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Plasma plumes help shield Earth from damaging solar storms

Earth's magnetic field, or magnetosphere, stretches from the planet's core out into space, where it meets the solar wind, a stream of charged particles emitted by the sun. For the most part, the magnetosphere acts as a shield to protect Earth from this high-energy solar activity.

But when this field comes into contact with the sun's magnetic field -- a process called "magnetic reconnection" -- powerful electrical currents from the sun can stream into Earth's atmosphere, whipping up geomagnetic storms and space weather phenomena that can affect high-altitude aircraft, as well as astronauts on the International Space Station.

Now scientists at MIT and NASA have identified a process in Earth's magnetosphere that reinforces its shielding effect, keeping incoming solar energy at bay.

By combining observations from the ground and in space, the team observed a plume of low-energy plasma particles that essentially hitches a ride along magnetic field lines -- streaming from Earth's lower atmosphere up to the point, tens of thousands of kilometers above the surface, where the planet's magnetic field connects with that of the sun. In this region, which the scientists call the "merging point," the presence of cold, dense plasma slows magnetic reconnection, blunting the sun's effects on Earth.

"The Earth's magnetic field protects life on the surface from the full impact of these solar outbursts," says John Foster, associate director of MIT's Haystack Observatory. "Reconnection strips away some of our magnetic shield and lets energy leak in, giving us large, violent storms. These plasmas get pulled into space and slow down the reconnection process, so the impact of the sun on the Earth is less violent."

Foster and his colleagues publish their results in this week's issue of Science. The team includes Philip Erickson, principal research scientist at Haystack Observatory, as well as Brian Walsh and David Sibeck at NASA's Goddard Space Flight Center.

Mapping Earth's magnetic shield

For more than a decade, scientists at Haystack Observatory have studied plasma plume phenomena using a ground-based technique called GPS-TEC, in which scientists analyze radio signals transmitted from GPS satellites to more than 1,000 receivers on the ground. Large space-weather events, such as geomagnetic storms, can alter the incoming radio waves -- a distortion that scientists can use to determine the concentration of plasma particles in the upper atmosphere. Using this data, they can produce two-dimensional global maps of atmospheric phenomena, such as plasma plumes.

These ground-based observations have helped shed light on key characteristics of these plumes, such as how often they occur, and what makes some plumes stronger than others. But as Foster notes, this two-dimensional mapping technique gives an estimate only of what space weather might look like in the low-altitude regions of the magnetosphere. To get a more precise, three-dimensional picture of the entire magnetosphere would require observations directly from space.

Toward this end, Foster approached Walsh with data showing a plasma plume emanating from Earth's surface, and extending up into the lower layers of the magnetosphere, during a moderate solar storm in January 2013. Walsh checked the date against the orbital trajectories of three spacecraft that have been circling the Earth to study auroras in the atmosphere.

As it turns out, all three spacecraft crossed the point in the magnetosphere at which Foster had detected a plasma plume from the ground. The team analyzed data from each spacecraft, and found that the same cold, dense plasma plume stretched all the way up to where the solar storm made contact with Earth's magnetic field.

A river of plasma

Foster says the observations from space validate measurements from the ground. What's more, the combination of space- and ground-based data give a highly detailed picture of a natural defensive mechanism in Earth's magnetosphere.

"This higher-density, cold plasma changes about every plasma physics process it comes in contact with," Foster says. "It slows down reconnection, and it can contribute to the generation of waves that, in turn, accelerate particles in other parts of the magnetosphere. So it's a recirculation process, and really fascinating."

Foster likens this plume phenomenon to a "river of particles," and says it is not unlike the Gulf Stream, a powerful ocean current that influences the temperature and other properties of surrounding waters. On an atmospheric scale, he says, plasma particles can behave in a similar way, redistributing throughout the atmosphere to form plumes that "flow through a huge circulation system, with a lot of different consequences."

"What these types of studies are showing is just how dynamic this entire system is," Foster adds.

Journal Reference:

B. M. Walsh, J. C. Foster, P. J. Erickson, D. G. Sibeck. Simultaneous Ground- and Space-Based Observations of the Plasmaspheric Plume and Reconnection. Science, 2014 DOI: 10.1126/science.1247212

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Seasonal Arctic summer ice extent still hard to forecast, study says

Will next year's summer Arctic ice extent be high or low? Can ship captains plan on navigating the famed Northwest Passage -- a direct shipping route from Europe to Asia across the Arctic Ocean -- to save on time and fuel? A new study says year-to-year forecasts of the Arctic's summer ice extent are not yet reliable.

Scientists at the National Snow and Ice Data Center (NSIDC), University College London, University of New Hampshire and University of Washington analyzed 300 summer Arctic sea ice forecasts from 2008 to 2013 and found that forecasts are quite accurate when sea ice conditions are close to the downward trend that has been observed in Arctic sea ice for the last 30 years. However, forecasts are not so accurate when sea ice conditions are unusually higher or lower compared to this trend.

"We found that in years when the sea ice extent departed strongly from the trend, such as in 2012 and 2013, predictions failed regardless of the method used to forecast the September sea ice extent," said Julienne Stroeve, a senior scientist at NSIDC and professor at University of College London. Stroeve is lead author of the study, published recently in Geophysical Research Letters.

"That downward trend reflects Arctic climate change, but the causes of yearly variations around the trend are harder to pin down," said Lawrence Hamilton, co-author and a researcher at the University of New Hampshire. "This collection of forecasts from many different sources highlights where they do well, and where more work is needed."

Arctic sea ice cover grows each winter as the sun sets for several months, and shrinks each summer as the sun rises higher in the northern sky. Each year, the Arctic sea ice reaches its minimum extent in September. Scientists consider Arctic sea ice as a sensitive climate indicator and track this minimum extent every year to see if any trends emerge.

Multi-channel passive microwave satellite instruments have been tracking sea ice extent since 1979. According to the data, September sea ice extent from 1979 to 2013 has declined 13.7 percent per decade. The recent years have shown an even more dramatic reduction in Arctic ice. In September 2012, Arctic sea ice reached a record minimum: 16 percent lower than any previous September since 1979, and 45 percent lower than the average ice extent from 1981 to 2010.

Long-term predictions of summer Arctic extent made by global climate models (GCMs) suggest that the downward trend will likely lead to an ice-free Arctic summer in the middle of the century. GCMs are in overall agreement on loss of Arctic summer sea ice as a result of anticipated warming from the rise in greenhouse gases this century.

Shorter-term forecasts of summer ice extent are harder to make but are now in high demand. The shrinking ice has caught the attention of coastal communities in the Arctic and industries interested in extracting resources and in a shorter shipping route between Europe and Asia.

Many of the forecasts analyzed in the study focused on the state of the ice cover prior to the summer melt season. According to the study, including sea ice thickness and concentration could improve the seasonal forecasts.

"It may even be possible to predict sea ice cover a year in advance with high-quality observations of sea ice thickness and snow cover over the whole Arctic," said Cecilia Bitz, co-author and professor of atmospheric sciences at the University of Washington.

"Short term predictions are achievable, but challenges remain in predicting anomalous years, and there is a need for better data for initialization of forecast models," Stroeve said. "Of course there is always the issue that we cannot predict the weather, and summer weather patterns remain important."

The study analyzed forecasts from the Study of Environmental Arctic Change (SEARCH) Sea Ice Outlook, a project that gathers and summarizes sea ice forecasts made by sea ice researchers and prediction centers. Contributors to the SEARCH Sea Ice Outlook project employ a variety of techniques to forecast the September sea ice extent, ranging from heuristic, to statistical, to sophisticated modeling approaches.


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Air pollution over Asia influences global weather and makes Pacific storms more intense

In the first study of its kind, scientists have compared air pollution rates from 1850 to 2000 and found that anthropogenic (human-made) particles from Asia impact the Pacific storm track that can influence weather over much of the world.

The team, which includes several researchers from Texas A&M University, has had its work published in the current issue of Proceedings of the National Academy of Sciences (PNAS).

Yuan Wang, Yun Lin, Jiaxi Hu, Bowen Pan, Misti Levy and Renyi Zhang of Texas A&M's Department of Atmospheric Sciences, along with colleagues from Pacific Northwest National Laboratory, the University of California at San Diego and NASA's Jet Propulsion Laboratory, contributed to the work.

The team used detailed pollution emission data compiled by the Intergovernmental Panel on Climate Change and looked at two scenarios: one for a rate in 1850 -- the pre-Industrial era -- and from 2000, termed present-day.

By comparing the results from an advanced global climate model, the team found that anthropogenic aerosols conclusively impact cloud formations and mid-latitude cyclones associated with the Pacific storm track.

"There appears to be little doubt that these particles from Asia affect storms sweeping across the Pacific and subsequently the weather patterns in North America and the rest of the world," Zhang says of the findings.

"The climate model is quite clear on this point. The aerosols formed by human activities from fast-growing Asian economies do impact storm formation and global air circulation downstream. They tend to make storms deeper and stronger and more intense, and these storms also have more precipitation in them. We believe this is the first time that a study has provided such a global perspective."

