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News Article | May 17, 2017
Site: www.nature.com

Fifty years ago this month, the climate modellers Syukuro Manabe and Richard Wetherald1 published arguably the greatest climate-science paper of all time in the Journal of the Atmospheric Sciences. The authors essentially settled the debate on whether carbon dioxide causes global warming, building a mathematically sound climate model that was the first to yield physically realistic results. Their work spawned both the development of modern climate models and the use of radiative forcing — a measure of the alteration in Earth's energy balance resulting from human or natural changes — to understand historical causes of climate change. Climate science was something of a slow burner. The fact that CO is a greenhouse gas has been known since the work of physicist John Tyndall in 1861 (ref. 2). Crude estimates of the warming effect of CO were subsequently made by the chemist Svante Arrhenius in 1896 (ref. 3), and by the engineer Guy Stewart Callendar in 1938 (ref. 4). But it was only in the 1950s that measurements showed atmospheric CO levels to be rising5, and that the physics of 'radiative transfer' was beginning to be understood. Radiative transfer quantifies how solar radiation and the thermal infrared spectrum emitted by Earth's surface are scattered, absorbed and re-emitted by gases in the atmosphere, and is fundamental to quantifying the warming effect of greenhouse gases. In 1963, Manabe's colleague Fritz Möller used the latest developments in the science of radiative transfer to question how important the global-warming effect of CO is6. This work, along with other early studies, happened to make reasonable estimates of the CO -induced warming that would occur if the climate system did not alter in some way, but did not account properly for how the system might respond. In particular, they failed to account correctly for how the distribution of atmospheric water vapour would change in a warming world. By contrast, Manabe and Wetherald properly understood how this water-vapour feedback worked, and used that information in their new one-dimensional radiative–convective equilibrium model. This model, developed from earlier work7, divided the atmosphere into multiple levels and redistributed energy between them in the vertical dimension from the surface, using a combination of radiation and convection. The authors used their model to estimate the warming that would occur if CO levels doubled from 150 to 300 parts per million (p.p.m.) and from 300 to 600 p.p.m. From these results, they estimated that a warming of about 2.3 °C would occur for a doubling of CO — in good agreement with modern estimates8. In fact, Manabe and Wetherald's paper was not focused on CO and global warming at all. The researchers worked at the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey, which had acquired one of the first commercial computers. Manabe had been brought in to lead the development of the world's first general circulation model (a computational climate model underpinned by a numerical description of atmospheric and ocean circulation), and a few years later built the first climate model that combined oceanic and atmospheric processes9. The 1967 paper described a crucial step in the construction of that model: how best to link the different levels of the atmosphere with Earth's surface, taking into account radiative transfer, convection and water-vapour feedback. What raises the paper to greatness in my mind is not its estimate of CO -induced warming, but how it exemplifies good practice in climate-modelling studies. First, its results are reproducible using a transparent and well-justified set of assumptions. For example, the authors used the latest observations of water vapour to justify their assumption that relative humidity will not be affected by climate change, and then used this assumption to model the water-vapour feedback. Second, the resulting model included just enough detail of physical processes to give first-order estimates of the surface and atmospheric temperature changes expected from several possible human or natural perturbations (such as changes to solar output, CO concentration and clouds), but was not too complex so as to make it difficult to run on early computers, or to muddy interpretation of the results. Moreover, the authors' radiative–convective model was entirely fit for purpose. The comprehensiveness of Manabe and Wetherald's paper also puts much subsequent work to shame: it was just as concerned with the effects of supersonic aircraft on temperatures in the upper atmosphere as it was about the effects of CO at Earth's surface. It was also the first paper to find that CO not only warms the surface of the planet, but also cools the stratosphere — although the authors devoted just 17 words to this major discovery. Nevertheless, it took some time for climate scientists to warm to the paper, and Manabe himself, keen to add more sophistication to his approach, never really used his 1D radiative–convective model in this way again. Instead, Manabe and Wetherald successfully repeated their calculation in 1975 using their fledgling general circulation model10, which could also account for high-latitude warming and changes to snow cover and sea ice. I believe that this more-sophisticated calculation was partly responsible for building trust in their earlier approach using the 1D radiative–convective model, so that other scientists then began to use such models to great effect to probe the multiple possible causes of observed increases in surface temperature during the twentieth century11, 12. For example, a study11 published in 1981 concluded that twentieth-century temperature variations were probably due to a combination of human-induced changes (in land use and in atmospheric levels of greenhouse gases, ozone and aerosols) and natural phenomena (changes in solar radiation and volcanic emissions). Such work fostered international concern about climate change, and eventually led to the establishment of the Intergovernmental Panel on Climate Change in 1988. Depending on your bent, Manabe and Wetherald's legacy can be interpreted as a justification for the ever-increasing sophistication of climate models (Fig. 1) or as a champion of simple modelling approaches. Today, radiative–convective models have been largely superseded by complex Earth-system models, or by even simpler concepts such as radiative forcing (developed in the 1970s from the radiative–convective modelling experiments highlighted above). This is a pity. Radiative–convective models are a great way of elucidating key climate processes and can still provide useful insights that other approaches cannot, especially into the uncertain role of clouds in climate13. Fifty years on, the time is right for their resurgence.


