Global Warming Will Bring Violent Storms And Tornadoes, NASA Predicts

Source:

http://www.sciencedaily.com/releases/2007/08/070830105911.htm

Science Daily — NASA scientists have developed a new climate model that indicates that the most violent severe storms and tornadoes may become more common as Earth's climate warms.

Previous climate model studies have shown that heavy rainstorms will be more common in a warmer climate, but few global models have attempted to simulate the strength of updrafts in these storms. The model developed at NASA's Goddard Institute for Space Studies by researchers Tony Del Genio, Mao-Sung Yao, and Jeff Jonas is the first to successfully simulate the observed difference in strength between land and ocean storms and is the first to estimate how the strength will change in a warming climate, including "severe thunderstorms" that also occur with significant wind shear and produce damaging winds at the ground.
This information can be derived from the temperatures and humidities predicted by a climate computer model, according to the new study published on August 17 in the American Geophysical Union's Geophysical Research Letters. It predicts that in a warmer climate, stronger and more severe storms can be expected, but with fewer storms overall.
Global computer models represent weather and climate over regions several hundred miles wide. The models do not directly simulate thunderstorms and lightning. Instead, they evaluate when conditions are conducive to the outbreak of storms of varying strengths. This model first was tested against current climate conditions. It was found to represent major known global storm features including the prevalence of lightning over tropical continents such as Africa and, to a lesser extent, the Amazon Basin, and the near absence of lightning in oceanic storms.
The model then was applied to a hypothetical future climate with double the current carbon dioxide level and a surface that is an average of 5 degrees Fahrenheit warmer than the current climate. The study found that continents warm more than oceans and that the altitude at which lightning forms rises to a level where the storms are usually more vigorous.
These effects combine to cause more of the continental storms that form in the warmer climate to resemble the strongest storms we currently experience.
Lightning produced by strong storms often ignites wildfires in dry areas. Researchers have predicted that some regions would have less humid air in a warmer climate and be more prone to wildfires as a result. However, drier conditions produce fewer storms. "These findings may seem to imply that fewer storms in the future will be good news for disastrous western U.S. wildfires," said Tony Del Genio, lead author of the study and a scientist at NASA's Goddard Institute for Space Studies, New York. "But drier conditions near the ground combined with higher lightning flash rates per storm may end up intensifying wildfire damage instead."
The central and eastern areas of the United States are especially prone to severe storms and thunderstorms that arise when strong updrafts combine with horizontal winds that become stronger at higher altitudes. This combination produces damaging horizontal and vertical winds and is a major source of weather-related casualties. In the warmer climate simulation there is a small class of the most extreme storms with both strong updrafts and strong horizontal winds at higher levels that occur more often, and thus the model suggests that the most violent severe storms and tornadoes may become more common with warming.
The prediction of stronger continental storms and more lightning in a warmer climate is a natural consequence of the tendency of land surfaces to warm more than oceans and for the freezing level to rise with warming to an altitude where lightning-producing updrafts are stronger. These features of global warming are common to all models, but this is the first climate model to explore the ramifications of the warming for thunderstorms.
Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center.

Fausto Intilla

www.oloscience.com

Next Ice Age Delayed By Rising Carbon Dioxide Levels

Source:

http://www.sciencedaily.com/releases/2007/08/070829193436.htm

Science Daily — Future ice ages may be delayed by up to half a million years by our burning of fossil fuels. That is the implication of recent work by Dr Toby Tyrrell of the University of Southampton's School of Ocean and Earth Science at the National Oceanography Centre, Southampton.