In recent years, researchers have learned that atmospheric aerosols affect the climate, either directly by scattering or absorbing solar radiation, and indirectly by altering cloud formations. Increasing levels of such particles have raised concerns because of their potential impacts on regional and global atmospheric circulation.

In addition, Zhang says large amounts of aerosols and their long-term transport from Asia across the Pacific can clearly be seen by satellite images.

The Pacific storm track represents a critical driver in the general global circulation by transporting heat and moisture, the team notes. The transfer of heat and moisture appears to be increased over the storm track downstream, meaning that the Pacific storm track is intensified because of the Asian air pollution outflow.

"Our results support previous findings that show that particles in the air over Asia tend to affect global weather patterns," Zhang adds.

"It shows they can affect the Earth's weather significantly."

Yuan Wang, who conducted the research with Zhang while at Texas A&M, currently works at NASA's Jet Propulsion Laboratory as a Caltech Postdoctoral Scholar.

The study was funded by grants from NASA, the Department of Energy, Texas A&M's Supercomputing facilities and the Ministry of Science and Technology of China.


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The ten best weather places in the world

Do you dream of a place that is always sunny? Where the temperature is perfect? Where there is virtually no severe weather? Ed Darack has. His article, "The 10 Best Weather Places in the World," featured in the March/April issue of Weatherwise magazine attempts to name the top ten places in the world that continually experience the best weather.

Darack defines what "best" weather consists of. The basis of this list is founded in weather that has positive effects on human fundamental needs (physical, mental, and emotional). "We can determine meteorological "best" criteria for ideal human physical, mental, and emotional health that includes temperature, humidity, average number of sunny days, and other criteria, by studying the results of research conducted on environmental effects on humans." With this in mind Darack creates a mythical place of weather perfection, 'Anthro-Weathertopia'. Here the temperature never strays too far from 68?F, the humidity is always comfortably 50%, and the clouds are never a threat. Unfortunately this perfect place does not exist, but his article lists the top ten places that come close.

The Manjimup region of the extreme south west region of Western Australia ranks at number ten on the list. It is a piece of lush land off the southern Indian Ocean. In February, the average summer temperature clocks in at 81?F during the day and 56.1?F at night. In the winter, the coldest month, July, records an average temperature high of 58?F and low of 43.5?F. There is an average rainfall of 39 inches per year. The only drawback is that, although rarely, the Manjimup region does experience extended periods of cold and rain.

Number six on the list is one of the most comfortable weather cities on the planet, Lisbon, Portugal. Lisbon, located on the Atlantic coast of Portugal, experiences moderate temperature throughout the year. In August, the warmest month, the daily average temperature is 82.9?F with a mean nighttime low of 65.5?F. January, the coldest month, Lisbon experiences a daily high on 58.6?F and a nighttime low of 46.9?F. The yearly average rainfall is 30.5 inches.

Next we visit the northwestern coast of Morocco, which stands at number three. The cold currents of the Atlantic Ocean provide little season variability and extremely mild temperatures year round. The heart of this region is Casablanca which records an average daily high of 63?F and a mean evening low of 45?F. The average rainfall in December, the wettest month, only comes to 5.75 inches and less than .5 inches in July, the driest. In addition, the northwestern coast almost never experiences any type of severe weather.

Can't imagine anywhere else having such perfect weather? Find out which other places made the list by accessing "The 10 Best Weather Places in the World."

Story Source:

The above story is based on materials provided by Taylor & Francis. Note: Materials may be edited for content and length.


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Warming climate may spread drying to a third of earth: Heat, not just rainfall, plays into new projections

Increasing heat is expected to extend dry conditions to far more farmland and cities by the end of the century than changes in rainfall alone, says a new study. Much of the concern about future drought under global warming has focused on rainfall projections, but higher evaporation rates may also play an important role as warmer temperatures wring more moisture from the soil, even in some places where rainfall is forecasted to increase, say the researchers.

The study is one of the first to use the latest climate simulations to model the effects of both changing rainfall and evaporation rates on future drought. Published this month in the journal Climate Dynamics, the study estimates that 12 percent of land will be subject to drought by 2100 through rainfall changes alone; but the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered. An increase in evaporative drying means that even regions expected to get more rain, including important wheat, corn and rice belts in the western United States and southeastern China, will be at risk of drought. The study excludes Antarctica.

"We know from basic physics that warmer temperatures will help to dry things out," said the study's lead author, Benjamin Cook, a climate scientist with joint appointments at Columbia University's Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. "Even if precipitation changes in the future are uncertain, there are good reasons to be concerned about water resources."

In its latest climate report, the International Panel on Climate Change (IPCC) warns that soil moisture is expected to decline globally and that already dry regions will be at greater risk of agricultural drought. The IPCC also predicts a strong chance of soil moisture drying in the Mediterranean, southwestern United States and southern African regions, consistent with the Climate Dynamics study.

Using two drought metric formulations, the study authors analyze projections of both rainfall and evaporative demand from the collection of climate model simulations completed for the IPCC's 2013 climate report. Both metrics agree that increased evaporative drying will probably tip marginally wet regions at mid-latitudes like the U.S. Great Plains and a swath of southeastern China into aridity. If precipitation were the only consideration, these great agricultural centers would not be considered at risk of drought. The researchers also say that dry zones in Central America, the Amazon and southern Africa will grow larger. In Europe, the summer aridity of Greece, Turkey, Italy and Spain is expected to extend farther north into continental Europe.

"For agriculture, the moisture balance in the soil is what really matters," said study coauthor Jason Smerdon, a climate scientist at Lamont-Doherty. "If rain increases slightly but temperatures also increase, drought is a potential consequence."

Today, while bad weather periodically lowers crop yields in some places, other regions are typically able to compensate to avert food shortages. In the warmer weather of the future, however, crops in multiple regions could wither simultaneously, the authors suggest. "Food-price shocks could become far more common," said study coauthor Richard Seager, a climate scientist at Lamont-Doherty. Large cities, especially in arid regions, will need to carefully manage their water supplies, he added.

The study builds on an emerging body of research looking at how evaporative demand influences hydroclimate. "It confirms something we've suspected for a long time," said Toby Ault, a climate scientist at Cornell University, who was not involved in the study. "Temperature alone can make drought more widespread. Studies like this give us a few new powerful tools to plan for and adapt to climate change."

Rainfall changes do not tell the whole story, agrees University of New South Wales researcher Steven Sherwood, in a recent Perspectives piece in the leading journal Science. "Many regions will get more rain, but it appears that few will get enough to keep pace with the growing evaporative demand."


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Southeast England most at risk of rising deaths due to climate change

Warmer summers brought on by climate change will cause more deaths in London and southeast England than the rest of the country, scientists predict.

Researchers at Imperial College London looked at temperature records and mortality figures for 2001 to 2010 to find out which districts in England and Wales experience the biggest effects from warm temperatures.

In the most vulnerable districts, in London and the southeast, the odds of dying from cardiovascular or respiratory causes increased by over 10 per cent for every 1C rise in temperature. Districts in the far north were much more resilient, seeing no increase in deaths at equivalent temperatures.

Writing in Nature Climate Change, the researchers say local variations in climate change vulnerability should be taken into account when assessing the risks and choosing policy responses.

Dr James Bennett, the lead author of the study from the MRC-PHE Centre for Environment and Health at Imperial College London, said: “It’s well known that warm weather can increase the risk of cardiovascular and respiratory deaths, especially in elderly people. Climate change is expected to raise average temperatures and increase temperature variability, so we can expect it to have effects on mortality even in countries like the UK with a temperate climate.”

Across England and Wales as a whole, a summer that is 2C warmer than average would be expected to cause around 1,550 extra deaths, the study found. Just over half would be in people aged over 85, and 62 per cent would be in women. The extra deaths would be distributed unevenly, with 95 out of 376 districts accounting for half of all deaths.

The effects of warm temperature were similar in urban and rural districts. The most vulnerable districts included deprived districts in London such as Hackney and Tower Hamlets, with the odds of dying more than doubling on very hot days like those of August 2003.

“The reasons for the uneven distribution of deaths in warm weather need to be studied,” said Professor Majid Ezzati, from the School of Public Health at Imperial, who led the research. “It might be due to more vulnerable individuals being concentrated in some areas, or it might be related to differences at the community level, like quality of healthcare, that require government action.

“We might expect that people in areas that tend to be warmer would be more resilient, because they adapt by installing air conditioning for example. These results show that this isn’t the case in England and Wales.

“While climate change is a global phenomenon, resilience and vulnerability to its effects are highly local. Many things can be done at the local level to reduce the impact of warm spells, like alerting the public and planning for emergency services. Detailed information about which communities are most at risk from high temperatures can help to inform these strategies.”

The researchers received funding from the Medical Research Council, Public Health England, and the National Institute for Health Research (NIHR) Imperial Biomedical Research Centre.

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Arctic melt season lengthening, ocean rapidly warming

The length of the melt season for Arctic sea ice is growing by several days each decade, and an earlier start to the melt season is allowing the Arctic Ocean to absorb enough additional solar radiation in some places to melt as much as four feet of the Arctic ice cap's thickness, according to a new study by National Snow and Ice Data Center (NSIDC) and NASA researchers.

