Cyclones in the Indian Ocean: Facts and figures

Greg O'Hare explains the what, why, when and how of cyclones, and reviews their effects in South Asia.

'Tropical cyclone' is the general term for low-pressure atmospheric circulations in the tropics. These have anticlockwise rotating winds in the northern hemisphere and clockwise rotating winds in the southern hemisphere.

Low to moderate intensity tropical cyclones bring much needed rain for agriculture around the northern Indian Ocean. But, when tropical cyclones strengthen, they can bring great loss of life and property to the region.

Cyclonic structures

All tropical cyclones have low atmospheric pressure at ground level, and a vortex of converging winds and rising air. They all have extensive rain-bearing layered clouds (deep nimbostratus) and towering vertically extensive cumulonimbus rain-bearing clouds. Yet despite these common features, tropical cyclones in South Asia vary greatly in size, frequency and intensity, and have varying effects on the land they cross.

Table 1 shows four types of tropical cyclones. These weather systems form a continuum — if conditions are right and surface pressure continually falls, a tropical low can develop over time into a tropical depression, then into a tropical storm and eventually into an intense tropical storm. In South Asia, as in the western world, the most intense tropical storms are called hurricanes. But, confusingly, the most intense circulations in the Pacific are called cyclones.

 

Type of tropical cyclonic system	Speed (m/sec)	Height (km)	Duration (days)	Width (km)	Frequency	Rainfall (cm)
Low	<8	2–4	1–3	150–300	frequent	5–10
Depression	8–17	4–8	2–5	250–500	common	10–20
Storm	17–32	8–10	3–10	300–600	occasional	20–50
Hurricane	>32	8–12	5–7	400–1000	rare	50–150

Table 1: Types of tropical cyclones in India [1]

Lows and depressions are the most frequent systems and produce most of India's annual rainfall (about 890mm). Indeed, with their lower intensity rainfalls, they form the backbone of South Asian agriculture.

But when a long series of deep tropical depressions occur (lasting three to four weeks), the cumulative rainfall can lead to extensive flooding, dam collapses and landslides. In southern Bangladesh, more than 100 families were washed away when a dam collapsed in July 2004. In 2008, summer monsoon flooding and landslides in India (especially in Bihar State) killed 1065 people and affected approximately 7.9 million people.

How do hurricanes form?

Tropical cyclones affecting south Asia originate over surrounding oceans, especially in the Bay of Bengal. They require at least five conditions to form and develop: low pressure at the surface; abundant moist air capable of convective or upward movement in the atmosphere; ocean surface temperatures over 26–27 degrees Celsius; small wind shear — the rate at which wind strength and direction change with height in the atmosphere — (especially for the taller more intense systems); and the power of the Earth's rotation to spin the system into a rotating vortex.

Tropical cyclones in South Asia derive their main energy from intense evaporation over warm water — not, as in mid-latitude cyclones, from contrasting temperatures between cold and warmer air masses.

Water vapour, evaporated from the sea, is drawn into the developing cyclone. As the rising air within the cyclone cools, the evaporated moisture becomes cloud, forming billions of tiny water droplets. Converting the water vapour to water droplets releases a great amount of (latent) heat, providing energy that helps invigorate and maintain the cyclone's development.

Timing and monsoon regulation

The tropical cyclones that influence South Asia are part of the regional monsoon wind system. The South Asian monsoon has moist south-westerly winds blowing from the southern oceans over the South Asian continental land mass in summer, and dry north-easterly winds blowing in the opposite direction in winter.

The differential heating of land and sea drives this movement. In the summer, the land heats up more quickly than the oceans, producing low pressure over land and high pressure at sea. Winds blow from high to low pressure, bringing strong, moist winds from the oceans towards South Asia. During the winter months, the differential heating and pressure systems are reversed, and strong dry north-easterly winds end up blowing from South Asia towards the southern oceans.

Most rainfall over the region comes in the summer months (June to September) from relatively weak but frequent tropical lows and depressions. Driven by monsoon winds, these systems eventually move over land along the west coast of India, but more frequently affect the eastern coast of India and Bangladesh.

The more intense tropical storms and hurricanes, which also tend to form mainly in the Bay of Bengal, often occur as the wet summer changes to a dry winter monsoon (October to November) when wind shear is low. Powerful cyclones, which tower up into the atmosphere, do not easily form during the main monsoon season (June to September) because high wind shear easily destabilises them, knocking them over.

Hurricane damage

The areas of South Asia most vulnerable to hurricanes are the low-lying coastal regions around the Bay of Bengal (Bangladesh, Eastern India and Myanmar). These are the first areas storms hit when they reach land and are also some of the most agriculturally fertile — and densely populated — areas in South Asia, including coastal river deltas like the Godavari, Ganges and Irrawaddy.