Arguably, this work demonstrates the most far-reaching disruption of long-term planetary processes yet suggested for human activity.
Dr Tyrrell's team used a mathematical model to study what would happen to marine chemistry in a world with ever-increasing supplies of the greenhouse gas, carbon dioxide.
The world's oceans are absorbing CO2 from the atmosphere but in doing so they are becoming more acidic. This in turn is dissolving the calcium carbonate in the shells produced by surface-dwelling marine organisms, adding even more carbon to the oceans. The outcome is elevated carbon dioxide for far longer than previously assumed.
Computer modelling in 2004 by a then oceanography undergraduate student at the University, Stephanie Castle, first interested Dr Tyrrell and colleague Professor John Shepherd in the problem. They subsequently developed a theoretical analysis to validate the plausibility of the phenomenon.
The work, which is part-funded by the Natural Environment Research Council, confirms earlier ideas of David Archer of the University of Chicago, who first estimated the impact rising CO2 levels would have on the timing of the next ice age.
Dr Tyrrell said: 'Our research shows why atmospheric CO2 will not return to pre-industrial levels after we stop burning fossil fuels. It shows that it if we use up all known fossil fuels it doesn't matter at what rate we burn them. The result would be the same if we burned them at present rates or at more moderate rates; we would still get the same eventual ice-age-prevention result.'
Ice ages occur around every 100,000 years as the pattern of Earth's orbit alters over time. Changes in the way the sun strikes the Earth allows for the growth of ice caps, plunging the Earth into an ice age. But it is not only variations in received sunlight that determine the descent into an ice age; levels of atmospheric CO2 are also important.
Humanity has to date burnt about 300 Gt C of fossil fuels. This work suggests that even if only 1000 Gt C (gigatonnes of carbon) are eventually burnt (out of total reserves of about 4000 Gt C) then it is likely that the next ice age will be skipped. Burning all recoverable fossil fuels could lead to avoidance of the next five ice ages.
Dr Tyrrell is a Reader in the University of Southampton's School of Ocean and Earth Science. This research was published in Tellus B, vol 59 p664.
Note: This story has been adapted from a news release issued by University Of South Hampton.

Fausto Intilla

www.oloscience.com

Drizzle Radar: A Gain For Climate Research

Source:

http://www.sciencedaily.com/releases/2007/08/070824102053.htm

Science Daily — TU Delft has taken a new weather radar system into use, the 'Drizzle Radar', which can observe even the lightest of drizzles. This is an enormous gain for climate researchers and is attracting international attention.

The radar was successfully installed on the 213 metre-high Royal Netherlands Meteorological Institute (KNMI) measurement tower in Cabauw, near Lopik, on Thursday, August 23. From this spot the highly sensitive radar, together with the other advanced instruments of the CESAR observatory (Cabauw Experimental Site for Atmospheric Research), is to provide a complete picture of the interaction between dust, clouds, rain and radiation. The latter is still one of the least understood factors in climate models.
Clouds and the climate
Clouds are of great importance for the greenhouse effect. On the one hand, clouds wrap a blanket round the Earth which retains heat, but they also cool the planet through the reflection of sunlight. Clouds can therefore compensate for some of the global warming, but the question is how much, and how precisely does it work. Dust particles play a crucial role in the formation of clouds and precipitation. They act as condensation nuclei, around which small droplets form. In an atmosphere without dust, clouds would not even be able to form. The more dust particles, the more clouds, the more solar radiation is reflected and the cooler the Earth stays.
A cooler Earth leads, in its turn, to less precipitation, because cooler air cannot hold as much moisture as warm air. Thus we have an extremely complicated interplay of factors that can be elucidated only through detailed measurements. The new 'Drizzle radar' is able to measure cloud droplets and precipitation extremely accurately. In addition, the measurement tower in Cabauw monitors the quantity and composition of dust particles and of clouds. Climate researchers are particularly interested in the extent to which dust particles influence rainfall.
IDRA
The International Research Centre for Telecommunications and Radar (IRCTR) Drizzle Radar, or IDRA, developed by TU Delft, is able to measure the smallest raindrops in a thirty kilometre zone around the observatory. The data are used to determine cloud life cycles, and their relationship to radiation and airborne dust These measurements, which will lead to a better understanding of the climate system, are unique in the world and can be done nowhere else.
CESAR
The CESAR Observatory in Cabauw is one of the world’s most advanced observatories for atmospheric research. Its highly accurate, multi-instrument array constantly measures atmospheric characteristics , to obtain a better picture of the atmosphere’s role in the climate system. The most eye-catching feature is the 213 metre-high measurement tower of the KNMI, where the Drizzle Radar has now been installed. CESAR is a consortium of KNMI (Royal Netherlands Meteorological Institute), TU Delft (Delft University of Technology), TNO (Netherlands Organisation for Applied Scientific Research), RIVM (National Institute of Public Health and Environmental Protection), ECN (Energy Research Centre of the Netherlands), Wageningen University and ESA (European Space Agency).
Note: This story has been adapted from a news release issued by Delft University of Technology.

Fausto Intilla

www.oloscience.com

Handling Turbulence On Titan And Earth

Source:

http://www.sciencedaily.com/releases/2007/08/070828115959.htm

Science Daily — Ever spilled your drink on an airline due to turbulence? Researchers on both sides of the Atlantic are finding new ways to understand the phenomenon - both on Earth and on Titan.