Arctic sea ice has been in sharp decline during the last four decades. The sea ice cover is shrinking and thinning, making scientists think an ice-free Arctic Ocean during the summer might be reached this century. The seven lowest September sea ice extents in the satellite record have all occurred in the past seven years.

"The Arctic is warming and this is causing the melt season to last longer," said Julienne Stroeve, a senior scientist at NSIDC, Boulder and lead author of the new study, which has been accepted for publication in Geophysical Research Letters. "The lengthening of the melt season is allowing for more of the sun's energy to get stored in the ocean and increase ice melt during the summer, overall weakening the sea ice cover."

To study the evolution of sea ice melt onset and freeze-up dates from 1979 to the present day, Stroeve's team used passive microwave data from NASA's Nimbus-7 Scanning Multichannel Microwave Radiometer, and the Special Sensor Microwave/Imager and the Special Sensor Microwave Imager and Sounder carried onboard Defense Meteorological Satellite Program spacecraft.

When ice and snow begin to melt, the presence of water causes spikes in the microwave radiation that the snow grains emit, which these sensors can detect. Once the melt season is in full force, the microwave emissivity of the ice and snow stabilizes, and it doesn't change again until the onset of the freezing season causes another set of spikes. Scientists can measure the changes in the ice's microwave emissivity using a formula developed by Thorsten Markus, co-author of the paper and chief of the Cryospheric Sciences Laboratory at NASA's Goddard Space Flight Center in Greenbelt, Md.

Results show that although the melt season is lengthening at both ends, with an earlier melt onset in the spring and a later freeze-up in the fall, the predominant phenomenon extending the melting is the later start of the freeze season. Some areas, such as the Beaufort and Chukchi Seas, are freezing up between six and 11 days later per decade. But while melt onset variations are smaller, the timing of the beginning of the melt season has a larger impact on the amount of solar radiation absorbed by the ocean, because its timing coincides with when the sun is higher and brighter in the Arctic sky.

Despite large regional variations in the beginning and end of the melt season, the Arctic melt season has lengthened on average by five days per decade from 1979 to 2013.

Still, weather makes the timing of the autumn freeze-up vary a lot from year to year.

"There is a trend for later freeze-up, but we can't tell whether a particular year is going to have an earlier or later freeze-up," Stroeve said. "There remains a lot of variability from year to year as to the exact timing of when the ice will reform, making it difficult for industry to plan when to stop operations in the Arctic."

To measure changes in the amount of solar energy absorbed by the ice and ocean, the researchers looked at the evolution of sea surface temperatures and studied monthly surface albedo data (the amount of solar energy reflected by the ice and the ocean) together with the incoming solar radiation for the months of May through October. The albedo and sea surface temperature data the researchers used comes from the National Oceanic and Atmospheric Administration's polar-orbiting satellites.

They found that the ice pack and ocean waters are absorbing more and more sunlight due both to an earlier opening of the waters and a darkening of the sea ice. The sea ice cover is becoming less reflective because it now mostly consists of thinner, younger ice, which is less reflective than the older ice that previously dominated the ice pack. Also, the young ice is flatter, allowing the dark melt ponds that form at the early stages of the melt season are able to spread more widely, further lowering its albedo.

The researchers calculated the increase in solar radiation absorbed by the ice and ocean for the period ranging from 2007 to 2011, which in some areas of the Arctic Ocean exceed 300 to 400 megajoules per square meter, or the amount of energy needed to thin the ice by an additional 3.1 to 4.2 feet (97 to 130 centimeters).

The increases in surface ocean temperatures, combined with a warming Arctic atmosphere due to climate change, explain the delayed freeze up in the fall.

"If air and ocean temperatures are similar, the ocean is not going to lose heat to the atmosphere as fast as it would when the differences are greater," said Linette Boisvert, co-author of the paper and a cryospheric scientist at Goddard. "In the last years, the upper ocean heat content is much higher than it used to be, so it's going to take a longer time to cool off and for freeze up to begin."


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Warm U.S. West, cold East: 4,000-year pattern; Global warming may bring more curvy jet streams during winter

These maps show winter temperature patterns (top) and winter precipitation patterns (bottom) associated with a curvy jet stream (not shown) that moves north from the Pacific to the Yukon and Alaska, then plunges down over the Canadian plains and into the eastern United States. A University of Utah-led study shows that starting 4,000 years ago, the jet stream tended to become curvier than it was between 8,000 and 4,000 years ago, and suggests global warming will enhance such curviness and thus frigid weather in the eastern states similar to this past winter's. The curvy jet stream brought abnormally warm temperatures (red and orange) to the West and Alaska and an abnormal deep freeze (blue) to the East this past winter, similar to what is shown in the top map, except the upper Midwest was colder than shown. The bottom map of a typical curvy jet stream precipitation pattern shows how that normally brings dry winters to reddish-orange areas and wet winters to blue regions. Precipitation patterns this winter matched the bottom map in many regions, except California was drier than expected and the upper Midwest was wetter than expected.Credit: Zhongfang Liu, Tianjin Normal University, China. Last winter's curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, and suggests it may worsen as Earth's climate warms.

"If this trend continues, it could contribute to more extreme winter weather events in North America, as experienced this year with warm conditions in California and Alaska and intrusion of cold Arctic air across the eastern USA," says geochemist Gabe Bowen, senior author of the study.

The study was published online April 16 by the journal Nature Communications.

"A sinuous or curvy winter jet stream means unusual warmth in the West, drought conditions in part of the West, and abnormally cold winters in the East and Southeast," adds Bowen, an associate professor of geology and geophysics at the University of Utah. "We saw a good example of extreme wintertime climate that largely fit that pattern this past winter," although in the typical pattern California often is wetter.

It is not new for scientists to forecast that the current warming of Earth's climate due to carbon dioxide, methane and other "greenhouse" gases already has led to increased weather extremes and will continue to do so.

The new study shows the jet stream pattern that brings North American wintertime weather extremes is millennia old -- "a longstanding and persistent pattern of climate variability," Bowen says. Yet it also suggests global warming may enhance the pattern so there will be more frequent or more severe winter weather extremes or both.

"This is one more reason why we may have more winter extremes in North America, as well as something of a model for what those extremes may look like," Bowen says. Human-caused climate change is reducing equator-to-pole temperature differences; the atmosphere is warming more at the poles than at the equator. Based on what happened in past millennia, that could make a curvy jet stream even more frequent and-or intense than it is now, he says.

Bowen and his co-authors analyzed previously published data on oxygen isotope ratios in lake sediment cores and cave deposits from sites in the eastern and western United States and Canada. Those isotopes were deposited in ancient rainfall and incorporated into calcium carbonate. They reveal jet stream directions during the past 8,000 years, a geological time known as middle and late stages of the Holocene Epoch.

Next, the researchers did computer modeling or simulations of jet stream patterns -- both curvy and more direct west to east -- to show how changes in those patterns can explain changes in the isotope ratios left by rainfall in the old lake and cave deposits.

They found that the jet stream pattern -- known technically as the Pacific North American teleconnection -- shifted to a generally more "positive phase" -- meaning a curvy jet stream -- over a 500-year period starting about 4,000 years ago. In addition to this millennial-scale change in jet stream patterns, they also noted a cycle in which increases in the sun's intensity every 200 years make the jet stream flatter.

Bowen conducted the study with Zhongfang Liu of Tianjin Normal University in China, Kei Yoshimura of the University of Tokyo, Nikolaus Buenning of the University of Southern California, Camille Risi of the French National Center for Scientific Research, Jeffrey Welker of the University of Alaska at Anchorage, and Fasong Yuan of Cleveland State University.

The study was funded by the National Science Foundation, National Natural Science Foundation of China, Japan Society for the Promotion of Science and a joint program by the society and Japan's Ministry of Education, Culture, Sports, Science and Technology: the Program for Risk Information on Climate Change.

Sinuous Jet Stream Brings Winter Weather Extremes

The Pacific North American teleconnection, or PNA, "is a pattern of climate variability" with positive and negative phases, Bowen says.

"In periods of positive PNA, the jet stream is very sinuous. As it comes in from Hawaii and the Pacific, it tends to rocket up past British Columbia to the Yukon and Alaska, and then it plunges down over the Canadian plains and into the eastern United States. The main effect in terms of weather is that we tend to have cold winter weather throughout most of the eastern U.S. You have a freight car of arctic air that pushes down there."

Bowen says that when the jet stream is curvy, "the West tends to have mild, relatively warm winters, and Pacific storms tend to occur farther north. So in Northern California, the Pacific Northwest and parts of western interior, it tends to be relatively dry, but tends to be quite wet and unusually warm in northwest Canada and Alaska."

This past winter, there were times of a strongly curving jet stream, and times when the Pacific North American teleconnection was in its negative phase, which means "the jet stream is flat, mostly west-to-east oriented," and sometimes split, Bowen says. In years when the jet stream pattern is more flat than curvy, "we tend to have strong storms in Northern California and Oregon. That moisture makes it into the western interior. The eastern U.S. is not affected by arctic air, so it tends to have milder winter temperatures."

