the American Meteorological Society, DOI: 10.1175/BAMS-D-13-00255.1Funders: National Science FoundationU.S. Department of EnergyIn the news: Stories about research using the CESM Large EnsembleCauses of California drought linked to climate change, Stanford scientists sayStanford University (UCAR Member)The difficulty of predicting an ice-free ArcticUniversity of Colorado Boulder (UCAR Member)Widespread loss of ocean oxygen to become noticeable in 2030sNCARCornell Scientist Predicts Climate Change Will Prompt Earlier Spring Start DateCornell University (UCAR Member)The 2-degree goal and the question of geoengineeringNCAR New climate model better predicts changes to ocean-carbon sinkUniversity of Wisconsin Madison (UCAR Member)Future summers could regularly be hotter than the hottest on recordNCARExtreme-Weather Winters Becoming More CommonStanford (UCAR Member)More frequent extreme precipitation ahead for western North AmericaPacific Northwest National LaboratoryCloudy With A Chance of WarmingUniversity of Colorado Boulder (UCAR Member)Climate change already accelerating sea level rise, study finds NCARLess ice, more water in Arctic Ocean by 2050s, new CU-Boulder study findsUniversity of Colorado Boulder (UCAR Member)California 2100: More frequent and more severe droughts and floods likelyPacific Northwest National Laboratory Searing heat waves detailed in study of future climateNCAR Did climate change, El Nino make Texas floods worse?Utah State University (UCAR Member)Writer/contact:Laura Snider, Senior Science Writer and Public Information Officer

Food security report wins USDA award

BOULDER, Colo. — A comprehensive report warning of the impacts of climate change on the world's food security has won a top U.S. Department of Agriculture (USDA) award."Climate Change, Global Food Security, and the U.S. Food System," with co-authors from the National Center for Atmospheric Research (NCAR), provides an overview of recent research in climate change and agriculture. It warns that warmer temperatures and altered precipitation patterns can threaten food production, disrupt transportation systems, and degrade food safety, among other impacts, and that the world's poor and those living in tropical regions are particularly vulnerable.Michael Scuse, USDA acting deputy secretary (center), with members of the team of experts who produced the award-winning report, "Climate Change, Global Food Security, and the U.S. Food System." Those pictured are (back row from left): William Easterling (The Pennsylvania State University), Edward Carr (Clark University), and Peter Backlund (Colorado State University); front row from left: Rachel Melnick (USDA), Margaret Walsh (USDA), Scuse, Moffat Ngugi (U.S. Agency for International Development/USDA), and Karen Griggs (NCAR). (Photo by USDA.) The USDA this month named it as the winner of the 2016 Abraham Lincoln Honor Award for Increasing Global Food Security. The Abraham Lincoln Honor Award is the most prestigious USDA award presented by the Secretary of Agriculture, recognizing noteworthy accomplishments that significantly contribute to the advancement of the USDA's strategic goals, mission objectives, and overall management excellence.The report was produced as part of a collaboration between NCAR, the USDA, and the University Corporation for Atmospheric Research (UCAR), which manages NCAR on behalf of the National Science Foundation. It was written by 32 experts from 19 federal, academic, nongovernmental, intergovernmental, and private organizations in the United States, Argentina, Britain, and Thailand. The authors included three NCAR scientists, as well as eight experts affiliated with UCAR member universities."This award highlights the importance of addressing climate change in order to maintain the progress the world has made on food security in recent decades," said NCAR program director Lawrence Buja, who helped oversee production of the report. "Scientists will continue to study this critical issue and work with decision makers to co-develop the information they need about potential climate impacts on future production, distribution, and other aspects of our U.S. and global food systems."Published under the auspices of the U.S. Global Change Research Program, the reportfocuses on identifying climate change impacts on global food security through 2100. The authors emphasize that food security — the ability of people to obtain and use sufficient amounts of safe and nutritious food — will be affected by several factors in addition to climate change, such as technological advances, increases in population, the distribution of wealth, and changes in eating habits."Climate change has a myriad of potential impacts, especially on food, water, and energy systems," said UCAR President Antonio J. Busalacchi. "I commend the authors of this report for clearly analyzing this very complex issue in the agriculture sector, which has implications for all of society, from the least developed nations to the most advanced economies."Report authorsMolly Brown, University of Maryland*John Antle, Oregon State University*Peter Backlund, Colorado State University *Edward Carr, Clark UniversityBill Easterling, Pennsylvania State University*Margaret Walsh, USDA Office of the Chief Economist/Climate Change Program OfficeCaspar Ammann, NCARWitsanu Attavanich, Kasetsart UniversityChris Barrett, Cornell University*Marc Bellemare, University of Minnesota*Violet Dancheck, U.S. Agency for International DevelopmentChris Funk, U.S. Geological SurveyKathryn Grace, University of Utah*John Ingram, University of OxfordHui Jiang, USDA Foreign Agricultural ServiceHector Maletta, Universidad de Buenos AiresTawny Mata, USDA/American Association for the Advancement of ScienceAnthony Murray, USDA-Economic Research ServiceMoffatt Ngugi, U.S. Agency for International Development/USDA Foreign Agricultural ServiceDennis Ojima, Colorado State University*Brian O'Neill, NCARClaudia Tebaldi, NCAR*UCAR member universityReport project teamLawrence Buja, NCARKaren Griggs, NCAR 

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