Turbulence plays an important role in Earth’s weather system, and can be more than an inconvenience - hundreds of injuries have occurred on commercial flights due to turbulence. It is studied both in Earth's atmosphere and in that of Saturn's moon, Titan, aided by data from ESA’s Huygens probe. The study of one is helping the other.
Giles Harrison, atmospheric physicist at the University of Reading in the UK, devised an inexpensive way to measure the effects of turbulence using weather balloons. The instrument package contains a magnetic field sensor which measures fluctuations in Earth’s magnetic field due to turbulence. As Earth's magnetic field is very stable, the measurements of magnetic changes taken with the weather balloon showed the effects of turbulence on the sensor, since the balloon itself was moving very violently.
All bodies, planets and moons, are subject to the same principles of physics. So by working together, researchers looking at Earth and those looking at our planetary neighbours can really test their models of the processes taking place and gain new insights into both.
Planetary scientist Ralph Lorenz, at the Johns Hopkins University Applied Physics Laboratory in the USA, found Harrison's results key to making sense of data from Huygens, which descended by parachute through Titan's atmosphere in January 2005.
The Surface Science Package (SSP) on board Huygens included a set of tilt sensors which measured motions of the probe during its descent. These tilt sensors act much like a drink in a glass, using a small slug of liquid to measure the tilt angle.
As the probe plummeted under the parachute through Titan’s atmosphere, there was a lot of buffeting, even though the air itself was fairly still. Knowing the signature of cloud-induced turbulence in Harrison's balloon data from Earth inspired Lorenz to look for a similar effect in the Huygens data using the tilt sensor.
“Huygens’ tilt history was just this long, squiggly, complex mess, but seeing the fingerprint of cloud turbulence in Harrison's work showed me what to look for,” said Lorenz.
Armed with that information, Lorenz found that a 20-minute period of Huygens' 2.5-hour descent, around an altitude of 20 km, was affected by this kind of in-cloud turbulence. Having experimented with instrumentation on small models, even frisbees, to understand the dynamics of aerospace vehicles like the probe, Lorenz was familiar with the sensors used by Harrison.
Lorenz’s analysis helped identify a turbulent cloud layer in Titan’s atmosphere - a significant result for the investigation of Titan’s meteorology. In the process, he also found a way to improve Harrison's magnetic sensor arrangement on the weather balloon, simply by changing its orientation.
Mark Leese, Project Manager for the SSP on Huygens at The Open University said “We knew Huygens had a bumpy ride down to Titan’s surface. Now we can separate out twenty minutes of air turbulence – probably due to a cloud layer - from other effects such as cross winds or air buffeting due to the irregular shape of the probe.”
Reference: Lorenz's analysis ‘Descent motions of the Huygens probe as measured by the Surface Science Package (SSP): turbulent evidence for a cloud layer’, by R. Lorenz, J. Zarnecki, M. Towner, M. Leese, A. Ball, B. Hathi, A. Hagermann and N. Ghafoor, in the online version of the Planetary and Space Science journal. It is expected to appear in print in November this year.
The original work by Harrison and Hogan was published last year in the Journal of Atmospheric and Oceanic Technology, in a paper titled ‘In Situ Atmospheric Turbulence Measurement Using the Terrestrial Magnetic Field— A Compass for a Radiosonde’ by R. Harrison and R. Hogan.
An exchange of ideas between Lorenz and Harrison appears in the August 2007 issue of the Journal of Oceanic and Atmospheric Technology.
Harrison's work is supported by the Paul Instrument Fund of the Royal Society, Lorenz is supported by NASA's Cassini Project. The Science and Technology Facilities Council funds UK participation in the Cassini Huygens mission, in particular, the research at The Open University.
Weather balloons carry packages known as radiosondes, which take (sounding) measurements of air temperature, moisture and wind direction used for weather forecasting. The balloons are filled with helium or hydrogen gas and the measurements are sent back to the surface by radio. When the balloon bursts, usually at 15 to 20 km altitude, the instruments fall to earth by parachute.
Note: This story has been adapted from a news release issued by European Space Agency.

Fausto Intilla

www.oloscience.com

Polar Ice Clouds May Be Climate Change Symptom

Source:

http://www.sciencedaily.com/releases/2007/08/070820145343.htm

Science Daily — As the late summer sun sets in the Arctic, bands of wispy, luminescent clouds shine against the deep blue of the northern sky.