The jet stream pattern -- whether curvy or flat -- has its greatest effects in winter and less impact on summer weather, Bowen says. The curvy pattern is enhanced by another climate phenomenon, the El Nino-Southern Oscillation, which sends a pool of warm water eastward to the eastern Pacific and affects climate worldwide.

Traces of Ancient Rains Reveal Which Way the Wind Blew

Over the millennia, oxygen in ancient rain water was incorporated into calcium carbonate deposited in cave and lake sediments. The ratio of rare, heavy oxygen-18 to the common isotope oxygen-16 in the calcium carbonate tells geochemists whether clouds that carried the rain were moving generally north or south during a given time.

Previous research determined the dates and oxygen isotope ratios for sediments in the new study, allowing Bowen and colleagues to use the ratios to tell if the jet stream was curvy or flat at various times during the past 8,000 years.

Bowen says air flowing over the Pacific picks up water from the ocean. As a curvy jet stream carries clouds north toward Alaska, the air cools and some of the water falls out as rain, with greater proportions of heavier oxygen-18 falling, thus raising the oxygen-18-to-16 ratio in rain and certain sediments in western North America. Then the jet stream curves south over the middle of the continent, and the water vapor, already depleted in oxygen-18, falls in the East as rain with lower oxygen-18-to-16 ratios.

When the jet stream is flat and moving east-to-west, oxygen-18 in rain is still elevated in the West and depleted in the East, but the difference is much less than when the jet stream is curvy.

By examining oxygen isotope ratios in lake and cave sediments in the West and East, Bowen and colleagues showed that a flatter jet stream pattern prevailed from about 8,000 to 4,000 years ago in North America, but then, over only 500 years, the pattern shifted so that curvy jet streams became more frequent or severe or both. The method can't distinguish frequency from severity.

The new study is based mainly on isotope ratios at Buckeye Creek Cave, W. Va.; Lake Grinell, N.J.; Oregon Caves National Monument; and Lake Jellybean, Yukon.

Additional data supporting increasing curviness of the jet stream over recent millennia came from seven other sites: Crawford Lake, Ontario; Castor Lake, Wash.; Little Salt Spring, Fla.; Estancia Lake, N.M.; Crevice Lake, Mont.; and Dog and Felker lakes, British Columbia. Some sites provided oxygen isotope data; others showed changes in weather patterns based on tree ring growth or spring deposits.

Simulating the Jet Stream

As a test of what the cave and lake sediments revealed, Bowen's team did computer simulations of climate using software that takes isotopes into account.

Simulations of climate and oxygen isotope changes in the Middle Holocene and today resemble, respectively, today's flat and curvy jet stream patterns, supporting the switch toward increasing jet stream sinuosity 4,000 years ago.

Why did the trend start then?

"It was a when seasonality becomes weaker," Bowen says. The Northern Hemisphere was closer to the sun during the summer 8,000 years ago than it was 4,000 years ago or is now due to a 20,000-year cycle in Earth's orbit. He envisions a tipping point 4,000 years ago when weakening summer sunlight reduced the equator-to-pole temperature difference and, along with an intensifying El Nino climate pattern, pushed the jet stream toward greater curviness.


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Corals don’t lie: Centuries of rising sea levels and temperature data revealed

AIMS scientists together with a team from The University of Western Australia, CSIRO and the University of San Diego have analysed coral cores from the eastern Indian Ocean to understand how the unique coral reefs of Western Australia are affected by changing ocean currents and water temperatures. The research was published today in the international journal Nature Communications. The findings give new insights into how La Ni?a, a climate swing in the tropical Pacific, affects the Leeuwin current and how our oceans are changing.

“Due to the lack of long-term observations of marine climate we used long coral cores, with annual growth bands similar to tree rings, to provide a record of the past. We obtained records of past sea temperatures by measuring the chemical composition of the coral skeleton from year to year. This showed how changing winds and ocean currents in the eastern Indian Ocean are driven by climate variability in the western tropical Pacific Ocean,” said Dr Jens Zinke (Assistant Professor at the UWA Oceans Institute and AIMS-UWA scientist). The long coral records allowed the scientists to look at these patterns of climate variability back to 1795 AD.

La Ni?a events in the tropical Pacific result in a strengthened Leeuwin Current and unusually warm water temperatures and higher sea levels off southwest Western Australia.

“A prominent example is the 2011 heat wave along WA’s reefs which led to coral bleaching and fish kills,” said Dr Ming Feng CSIRO Principal Research Scientist.?

The international team found that in addition to warming sea surface temperatures, sea-level variability and Leeuwin Current strength have increased since 1980. The coral cores also reveal that the strong winds and extreme weather of 2011 off Western Australia are highly unusual in the context of the past 215 years. The authors conclude that this is clear evidence that global warming and sea-level rise is increasing the severity of these extreme events which impact the highly diverse coral reefs of Western Australia, including the Ningaloo Reef World Heritage site.

“Given ongoing global climate change, It is likely that future La Ni?a events will result in more extreme warming and high sea-level events with potentially significant consequences for the maintenance of Western Australia's unique marine ecosystems,” said Dr Janice Lough, AIMS Senior Principal Research Scientist.

The researchers used core samples of massive Porites colonies from the Houtman-Abrolhos Islands, the most southerly reefs in the Indian Ocean which are directly in the path of the Leeuwin Current. Using the chemical composition of the annual coral growth bands they were able to reconstruct sea surface temperature and Leeuwin Current for 215 years, from 1795 to 2010.

Journal Reference:

J. Zinke, A. Rountrey, M. Feng, S.-P. Xie, D. Dissard, K. Rankenburg, J.M. Lough, M.T. McCulloch. Corals record long-term Leeuwin current variability including Ningaloo Ni?o/Ni?a since 1795. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4607

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New NASA Van Allen Probes observations helping to improve space weather models

Using data from NASA's Van Allen Probes, researchers have tested and improved a model to help forecast what's happening in the radiation environment of near-Earth space -- a place seething with fast-moving particles and a space weather system that varies in response to incoming energy and particles from the sun.

NASA's Van Allen Probes orbit through two giant radiation belts that surround Earth. Their observations help improve computer simulations of events in the belts that can affect technology in space.

When events in the two giant doughnuts of radiation around Earth -- called the Van Allen radiation belts -- cause the belts to swell and electrons to accelerate to 99 percent the speed of light, nearby satellites can feel the effects. Scientists ultimately want to be able to predict these changes, which requires understanding of what causes them.

Now, two sets of related research published in the Geophysical Research Letters improve on these goals. By combining new data from the Van Allen Probes with a high-powered computer model, the new research provides a robust way to simulate events in the Van Allen belts.

"The Van Allen Probes are gathering great measurements, but they can't tell you what is happening everywhere at the same time," said Geoff Reeves, a space scientist at Los Alamos National Laboratory, or LANL, in Los Alamos, N.M., a co-author on both of the recent papers. "We need models to provide a context, to describe the whole system, based on the Van Allen Probe observations."

Prior to the launch of the Van Allen Probes in August 2012, there were no operating spacecraft designed to collect real-time information in the radiation belts. Understanding of what might be happening in any locale was forced to rely mainly on interpreting historical data, particularly those from the early 1990s gathered by the Combined Release and Radiation Effects Satellite, or CRRES.

Imagine if meteorologists wanted to predict the temperature on March 5, 2014, in Washington, D.C. but the only information available was from a handful of measurements made in March over the last seven years up and down the East Coast. That's not exactly enough information to decide whether or not you need to wear your hat and gloves on any given day in the nation's capital.

Thankfully, we have much more historical information, models that help us predict the weather and, of course, innumerable thermometers in any given city to measure temperature in real time. The Van Allen Probes are one step toward gathering more information about space weather in the radiation belts, but they do not have the ability to observe events everywhere at once. So scientists use the data they now have available to build computer simulations that fill in the gaps.

The recent work centers around using Van Allen Probes data to improve a three-dimensional model created by scientists at LANL, called DREAM3D, which stands for Dynamic Radiation Environment Assimilation Model in 3 Dimensions. Until now the model relied heavily on the averaged data from the CRRES mission.

One of the recent papers, published Feb. 7, 2014, provides a technique for gathering real-time global measurements of chorus waves, which are crucial in providing energy to electrons in the radiation belts. The team compared Van Allen Probes data of chorus wave behavior in the belts to data from the National Oceanic and Atmospheric Administration's Polar-orbiting Operational Environmental Satellites, or POES, flying below the belts at low altitude. Using this data and some other historical examples, they correlated the low-energy electrons falling out of the belts to what was happening directly in the belts.

"Once we established the relationship between the chorus waves and the precipitating electrons, we can use the POES satellite constellation -- which has quite a few satellites orbiting Earth and get really good coverage of the electrons coming out of the belts," said Los Alamos scientist Yue Chen, first author of the chorus waves paper. "Combining that data with a few wave measurements from a single satellite, we can remotely sense what's happening with the chorus waves throughout the whole belt."

The relationship between the precipitating electrons and the chorus waves does not have a one-to-one precision, but it does provide a much narrower range of possibilities for what's happening in the belts. In the metaphor of trying to find the temperature for Washington on March 5, it's as if you still didn't have a thermometer in the city itself, but can make a better estimate of the temperature because you have measurements of the dewpoint and humidity in a nearby suburb.

