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The legend of the Kamikaze typhoons

In the late 13th century, Kublai Khan, ruler of the Mongol Empire, launched one of the world's largest armada of its time in an attempt to conquer Japan. Early narratives describe the decimation and dispersal of these fleets by the "Kamikaze" of CE 1274 and CE 1281 -- a pair of intense typhoons divinely sent to protect Japan from invasion.

These historical accounts are prone to exaggeration, and significant questions remain regarding the occurrence and true intensity of these legendary typhoons. For independent insight, we provide a new 2,000 year sedimentary reconstruction of typhoon overwash from a coastal lake near the location of the Mongol invasions. Two prominent storm deposits date to the timing of the Kamikaze typhoons and support them being of significant intensity.

Our new storm reconstruction also indicates that events of this nature were more frequent in the region during the timing of the Mongol invasions. Results support the paired Kamikaze typhoons in having played an important role in preventing the early conquest of Japan by Mongol fleets. In doing so, the events may provide one of the earliest historical cases for the shaping of a major geopolitical boundary by an increased probability of extreme weather due to changing atmospheric and oceanic conditions.

Journal Reference:

J. D. Woodruff, K. Kanamaru, S. Kundu, T. L. Cook. Depositional evidence for the Kamikaze typhoons and links to changes in typhoon climatology. Geology, 2014; DOI: 10.1130/G36209.1

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Summer no sweat for Aussies but winter freeze fatal

Australians are more likely to die during unseasonably cold winters than hotter than average summers, QUT research has found.

Across the country severe winters that are colder and drier than normal are a far bigger risk to health than sweltering summers that are hotter than average.

QUT Associate Professor Adrian Barnett, a statistician with the Institute of Health and Biomedical Innovation and the lead researcher of the study, said death rates in Australian cities were up to 30 per cent higher in winter than summer.

The researchers analyzed temperature, humidity and mortality data from 1988 to 2009 for Adelaide Brisbane, Melbourne, Perth and Sydney.

Professor Barnett said the finding that hotter or more humid summers had no effect on mortality was "surprising."

"We know that heatwaves kill people in the short-term, but our study did not find any link between hotter summers and higher deaths," he said.

"The increase in deaths during colder winter could be because Australians are well-prepared for whatever summer throws at them, but are less able to cope with cold weather. There isn't the same focus on preparing for cold weather as there is for hot weather, for example through public health campaigns or even wearing the right sort of clothes.

"The strongest increase in deaths during a colder winter was in Brisbane, the city with the warmest climate, with an extra 59 deaths a month on average for a one degree decrease in mean winter temperature."

"Brisbane has the mildest winter of the five cities but has the greatest vulnerability. We believe this is because most homes are designed to lose heat in summer, which also allows cold outdoor air to get inside during winter."

Professor Barnett said the findings of the study, published in the journal Environmental Research, could trigger more prevention programs to help reduce the future burden on the health system.

"Excess winter deaths have a significant impact on health systems across Australia," he said.

"There are extra demands on doctors, hospitals and emergency departments in winter months, especially for cardiovascular and respiratory diseases which are triggered by exposure to cold weather.

"Our findings show the winter increases in mortality are predictable so ramping up public health measures, such as influenza vaccinations and insulating homes, particularly for vulnerable groups, should be considered to try to reduce the impact of severe winters."

Journal Reference:

Cunrui Huang, Cordia Chu, Xiaoming Wang, Adrian G. Barnett. Unusually cold and dry winters increase mortality in Australia. Environmental Research, 2015; 136: 1 DOI: 10.1016/j.envres.2014.08.046

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Birds sensed severe storms and fled before tornado outbreak

Golden-winged warblers apparently knew in advance that a storm that would spawn 84 confirmed tornadoes and kill at least 35 people last spring was coming, according to a report in the Cell Press journal Current Biology on December 18. The birds left the scene well before devastating supercell storms blew in.