News Article | May 25, 2017
Site: grist.org

Less than a year after Hurricane Matthew raked the East Coast, killing 34 people and causing $10 billion in damage in the U.S. alone, coastal areas are once again preparing for the onset of the Atlantic hurricane season. This year, forecasters with the National Oceanic and Atmospheric Administration are expecting to see above average storm numbers in the Atlantic, despite the uncertainty of whether an El Niño will develop over the summer. The forecast is currently for 11 to 17 named storms to form, of which five to nine are expected to become hurricanes, and two to four major hurricanes (Category 3 or above). The forecast, though, “does not predict when, where, and how these storms might hit,” Ben Friedman, the acting NOAA administrator, said during a press conference, as he and other officials urged coastal residents to begin their preparations. During Thursday’s press conference, officials also touted the updated models and tools they have to produce better forecasts for individual storms, part of a concerted effort that has greatly improved hurricane forecasts over the past couple of decades. Those comments, though, come just a few days after the release of President Trump’s budget request, which calls for reductions to some of those very programs. The 2017 hurricane season got off to an early start, with Tropical Storm Arlene forming in April, only the second April storm in the satellite era. Early storms, however, are not necessarily indicators of how active a given season will be. To gauge the hurricane season, forecasters use various climatological clues, such as the state of the El Niño cycles, as well as expected trends in ocean temperatures and a measure called wind shear, which can cut off storm formation. El Niño is a key factor in making hurricane seasonal forecasts because the changes in atmospheric patterns over the tropical Pacific that it ushers in have a domino effect on patterns over the Atlantic, tending to suppress hurricane formation. Whether an El Niño will develop is currently something of a question mark, though, with the odds about even for El Niño or neutral conditions this summer and fall. Also uncertain is whether any El Niño that does materialize will be strong enough to influence the Atlantic. But sea surface temperatures across swaths of the Atlantic are currently above average and are expected to stay that way, and wind shear is also expected to stay low, both of which would tend to support more storm formation. So given the signals that forecasters have to work with, they expect a 45 percent chance of above average storm numbers, a 35 percent chance of near normal, and only a 20 percent chance of below normal activity. Those percentages translate to the ranges of numbers of storms expected at different strengths. The 11 to 16 named storms include those that reach tropical storm status or higher, defined as a storm with wind speeds of 39 mph or higher. Five to nine of those storms would be expected to strengthen into hurricanes, with winds in excess of 74 mph. And then two to four of those hurricanes would be expected to reach major hurricane status, defined as Category 3 or above on the Saffir-Simpson scale of hurricane strength, or winds above 111 mph. An average Atlantic season has 12 named storms, six hurricanes, and three major hurricanes. NOAA evaluates the accuracy of its seasonal forecasts each year, with the aim of seeing the number of storms fall in the given ranges at least 70 percent of the time, which they do consistently, Gerry Bell, lead seasonal hurricane forecaster with NOAA’s Climate Prediction Center, said. It has been a record-setting 12 years since a major hurricane made landfall on the U.S. coast; the last to do so was Hurricane Wilma during the blockbuster 2005 season. “While some may think that’s lucky … in fact, tropical storms and lesser hurricanes can be just as damaging and just as deadly,” Friedman said, citing Matthew as a prime example. Matthew, which was for a time the first Category 5 hurricane to form in the Atlantic since Hurricane Felix in 2007, had weakened to a Category 1 storm by the time it made landfall in South Carolina last October. The punishing storm surge that pushed ashore from Florida to the Carolinas and the torrential rains it dropped inland still made it the 10th costliest storm recorded in the Atlantic basin, according to the reinsurance firm Aon Benfield. Storm surge and heavier downpours are two areas where climate change is exerting an influence on the damage produced by hurricanes. As global temperature rise, sea level rises too, meaning hurricane surges can reach further inland. Rising temperatures also concentrate moisture in the atmosphere, providing more fuel for heavy rains. The impact of climate change on hurricanes themselves is active area of research; the general consensus is that there may be fewer storms overall in a warmer world, but a higher proportion of them will be major hurricanes. Major hurricanes have already increased in the Atlantic since 1970. Some research has also suggested that the hurricane season could become longer, meaning more pre-season storms like Arlene. During the press conference, Mary Erickson, deputy director of National Weather Service, touted the increased accuracy of hurricane forecasts resulting from investments into improving models. In the 25 years since Hurricane Andrew devastated southeastern Florida, the three-day track forecast for hurricanes has improved by 65 percent, she said. Two new models coming online this season could improve forecasts even more. One, the Hurricane Weather Research Forecast model, includes better resolution of storms, advanced ways of feeding data into the model, and more accurate atmospheric physics, all of which could improve intensity forecasts for storms by up to 10 percent and track forecasts by up to 7 percent, Erickson said. Another model replaces the retiring Geophysical Fluid Dynamics Laboratory Hurricane Model after 22 years, and it also improves track and intensity forecasts. Many of the improvements to those models have come as part of a concerted effort called the Hurricane Forecast Improvement Program. That program was established by NOAA in 2009, in part as a response to the pummeling the U.S. received from a number of hurricanes during the early years of that decade and the relative lack of progress made in improving forecasts up to that point. Trump’s 2018 budget request currently includes a $5 million reduction in funding “to slow the transition of advanced modeling research into operations for improved warnings and forecasts,” including the HFIP. That budget provision doesn’t jibe with the bipartisan-supported Weather Research and Forecasting Innovation Act of 2017, which the president signed into law last month and which states that “NOAA must plan and maintain a project to improve hurricane forecasting.” “I don’t think Congress will take his proposal seriously at all … so it can probably be ignored in favor of the legislation that has actually passed,” Brian McNoldy, a hurricane researcher at the University of Miami, said in an email. “But supposing Congress did pass his budget as-is, yes, it would be devastating to weather prediction across the board, including hurricanes.” Forecasters will also be able to use the improved observations of the GOES-16 satellite, which has four times the resolution and updates five times faster than its predecessors. In particular, its lightning mapper will help forecasters better understand how a storm is developing, as lightning often accompanies rapid storm development. When it becomes operational later this year, GOES-16 will move into orbit over the East Coast, in prime hurricane-watching position, Friedman said. NOAA is also making its previously experimental storm surge watches and warnings operational this year, in an effort to better prepare coastal areas under threat of flooding. Hurricane graphics will also include an experimental visualization of how far damaging winds extend out from the center of a storm. NOAA will update its forecast in early August, just before the typical peak of the hurricane season.