The second paper describes a process of augmenting the DREAM3D model with data from the chorus wave technique, from the Van Allen Probes, and from NASA's Advanced Composition Explorer, or ACE, which measures particles from the solar wind. Los Alamos researchers compared simulations from their model -- which now was able to incorporate real-time information for the first time -- to a solar storm from October 2012.

"This was a remarkable and dynamic storm," said lead author Weichao Tu at Los Alamos. "Activity peaked twice over the course of the storm. The first time the fast electrons were completely wiped out -- it was a fast drop out. The second time many electrons were accelerated substantially. There were a thousand times more high-energy electrons within a few hours."

Tu and her team ran the DREAM3D model using the chorus wave information and by including observations from the Van Allen Probes and ACE. The scientists found that their computer simulation made by their model recreated an event very similar to the October 2012 storm.

What's more the model helped explain the different effects of the different peaks. During the first peak, there simply were fewer electrons around to be accelerated.

However, during the early parts of the storm the solar wind funneled electrons into the belts. So, during the second peak, there were more electrons to accelerate.

"That gives us some confidence in our model," said Reeves. "And, more importantly, it gives us confidence that we are starting to understand what's going on in the radiation belts."


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Fire and drought may push Amazonian forests beyond tipping point

Future simulations of climate in the Amazon suggest a longer dry season leading to more drought and fires. Woods Hole Research Center scientists Michael Coe, Paulo Brando, Marcia Macedo and colleagues have published a new study on the impacts of fire and drought on Amazon tree mortality.

Their paper, published in PNAS, found that prolonged droughts caused more intense and widespread wildfires, which consumed more forests in Amazonia than previously understood.

Over an eight-year period, the team repeatedly burned 50-hectare forest plots in southeast Amazonia to learn how fire frequency and weather conditions affected tree deaths. The surprise, according to Dr. Coe, was "the importance of drought. The forest didn't burn much in average years, but burned extensively in drought years." Climate change is expected to cause shorter more intense rainy seasons and longer dry seasons, with more frequent droughts like those observed in this study. According to Dr. Coe, "We tend to think only about average conditions but it is the non-average conditions we have to worry about."

NASA satellite data provide a regional context for results from the experimental burns. In 2007, fires in southeast Amazonia burned 10 times more forest than in an average climate year, "an area equivalent to a million soccer fields" according to co-author Douglas Morton of NASA.

Large portions of Amazonian forests are already experiencing droughts and are increasingly susceptible to fire. "Agricultural development has created smaller forest fragments, which exposes forest edges to the hotter dryer conditions in the surrounding landscape and makes them vulnerable to escaped fires," said Dr. Macedo. "These fragmented forests are more likely to be invaded by flammable grasses, which further increase the likelihood and intensity of future fires."

According to lead-author Dr. Paulo Brando, "This study shows that fires are already degrading large areas of forests in Southern Amazonia and highlights the need to include interactions between extreme weather events and fire when attempting to predict the future of Amazonian forests under a changing climate."

"None of the models used to evaluate future Amazon forest health include fire, so most predictions grossly underestimate the amount of tree death and overestimate overall forest health," said Dr. Coe. The results of this project show that extreme droughts may interact with fires to push Amazonian forests beyond a tipping point that may abruptly increase tree mortality and change vegetation over large areas.


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How ancient Greek plays allow us to reconstruct Europe's climate

The open air plays of the ancient Greeks may offer us a valuable insight into the Mediterranean climate of the time, reports new research. Using historical observations from artwork and plays, scientists identified 'halcyon days', of theater friendly weather in mid-winter.The open air plays of the ancient Greeks may offer us a valuable insight into the Mediterranean climate of the time, reports new research in Weather. Using historical observations from artwork and plays, scientists identified 'halcyon days', of theatre friendly weather in mid-winter.

"We explored the weather conditions which enabled the Athenians of the classical era to watch theatre performances in open theatres during the midwinter weather conditions," said Christina Chronopoulou, from the National and Kapodestrian University of Athens. "We aimed to do so by gathering and interpreting information from the classical plays of Greek drama from 5th and 4th centuries B.C."

Ancient Athenians would enjoy the open theatre of Dionysus in the southern foothills of the Acropolis and when possible they would have watched drama in the middle of winter between 15 January and 15 February.

From Second World War bombing raids, to medieval Arabic writings historians and climatologists continue to turn to surprising sources to help piece together the climate of our ancestors. In this case the team turned to the writings of 43 plays by Aeschylus, Sophocles, Euripides and Aristophanes and several were found to contain references about the weather. Greece enjoys long, hot, dry summers, yet in contrast the rare theatre friendly 'halcyon days' of clear, sunny weather during winter appeared to be especially noteworthy.

"The comedies of Aristophanes, often invoke the presence of the halcyon days," concluded said Dr. Chronopoulou. "Combining the fact that dramatic contests were held in mid-winter without any indication of postponement, and references from the dramas about the clear weather and mild winters, we can assume that those particular days of almost every January were summery in the fifth and maybe in the fourth centuries BC."

Story Source:

The above story is based on materials provided by Wiley. Note: Materials may be edited for content and length.

Journal Reference:

Christina Chronopoulou, A. Mavrakis. Ancient Greek drama as an eyewitness of a specific meteorological phenomenon: indication of stability of the Halcyon days. Weather, 2014; 69 (3): 66 DOI: 10.1002/wea.2164

Cite This Page:

Wiley. "How ancient Greek plays allow us to reconstruct Europe's climate." ScienceDaily. ScienceDaily, 3 March 2014. .Wiley. (2014, March 3). How ancient Greek plays allow us to reconstruct Europe's climate. ScienceDaily. Retrieved April 19, 2014 from www.sciencedaily.com/releases/2014/03/140303083925.htmWiley. "How ancient Greek plays allow us to reconstruct Europe's climate." ScienceDaily. www.sciencedaily.com/releases/2014/03/140303083925.htm (accessed April 19, 2014).

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Moderate resource use, reduced economic inequality keys to sustainability

A new analytical tool adds human factors to a widely-used biological model of how animal populations interact, suggesting that human societies can reach a steady state that is sustainable when they do not over-deplete natural resources and avoid extreme economic inequality.

The paper, titled "Human and nature dynamics (HANDY): modeling inequality and use of resources in the collapse or sustainability of societies," was published in the May 2014 issue of the journal Ecological Economics. Its authors are Safa Motesharrei, a Ph.D. candidate in applied mathematics at UMD; Jorge Rivas of the Institute of Global Environment and Society; and Eugenia Kalnay, Distinguished University Professor in the Department of Atmospheric and Oceanic Science and the Institute for Physical Science and Technology at UMD.

Kalnay, an internationally recognized weather and climate scientist, worked in leadership positions at NASA and the National Oceanic and Atmospheric Administration (NOAA) for two decades and currently serves on the UN Secretary General's Scientific Advisory Board on Sustainability. She is renowned, in part, for leading the National Weather Service's advances in weather modeling in the 1990s. Her recent work has focused on advancing understanding of climate change and environmental sustainability through improved modeling of the coupled interaction of earth and human systems.

HANDY's starting point is a well-known model in biology and population ecology, commonly known as the "predator-prey model," which is used to understand the dynamics of animal populations. The researchers applied that model's concepts to human societies, and incorporated two new variables that are not included in existing models: accumulation of wealth and economic stratification between rich and poor. These changes are necessary, the researchers say, to reflect that some segments of human society use more resources than others, and accumulated wealth can delay, but not prevent, the decline that occurs when a population exceeds the carrying capacity of its environment. With HANDY, the researchers say, they have developed a practical method for using the relevant natural, social and economic conditions to estimate a human society's carrying capacity.

While some HANDY scenarios are suggestive of past civilizations that flourished and then collapsed, such as the ancient Romans and Mayans, the model was not created to explain specific societies' collapse, team members said.

The model is "not intended to describe actual individual cases" -- such as modern Western society -- "but rather to provide a general framework that allows carrying out 'thought experiments' for the phenomenon of collapse and to test changes that would avoid it," the authors wrote in the research paper.

"The model does not say that society's collapse is imminent," said Rivas, "nor does it predict a collapse for 'Western' or 'industrial' civilization despite some pre-publication reports to the contrary."

"HANDY is not a forecasting model," Motesharrei said. "It cannot be used to predict the future of any society. It can, however, help us understand the possible underlying mechanisms in the evolution of a society."

This minimal modeling approach focuses on the long-term behavioral properties of dynamical systems, the authors explain. The goal is not to find precise solutions for the variables of the real system, but instead to address questions such as:

In the long run, will the system settle at a steady state?What are these possible steady states?What factors determine which long-term behavior is followed?

"The results of our model are optimistic, because they show that by making certain decisions, we can bring about a sustainable future," said Rivas. Unlike physical and natural systems, such as the solar system or an ecosystem, "we can, as humans, make critical choices that can change the long-term path that our social system will take, and we can optimize such choices using scientific models. This is a key takeaway lesson of this paper."

