Report says soot is neglected in climate debate, and reducing particles polluting the air could cut global warming by 0.5C
Fiona Harvey guardian.co.uk, Wednesday 23 February 2011 17.59 GMT
Cutting the amount of soot we pour into the atmosphere, and emissions of methane from agriculture, would be one of the most powerful ways to tackle climate change (pdf) , a new report from the United Nations environment programme (Unep) has concluded.
Preventing "black carbon" – particles of soot from industry and cooking fires – from polluting the air would help to cut global warming by as much as 0.5C, and reduce warming in the Arctic by about two thirds by 2030. Scientists say a rise in temperature of about 2C is the limit of safety, beyond which climate change would become catastrophic and irreversible.
Black carbon, methane and ozone are known as "short-lived climate forcers", because they have a strong warming effect but do not persist in the atmosphere as long as carbon dioxide, which has been the main focus of international emissions-cutting efforts until now.
Soot is a particular problem because when it falls on snow and ice it darkens the surface, increasing the absorption of sunlight, in turn hastening the melting process. Black carbon has been shown to have a dramatic effect in the rapid melting of the Arctic, and affects the water cycle in regions such as the Himalayas.
But a variety of measures could be put in place relatively easily that would dramatically reduce these short-lived emissions. For instance, fitting diesel vehicles with exhaust-pipe filters, using clean-burning stoves in place of open wood fires, capturing methane from coal mines and landfill sites, and banning the burning of agricultural waste in fields.
A key reason for pursuing the short-lived emissions is that it could be a quick gain, in contrast to carbon policies which take years to have an effect. "The very good news is that, unlike carbon dioxide and other long-lived greenhouse gas emissions, where cuts will require many decades before temperature reductions can be measured, mitigation strategies for reducing short-lived climate forcers can be implemented quickly, and positive results can be expected over a much shorter time frame," says Ellen Baum, senior scientist at the Clean Air Task Force, a campaigning group in the US.
Unep concludes: "Widespread implementation is achievable with existing technology but would require significant strategic investment and institutional arrangements."
Cost is a key issue, adds Baum. Fitting filters and other technology adds an extra burden to car manufacturers or vehicle owners, for instance. Another obstacle is the lack of availability of clean-burning stoves and alternatives such as solar stoves.
In some countries, new regulations are bringing down emission rates. Baum points to China and Vietnam, where soot from brick kilns is now coming under strict regulations.
Governments should wake up to the advantages of tackling the short-lived emissions, according to Unep. Measures to reduce soot would have many additional benefits, such as improvements to health from lower air pollution.
Unep estimates that if its recommendations are fully adopted, 2.4 million premature deaths could be avoided annually and the global production of staple crops including wheat, rice and soybean would be 1% to 4% higher each year.
Tuesday, 22 February 2011
Researchers Create Novel Light-Emitting Material
February 17, 2011 – 1:05 pm
Researchers have developed pure organic phosphorescent crystals.
Pure organic compounds that glow in jewel tones could potentially be used in biosensors and in new types of display screens. University of Michigan researcher Jinsang Kim and his colleagues have developed the new class of material that shines with phosphorescence—a property that has previously been seen only in non-organic compounds or organometallics.
Kim and his colleagues made metal-free organic crystals that are white in visible light and radiate blue, green, yellow and orange when triggered by ultraviolet light. By changing the materials’ chemical composition, the researchers can make them emit different colours.
The new luminous materials, or phosphors, could improve upon current organic light-emitting diodes (OLEDs) and solid-state lighting. Bright, low-power OLEDs are used in some small screens on cell phones or cameras.
“Purely organic materials haven’t been able to generate meaningful phosphorescence emissions. We believe this is the first example of an organic that can compete with an organometallic in terms of brightness and color tuning capability,” says Kim, an associate professor of materials science and engineering, chemical engineering, macromolecular science and engineering, and biomedical engineering.
The new phosphors exhibit “quantum yields” of 55%. Quantum yield, a measure of a material’s efficiency and brightness, refers to how much energy an electron dissipates as light instead of heat as it descends from an excited state to a ground state. Current pure organic compounds have a yield of essentially zero.
In Kim’s phosphors, the light comes from molecules of oxygen and carbon known as “aromatic carbonyls,” compounds that produce phosphorescence, but weakly and under special circumstances such as extremely low temperatures. What’s unique about these new materials is that the aromatic carbonyls form strong halogen bonds with halogens in the crystal to pack the molecules tightly. This arrangement suppresses vibration and heat energy losses as the excited electrons fall back to the ground state, leading to strong phosphorescence.
This new method offers an easier way to make high-energy blue organic phosphors, which are difficult to achieve with organometallics.
“This is in the beginning stage, but we expect that it will not be long before our simple materials will be available commercially for device applications,” Kim says.
Former doctoral student Kangwon Lee discovered the unique properties of these materials while developing a biosensor—a compound that detects biological molecules and can be used in medical testing and environmental monitoring. The phosphors have applications in this area as well.
The university is pursuing patent protection for the intellectual property, and is seeking commercialisation partners to help bring the technology to market.
More information on the jewel-toned organic phosphorescent crystals is research is available from the University of Michigan.
Researchers have developed pure organic phosphorescent crystals.
Pure organic compounds that glow in jewel tones could potentially be used in biosensors and in new types of display screens. University of Michigan researcher Jinsang Kim and his colleagues have developed the new class of material that shines with phosphorescence—a property that has previously been seen only in non-organic compounds or organometallics.
Kim and his colleagues made metal-free organic crystals that are white in visible light and radiate blue, green, yellow and orange when triggered by ultraviolet light. By changing the materials’ chemical composition, the researchers can make them emit different colours.
The new luminous materials, or phosphors, could improve upon current organic light-emitting diodes (OLEDs) and solid-state lighting. Bright, low-power OLEDs are used in some small screens on cell phones or cameras.
“Purely organic materials haven’t been able to generate meaningful phosphorescence emissions. We believe this is the first example of an organic that can compete with an organometallic in terms of brightness and color tuning capability,” says Kim, an associate professor of materials science and engineering, chemical engineering, macromolecular science and engineering, and biomedical engineering.
The new phosphors exhibit “quantum yields” of 55%. Quantum yield, a measure of a material’s efficiency and brightness, refers to how much energy an electron dissipates as light instead of heat as it descends from an excited state to a ground state. Current pure organic compounds have a yield of essentially zero.
In Kim’s phosphors, the light comes from molecules of oxygen and carbon known as “aromatic carbonyls,” compounds that produce phosphorescence, but weakly and under special circumstances such as extremely low temperatures. What’s unique about these new materials is that the aromatic carbonyls form strong halogen bonds with halogens in the crystal to pack the molecules tightly. This arrangement suppresses vibration and heat energy losses as the excited electrons fall back to the ground state, leading to strong phosphorescence.
This new method offers an easier way to make high-energy blue organic phosphors, which are difficult to achieve with organometallics.
“This is in the beginning stage, but we expect that it will not be long before our simple materials will be available commercially for device applications,” Kim says.
Former doctoral student Kangwon Lee discovered the unique properties of these materials while developing a biosensor—a compound that detects biological molecules and can be used in medical testing and environmental monitoring. The phosphors have applications in this area as well.
The university is pursuing patent protection for the intellectual property, and is seeking commercialisation partners to help bring the technology to market.
More information on the jewel-toned organic phosphorescent crystals is research is available from the University of Michigan.
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