Hurricanes' high wind speeds, intense rainfalls and storm surges (unusually high sea levels) destroy life and property, and can leave areas devastated. Winds, often travelling at more than 117 kilometres per hour, remove or seriously damage flimsy housing.

High intensity rainfall over a relatively short period (up to and above 50 centimetres over three to seven days) can cause serious flooding and major crop loss. As with the less intense cyclones, such flooding can increase loss of life and property if it causes reservoir collapses and landslides.

But the most destructive part of a cyclone is the storm surge at the front of the storm pushed up to high levels as it moves inland. Storm surges from powerful hurricanes can reach two to five metres in height along the eastern coast of Andhra Pradesh in India. At the head of the Bay of Bengal, where the coastline becomes restricted, storm surges can reach a staggering 12 or 13 metres and kill many people (see Table 2).

Region	Date	Deaths
Andhra Pradesh	10 Oct 1679	20,000
Bangladesh	07 Oct 1737	300,000
Bangladesh	13 Nov 1970	500,000
Andhra Pradesh	26 Nov 1977	>10,000
West Bengal	29 Apr 1991	140,000

Table 2: Hurricane deaths in the Bay of Bengal region [1]

Hurricanes in a warming world

There is every chance that hurricanes will do more damage in South Asia in the future as population densities increase in coastal areas. The numbers of people at risk may also rise if hurricanes become more intense as the world and oceans warm up.

Some studies have found no evidence for an increase in hurricanes' frequency or intensity in the Caribbean. [2,3] Others have found little change in the frequency and intensity of hurricanes globally during the last 20 years. [4]

By contrast, other strong evidence based on good quality data has shown that in recent years hurricanes, particularly the stronger ones (categories four and five), have become more intense in all hurricane regions, including the northern Indian Ocean (Table 3). [5,6]

Basin	1975–1989		1990–2004
	No.	Percentage of all hurricanes	No.	Percentage of all hurricanes
East Pacific	36	25	49	35
West Pacific	85	25	116	41
North Atlantic	16	20	25	25
South West Pacific	10	12	22	28
Indian Ocean	24	13	57	29

Table 3: Changes in the number and percentage of category four and five hurricanes for the periods 1975–89 and 1990–2004 for different ocean basins. [5]

Vulnerable populations

The people most vulnerable to hurricanes around the world include those with limited economic resources, low levels of technology, poor information and skills, minimal infrastructure and unstable or weak political institutions (Table 4). Such groups are not fully able to prepare for, or protect themselves from, hurricanes, nor to respond and cope with their effects.

Low cast communities

Ethnic minorities

Women, especially those who may be widowed or deserted

Old men and women

Children, particularly girls

The disabled

People dependent on low incomes

People in debt

People isolated from transport, communication and health services infrastructure

Table 4: Disaster prone groups in India [1]

When a category four hurricane hit the Godavari delta region of eastern India in November 1986, various marginalised groups responded differently to the hurricane's impact. For example, poor female agricultural labourers working in flood damaged rice fields had to sell their few possessions and become maids in nearby villages, or migrate to other paddy regions in order to cope. By contrast, poor fishing communities along the delta coast (where many people died due to storm surges) relied on close family and kinship links for money, food and fishing tackle to get over the storm's effects.

Basic precautions

There are ways to make the likely rise in hurricane impact less damaging in the region. One solution is to improve the physical structures that protect people. For example, many new hurricane shelters are being built along the coast of eastern India. Deaths from hurricanes will certainly decline if more local people can be encouraged to use the shelters.

Improvements in government-built early warning and evacuation procedures will also help save lives, although access to these may be limited because many communities suffer from isolation, language barriers, and poor transport and communication (including radio/phone) systems. Still, because of improvements, albeit slow, in the introduction and uptake of such systems, hurricanes that would have killed 10,000 people in Andhra Pradesh in the late 1970s kill around 1,000 today.

Governments and international agencies can also do a lot more to mitigate storm impacts through rehabilitation policies, such as providing basic relief (food, shelter, cooking oil and clean water). It is also crucial that affected communities get better health services, since the spread of water-borne diseases (like typhoid and dysentery) after hurricanes often kills far more people than flooding, landslides or even storm surges.

Greg O'Hare is a professor of geography at the University of Derby, United Kingdom.

