Monday, January 21, 2008

How Ultrafine Particles In Air Pollution May Cause Heart Disease


ScienceDaily (Jan. 21, 2008) — Patients prone to heart disease may one day be told by physicians to avoid not only fatty foods and smoking but air pollution too.

A new academic study led by UCLA researchers has revealed that the smallest particles from vehicle emissions may be the most damaging components of air pollution in triggering plaque buildup in the arteries, which can lead to heart attack and stroke.

The scientists identified a way in which pollutant particles may promote hardening of the arteries — by inactivating the protective qualities of high density lipoprotein (HDL) cholesterol, known as "good" cholesterol.

A multicampus team from UCLA, the University of Southern California, the University of California, Irvine, and Michigan State University contributed to the research, which was led by Dr. Andre Nel, UCLA's chief of nanomedicine. The study was primarily funded by the National Institute of Environmental Health Sciences and the U.S. Environmental Protection Agency (EPA).

"It appears that the smallest air pollutant particles, which are the most abundant in an urban environment, are the most toxic," said first author Dr. Jesus Araujo, assistant professor of medicine and director of environmental cardiology at the David Geffen School of Medicine at UCLA. "This is the first study that demonstrates the ability of nano-sized air pollutants to promote atherosclerosis in an animal model."

Nanoparticles are the size of a virus or molecule — less than 0.18 micrometers, or about one-thousandth the size of a human hair. The EPA currently regulates fine particles, which are the next size up, at 2.5 micrometers, but doesn't monitor particles in the nano or ultrafine range. These particles are too small to capture in a filter, so new technology must be developed to track their contribution to adverse health effects.

"We hope our findings offer insight into the impact of nano-sized air pollutant particles and help explore ways for stricter air quality regulatory guidelines," said Nel, principal investigator and a researcher at UCLA's California NanoSystems Institute.

Nel added that the consequences of air pollution on cardiovascular health may be similar to the hazards of secondhand smoke.

Pollution particles emitted by vehicles and other combustion sources contain a high concentration of organic chemicals that could be released deep into the lungs or even spill over into the systemic circulation.

The UCLA research team previously reported that diesel exhaust particles interact with artery-clogging fats in low-density lipoprotein (LDL) cholesterol to activate genes that cause the blood-vessel inflammation that can lead to heart disease.

In the current study, researchers exposed mice with high cholesterol to one of two sizes of air pollutant particles from downtown Los Angeles freeway emissions and compared them with mice that received filtered air that contained very few particles.

The study, conducted over a five-week period, required a complex exposure design that was developed by teams led by Dr. Michael Kleinman, professor of community and environmental medicine at UC Irvine, and Dr. Constantinos Sioutas, professor of civil and environmental engineering at USC.

Researchers found that mice exposed to ultrafine particles exhibited 55 percent greater atherosclerotic-plaque development than animals breathing filtered air and 25 percent greater plaque development than mice exposed to fine-sized particles.

"This suggests that ultrafine particles are the more toxic air pollutants in promoting events leading to cardiovascular disease," Araujo said.

Pollutant particles are coated in chemicals sensitive to free radicals, which cause the cell and tissue damage known as oxidation. Oxidation leads to the inflammation that causes clogged arteries. Samples from polluted air revealed that ultrafine particles have a larger concentration of these chemicals and a larger surface area where these chemicals thrive, compared with larger particles, Sioutas noted.

"Ultrafine particles may deliver a much higher effective dose of injurious components, compared with larger pollutant particles," Nel said.

Scientists also identified a key mechanism behind how these air pollutants are able to affect the atherosclerotic process. Using a test developed by Dr. Mohamad Navab, study co-author and a UCLA professor of medicine, researchers found that exposure to air pollutant particles reduced the anti-inflammatory protective properties of HDL cholesterol.

"HDL normally helps reduce the vascular inflammation that is part of the atherosclerotic process," said Dr. Jake Lusis, study co-author and a UCLA professor of cardiology, human genetics and microbiology, immunology and molecular genetics. "Surprisingly, we found that exposure to air pollutant particles, and especially the ultrafine size, significantly decreased the positive effects of HDL."

To explore if air particle exposure caused oxidative stress throughout the body — which is an early process triggering the inflammation that causes clogged arteries — researchers checked for an increase in genes that would have been activated to combat this inflammatory progression.

"We found greater levels of gene activation in mice exposed to ultrafine particles, compared to the other groups," Lusis said. "Our next step will be to develop a biomarker that could enable physicians to assess the degree of cardiovascular damage caused by air pollutants or measure the level of risk encountered by an exposed person."