News Article | May 23, 2017
Site: www.rdmag.com

Scientists have developed a new method to forecast the extent of sea ice in some regions of the Arctic up to 11 months in advance. The method, which incorporates information about ocean temperatures and focuses on regions rather than the entire Arctic Sea, could help in the planning of activities ranging from shipping to oil and gas extraction, fishing and tourism. The model improves on previous methods capable of predicting the ice over the entire Arctic Sea up to six months in advance. The new approach, detailed in a study published this week in the journal Geophysical Research Letters, was developed by an international team including researchers from Princeton University, the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory and the French National Center for Scientific Research. Most efforts to predict sea ice extent have focused on determining the total area of sea ice coverage over the northern hemisphere. But stakeholders are primarily interested in predictions on regional and seasonal scales, according to Mitchell Bushuk, who led the research while a postdoctoral research associate in Princeton University’s Program in Atmospheric and Oceanic Sciences. Companies involved in shipping, tourism and resource management, as well as local communities in the Arctic, are affected by the location and thickness of sea ice and rely on accurate reporting and forecasting of sea ice conditions. Climate prediction systems combine observations of real-world conditions with computer models to make predictions about future events. The more accurate these observational data are, the more accurate the forecast, explained Bushuk, who is now a scientist at the Geophysical Fluid Dynamics Laboratory located about three miles from Princeton University’s main campus. For the current study, Bushuk and co-authors determined that including surface and subsurface ocean temperature data in the model was crucial to predicting winter sea ice extent in the Labrador Sea, located between Greenland and Canada, and the Barents Sea, located north of Scandinavia and Russia. Similarly, the inclusion of accurate sea ice thickness data was fundamental to predicting summer sea ice extent in the East Siberian and Chukchi seas north of Siberia and the Beaufort Sea north of Alaska. The new model accurately predicted the area covered by sea ice in the Barents and Greenland-Iceland-Norwegian seas and in the Labrador Sea up to 11 months in advance. The system was also able to accurately predict summer sea ice coverage in the East Siberian, Laptev, Chukchi and Beaufort seas up to four months in advance. “Summer prediction is a more challenging problem,” Bushuk said. “We think the key reason is the surface albedo effect,” he said, referring to how much radiation from the sun is reflected by surfaces on Earth. As ice melts in the Arctic, it is replaced by water or ground. Both are darker than ice and snow and tend to absorb light rather than reflect it. Less reflection by ice and snow means more energy is absorbed, which heats the surface of the planet and leads to an increase in warming in a positive feedback loop. In addition to predicting the minimum and maximum values of regional sea ice extent, the model can also forecast the extent of sea ice in the Hudson Bay from June to August and from November to December at lead times of three to 11 months. Bushuk said there is still work to be done to improve scientists’ understanding of sea ice physics and to provide better regional forecasts. His team will next compare their results to similar seasonal prediction systems to determine how consistent their findings are. Since accurate data about the current state of the atmosphere, ocean, sea ice and land are so crucial to the success of these forecasts, Bushuk hopes that this research will motivate future work.