The discovery was made quite by accident while researchers were testing whether the warblers, which weigh "less than two nickels," could carry geolocators on their backs. It turns out they can, and much more. With a big storm brewing, the birds took off from their breeding ground in the Cumberland Mountains of eastern Tennessee, where they had only just arrived, for an unplanned migratory event. All told, the warblers travelled 1,500 kilometers in 5 days to avoid the historic tornado-producing storms.

"The most curious finding is that the birds left long before the storm arrived," says Henry Streby of the University of California, Berkeley. "At the same time that meteorologists on The Weather Channel were telling us this storm was headed in our direction, the birds were apparently already packing their bags and evacuating the area."

The birds fled from their breeding territories more than 24 hours before the arrival of the storm, Streby and his colleagues report. The researchers suspect that the birds did it by listening to infrasound associated with the severe weather, at a level well below the range of human hearing.

"Meteorologists and physicists have known for decades that tornadic storms make very strong infrasound that can travel thousands of kilometers from the storm," Streby explains. While the birds might pick up on some other cue, he adds, the infrasound from severe storms travels at exactly the same frequency the birds are most sensitive to hearing.

The findings show that birds that follow annual migratory routes can also take off on unplanned trips at other times of the year when conditions require it. That's probably good news for birds, as climate change is expected to produce storms that are both stronger and more frequent. But there surely must be a downside as well, the researchers say.

"Our observation suggests [that] birds aren't just going to sit there and take it with regards to climate change, and maybe they will fare better than some have predicted," Streby says. "On the other hand, this behavior presumably costs the birds some serious energy and time they should be spending on reproducing." The birds' energy-draining journey is just one more pressure human activities are putting on migratory songbirds.

In the coming year, Streby's team will deploy hundreds of geolocators on the golden-winged warblers and related species across their entire breeding range to find out where they spend the winter and how they get there and back.

"I can't say I'm hoping for another severe tornado outbreak," Streby says, "but I am eager to see what unpredictable things happen this time."


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NASA, NOAA find 2014 warmest year in modern record

The year 2014 ranks as Earth's warmest since 1880, according to two separate analyses by NASA and National Oceanic and Atmospheric Administration (NOAA) scientists.

The 10 warmest years in the instrumental record, with the exception of 1998, have now occurred since 2000. This trend continues a long-term warming of the planet, according to an analysis of surface temperature measurements by scientists at NASA's Goddard Institute of Space Studies (GISS) in New York.

In an independent analysis of the raw data, also released Friday, NOAA scientists also found 2014 to be the warmest on record.

"NASA is at the forefront of the scientific investigation of the dynamics of the Earth's climate on a global scale," said John Grunsfeld, associate administrator for the Science Mission Directorate at NASA Headquarters in Washington. "The observed long-term warming trend and the ranking of 2014 as the warmest year on record reinforces the importance for NASA to study Earth as a complete system, and particularly to understand the role and impacts of human activity."

Since 1880, Earth's average surface temperature has warmed by about 1.4 degrees Fahrenheit (0.8 degrees Celsius), a trend that is largely driven by the increase in carbon dioxide and other human emissions into the planet's atmosphere. The majority of that warming has occurred in the past three decades.

"This is the latest in a series of warm years, in a series of warm decades. While the ranking of individual years can be affected by chaotic weather patterns, the long-term trends are attributable to drivers of climate change that right now are dominated by human emissions of greenhouse gases," said GISS Director Gavin Schmidt.

While 2014 temperatures continue the planet's long-term warming trend, scientists still expect to see year-to-year fluctuations in average global temperature caused by phenomena such as El Ni?o or La Ni?a. These phenomena warm or cool the tropical Pacific and are thought to have played a role in the flattening of the long-term warming trend over the past 15 years. However, 2014's record warmth occurred during an El Ni?o-neutral year.

"NOAA provides decision makers with timely and trusted science-based information about our changing world," said Richard Spinrad, NOAA chief scientist. "As we monitor changes in our climate, demand for the environmental intelligence NOAA provides is only growing. It's critical that we continue to work with our partners, like NASA, to observe these changes and to provide the information communities need to build resiliency."