Researchers added that previous studies assessing the cardiovascular impact of air pollution have taken place over longer periods of exposure time, such as five to six months. The current study demonstrated that ill effects can occur more quickly, in just five weeks.

"Further study will pinpoint critical chemical and toxic properties of ultrafine particles that may affect humans," Nel said.

The findings appear in the Jan. 17 online edition of the journal Circulation Research. The research team included investigators from the fields of nanomedicine, cardiology and genetics. Additional co-authors included Berenice Barajas, Xuping Wang, Brian J. Bennett and Ke Wei Gong of the David Geffen School of Medicine at UCLA, and Jack Harkema from the department of pathobiology and diagnostic investigation at Michigan State University.

Additional grant support was provided by the National Institute of Allergy and Infectious Diseases; the National Heart, Lung and Blood Institute; and the Robert Wood Johnson Foundation.

Adapted from materials provided by University of California, Los Angeles.

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Paired Microbes Eliminate Methane Using Sulfur Pathway
January 21, 2008 — Anaerobic microbes in the Earth's oceans consume 90 percent of the methane produced by methane hydrates -- methane trapped in ice -- preventing large amounts of methane from reaching the atmosphere. ... > full story
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Wednesday, January 16, 2008

NASA Observes La Niña: This 'Little Girl' Makes A Big Impression

ScienceDaily (Jan. 16, 2008) — Cool, wet conditions in the Northwest, frigid weather on the Plains, and record dry conditions in the Southeast, all signs that La Niña is in full swing.

With winter gearing up, a moderate La Niña is hitting its peak. And we are just beginning to see the full effects of this oceanographic phenomenon, as La Niña episodes are typically strongest in January.

A La Niña event occurs when cooler than normal sea surface temperatures form along the equator in the Pacific Ocean, specifically in the eastern to central Pacific. The La Niña we are experiencing now has a significant presence in the eastern part of the ocean.

The cooler water temperatures associated with La Niña are caused by an increase in easterly sea surface winds. Under normal conditions these winds force cooler water from below up to the surface of the ocean. When the winds increase in speed, more cold water from below is forced up, cooling the ocean surface.

“With this La Niña, the sea-surface temperatures are about two degrees colder than normal in the eastern Pacific and that’s a pretty significant difference,” says David Adamec of NASA’s Goddard Space Flight Center, Greenbelt, Md. “I know it doesn’t sound like much, but remember this is water that probably covers an area the size of the United States. It’s like you put this big air conditioner out there -- and the atmosphere is going to feel it.”

While this “air conditioner” may be located in the equatorial Pacific Ocean, it has a great influence on the weather here in the United States and across the globe.

The cool water temperatures of a La Niña slow down cloud growth overhead, causing changes to the rainfall patterns from South American to Indonesia. These changes in rainfall affect the strength and location of the jet stream -- the strong winds that guide weather patterns over the United States. Since the jet stream regulates weather patterns, any changes to it will have a great impact on the United States.

Those changes can be felt throughout the country. The Northwest generally experiences cooler, wetter weather during a La Niña. On the Great Plains, residents normally see a colder than normal winter and southeastern states traditionally experience below average rainfall.

The cooler waters of a La Niña event also increase the growth of living organisms in this part of the ocean. La Niñas amplify the normal conditions in the Pacific. These typically cool and abundant waters experience an increase in phytoplankton growth when the water temperature drops even further.

The increased circulation that brings up cold water from below also brings up with it nutrients from the deeper waters. These nutrients feed the organisms at the bottom of the food chain, starting a reaction that increases life in the ocean. NASA’s SeaWiFS satellite documented this increase in phytoplankton during the last La Niña period in 1998.

La Niña and El Niño episodes tend to occur every three to five years. La Niñas are often preceded by an El Niño, however this cycle is not guaranteed.

The lengths of La Niña events vary as well. “We need to watch to see if this La Niña diminishes, because they can last for multiple years. And if it does last for multiple years, the southern tier of the United States, especially the Southeast, can expect dryer weather. That is not a good situation. If this La Niña behaves like a normal event, we should see signs that it is beginning to weaken by February,” says Adamec.

So far this La Niña is behaving like a textbook case: following the predicted weather patterns, strengthening throughout the winter, and peaking toward January. According to NOAA’s Climate Prediction Center, this La Niña episode is expected to continue until the spring of 2008, with a gradual weakening starting in February.