However, the model shows that "if we continue to over-deplete nature, and if inequality continues such that the rich consume far more than the poor, the system eventually collapses," Kalnay said.


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Crowdsourced rain samples map Hurricane Sandy's evolution

A unique method to collect rain water samples during Hurricane Sandy has revealed the storm's chemical "signature" with a new level of detail. The technique may also lead to weather model advances that will ultimately improve storm prediction, say researchers at the University of Utah whose study was published online today in PLOS ONE.

Hurricane Sandy, also known as Superstorm Sandy, was the deadliest and most destructive hurricane of the 2012 Atlantic hurricane season, according to government sources. Damage estimates exceed $65 billion and nearly 300 people perished along the path of the storm in seven countries.

"As the climate changes in the 21st century, there is a possibility that more hurricanes will stray farther north along the eastern seaboard, like Sandy did," says Stephen Good, a postdoctoral fellow in geology and geophysics at the University of Utah, and lead author on the study. "It therefore becomes increasingly important to better understand the processes at work in these large storm systems."

To that end, researchers at the U took to the Internet to invite volunteers to collect water samples as the storm passed.

"During Sandy, we used crowdsourcing to obtain an unprecedented collection of hurricane rain waters," says Gabriel Bowen, associate professor of geology and geophysics, who launched the sampling effort after realizing the storm was on track to impact a large part of the eastern United States. "By taking advantage of data and samples gathered from residents on the ground, we were able to pinpoint where and when key features of the storm system developed and how they evolved, allowing us to develop a more complete picture of the storm."

Tropical cyclones, also referred to as hurricanes when they occur over the North Atlantic Ocean, are rapidly rotating storm systems that cause strong winds and heavy rain. They form over large bodies of relatively warm water, deriving their energy from evaporation and eventual condensation of water from the ocean's surface.

"Sandy left a distinctive isotopic signature in rain collected from the mid-Atlantic up into in New England that shows how a dry cold front originating out of the Midwest joined with Sandy -- which developed from a tropical wave over warm water in the Caribbean -- and likely prolonged and expanded the storm," says Bowen.

The sampling technique provides a new way of studying how these "extra-tropical" hurricanes interact with the weather systems of the northern latitudes, and thereby aids in hurricane forecasting and analysis.

How to Catch the Rain

The team used a variety of electronic means -- including science community email lists, Twitter, Facebook, blogs and crowdsourcing sites -- to alert the public to the study and to solicit samples.

For consistency, samples were collected on private property, from well-anchored containers in open, outdoor locations every 12 hours (8 a.m. and 8 p.m. Eastern time).

A total of 685 samples were collected from more than 125 volunteers at sites from North Carolina to Indiana to New Brunswick, Canada. The majority of the samples were obtained in regions of the U.S. mid-Atlantic -- where the storm's impact was greatest -- but having samples from the further reaches of the storm was key in allowing the researchers to investigate processes occurring at Sandy's margins.

The samples were shipped to the Utah lab in November 2012 and analyzed for their composition of hydrogen and oxygen isotopes, which provide a fingerprint of water sources, transport and rainout in the storm.

Inside the storm

Isotopes are subtly different forms of chemical elements that vary in their weight and, as a result, their physical behavior. For example, heavier isotopes evaporate from liquids less readily and condense out of vapor more readily. As water changes state from liquid to vapor and vice versa, the variations in oxygen and hydrogen isotope ratios give researchers a sensitive tool to calculate the hydrologic budget -- that is, the inflow, outflow and storage of water -- of large cyclones.

For the analysis of the rain isotope data Bowen and Good teamed up with graduate student Derek Mallia and associate professor John Lin in the U's department of atmospheric sciences. Mallia and Lin made use of a computer model of the atmosphere which was able to "run the tape backwards" and track the source of the rainwater backwards to the locations that contributed moisture to the storm.

In this study, exceptionally low levels of the heavy isotope oxygen-18 were found in samples from the southwest area of the storm, tracking extreme losses of water as precipitation neared the storm's center. Using their dense network of samples, the researchers were able to show this signature, which has also been used to reconstruct the occurrence of prehistoric hurricanes, was limited to a narrow region of the storm where the most intense precipitation was found.

As Sandy traveled north and its intensity decreased, the oxygen-18 levels moderated. However, levels of another isotope -- deuterium -- increased in parts of the storm when Sandy collided with the dry air from a continental cold front. The researchers argue that this signal shows that the storm picked up more moisture, and energy, from the frontal system and from evaporation off of the Atlantic, which led to intense rainfall over New England.

"The isotope data give fundamentally different information than can be obtained from satellite imagery or other conventional means of tracking storms," says Good. "Satellite imagery gives you information about the location of clouds and rain, but it cannot tell you where this water, and the energy that it contributes to the storm, came from."

Researchers anticipate that as these types of interactions are better documented and further studied, they may lead to advances in weather models that will ultimately improve storm prediction.


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Mongol Empire rode wave of mild climate, but warming now may be tipping region into unparalleled drought

Researchers studying the rings of ancient trees in mountainous central Mongolia think they may have gotten at the mystery of how small bands of nomadic Mongol horsemen united to conquer much of the world within a span of decades, 800 years ago. The rise of the great leader Genghis Khan and the start of the largest contiguous empire in human history was propelled by a temporary run of nice weather.

The rings show that exactly when the empire rose, the normally cold, arid steppes of central Asia saw their mildest, wettest weather in more than 1,000 years. Grass production must have boomed, as did vast numbers of war horses and other livestock that gave the Mongols their power. But the tree rings, spanning 1,112 years from 900 to 2011, also exhibit an ominous modern trend. Since the mid-20th century, the region has warmed rapidly, and the rings show that recent drought years were the most extreme in the record -- possibly a side effect of global warming. In a region already pressed for water, the droughts have already helped spark a new migration in a vast region where people until now have lived the same way for centuries, moving herds from place to place and living in tents. Now, those herders are being driven rapidly into cities, and there could be greater future upheavals. The study appears in this week's early online edition of the Proceedings of the National Academy of Sciences.

"Before fossil fuels, grass and ingenuity were the fuels for the Mongols and the cultures around them," said lead author Neil Pederson, a tree-ring scientist at Columbia University's Lamont-Doherty Earth Observatory. "Energy flows from the bottom of an ecosystem, up the ladder to human society. Even today, many people in Mongolia live just like their ancestors did. But in the future, they may face serious conditions."

In the late 1100s, the Mongol tribes were racked by disarray and internal warfare, but this ended with the sudden ascendance of Genghis (also known as Chinggis) Khan in the early 1200s. In just a matter of years, he united the tribes into an efficient horse-borne military state that rapidly invaded its neighbors and expanded outward in all directions. Genghis Khan died in 1227, but his sons and grandsons continued conquering and soon ruled most of what became modern Korea, China, Russia, eastern Europe, southeast Asia, Persia, India and the Mideast. The empire eventually fragmented, but the Mongols' vast geographic reach and their ideas -- an international postal system, organized agriculture research and meritocracy-based civil service among other things--shaped national borders, languages, cultures and human gene pools in ways that resound today. Genghis Khan's last ruling descendants ran parts of central Asia into the 1920s.

Some researchers have postulated that the Mongols expanded because they were fleeing harsh weather at home--but Pederson and colleagues found the opposite. In 2010, Pederson and coauthor Amy Hessl, a tree-ring scientist at West Virginia University, were studying wildfires in Mongolia when they came across a stand of gnarled, stunted Siberian pines growing out of cracks in an old solid-rock lava flow in the Khangai Mountains. They knew that on such dry, nearly soil-less surfaces, trees grow very slowly, are exquisitely sensitive to yearly weather shifts, and may live to fantastic ages.

In a series of expeditions, Pederson, Hessl and colleagues sampled the pines' rings, sawing cross-sections from dead specimens, and removing harmless straw-like cores from living ones. They found that some trees had lived for more than 1,100 years, and likely could survive another millennium; even dead trunks stayed largely intact for another 1,000 years before rotting. One piece of wood they found had rings going back to about 650 B.C. These yearly rings change with temperature and rainfall, so they could read past weather by calibrating ring widths of living trees with instrumental data from 1959-2009, then comparing these with the innards of much older trees. The trees had a clear and startling story to tell. The turbulent years preceding Genghis Khan's rule were stoked by intense drought from 1180 to 1190. Then, from 1211 to 1225 -- exactly coinciding with the empire's meteoric rise--Mongolia saw sustained rainfall and mild warmth never seen before or since.

"The transition from extreme drought to extreme moisture right then strongly suggests that climate played a role in human events," said Hessl. "It wasn't the only thing, but it must have created the ideal conditions for a charismatic leader to emerge out of the chaos, develop an army and concentrate power. Where it's arid, unusual moisture creates unusual plant productivity, and that translates into horsepower. Genghis was literally able to ride that wave." (Each Mongol warrior had five or more horses, and ever-moving herds of livestock provided nearly all food and other resources. The rest probably depended on the Mongols' brilliant cavalry skills, smart political maneuvering and savvy adaptions of urbanized peoples' technologies.)