To the casual observer, they may simply be a curiosity, dismissed as the waning light of the midnight sun. But to scientists, these noctilucent ice clouds could be an upper-atmospheric symptom of a changing climate.
“The question which everyone in Alaska is dealing with is what are the symptoms of climate change and, as in medicine, how do these symptoms reflect the underlying processes,” said Richard Collins, a researcher at the Geophysical Institute at the University of Alaska Fairbanks. “It is believed that [these clouds] are an indicator of climate change.”
Dozens of scientists from several countries will gather at the University of Alaska Fairbanks Aug. 20-23 to discuss the latest findings on noctilucent clouds and other phenomena of the earth’s upper atmosphere during the Eighth International Workshop on Layered Phenomena in the Mesopause Region. Sessions will include information on the latest ground-based and satellite data on the mesopause region, an area of the atmosphere 50 miles above Earth’s surface and the site of the coldest atmospheric temperatures.
Noctilucent clouds form under conditions that counter common logic. They only form in the summer, when solar radiation is most intense, Collins said. That solar heating, rather than warming the mesopause, causes cooling, he said. “The mesopause region is colder in summer under perpetual daylight than it is in winter under perpetual darkness.”
The reason lies in the movement of air within the atmosphere, Collins said. Solar radiation heats the lower atmosphere, causing a rising cell of air over the summer pole, he said. “As the air rises it cools and that beats out the radiative heating.” Those cold temperatures allow the ice clouds to form in the mesopause. The clouds could serve as an indicator of climate change because an increase in carbon dioxide, which causes heating in the lower atmosphere, causes cooling in the upper atmosphere.
Collins said the noctilucent clouds are a relatively new phenomenon. History indicates that humans first recorded their presence in the 19th century, he said. Satellite and ground-based data has been limited, he said, but it appears that the clouds have become more prevalent over time. A new satellite, Aeronomy of Ice in the Mesosphere, or AIM, was launched in April 2007 to observe clouds and their environment in the mesopause, Collins said scientists are looking forward to having more reliable data, which could contribute to a broader understanding of the upper atmosphere, noctilucent clouds and how both fit into the climate system.
Note: This story has been adapted from a news release issued by University of Alaska Fairbanks.

Fausto Intilla

www.oloscience.com

Earth's Core More Complex Than Thought: Atoms Form Layers Of Spiral Patterns

Source:

http://www.sciencedaily.com/releases/2007/08/070816102523.htm

Science Daily — It is hard to know what is going on over 3000 km beneath our feet, but until recently scientists were fairly confident that they understood the way the iron atoms in the Earth's core packed together. However, new research has overturned conventional thinking and revealed that the structure of the core is not as straightforward as was once thought.
Pressures and temperatures at the Earth's core are stupendous -- more than 3.5 Mbar and 7000°K -- and currently it is impossible to recreate these conditions in the laboratory. Our information about the core comes from observing the way that seismic waves travel through the core, extrapolating from experimental studies and studying iron rich meteorites.
As a result we know that the core is mostly iron, but that it also must contain some light impurities such as oxygen, silicon, sulphur, hydrogen and magnesium (because the density of the core is too low to be pure iron). The most significant impurity is thought to be nickel, which makes up between 5 and 15% of the composition.
Most studies on the Earth's core have approximated the composition to be pure iron. "It was assumed that the alloy elements were not very important for the structural and elastic properties of the core," says Igor Abrikosov, a theoretical physicist at Linköping University in Sweden.
Experimental and theoretical studies on pure iron led to a 'standard model' for the core, which said that the iron atoms were packed in a 'hexagonal close packed' formation. This resembles a honeycomb structure in which the atoms are in densely packed layers of hexagons, with every other layer lying directly above its partner two layers below.
Other packing structures were ruled out because they were assumed to be less energetically efficient. "At moderate pressures other structures have some magnetism and they turn out to have lower stability," explains Abrikosov.
Carrying out experiments at anything close to the pressures and temperatures experienced at the core is pretty much impossible. "To achieve high pressures the sample has to be made very small and then it is difficult to see the diffraction patterns from the structures," explains Leonid Dubrovinsky, a geo-scientist at the University of Bayreuth in Germany. What is more, at high temperatures the iron tends to diffuse and react with the carbon in the diamond anvil cell -- a device that pinches samples between two diamond points and creates extreme pressures.
An inability to recreate core conditions hampered our understanding of the core, but in recent years powerful computer models have stepped in the breach. "Expertise has been developed in 'Ab intio' (first principles) calculations and we are able to do higher quality extrapolations to understand core conditions," says Abrikosov.
In addition experiments have improved greatly, with very high pressures and temperatures reached recently in new diamond anvil cells. Combined with the use of synchrotron radiation scientists have been able to observe structures at conditions that are ever closer to conditions at the Earth's outer core.
Using this combination of theory, experiments and powerful simulations Abrikosov, Dubrovinsky and their colleagues have revisited the core. This time they have also included alloy elements such as Nickel and Magnesium in their calculations and, to their surprise, they found that it has a significant effect.
"At high pressures the magnetism is squeezed out of the other structures and they all have similar stability," says Abrikosov, who presented his findings at the 1st EuroMinScI* Conference near Nice, France in March this year. The new research has revealed that 'face centred cubic' and 'body centred cubic' structures can not be ruled out and that all of these structures are energetically possible. "The standard model has been killed," says Abrikosov.
Face centred cubic structures have an atom in the centre of every face, as well as at each of the corners, while body centred cubic has one atom in the centre of the cube. Compared to the hexagonal close packed the face centred cubic structure alternates every third layer, with the atoms making a spiral pattern up through the layers.
Elements like nickel, silicon, oxygen and magnesium are also likely to play a key part in way atoms pack in the core. Recent experiments have shown that at very high pressures magnesium atoms are compressed to such an extent that they can fit easily into iron structures. In addition the element nickel is more comfortable than iron in a 'face centred cubic' structure.
So why does this matter and what kind of difference could these structures make in the core? "It has implications for the anisotropy of the core," says Dubrovinsky.
Studies of seismic waves have revealed that the waves travel faster in a north-south direction and slower in an east-west direction through the core -- a phenomenon that scientists call anisotropic. The way the atoms pack in the core is vital for understanding this anisotropy.
What is more, the Earth's core produces our magnetic field. Without it the Earth would be bombarded with dangerous cosmic rays and life would struggle to survive. As well as relying on Earth's magnetic field to protect us, we now use it to navigate and keep satellites in place. Life on Earth depends upon the magnetic field, but until we understand the core we can't fully understand how this field is created, or how it is likely to change.
For scientists studying the Earth's core it is time to go back to the drawing board and rethink what lies underneath our feet. However, a new generation of powerful computer simulations, along with experiments that we could previously only dream about, mean that optimism is high and scientists are confident that the core will reveal its secrets soon.
* EuroMinScI is the European Collaborative Research (EUROCORES) Programme on "European Mineral Science Initiative" developed by the European Science Foundation (ESF).
Note: This story has been adapted from a news release issued by European Science Foundation.