NASA will continue to monitor this phenomenon with several of its key Earth observing satellites.

Instruments on NASA’s Terra and Aqua satellites measure sea surface temperature and observe changes to life in the ocean, changes of great importance to the fishing industry. The MODIS instruments on these satellites detected the temperature drop that signaled this La Niña period, and SeaWiFS continues to monitor ocean life.

Scientists also look at sea surface height to understand La Niña. The cooler ocean water associated with a La Niña contracts, lowering sea-surface heights. Over the past year, NASA’s Jason satellite has observed a lower than normal sea level along the equatorial Pacific where this current La Niña episode is taking place.

NASA also looks at changes in wind and rain patterns to study La Niña. The QuikSCAT satellite measures changes in oceanic surface winds, while the Tropical Rainfall Measuring Mission satellite observes changes in rainfall. These observations add to a fuller understanding of this phenomenon.

The current La Niña episode has far many reaching effects. What some may see as just a small change in sea surface temperature has a much greater impact on our climate here in the U.S. and across the globe, as well as implications for the fishing industry and the global economy. With the help of NASA’s earth observing fleet, scientists are becoming better equipped to observe and understand this phenomenon.

Adapted from materials provided by National Aeronautics And Space Administration.

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News Stories

Climate Influences Deep Sea Populations
January 16, 2008 — Ecologists have discovered a mechanism of interaction across ecosystems and can show how a climate-driven phenomenon originated in shelf environments can control the biological processes of a ... > full story
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Friday, January 11, 2008

Eco-Capitalists Save Mother Nature by Charging for Her Services

This past spring, David Brand went on a property-scouting trip to Malaysian Borneo. Deep in the rain forest, Brand — founder and director of a forestry investment business — met locals who just couldn’t grasp what this Westerner was doing there. They were mystified he did not want to build an illegal logging mill. One of them put his arm around Brand’s shoulder. “No one can see what we do here, my friend,” he said. “We can cut it all down for you.”

Brand sighed. He wasn’t there to clear-cut the rain forest. In fact, soon after scoping out that land, he hopped on a plane to London where, in a matter of weeks, he raised $200 million to buy tracts of forest like the one in Borneo — and he’s not going to raze those, either. They’re investments. The return will come from deals with companies shopping for pollution offsets or with NGOs and governments that will pay to protect the planet’s wild places — not because they’re pretty, but because they perform a service.

The eco-capitalists are coming, and they aren’t wielding Thoreauvian platitudes about the sanctity of nature. Their jargon is far less lyrical: ecological assets, environmental markets, ecosystem services, natural capital. For these guys, biofuels and long-lasting lightbulbs are fine but they’re nothing more than a short-term play. The real money is in nascent markets indexed to the health of Mother Nature.

People understand the economic value of nature’s goods because we constantly pay for them: seafood, timber, copper, cut flowers, natural gas. But nature also provides services that stabilize spaceship Earth. Insects pollinate crops, wooded hillsides purify water, trees sequester CO2, and wetlands buffer cities against storm surges. How much are those services worth? Who knows. They’ve always been free, or treated as such. Nature has never submitted an invoice.

But they’re not free, of course. We can tell by the enormous price we pay when they decline or disappear. Think Hurricane Katrina, unpollinated crops, and deadly mudslides caused by deforestation. As the new age of environmental awareness dawns, people and governments are starting to put a dollar value on these services. In practice, that means paying to protect the land where services are most concentrated. And whoever owns the land can reap the profits.

It’s a twist on carbon cap-and-trade systems. In Europe, governments force companies that emit too much carbon to buy credits from those with excess credits (because they’ve cut back their own emissions). As the economy expands, the demand for — and thus the price of — carbon credits increases. Despite its growing pains, the European Emissions Trading Scheme has created a $4 billion-a-year carbon market, and no amount of cynicism about its efficacy can change the fact that skyrocketing public interest in carbon neutrality equals big money for carbon traders.

A similar setup in the US is wetland banking. Thanks to the Clean Water Act of 1972, developers must compensate the state for wetlands they pave over. Specialized businesses from Florida to California now buy up wetland areas and sell mitigation credits to developers.

Brand and others are betting that successful trading of carbon will kick-start the creation of other cap-and-trade systems for ecological services like watershed protection, biodiversity, and erosion control. But it’s more complicated than it sounds. Carbon disperses and has a global impact. A Latin American butterfly or a Myanmar riverbank? Not so much. “Those are local assets,” explains Jesse Fink, a cofounder of Priceline.com and a prominent eco- capitalist. The challenge is connecting global capital markets so that a butterfly matters as much, financially, to an investor in Chicago as it does to a farmer in Costa Rica. That will require the creation of a whole new financial transaction infrastructure, combining local businesses that can authenticate commodities on the ground with international registries, remote sensing, canopy monitoring, and other mechanisms to monitor and standardize trades.