The findings, reported in Progress in Oceanography, suggest ocean temperature will continue to play a major role in where commercially and recreationally important species will find suitable habitat. Sea surface temperatures in the Gulf of Maine have warmed faster than 99 percent of the global ocean over the past decade. Northward shifts of many species are already happening, with major changes expected in the complex of species occurring in different regions on the shelf, and shifts from one management jurisdiction to another. These changes will directly affect fishing communities, as species now landed at those ports move out of range, and new species move in. "Species that are currently found in the Mid-Atlantic Bight and on Georges Bank may have enough suitable habitat in the future because they can shift northward as temperatures increase," said lead author Kristin Kleisner, formerly of the Northeast Fisheries Science Center (NEFSC)'s Ecosystems Dynamics and Assessment Branch and now a senior scientist at the Environmental Defense Fund. "Species concentrated in the Gulf of Maine, where species have shifted to deeper water rather than northward, may be more likely to experience a significant decline in suitable habitat and move out of the region altogether." The researchers used bottom trawl survey data collected between 1968 and 2013 on the shelf to estimate niches for 58 demersal and pelagic species. A high-resolution global climate model known as CM2.6, developed by the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) in Princeton, New Jersey, was used to generate projections of future surface and bottom ocean temperatures across the region. The future temperatures were then used to project where marine species would find suitable habitat. "Similar studies in the past used a coarse model with a roughly 100-kilometer or 62-mile ocean resolution, while the new model has a 10-kilometer or 6.2-mile ocean resolution, making the simulation of oceanic and atmospheric features much more accurate," said Vincent Saba of the NEFSC's Ecosystems Dynamics and Assessment Branch, who works at GFDL and is a co-author of the study. Saba has compared the difference between the coarse model and the new high-resolution model as being similar to the difference between an old standard definition television set and today's ultra high definition screens. Researchers looked at species distributions in spring and fall in the Gulf of Maine on the northern part of the Northeast Shelf and those on the southern end, from Georges Bank to the Mid-Atlantic Bight. They also examined what the shifting distributions might mean for fishing communities by looking at the current and potential future distance between the main fishing port in each state and the center of the distribution of suitable thermal area for the top-landed species by weight in each state. Key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorny skate may lose thermal habitat, while spiny dogfish and American lobster may gain. Projected ocean warming in the Gulf of Maine may create beneficial conditions for American lobster populations, and they may continue to be accessible to fishing ports in the region. In contrast, species like monkfish, witch flounder, white hake and sea scallops may remain accessible to major local fishing ports but could experience strong declines in habitat due to ocean warming. Atlantic cod, which is at the southern end of its range, may find suitable thermal habitat off the shelf entirely or in more northern waters in Canada. In states south of New York, the distance to the centers of species distribution from ports may increase for some species, including summer flounder, which is currently the third most-landed species in Virginia. In North Carolina, the distance from ports to the center of distribution may increase for all six of the top landed species. Among the top six species landed in Virginia, only Atlantic croaker and striped bass are projected to have more suitable habitat. "Warming waters may have a positive effect on smooth dogfish, Atlantic croaker, and striped bass in the southern part of the Northeast Shelf, with increases in suitable habitat in terms of area and species abundance, " Kleisner said. "But these species are also shifting northward and the bulk of the biomass of some species may be further from the main ports in southern states, making it more costly for fishermen to access these species. Conversely, as species move into new regions, fishermen may have new opportunities." The projections indicate that as species shift from one management jurisdiction to another, or span state and federal jurisdictions, increased collaboration among management groups will be needed to set quotas and establish allocations. "These changes will depend on the pace of climate change and on the ability of species to adapt or shift elsewhere to maintain a preferred habitat," said Kleisner. "We did not examine fishing pressure, species interactions and other factors that may influence future distributions. However, given the historical changes observed on the Northeast Shelf over the past five decades and confidence in the projection of continued ocean warming in the region, it is likely there will be major changes within this ecosystem." "Those changes will result in ecological, economic, social, and natural resource management challenges throughout the region," Kleisner said. "It is important to understand large-scale patterns in these changes so that we can plan for and mitigate adverse effects as much as possible." Explore further: Species groups follow patterns reacting to climate change on US northeast shelf More information: Kristin M. Kleisner et al, Marine species distribution shifts on the U.S. Northeast Continental Shelf under continued ocean warming, Progress in Oceanography (2017). DOI: 10.1016/j.pocean.2017.04.001


News Article | May 28, 2017
Site: www.sciencedaily.com

Scientists using a high-resolution global climate model and historical observations of species distributions on the Northeast U.S. Shelf have found that commercially important species will continue to shift their distribution as ocean waters warm two to three times faster than the global average through the end of this century. Projected increases in surface to bottom waters of 6.6 to 9 degrees F (3.7 to 5.0 degrees Celsius) from current conditions are expected. The findings, reported in Progress in Oceanography, suggest ocean temperature will continue to play a major role in where commercially and recreationally important species will find suitable habitat. Sea surface temperatures in the Gulf of Maine have warmed faster than 99 percent of the global ocean over the past decade. Northward shifts of many species are already happening, with major changes expected in the complex of species occurring in different regions on the shelf, and shifts from one management jurisdiction to another. These changes will directly affect fishing communities, as species now landed at those ports move out of range, and new species move in. "Species that are currently found in the Mid-Atlantic Bight and on Georges Bank may have enough suitable habitat in the future because they can shift northward as temperatures increase," said lead author Kristin Kleisner, formerly of the Northeast Fisheries Science Center (NEFSC)'s Ecosystems Dynamics and Assessment Branch and now a senior scientist at the Environmental Defense Fund. "Species concentrated in the Gulf of Maine, where species have shifted to deeper water rather than northward, may be more likely to experience a significant decline in suitable habitat and move out of the region altogether." The researchers used bottom trawl survey data collected between 1968 and 2013 on the shelf to estimate niches for 58 demersal and pelagic species. A high-resolution global climate model known as CM2.6, developed by the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) in Princeton, New Jersey, was used to generate projections of future surface and bottom ocean temperatures across the region. The future temperatures were then used to project where marine species would find suitable habitat. "Similar studies in the past used a coarse model with a roughly 100-kilometer or 62-mile ocean resolution, while the new model has a 10-kilometer or 6.2-mile ocean resolution, making the simulation of oceanic and atmospheric features much more accurate," said Vincent Saba of the NEFSC's Ecosystems Dynamics and Assessment Branch, who works at GFDL and is a co-author of the study. Saba has compared the difference between the coarse model and the new high-resolution model as being similar to the difference between an old standard definition television set and today's ultra high definition screens. Researchers looked at species distributions in spring and fall in the Gulf of Maine on the northern part of the Northeast Shelf and those on the southern end, from Georges Bank to the Mid-Atlantic Bight. They also examined what the shifting distributions might mean for fishing communities by looking at the current and potential future distance between the main fishing port in each state and the center of the distribution of suitable thermal area for the top-landed species by weight in each state. Key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorny skate may lose thermal habitat, while spiny dogfish and American lobster may gain. Projected ocean warming in the Gulf of Maine may create beneficial conditions for American lobster populations, and they may continue to be accessible to fishing ports in the region. In contrast, species like monkfish, witch flounder, white hake and sea scallops may remain accessible to major local fishing ports but could experience strong declines in habitat due to ocean warming. Atlantic cod, which is at the southern end of its range, may find suitable thermal habitat off the shelf entirely or in more northern waters in Canada. In states south of New York, the distance to the centers of species distribution from ports may increase for some species, including summer flounder, which is currently the third most-landed species in Virginia. In North Carolina, the distance from ports to the center of distribution may increase for all six of the top landed species. Among the top six species landed in Virginia, only Atlantic croaker and striped bass are projected to have more suitable habitat. "Warming waters may have a positive effect on smooth dogfish, Atlantic croaker, and striped bass in the southern part of the Northeast Shelf, with increases in suitable habitat in terms of area and species abundance, " Kleisner said. "But these species are also shifting northward and the bulk of the biomass of some species may be further from the main ports in southern states, making it more costly for fishermen to access these species. Conversely, as species move into new regions, fishermen may have new opportunities." The projections indicate that as species shift from one management jurisdiction to another, or span state and federal jurisdictions, increased collaboration among management groups will be needed to set quotas and establish allocations. "These changes will depend on the pace of climate change and on the ability of species to adapt or shift elsewhere to maintain a preferred habitat," said Kleisner. "We did not examine fishing pressure, species interactions and other factors that may influence future distributions. However, given the historical changes observed on the Northeast Shelf over the past five decades and confidence in the projection of continued ocean warming in the region, it is likely there will be major changes within this ecosystem." "Those changes will result in ecological, economic, social, and natural resource management challenges throughout the region," Kleisner said. "It is important to understand large-scale patterns in these changes so that we can plan for and mitigate adverse effects as much as possible."