The tree rings show that after the empire's initial expansion, Mongolia's weather turned back to its more normal dryness and cold, though with many ups and downs over the hundreds of years since. The 20th and early 21st centuries are the exception. In the last 40 years, temperatures in parts of the country have gone up by as much 4.5 degrees F -- well over the global mean rise of 1 degree. And, since the 1990s, the country has suffered a series of devastating summer droughts, often followed by a dzud -- an unusually long, cold winter. The tree rings show that the most recent drought, from 2002-2009, compares in length and paucity of rainfall only to those of the pre-empire 1120s and 1180s. Perhaps more important: the drought of the 2000s was the hottest in the entire record. The heat evaporated water stored in soil, lakes and vegetation, and, in combination with repeated dzuds, devastated livestock. The last dzud alone, in 2009-10, killed at least 8 million animals and destroyed the livelihoods of countless herders. Now, displaced Mongol herders have formed a new invasion force -- this time all headed to the capital city of Ulaanbaatar, which has swollen to hold nearly half the country's population of 3 million.

Climate models predict that as the world warms, heat in inner Asia will continue to rise substantially faster than the global mean. Pederson says this means that droughts and other extreme weather will probably worsen and become more frequent. This could further reduce livestock and hurt the few crops the region grows (only 1 percent of Mongolia is arable land). New mining ventures and other industrial activities may employ some of the many people fleeing the countryside -- but these also consume water, and it is not clear where that will come from.

"This last big drought is an example of what may happen in the future, not just in Mongolia but in a lot of inner Asia," said Pederson. "The heat is a double whammy -- even if rainfall doesn't change, the landscape is going to get drier."

Previous studies by others have advanced the idea that climate swings can change history. These include events such as the disappearance of the Maya, the expansion and fall of Roman imperial power, and, in a separate Lamont-led study, the 13th-century collapse of southeast Asia's Angkor civilization. Most focus on droughts, floods or other disasters that arguably have cut off empires; the new study is one of the few to explore the more complex question how climate might have invigorated one.

The researchers "make a compelling argument that climate played a role in facilitating the Mongol migration," said David Stahle, a paleoclimatologist at the University of Arkansas who has studied the mysterious disappearance of the English Roanoke colony off North Carolina, coinciding with what tree rings show was a disastrous drought. "But," said Stahle, "we live in a sea of coincidence -- something like that is hard to prove. There could be a lot of other factors. They've provided an incredibly important climate record, and put the idea out there, so it will stimulate a lot of historical and archeological research."

The tree-ring study is the first in a related series by a larger interdisciplinary team working with Pederson and Hessl. Hanqin Tian, an ecologist at Auburn University in Alabama who studies modern grasslands, is working on models to correlate ancient grass production with the tree-ring records of weather. In coming months, team member Avery Cook Shinneman, a biologist at the University of Washington, plans to analyze sediments taken from the bottoms of Mongolian lakes. These can be read somewhat like tree rings to estimate the abundance of livestock over time, via layers of fungal spores that live in the dung of animals; this would confirm whether animal populations did indeed boom. The conquering Mongols left very few written records of their own, but Nicola Di Cosmo, a historian at the Institute for Advanced Study in New Jersey and coauthor of the current paper, will study accounts of the time left in China, Persia and Europe that might provide further clues.


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

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

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

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

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

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

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

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

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

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

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

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

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

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

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


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Model now capable of street-level storm-tide predictions

The water that surged into the intersection of New York City's Canal and Hudson streets during Hurricane Sandy -- to choose just one flood-ravaged locale -- was ultimately driven ashore by forces swirling hundreds of miles out in the Atlantic.

That simple fact shows not only the scale and power of a tropical cyclone, but the difficulty of modeling and forecasting its potential for coastal flooding on the fine scale needed to most effectively prepare a response.

Now, a study led by Professor Harry Wang of William & Mary's Virginia Institute of Marine Science demonstrates the ability to predict a hurricane's storm tide at the level of individual neighborhoods and streets -- a much finer scale than current operational methods.

The study, published in today's issue of the Journal of Marine Science and Engineering, shows that with the right input, the team's high-resolution computer model was able to simulate water levels to within 6-8 inches of those observed in New York City and surrounding areas during Hurricane Sandy's approach and landfall in late October 2012. This includes sections of Manhattan where buildings and other infrastructure divert and channel floodwaters in exceptionally complex ways.

"Storm-surge modeling is a tough problem," says Wang. "People are interested in the possibility of flooding on a very fine scale, on the order of their house, office, or street." But for a forecast model to work, he says, "We have to resolve the boundary conditions -- -- data on tides and winds -- very far away, out into the open ocean. And we have to have that information far enough beforehand to provide time for people and agencies to respond."

Wang and his modeling team -- fellow VIMS researchers Derek Loftis, Zhuo Liu, David Forrest, and Joseph Zhang -- conducted their study by "hindcasting" Hurricane Sandy's landfall along the U.S. Atlantic coast. In this technique, scientists initiate a computer model with data collected before a past event, and then test the model's accuracy by comparing its output with observations recorded as the event unfolded.

For their test case, Wang and colleagues first used a large-scale model called SELFE to hindcast Sandy-driven changes in water level along the entire East Coast, from Florida to Nova Scotia. They initialized SELFE by entering data on normal tidal conditions along the model's open-ocean boundary, which is drawn almost 1,500 miles offshore. They allowed the model to "spin-up" for 10 days ahead of Sandy's approach, then another 5 days forward in time once the storm had entered the model grid, adding data on wind speed, wind direction, and air pressure in 6-minute time steps. They derived these data from NOAA's large-scale NAM (North American Mesoscale) model and a separate fine-scale atmospheric model called RAMS. RAMS -- short for Regional Atmospheric Modeling System -- was developed by the Poquoson office of Weatherflow Inc., a private-sector provider of weather data.

Wang stresses the importance of a good atmospheric model. "You cannot accurately forecast storm surge without accurate wind forcing," he says. "We are happy to be able to use RAMS, and it seems to be working quite well."

Wang says the 6-minute time-step is also key to their model's success. Some storm-surge models resolve time in increments as short as 3 seconds, but doing so requires computing power that exceeds even that available in W&M's SciClone Computing Complex. "A 6-minute time-step allows us to run a 5-day simulation in 40 minutes," says Wang. "That's the kind of rapid run-time you need for forecasting."

The second step for Wang's team was to use output from the "large-domain" SELFE model -- which they verified by comparing with actual readings from NOAA tide gauges between Long Island and Chesapeake Bay -- to drive a model of much higher resolution focused on New York City and its harbor. This "sub-grid inundation model" incorporates high-resolution elevation data collected with LIDAR, a mapping technique that uses airborne lasers to map the ground surface to within a few inches of its actual height.

"High-resolution hydrodynamic models are essential to account for the effects of local features," says Wang. "When water floods into a city, it encounters everything from waterfront berms to streets, railroads, parks, highways, subway stations, bridges, and building of all different kinds." These structures and surfaces not only divert and channel the water, but provide different levels of friction that must be modeled as well.

VIMS Dean & Director John Wells calls the results of the team's sub-grid inundation model a "breakthrough" in storm-tide forecasting -- with model output within 6 to 8 inches of the water levels recorded in New York City during Sandy by the U.S. Geological Survey. The USGS measured Sandy's flooding by deploying temporary tide gauges at selected sites during the storm, and by sending out teams of observers afterward to record mud and wrack lines on buildings, roadways, and other infrastructure.

Says Wang, "Our results compared very favorably with the USGS' Hurricane Sandy Mapper database in terms of timing, area of inundation, and depth of floodwaters. The maximum extent of horizontal inundation was within 30 meters [90 feet] of the USGS values."

Animations created by Assistant Research Scientist David Forrest show the accuracy of the sub-grid inundation model in stunning detail. "The animation clearly shows water going around buildings and rushing through the streets," says Wang.

"What we've achieved is an efficient platform that addresses both large-scale storm tide and high-resolution inundation problems simultaneously," he adds. "Our future plans are to add the many other processes that are at play during a hurricane -- rainfall, filtration, storm-water drainage, and the effect of waves. That's the goal for our future development and further improvements."


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Rainy day can ruin online restaurant review

After looking at 1.1 million online reviews for 840,000 restaurants in more than 32,000 cities across the country, Georgia Tech and Yahoo Labs researchers have found that the weather outside can be just as significant a factor for reviews as what happens inside a restaurant. Their study shows evaluations written on rainy or snowy days, or very cold or hot days, are more negative than those written on nice days.

"People love to describe themselves as foodies. But in the end, it looks like we're all weather people, whether we realize it or not," said Saeideh Bakhshi, a Georgia Tech College of Computing Ph.D. candidate who led the study.

The study also found a nationwide spike in the number of reviews written during the summer, but July and August were the worst months of the year for ratings. November was the best.

"The best reviews are written on sunny days between 70 and 100 degrees," said Bakhshi. "Science has shown that weather impacts our mood, so a nice day can lead to a nice review. A rainy day can mean a miserable one."

The study covered a period of 10 years of reviews on sites that included Foursquare, Citysearch and TripAdvisor. It also found that demographic factors such as neighborhood diversity, education levels and population density have a significant impact.