Tough? Sure. But many experts see these kinds of deals as inevitable. When carbon cap-and-trade comes online in the US, there will be no shortage of demand, because most of corporate America will be shopping for mitigation credits. Build a cap-and-trade framework for other eco-assets and firms will profit not just from the sale of carbon offsets but from quantifiable gains in soil conservation, biodiversity, and watershed protection.

Still, the world’s investment institutions haven’t bought in just yet. As one former Goldman Sachs strategist explains: “First there needs to be 50 or 100 funds out there like Brand’s. People need to invest in it to make it real.” The big banks “are on board conceptually,” Fink adds, “but they’re not going to be first in line to make this investment. The first people in are people like me. I’m willing to take a chance that I will get the return, but I’m also trying to get the market started.” In emerging markets, the first investors reap the benefits. And in an eco-market, you reap what you don’t sow.

David Wolman wrote about high-speed railroads in issue 15.07. Original article from http://www.wired.com/
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Thursday, January 10, 2008

New Nanostructured Thin Film Shows Promise For Efficient Solar Energy Conversion


ScienceDaily (Jan. 10, 2008) — In the race to make solar cells cheaper and more efficient, many researchers and start-up companies are betting on new designs that exploit nanostructures--materials engineered on the scale of a billionth of a meter. Using nanotechnology, researchers can experiment with and control how a material generates, captures, transports, and stores free electrons--properties that are important for the conversion of sunlight into electricity.

Two nanotech methods for engineering solar cell materials have shown particular promise. One uses thin films of metal oxide nanoparticles, such as titanium dioxide, doped with other elements, such as nitrogen. Another strategy employs quantum dots--nanosize crystals--that strongly absorb visible light. These tiny semiconductors inject electrons into a metal oxide film, or "sensitize" it, to increase solar energy conversion. Both doping and quantum dot sensitization extend the visible light absorption of the metal oxide materials.

Combining these two approaches appears to yield better solar cell materials than either one alone does, according to Jin Zhang, professor of chemistry at the University of California, Santa Cruz. Zhang led a team of researchers from California, Mexico, and China that created a thin film doped with nitrogen and sensitized with quantum dots. When tested, the new nanocomposite material performed better than predicted--as if the functioning of the whole material was greater than the sum of its two individual components.

"We have discovered a new strategy that could be very useful for enhancing the photo response and conversion efficiency of solar cells based on nanomaterials," said Zhang.

"We initially thought that the best we might do is get results as good as the sum of the two, and maybe if we didn't make this right, we'd get something worse. But surprisingly, these materials were much better."

The group's findings were reported in the Journal of Physical Chemistry in a paper posted online on January 4. Lead author of the paper was Tzarara Lopez-Luke, a graduate student visiting in Zheng's lab who is now at the Instituto de Investigaciones Metalurgicas, UMSNH, Morelia, Mexico.

Zhang's team characterized the new nanocomposite material using a broad range of tools, including atomic force microscopy (AFM), transmission electron microscopy (TEM), Raman spectroscopy, and photoelectrochemistry techniques. They prepared films with thicknesses between 150 and 1100 nanometers, with titanium dioxide particles that had an average size of 100 nanometers. They doped the titanium dioxide lattice with nitrogen atoms. To this thin film, they chemically linked quantum dots made of cadmium selenide for sensitization.

The resulting hybrid material offered a combination of advantages. Nitrogen doping allowed the material to absorb a broad range of light energy, including energy from the visible region of the electromagnetic spectrum. The quantum dots also enhanced visible light absorption and boosted the photocurrent and power conversion of the material.

When compared with materials that were just doped with nitrogen or just embedded with cadmium selenide quantum dots, the nanocomposite showed higher performance, as measured by the "incident photon to current conversion efficiency" (IPCE), the team reported. The nanocomposite's IPCE was as much as three times greater than the sum of the IPCEs for the two other materials, Zhang said.

"We think what's happening is that it's easier for the charge to hop around in the material," he explained. "That can only happen if you have both the quantum dot sensitizing and the nitrogen doping at the same time."