News Article | May 26, 2017
Site: www.eurekalert.org

Scientists using a high-resolution global climate model and historical observations of species distributions on the Northeast U.S. Shelf have found that commercially important species will continue to shift their distribution as ocean waters warm two to three times faster than the global average through the end of this century. Projected increases in surface to bottom waters of 6.6 to 9 degrees F (3.7 to 5.0 degrees Celsius) from current conditions are expected. The findings, reported in Progress in Oceanography, suggest ocean temperature will continue to play a major role in where commercially and recreationally important species will find suitable habitat. Sea surface temperatures in the Gulf of Maine have warmed faster than 99 percent of the global ocean over the past decade. Northward shifts of many species are already happening, with major changes expected in the complex of species occurring in different regions on the shelf, and shifts from one management jurisdiction to another. These changes will directly affect fishing communities, as species now landed at those ports move out of range, and new species move in. "Species that are currently found in the Mid-Atlantic Bight and on Georges Bank may have enough suitable habitat in the future because they can shift northward as temperatures increase," said lead author Kristin Kleisner, formerly of the Northeast Fisheries Science Center (NEFSC)'s Ecosystems Dynamics and Assessment Branch and now a senior scientist at the Environmental Defense Fund. "Species concentrated in the Gulf of Maine, where species have shifted to deeper water rather than northward, may be more likely to experience a significant decline in suitable habitat and move out of the region altogether." The researchers used bottom trawl survey data collected between 1968 and 2013 on the shelf to estimate niches for 58 demersal and pelagic species. A high-resolution global climate model known as CM2.6, developed by the NOAA Geophysical Fluid Dynamics Laboratory (GFDL) in Princeton, New Jersey, was used to generate projections of future surface and bottom ocean temperatures across the region. The future temperatures were then used to project where marine species would find suitable habitat. "Similar studies in the past used a coarse model with a roughly 100-kilometer or 62-mile ocean resolution, while the new model has a 10-kilometer or 6.2-mile ocean resolution, making the simulation of oceanic and atmospheric features much more accurate," said Vincent Saba of the NEFSC's Ecosystems Dynamics and Assessment Branch, who works at GFDL and is a co-author of the study. Saba has compared the difference between the coarse model and the new high-resolution model as being similar to the difference between an old standard definition television set and today's ultra high definition screens. Researchers looked at species distributions in spring and fall in the Gulf of Maine on the northern part of the Northeast Shelf and those on the southern end, from Georges Bank to the Mid-Atlantic Bight. They also examined what the shifting distributions might mean for fishing communities by looking at the current and potential future distance between the main fishing port in each state and the center of the distribution of suitable thermal area for the top-landed species by weight in each state. Key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorny skate may lose thermal habitat, while spiny dogfish and American lobster may gain. Projected ocean warming in the Gulf of Maine may create beneficial conditions for American lobster populations, and they may continue to be accessible to fishing ports in the region. In contrast, species like monkfish, witch flounder, white hake and sea scallops may remain accessible to major local fishing ports but could experience strong declines in habitat due to ocean warming. Atlantic cod, which is at the southern end of its range, may find suitable thermal habitat off the shelf entirely or in more northern waters in Canada. In states south of New York, the distance to the centers of species distribution from ports may increase for some species, including summer flounder, which is currently the third most-landed species in Virginia. In North Carolina, the distance from ports to the center of distribution may increase for all six of the top landed species. Among the top six species landed in Virginia, only Atlantic croaker and striped bass are projected to have more suitable habitat. "Warming waters may have a positive effect on smooth dogfish, Atlantic croaker, and striped bass in the southern part of the Northeast Shelf, with increases in suitable habitat in terms of area and species abundance, " Kleisner said. "But these species are also shifting northward and the bulk of the biomass of some species may be further from the main ports in southern states, making it more costly for fishermen to access these species. Conversely, as species move into new regions, fishermen may have new opportunities." The projections indicate that as species shift from one management jurisdiction to another, or span state and federal jurisdictions, increased collaboration among management groups will be needed to set quotas and establish allocations. "These changes will depend on the pace of climate change and on the ability of species to adapt or shift elsewhere to maintain a preferred habitat," said Kleisner. "We did not examine fishing pressure, species interactions and other factors that may influence future distributions. However, given the historical changes observed on the Northeast Shelf over the past five decades and confidence in the projection of continued ocean warming in the region, it is likely there will be major changes within this ecosystem." "Those changes will result in ecological, economic, social, and natural resource management challenges throughout the region," Kleisner said. "It is important to understand large-scale patterns in these changes so that we can plan for and mitigate adverse effects as much as possible."