Regional differences in temperature are more strongly affected by weather dynamics than the global mean. For example, in the U.S. in 2014, parts of the Midwest and East Coast were unusually cool, while Alaska and three western states -- California, Arizona and Nevada -- experienced their warmest year on record, according to NOAA.

The GISS analysis incorporates surface temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea surface temperatures, and temperature measurements from Antarctic research stations. This raw data is analyzed using an algorithm that takes into account the varied spacing of temperature stations around the globe and urban heating effects that could skew the calculation. The result is an estimate of the global average temperature difference from a baseline period of 1951 to 1980.

NOAA scientists used much of the same raw temperature data, but a different baseline period. They also employ their own methods to estimate global temperatures.

GISS is a NASA laboratory managed by the Earth Sciences Division of the agency's Goddard Space Flight Center, in Greenbelt, Maryland. The laboratory is affiliated with Columbia University's Earth Institute and School of Engineering and Applied Science in New York.

NASA monitors Earth's vital signs from land, air and space with a fleet of satellites, as well as airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

The data set of 2014 surface temperature measurements is available at:

http://data.giss.nasa.gov/gistemp/

The methodology used to make the temperature calculation is available at:

http://data.giss.nasa.gov/gistemp/sources_v3/

For more information about NASA's Earth science activities, visit:

http://www.nasa.gov/earthrightnow


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Global warming's influence on extreme weather

Understanding the cause-and-effect relationship between global warming and record-breaking weather requires asking precisely the right questions.

Extreme climate and weather events such as record high temperatures, intense downpours and severe storm surges are becoming more common in many parts of the world. But because high-quality weather records go back only about 100 years, most scientists have been reluctant to say if global warming affected particular extreme events.

On Wednesday, Dec. 17, at the American Geophysical Union's Fall Meeting in San Francisco, Noah Diffenbaugh, an associate professor of environmental Earth system science at the Stanford School of Earth Sciences, will discuss approaches to this challenge in a talk titled "Quantifying the Influence of Observed Global Warming on the Probability of Unprecedented Extreme Climate Events." He will focus on weather events that -- at the time they occur -- are more extreme than any other event in the historical record.

Diffenbaugh emphasizes that asking precisely the right question is critical for finding the correct answer.

"The media are often focused on whether global warming caused a particular event," said Diffenbaugh, who is a senior fellow at the Stanford Woods Institute for the Environment. "The more useful question for real-world decisions is: 'Is the probability of a particular event statistically different now compared with a climate without human influence?'"

Diffenbaugh said the research requires three elements: a long record of climate observations; a large collection of climate model experiments that accurately simulate the observed variations in climate; and advanced statistical techniques to analyze both the observations and the climate models.

One research challenge involves having just a few decades or a century of high-quality weather data with which to make sense of events that might occur once every 1,000 or 10,000 years in a theoretical climate without human influence.

But decision makers need to appreciate the influence of global warming on extreme climate and weather events.

"If we look over the last decade in the United States, there have been more than 70 events that have each caused at least $1 billion in damage, and a number of those have been considerably more costly," said Diffenbaugh. "Understanding whether the probability of those high-impact events has changed can help us to plan for future extreme events, and to value the costs and benefits of avoiding future global warming."


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NASA's Fermi Mission brings deeper focus to thunderstorm gamma rays

Each day, thunderstorms around the world produce about a thousand quick bursts of gamma rays, some of the highest-energy light naturally found on Earth. By merging records of events seen by NASA's Fermi Gamma-ray Space Telescope with data from ground-based radar and lightning detectors, scientists have completed the most detailed analysis to date of the types of thunderstorms involved.

"Remarkably, we have found that any thunderstorm can produce gamma rays, even those that appear to be so weak a meteorologist wouldn't look twice at them," said Themis Chronis, who led the research at the University of Alabama in Huntsville (UAH).