The nanocomposite material could be used not only to enhance solar cells, but also to serve as part of other energy technologies. One of Zhang's long-term goals is to marry a highly efficient solar cell with a state-of-the-art photoelectrochemical cell. Such a device could, in theory, use energy generated from sunlight to split water and produce hydrogen fuel. The nanocomposite material could also potentially be useful in devices for converting carbon dioxide into hydrocarbon fuels, such as methane.

The new strategy for engineering solar cell materials offers a promising path for Zhang's lab to explore for years to come.

"I'm very excited because this work is preliminary and there's a lot of optimizing we can do now," Zhang noted. "We have three materials--or three parameters--that we can play with to make the energy levels just right."

In essence, the team has been trying to manipulate materials so that when sunlight strikes them, the free electrons generated can easily move from one energy level to another--or jump across the different materials--and be efficiently converted to electricity.

"What we're doing is essentially 'band-gap engineering.' We're manipulating the energy levels of the nanocomposite material so the electrons can work more efficiently for electricity generation," Zhang said. "If our model is correct, we're making a good case for this kind of strategy."

Sources of funding for this research included the U.S. Department of Energy, the National Science Foundation of China, and the University of California Institute for Mexico and the United States (UC-MEXUS).

Research collaborators included Abraham Wolcott, Li-ping Xu and Shaowei Chen at UCSC; Zhenhai Wen and Jinghong Li at Tsinghua University in Beijing, China; and Elder De La Rosa of the Centro de Investigaciones en Optica, A.C., in Leon, Guanajuato, Mexico.

Adapted from materials provided by University of California - Santa Cruz.

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Brighter LED Lights Could Replace Household Light Bulbs Within Three Years
January 10, 2008 — Researchers are developing new technology that could replace the household light-bulb within three years. Light Emitting Diodes (LEDs), already used in electrical equipment such as computers and ... > full story
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Tuesday, January 8, 2008

2008 Likely To Be One Of The Top-ten Warmest Years


ScienceDaily (Jan. 8, 2008) — 2008 is set to be cooler globally than recent years say Met Office and University of East Anglia climate scientists, but is still forecast to be one of the top-ten warmest years.

Each January the Met Office, in conjunction with the University of East Anglia, issues a forecast of the global surface temperature for the coming year. The forecast takes into account known contributing factors, such as El Niño and La Niña, increasing greenhouse gas concentrations, the cooling influences of industrial aerosol particles, solar effects and natural variations of the oceans.

Global temperature for 2008 is expected to be 0.37 °C above the long-term (1961-1990) average of 14.0 °C, the coolest year since 2000, when the value was 0.24 °C.

For 2008, the development of a strong La Niña in the tropical Pacific Ocean will limit the warming trend of the global climate. During La Niña, cold waters upwell to cool large areas of the ocean and land surface temperatures. The forecast includes for the first time a new decadal forecast using a climate model. This indicates that the current La Niña event will weaken only slowly through 2008, disappearing by the end of the year.

Prof. Chris Folland from the Met Office Hadley Centre said: "Phenomena such as El Niño and La Niña have a significant influence on global surface temperature and the current strong La Niña will act to limit temperatures in 2008. However, mean temperature is still expected to be significantly warmer than in 2000, when a similar strength La Niña pegged temperatures to 0.24 °C above the 1961-90 average. Sharply renewed warming is likely once La Niña declines."

These cyclical influences can mask underlying warming trends with Prof. Phil Jones, Director of the Climatic Research Unit, University of East Anglia, saying: "The fact that 2008 is forecast to be cooler than any of the last seven years (and that 2007 did not break the record warmth set on 1998) does not mean that global warming has gone away. What matters is the underlying rate of warming - the period 2001-2007 with an average of 0.44 °C above the 1961-90 average was 0.21 °C warmer than corresponding values for the period 1991-2000."

It is most unlikely that 2008 will be as warm as or warmer than the current warmest year of 1998, which was 0.52 °C above the long-term 1961-1990 average because it was dominated by an extreme El Niño.

Interannual variations of global surface temperature are strongly affected by the warming influences of El Niño events the cooling influences of La Niña events. The year 2007, with a provisionally assessed temperature of 0.41 °C (above long-term average), was colder than forecast. This was due to a much quicker than expected decline of a moderate El Niño that warms the climate, followed by the development of the strong cooling influence of the current La Niña.

The current La Niña event is now the strongest since 1999-2000. The lag between La Niña and the full global surface temperature response means that the cooling effect of La Niña is expected to be a little greater in 2008 than it was during 2007.

Over the eight years, 2000-2007, since the Met Office has issued forecasts of annual global temperature, the mean value of the forecast error was just 0.07 °C.