News Article | March 1, 2017
Site: www.eurekalert.org

PRINCETON, N.J. -- An influx of pollution from Asia in the western United States and more frequent heat waves in the eastern U.S. are responsible for the persistence of smog in these regions over the past quarter century despite laws curtailing the emission of smog-forming chemicals from tailpipes and factories. The study, led by researchers at Princeton University and the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory (GFDL), highlights the importance of maintaining domestic emission controls on motor vehicles, power plants and other industries at a time when pollution is increasingly global. Published March 1 in the journal Atmospheric Chemistry and Physics, the study looked at the sources of smog, also known as ground-level ozone, across a period ranging from the 1980s to today. Ground-level ozone, which is distinct from the ozone in the upper atmosphere that protects the planet from ultraviolet radiation, is harmful to human health, exacerbating asthma attacks and causing difficulty breathing. It also harms sensitive trees and crops. Despite a 50 percent cut in smog-forming chemicals such as nitrogen oxides, commonly known as "NOx", over the past 25 years, ozone levels measured in rural areas of the west have actually climbed. And while ozone in the eastern U.S. has decreased overall, the levels can spike during heat waves. The study traced the increase of ozone in the west to the influx of pollution from Asian countries, including China, North and South Korea, Japan, India, and other South Asian countries. Collectively, the region has tripled its emissions of NOx since 1990. In the eastern U.S., meanwhile, heat waves -- which have become more frequent in the past few decades -- trap polluted air in place, leading to temporary escalations in locally produced ozone. The study explains why springtime ozone levels measured in Yellowstone National Park and other western parks far from urban areas have climbed over the past quarter century. According to the study, springtime ozone levels in the national parks rose during that period by 5 to 10 parts per billion (ppb), which is significant given that the federal ozone standard is 70 ppb. The influx of pollution from Asia could make it difficult for these areas to comply with the federal ozone standards, according to the study's authors. "Increasing background ozone from rising Asian emissions leaves less room for local production of ozone before the federal standard is violated," said lead author Meiyun Lin, a research scholar in the Program in Atmospheric and Oceanic Sciences at Princeton University and a scientist at GFDL. Lin's co-authors were Larry Horowitz, also of GFDL; Richard Payton and Gail Tonnesen of the U.S. Environmental Protection Agency; and Arlene Fiore of the Lamont-Doherty Earth-Observatory and Department of Earth and Environmental Sciences at Columbia University. Using ozone measurements combined with climate models developed at GFDL, the authors identified pollution from Asia as driving the climb in ozone in western U.S. national parks in the spring, when wind and weather patterns push Asian pollution across the Pacific Ocean. In the summer, when these weather patterns subside, ozone levels in national parks are still above what would be expected given U.S. reductions in ozone-precursors. While it has been known for over a decade that Asian pollution contributes to ozone levels in the United States, this study is one of the first to categorize the extent to which rising Asian emissions contribute to U.S. ozone, according to Lin. In the eastern United States, where Asian pollution is a minor contributor to smog, NOx emission controls have been successful at reducing ozone levels. However, periods of extreme heat and drought can trap pollution in the region, making bad ozone days worse. Regional NOx emission reductions alleviated the ozone buildup during the recent heat waves of 2011 and 2012, compared to earlier heat waves such as in 1988 and 1999. As heat waves appear to be on the rise due to global climate change, smog in the eastern U.S. is likely to worsen, according to the study. Climate models such as those developed at GFDL can help researchers predict future levels of smog, enabling cost-benefit analyses for costly pollution control measures. The researchers compared results from a model called GFDL-AM3 to ozone measurements from monitoring stations over the course of the last 35 years, from 1980 to 2014. Prior studies using global models poorly matched the ozone increases measured in western national parks. Lin and co-authors were able to match the measurements by narrowing their analysis to days when the airflow is predominantly from the Pacific Ocean. Modeling the sources of air pollution can help explain where the ozone measured in the national parks is coming from, explained Lin. "The model allows us to divide the observed air pollution into components driven by different sources," she said. The team also looked at other contributors to ground-level ozone, such as global methane from livestock and wildfires. Wildfire emissions contributed less than 10 percent and methane about 15 percent of the western U.S. ozone increase, whereas Asian air pollution contributed as much as 65 percent. These new findings suggest that a global perspective is necessary when designing a strategy to meet U.S. ozone air quality objectives, said Lin. The negative effect of imported pollution on the US's ability to achieve its air quality goals is not wholly unexpected, according to Owen Cooper, a senior research scientist at the University of Colorado and the NOAA Earth System Research Laboratory, who is familiar with the current study but not directly involved. "Twenty years ago, scientists first speculated that rising Asian emissions would one day offset some of the United States' domestic ozone reductions," Cooper said. "This study takes advantage of more than 25 years of observations and detailed model hindcasts to comprehensively demonstrate that these early predictions were right."