Fausto Intilla
www.oloscience.com

San Andreas Fault Likely Much More Destructive Than Current Models Predict

Source:

http://www.sciencedaily.com/releases/2007/08/070819085711.htm

Science Daily — High-speed ruptures travelling along straight fault lines could explain why some earthquakes are more destructive than others, according to an Oxford University scientist. In this week’s Science, Professor Shamita Das suggests that ruptures in the Earth’s surface moving at 6km per second could make future earthquakes along California’s San Andreas fault much more destructive than current models predict.

Professor Das compared data from the 1906 California earthquake with data from a similar earthquake that occurred in 2001 in Kunlunshan, Tibet. The comparison suggests that, in both, the long straight portions of the fault enabled ruptures to travel twice as fast as the original ‘shear’ wave travelling through the rock. Such ‘super-shear’ waves were once thought to be impossible but could now explain why similar magnitudes of earthquake can cause much greater devastation in some areas than others.
‘Long straight faults are more likely to reach high rupture speeds,’ said Professor Das of the Department of Earth Sciences. ‘The fault starts from rest, then accelerates to the maximum permissible speed and continues at this speed until it reaches an obstacle such as a large ‘bend’. If the next earthquake in southern California follows the same pattern as the ones in California in 1857 and 1906, and in Tibet in 2001, a super-shear rupture travelling southward would strongly focus shock waves on Santa Barbara and Los Angeles.’
The 2001 Kunlunshan earthquake is of particular interest to scientists because it was so well preserved owing to its remote location and dry desert environment. Studies of the earthquake revealed telltale off-fault open cracks only at the portions where it was found to have a very high rupture speed. ‘These cracks confirm that the earthquake reached super-shear speeds on the long, straight section of the fault. This is the first earthquake where such direct evidence is available and it is exactly the kind of evidence that we do not have for the similar earthquake in California 1906, due to the heavy rains and rapid rebuilding that occurred there immediately afterwards.’
Professor Das believes that future research into rupture speeds could take scientists one step closer to predicting the potential impact of earthquakes in particular regions. She commented: ‘It appears that the 1857 and 1906 California earthquakes may have propagated faster than was previously thought. If this is the case then we need to apply the same analysis to other similar faults around the world. By developing a measure of the ‘straightness’ of faults and finding and recording evidence such as off-fault open cracks we hope to better understand these potentially devastating phenomena.’ The full article, entitled ‘The Need to Study Speed’, is published in Science on 17 August 2007.
Note: This story has been adapted from a news release issued by University of Oxford.

Fausto Intilla

www.oloscience.com