The outbursts, called terrestrial gamma-ray flashes (TGFs), were discovered in 1992 by NASA's Compton Gamma-Ray Observatory, which operated until 2000. TGFs occur unpredictably and fleetingly, with durations less than a thousandth of a second, and remain poorly understood.

In late 2012, Fermi scientists employed new techniques that effectively upgraded the satellite's Gamma-ray Burst Monitor (GBM), making it 10 times more sensitive to TGFs and allowing it to record weak events that were overlooked before.

"As a result of our enhanced discovery rate, we were able to show that most TGFs also generate strong bursts of radio waves like those produced by lightning," said Michael Briggs, assistant director of the Center for Space Plasma and Aeronomic Research at UAH and a member of the GBM team.

Previously, TGF positions could be roughly estimated based on Fermi's location at the time of the event. The GBM can detect flashes within about 500 miles (800 kilometers), but this is too imprecise to definitively associate a TGF with a specific storm.

Ground-based lightning networks use radio data to pin down strike locations. The discovery of similar signals from TGFs meant that scientists could use the networks to determine which storms produce gamma-ray flashes, opening the door to a deeper understanding of the meteorology powering these extreme events.

Chronis, Briggs and their colleagues sifted through 2,279 TGFs detected by Fermi's GBM to derive a sample of nearly 900 events accurately located by the Total Lightning Network operated by Earth Networks in Germantown, Maryland, and the World Wide Lightning Location Network, a research collaboration run by the University of Washington in Seattle. These systems can pinpoint the location of lightning discharges -- and the corresponding signals from TGFs -- to within 6 miles (10 km) anywhere on the globe.

From this group, the team identified 24 TGFs that occurred within areas covered by Next Generation Weather Radar (NEXRAD) sites in Florida, Louisiana, Texas, Puerto Rico and Guam. For eight of these storms, the researchers obtained additional information about atmospheric conditions through sensor data collected by the Department of Atmospheric Science at the University of Wyoming in Laramie.

"All told, this study is our best look yet at TGF-producing storms, and it shows convincingly that storm intensity is not the key," said Chronis, who will present the findings Wed., Dec. 17, in an invited talk at the American Geophysical Union meeting in San Francisco. A paper describing the research has been submitted to the Bulletin of the American Meteorological Society.

Scientists suspect that TGFs arise from strong electric fields near the tops of thunderstorms. Updrafts and downdrafts within the storms force rain, snow and ice to collide and acquire electrical charge. Usually, positive charge accumulates in the upper part of the storm and negative charge accumulates below. When the storm's electrical field becomes so strong it breaks down the insulating properties of air, a lightning discharge occurs.

Under the right conditions, the upper part of an intracloud lightning bolt disrupts the storm's electric field in such a way that an avalanche of electrons surges upward at high speed. When these fast-moving electrons are deflected by air molecules, they emit gamma rays and create a TGF.

About 75 percent of lightning stays within the storm, and about 2,000 of these intracloud discharges occur for each TGF Fermi detects.

The new study confirms previous findings indicating that TGFs tend to occur near the highest parts of a thunderstorm, between about 7 and 9 miles (11 to 14 kilometers) high. "We suspect this isn't the full story," explained Briggs. "Lightning often occurs at lower altitudes and TGFs probably do too, but traveling the greater depth of air weakens the gamma rays so much the GBM can't detect them."

Based on current Fermi statistics, scientists estimate that some 1,100 TGFs occur each day, but the number may be much higher if low-altitude flashes are being missed.

While it is too early to draw conclusions, Chronis notes, there are a few hints that gamma-ray flashes may prefer storm areas where updrafts have weakened and the aging storm has become less organized. "Part of our ongoing research is to track these storms with NEXRAD radar to determine if we can relate TGFs to the thunderstorm life cycle," he said.

Video: https://www.youtube.com/watch?v=JgK4Ds_Sj6Q#t=66


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