News Article | February 15, 2017
Site: news.mit.edu

Last spring, MIT research scientist C. Adam Schlosser, who serves as deputy director of the MIT Joint Program on the Science and Policy of Global Change, and colleagues published a paper in the journal PLOS One that projected a “high risk of severe water stress” in much of Asia by midcentury. Attributing the projection to rising demands driven by population and economic growth and exacerbated by climate change, they estimated that within 35 years, 1 billion more people in the area would be affected. The region in question is home to about half of the global population, so this finding matters. News outlets from the Christian Science Monitor to TIME picked up the story, disseminating it to millions of potential readers. “The response to this study illustrates the kind of scientific finding that makes people — including decision-makers and other stakeholders — listen and react,” says Schlosser. “We presented not only the science but also its potential impact on people’s lives. That’s a hallmark of the Joint Program.” So, too, is a methodology that underlies not only the Asia water-stress study but much of Schlosser’s research: the practice of running a computer model multiple times under varying assumptions (e.g., about the climate, population growth, or economic growth) to produce an exhaustive range of plausible future scenarios for a particular aspect of global change — such as water availability — and qualify each scenario with a level of uncertainty. In the vernacular, this is known as the application of Monte Carlo methods. By “rolling the dice” hundreds to thousands of times under different assumptions about Earth and human systems, Schlosser and colleagues can determine the odds of outcomes that policymakers are either targeting or trying to prevent. This information can then help guide decision-makers on how best to “weight the dice” to minimize risk to lives and infrastructure. “The challenge with addressing and quantifying risks is to identify the bounds of your knowledge and everything in between, and then to simulate that environment with computer models,” notes Schlosser. “That demands that we not only use models in creative ways but also bring to bear observations that can help us isolate meaningful signals in the results we obtain from those models.” Applying Monte Carlo methods to the Joint Program’s Integrated Global System Modeling (IGSM) framework to simulate the response of Earth and human systems to global change and assess risks that may lie ahead in the coming decades, Schlosser is now working to identify potential threats to regional water supplies and ecosystems, optimal locations for renewable energy generation around the globe, and trends in extreme events and their potential impact on the built environment. Charting the future of water supplies, renewable energy, and the grid Having recently upgraded the Water Resource Systems (WRS) model used in the Asia water-stress study — an extension of the IGSM framework — to more precisely represent water-demand sectors (regional watersheds) and the quality of water within them, Schlosser aims to simulate a large number of plausible futures for the U.S. water supply. The goal of his research team is to pinpoint any significant threats to the water system and project when water availability may become severely stressed by changes in the agricultural, energy, industrial, and other sectors of the economy. Over the next two years, he plans to explore the range of risks that different climate pathways pose for the U.S. water system, and how those risks may be avoided through mitigation or adaptation measures, such as efficiency improvements in water use (e.g. irrigation) and transport. He also aims to account for the uncertainty in runoff changes that occur under climate change, and their impact on risks to water demand sectors. Another key research objective of Schlosser’s is to determine how regional patterns of precipitation and temperature will impact the deployment of renewable energy technologies such as wind turbines and photovoltaics. As the world shifts away from fossil fuels and toward lower-carbon energy sources, it will become increasingly important to identify the prime locations where wind and solar power can thrive. By enhancing the IGSM framework to generate multiple simulations of wind and clouds on a regional basis, Schlosser aims to provide policymakers with more precise estimates of the times and locations at which wind and solar energy resources will be plentiful and reliable. “In a world where wind and solar farm installations are ubiquitous, it would be very beneficial if the science of climate predictability could tell when and where those fundamentally intermittent resources are the most reliable without constantly relying on backup technologies which are the very same greenhouse gas-emitting technologies we’re trying to avoid in the first place,” he says. Schlosser is also applying Monte Carlo methods to assess the risk to infrastructure posed by extreme weather events that range from storms to heatwaves. He and colleagues first developed a technique that draws upon the Joint Program’s climate model and those used by the institutions that have participated in the Intergovernmental Panel on Climate Change (IPCC) to explore how precipitation extremes shift under various climate policies — and which policies are likely to minimize the likelihood of shifts in extreme precipitation events that threaten infrastructure and livelihoods. In a pilot project conducted in collaboration with the MIT Lincoln Laboratory, they next looked at how human-induced changes in climate affect the occurrence of heatwaves that could damage expensive transformers that are critical to the functioning of the electric power grid in the U.S. Northeast. The next step is to expand this analysis and evaluate the grid more comprehensively, so as to provide actionable information for how to make the grid more stable, reliable, and environmentally responsible. “Our approach shrinks down the range of possible outcomes,” says Schlosser. “We’ll never be able to completely eliminate all uncertainty, but there are opportunities to constrain the uncertainty and give people an outlook of the future that we can act upon.” Schlosser came to this work out of a love for snow. Growing up in Rhode Island, he lived for snow days, when he could trade reading, writing, and arithmetic for sledding, skating, and skiing. Over the years, as climate change emerged as a global threat, his affinity for winter storms and activities fueled a growing concern about how winter would change on a warmer planet. That led to an interest in hydrology: Studies of hydrology in graduate school at the University of Maryland, where he received a PhD in meteorology, deepened his focus on winter processes and raised his awareness about the challenges in representing hydrology in climate or earth system models. After completing postgraduate work in climate predictability at NOAA’s Geophysical Fluid Dynamics Laboratory and further research at the Center for Ocean Land Atmosphere Studies, he served as a research scientist at the NASA Goddard Spaceflight Center, where he developed an ongoing program, the NASA Energy and Water Cycle Study, that uses multiple observations to generate a comprehensive picture of the global water and energy cycle. While Schlosser’s work at Goddard nurtured his scientific curiosity, there was something missing that he would find in his next position at the Joint Program, and keep him here for 12 years and counting. “Throughout my career, my research has been personally compelling from a scientific discovery standpoint, but there’s nothing like advancing science that can make a substantive contribution to decision-making, strategic planning, and policy formation concerning critical global challenges,” he says. “I never had an appreciation for that until I came here.” A version of this article originally appeared in the Fall 2016 issue of Global Changes, a triennial publication of the MIT Joint Program on the Science and Policy of Global Change.