The Met Office Hadley Centre is the UK's foremost centre for climate change research. Partly funded by Defra (the Department for Environment, Food and Rural Affairs) and the Ministry of Defence.

Adapted from materials provided by Met Office Hadley Centre.

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Rare Albino Alligators Stolen in Brazil
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Alien Iguanas Fall From Florida Trees During Cold Snap
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"Their bodies shut off, and they lose their grip on the tree, and they start falling," a Miami zoo official said of the non-native reptiles.


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In a spectacular show of fire and smoke, Ecuador's Tungurahua volcano is forcing the evacuation of 1,000 nearby villagers.


Three New Salamanders Found in Remote Cloud Forests
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Seven rare albino alligators recently disappeared from a Brazilian zoo. Authorities suspect smugglers stole the reptiles, which are valued at more than $9,000 each.


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Saturday, January 5, 2008

North Atlantic Warming Tied To Natural Variability


ScienceDaily (Jan. 5, 2008) — A Duke University-led analysis of available records shows that while the North Atlantic Ocean's surface waters warmed in the 50 years between 1950 and 2000, the change was not uniform. In fact, the subpolar regions cooled at the same time that subtropical and tropical waters warmed.

This striking pattern can be explained largely by the influence of a natural and cyclical wind circulation pattern called the North Atlantic Oscillation (NAO), wrote authors of a study published Jan. 3, in Science Express, the online edition of the journal Science.

Winds that power the NAO are driven by atmospheric pressure differences between areas around Iceland and the Azores. "The winds have a tremendous impact on the underlying ocean," said Susan Lozier, a professor of physical oceanography at Duke's Nicholas School of the Environment and Earth Sciences who is the study's first author.

Other studies cited in the Science Express report suggest human-caused global warming may be affecting recent ocean heating trends. But Lozier and her coauthors found their data can't support that view for the North Atlantic. "It is premature to conclusively attribute these regional patterns of heat gain to greenhouse warming," they wrote.

"The take-home message is that the NAO produces strong natural variability," said Lozier in an interview. "The simplistic view of global warming is that everything forward in time will warm uniformly. But this very strong natural variability is superimposed on human-caused warming. So researchers will need to unravel that natural variability to get at the part humans are responsible for."

In research supported by the National Science Foundation in the United States and the Natural Environment Research Council in the United Kingdom, her international team analyzed 50 years of North Atlantic temperature records collected at the National Oceanic Data Center in Washington, D.C.

To piece together the mechanisms involved in the observed changes, their analysis employed an ocean circulation model that predicts how winds, evaporation, precipitation and the exchange of heat with the atmosphere influences the North Atlantic's heat content over time. They also compared those computer predictions to real observations "to test the model's skill," the authors wrote.

Her group's analysis showed that water in the sub-polar ocean --- roughly between 45 degrees North latitude and the Arctic Circle --- became cooler as the water directly exchanged heat with the air above it.

By contrast, NOA-driven winds served to "pile up" sun-warmed waters in parts of the subtropical and tropical North Atlantic south of 45 degrees, Lozier said. That retained and distributed heat at the surface while pushing underlying cooler water further down.

The group's computer model predicted warmer sea surfaces in the tropics and subtropics and colder readings within the sub-polar zone whenever the NAO is in an elevated state of activity. Such a high NAO has been the case during the years 1980 to 2000, the scientists reported.

"We suggest that the large-scale, decadal changes...associated with the NAO are primarily responsible for the ocean heat content changes in the North Atlantic over the past 50 years," the authors concluded.

However, the researchers also noted that this study should not be viewed in isolation. Given reported heat content gains in other oceans basins, and rising air temperatures, the authors surmised that other parts of the world's ocean systems may have taken up the excess heat produced by global warming.

"But in the North Atlantic, any anthropogenic (human-caused) warming would presently be masked by such strong natural variability," they wrote.

Other authors of the report included Richard Williams and Vassil Roussenov of Liverpool University; Susan Leadbetter, previously at Liverpool University but now a postdoctoral researcher with Lozier; Mark Reed, a computational scientist who also works with Lozier at Duke; and Nathan Moore, a former Duke graduate student now at Michigan State University.

Adapted from materials provided by Duke University.

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Why Do Some Animals Live Longer Than Others?
January 5, 2008 — Why do some live longer than others? Researchers turned to tropical African butterflies to find the answer. In the field, the temperature experienced by the caterpillar sets up the butterfly to ... > full story
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