For instance, areas with a high percentage of people with college degrees (more than 50 percent) average nearly three times more reviews than places where fewer than 10 percent have diplomas. However, higher education levels don't have much of an effect on ratings.

The study shows that population density of cities is closely tied to the expectations of service options. Based on reviews in busy cities, people are more patient with wait times and expect restaurants to have delivery options. In smaller cities, carryout service was rated more positively than places with delivery, but reviewers were harsher on pace of service.

"We also found that restaurants in the Northeast and Pacific get more reviews than places in the South and Midwest," Bakhshi added. "I think the difference between the South and Pacific comes mostly from the differences in education, diversity and liberal versus conservative. Blue states such as California, Washington and Oregon have a higher number of reviews per restaurant."

The research team also included Eric Gilbert, an assistant professor in Georgia Tech's School of Interactive Computing, and Partha Kanuparthy, a Yahoo Labs research scientist and 2012 Ph.D. Georgia Tech graduate in computer science.

"Our findings could help consumers better understand online reviews and ratings and help review sites calibrate recommendations," said Gilbert. "Outside factors apparently introduce bias in online ratings of a highly reviewed restaurant in big cities compared to a similar place in a rural area."

As for the ultimate "outside factor," Kanuparthy says restaurants face the same challenge as everyone else.

"You can plan the best wedding or birthday party. Restaurants can serve great food and provide spectacular service," he notes. "But no one can control the weather. In the end, you can't beat Mother Nature."

Abstract to the study can be found at: http://labs.yahoo.com/external_publication/2014/02/27/32842/

Cite This Page:

Georgia Institute of Technology. "Rainy day can ruin online restaurant review." ScienceDaily. ScienceDaily, 2 April 2014. .Georgia Institute of Technology. (2014, April 2). Rainy day can ruin online restaurant review. ScienceDaily. Retrieved April 19, 2014 from www.sciencedaily.com/releases/2014/04/140402105557.htmGeorgia Institute of Technology. "Rainy day can ruin online restaurant review." ScienceDaily. www.sciencedaily.com/releases/2014/04/140402105557.htm (accessed April 19, 2014).

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Harsh weather conditions increase cost of food

Many of your favorite products at the grocery store are going to cost more, according to Glynn Tonsor, associate professor of agricultural economics at Kansas State University.

"When consumers walk in the grocery store, they are going to have to continue to juggle what they put in those baskets," Tonsor said.

Several items will cost more this year, including beef, pork, vegetables and nuts. Most of the increase in price is because of extreme drought facing several states.

"Most people recognize weather has a big hand in food production," Tonsor said. "What they might not recognize is the actual location of food production around the country and therefore how weather across the country impacts the food prices they see."

California, described as the salad bowl of the United States, produces more than 90 percent of select vegetables and nut products. However, the state is facing extreme drought conditions. That means fewer of these products are available. Tonsor says the limited supply will increase the price of the products anywhere from 5 to 20 percent.

Drought is also taking a toll on beef. The drought in Oklahoma, coupled with the already historically low amount of cattle in the United States, will hike up the price for beef.

"It's not just a weather story," Tonsor said. "The other thing that's getting talked a lot about that will show up at the meat counter is animal health issues, particularly in the pork industry.

These animal health issues do not affect human health, but they do decrease the amount of pork available. That could affect the prices at the grocery store by summer, Tonsor said.


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European climate at the 2 degrees Celsius global warming threshold

A global warming of 2??C relative to pre-industrial climate has been considered as a threshold which society should endeavor to remain below, in order to limit the dangerous effects of anthropogenic climate change.

However, a new study shows that, even at this threshold, substantial and robust changes may be expected across Europe. Most of Europe will warm more than the global average with increases over +3 degrees over Northern Europe in winter and Central-Southern Europe in summer.

Similar increases are also shown for extremes of temperature. Precipitation patterns at +2C global warming show the now familiar wet-north and dry-south patterns and increasing heavy precipitation across much of Europe in both winter and summer.

These conclusions appear in a new study published in Environmental Research Letters in March and recently highlighted in Nature. Stefan Sobolowski at Uni Research and the Bjerknes Centre is co-author in the study led by Robert Vautard at the Pierre-Simon Laplace Institute in Gif-sur-Yvette, France.

This research was performed as part of an EU-FP7 project called IMPACT2C, which investigates the potential impacts in Europe and abroad even if society manages to keep globally averaged warming to around 2 degrees celsius. Crossing the +2 degree threshold is essentially a mid-century or earlier event under both the older IPCC scenarios and the new representative concentration pathways (RCPs).

Weather and climate is experienced locally The only way it is avoided is under the very aggressive, and increasingly unlikely, RCP2.6 scenario. The patterns of change, with the exception of regional variations, are now well known. What is new in this study is the fact that it can be shown that even at the global threshold of +2C substantial regional to local scale changes occur.

A global warming of +2C is somewhat abstract concept to many people. We do not experience weather and climate globally, we experience it locally. And this study places these changes in a spatial context that is relevant for the public.

Further, this study shows that these changes not as far away as we might think; a few decades at most.

"To put this in perspective," Dr. Sobolowski says, "this will be about the time that my daughter reaches adulthood."

Story Source:

The above story is based on materials provided by Uni Research. Note: Materials may be edited for content and length.


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Salamanders shrinking as their mountain havens heat up

Wild salamanders living in some of North America's best salamander habitat are getting smaller as their surroundings get warmer and drier, forcing them to burn more energy in a changing climate.

That's the key finding of a new study, published March 25 in the journal Global Change Biology, that examined museum specimens caught in the Appalachian Mountains from 1957 to 2007 and wild salamanders measured at the same sites in 2011-2012. The salamanders studied from 1980 onward were, on average, 8% smaller than their counterparts from earlier decades. The changes were most marked in the Southern Appalachians and at low elevations -- settings where detailed weather records showed the climate has warmed and dried out most.

Scientists have predicted that some animals will get smaller in response to climate change, and this is strongest confirmation of that prediction.

"This is one of the largest and fastest rates of change ever recorded in any animal," said Karen R. Lips, an associate professor of biology at the University of Maryland and the study's senior author. "We don't know exactly how or why it's happening, but our data show it is clearly correlated with climate change." And it's happening at a time when salamanders and other amphibians are in distress, with some species going extinct and others dwindling in number.

"We don't know if this is a genetic change or a sign that the animals are flexible enough to adjust to new conditions," Lips said. "If these animals are adjusting, it gives us hope that some species are going to be able to keep up with climate change."

The study was prompted by the work of University of Maryland Prof. Emeritus Richard Highton, who began collecting salamanders in the Appalachian Mountains in 1957. The geologically ancient mountain range's moist forests and long evolutionary history make it a global hot spot for a variety of salamander species. Highton collected hundreds of thousands of salamanders, now preserved in jars at the Smithsonian Institution's Museum Service Center in Suitland, MD.

But Highton's records show a mysterious decline in the region's salamander populations beginning in the 1980s. Lips, an amphibian expert, saw a similar decline in the frogs she studied in Central America, and tracked it to a lethal fungal disease. She decided to see whether disease might explain the salamander declines in the Appalachians.

Between summer 2011 and spring 2012, Lips and her students caught, measured and took DNA samples from wild salamanders at 78 of Highton's collecting sites in Maryland, Virginia, West Virginia, Tennessee and North Carolina. Using relatively new techniques for analyzing DNA from preserved specimens, the researchers tested some of Highton's salamanders for disease.

Lips found virtually no fungal disease in the museum specimens or the living animals. But when she compared size measurements of the older specimens with today's wild salamanders, the differences were striking.

Between 1957 and 2012, six salamander species got significantly smaller, while only one got slightly larger. On average, each generation was one percent smaller than its parents' generation, the researchers found.

The researchers compared changes in body size to the animals' location and their sites' elevation, temperature and rainfall. They found the salamanders shrank the most at southerly sites, where temperatures rose and rainfall decreased over the 55-year study.

To find out how climate change affected the animals, Clemson University biologist Michael W. Sears used a computer program to create an artificial salamander, which allowed him to estimate a typical salamander's daily activity and the number of calories it burned. Using detailed weather records for the study sites, Sears was able to simulate the minute-by-minute behavior of individual salamanders, based on weather conditions at their home sites during their lifetimes.

The simulation showed the modern salamanders were just as active as their forbears had been. But to maintain that activity, they had to burn 7 to 8 percent more energy. Cold-blooded animals' metabolisms speed up as temperatures rise, Sears explained.

To get that extra energy, salamanders must make trade-offs, Lips said. They may spend more time foraging for food or resting in cool ponds, and less time hunting for mates. The smaller animals may have fewer young, and may be more easily picked off by predators.

"Right now we don't know what this means for the animals," Lips said. "If they can start breeding smaller, at a younger age, that might be the best way to adapt to this warmer, drier world. Or it may be tied in with the losses of some of these species."

The research team's next step will be to compare the salamander species that are getting smaller to the ones that are disappearing from parts of their range. If they match, the team will be one step closer to understanding why salamanders are declining in a part of the world that once was a haven for them.

This research was funded by the University of Maryland-Smithsonian Institution Seed Grant Program.


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