Seager R.,Lamont Doherty Earth Observatory | Naik N.,Lamont Doherty Earth Observatory | Vecchi G.A.,Geophysical Fluid Dynamics Laboratory
Journal of Climate | Year: 2010

The mechanisms of changes in the large-scale hydrological cycle projected by 15 models participating in the Coupled Model Intercomparison Project phase 3 and used for the Intergovernmental Panel on Climate Change's Fourth Assessment Report are analyzed by computing differences between 2046 and 2065 and 1961 and 2000. The contributions to changes in precipitation minus evaporation, P-E, caused thermodynamically by changes in specific humidity, dynamically by changes in circulation, and by changes in moisture transports by transient eddies are evaluated. The thermodynamic and dynamic contributions are further separated into advective and divergent components. The nonthermodynamic contributions are then related to changes in the mean and transient circulation. The projected change in P-E involves an intensification of the existing pattern of P-E with wet areas [the intertropical convergence zone (ITCZ) and mid-to high latitudes] getting wetter and arid and semiarid regions of the subtropics getting drier. In addition, the subtropical dry zones expand poleward. The accentuation of the twentieth-century pattern of P-E is in part explained by increases in specific humidity via both advection and divergence terms. Weakening of the tropical divergent circulation partially opposes the thermodynamic contribution by creating a tendency to decreased P-E in the ITCZ and to increased P-E in the descending branches of the Walker and Hadley cells. The changing mean circulation also causes decreased P-E on the poleward flanks of the subtropics because the descending branch of the Hadley Cell expands and the midlatitude meridional circulation cell shifts poleward. Subtropical drying and poleward moistening are also contributed to by an increase in poleward moisture transport by transient eddies. The thermodynamic contribution to changing P-E, arising from increased specific humidity, is almost entirely accounted for by atmospheric warming under fixed relative humidity. © 2010 American Meteorological Society.


News Article | March 7, 2016
Site: www.sciencenews.org

Using records of ships wrecked by Atlantic hurricanes dating as far back as the days of Christopher Columbus, researchers have extended the hurricane record by hundreds of years. The work reveals that hurricane frequency plummeted 75 percent between 1645 and 1715, a time called the Maunder Minimum when the sun dimmed to its lowest recorded brightness. “We didn’t go looking for the Maunder Minimum; it just popped out of the data,” says study coauthor Valerie Trouet, a paleoclimate scientist at the University of Arizona in Tucson. The findings should help scientists better predict how hurricanes will behave under climate change, the researchers report in a paper to appear in the Proceedings of the National Academy of Sciences. Detailed hurricane observational records go back to 1851. Scouring an Atlantic shipwreck catalog, Trouet and colleagues identified more than 650 Spanish ships sunk by hurricanes from 1495 through 1825. The researchers bridged the shipwreck and observational records using tree rings from slash pines (Pinus elliottii) collected along the Florida coast and dating to as early as 1707. Hurricane damage stunts tree growth, narrowing the annual rings. All three records agreed, allowing the researchers to stitch together one long hurricane frequency record. The number of hurricane-caused shipwrecks during the Maunder Minimum, which makes up a large portion of a period nicknamed the “Little Ice Age,” was less than a third the number of wrecks in the preceding decades. A hurricane slowdown during the solar dim period makes sense, Trouet says. Warm seawater fuels hurricanes. As temperatures dropped around the Maunder Minimum, less heat was available to power storms. The finding doesn’t mean that global warming will increase hurricane frequency, says Gabriel Vecchi, an oceanographer at the National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton, N.J. While both solar brightness and heat-trapping greenhouse gases cause warming, their effects on hurricanes “aren’t perfect analogs,” he says. Still, the new data can provide a test for climate simulations, Vecchi says. “We can ask a model, ‘When we give you less sun, what do you do?’ If it doesn’t give us fewer hurricanes, we can then ask why. This gives us something to aim at.”

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