REFERENCES

[1] O'Hare, G. Hurricane 07b in the Godavari Delta, Andhra Pradesh, India: vulnerability, mitigation and the spatial impact. The Geographical Journal167, 23–38 (2001)

[2] Michaels P.J., Knappenberger, P.C. & Davis, R.E. Sea surface temperatures and tropical cyclones in the Atlantic basin. Geophysical Research Letters 33, (2006)

[3] Hoyos, C.D., Agudelo, P.A., Webster, P.J. et al. Deconvolution of the factors contributing to the increase in global hurricane intensity. Science 312, 94–97 (2006)

[4] Klotzbach, P.J. Trends in global cyclone activity over the past 20 years (1986-2005) Geophysical Research Letters 33, (2006)

[5] Webster P.J., Holland, G.J., Curry, J.A. et al. Changes in tropical cyclone number, duration and intensity in a warming environment. Science 309, 1844–1846 (2005)

[6] Elsner, J.B., Kossin, J.P. & Jagger, T.H. The increasing intensity of the strongest tropical cyclones. Nature 455, 92–95 (2008)

 

 

RISING TEMPERATURES, MORE EXTREME WEATHER

The planet's temperature is rising, and it's rising at an accelerated pace that most scientists say is down to manmade factors. As the climate changes, they predict it will lead to more dramatic weather and disasters - not just droughts, but storms, floods and spreading disease too.
Climate change increases risk of conflict 250 million people could be displaced by climate-related disasters by 2050 The world's poor - the most vulnerable to climage change - need help adapting

Statistics from the International Disaster Database show a steep rise in weather-related disasters since the middle of the 20th century, and the number of people affected is also going up. The Intergovernmental Panel on Climate Change (IPCC) says the world can expect more heatwaves and droughts, heavier rains, stronger storms and rising sea levels due to global warming caused by emissions of greenhouse gases.

Africa, Latin America and parts of Asia - where the climate is already more extreme and arid regions are common - are likely to be most affected as rainfall declines and its timing becomes less predictable. Large numbers of people could be forced to find new homes as their living environments are submerged, or food and water become scarce. British-based aid and development agency Christian Aid quotes a scientist's estimate that up to 250 million people could be displaced by climate-related disasters by the middle of the century. And experts say diseases will spread to new places as the planet changes. In 2007, the Nobel Peace Prize was awarded jointly to the IPCC and former U.S. Vice President Al Gore for their work in building up and spreading knowledge about climate change. This underlined growing awareness of the potential impact climate change could have on security. Most experts say tensions caused by the environmental impact of climate change won't necessarily lead to conflict - but where they add to or make other stresses worse, there is an increased risk of violence. There's intense debate and a wide range of competing ideas on how to tackle what could be the most important issue of our time. Many developing countries believe richer nations should make greater commitments to curbing their carbon emissions, and provide more funding to help them adapt to climate change.
In December 2007, at a major meeting in Bali, nearly 200 nations agreed to launch negotiations on a new pact to follow the Kyoto Protocol, which binds rich nations to cap emissions of greenhouse gases until 2012. The United States is the only industrialised country that has not signed the Kyoto Protocol. Aid agencies are also waking up to the impact of climate change on their projects and the communities with which they work. Increasingly, they are helping local people reduce the risk of climate-related disasters, and calling for more international support to cope with the negative consquences of climate change.

Source: Reuters

Glaciers Are Melting Faster Than Expected, UN Reports

ScienceDaily (Mar. 18, 2008) — The world's glaciers are continuing to melt away with the latest official figures showing record losses, the UN Environment Programme (UNEP) announced today

Hanging glaciers on Dome Blanc Langtang Himal, Himalayas, Nepal. Himalayan glaciers are receding in a similar way as glaciers in other mountain ranges at low latitudes. Many glaciers in these areas could disappear within the coming decades. (Credit: iStockphoto/Steve Estvanik)

Data from close to 30 reference glaciers in nine mountain ranges indicate that between the years 2004-2005 and 2005-2006 the average rate of melting and thinning more than doubled.
The findings come from the World Glacier Monitoring Service (WGMS), a centre based at the University of Zurich in Switzerland and that is supported by UNEP. It has been tracking the fate of glaciers for over a century. Continuous data series of annual mass balance, expressed as thickness change, are available for 30 reference glaciers since 1980. Prof. Dr. Wilfried Haeberli, Director of the Service said: "The latest figures are part of what appears to be an accelerating trend with no apparent end in sight." The Service calculates thickening and thinning of glaciers in terms of 'water equivalent'. The estimates for the year 2006 indicate that further shrinking took place equal to around 1.4 metres of water equivalent compared to losses of half a metre in 2005. "This continues the trend in accelerated ice loss during the past two and a half decades and brings the total loss since 1980 to more than 10.5 metres of water equivalent," said Professor Haberli. During 1980-1999, average loss rates had been 0.3 metres per year. Since the turn of the millennium, this rate had increased to about half a metre per year.
The record loss during these two decades – 0.7 metres in 1998 – has now been exceeded by three out of the past six years: 2003, 2004 and 2006. On average, one metre water equivalent corresponds to 1.1 metres in ice thickness indicating a further shrinking in 2006 of 1.5 actual metres and since 1980 a total reduction in thickness of ice of just over 11.5 metres or almost 38 feet. Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: "Millions if not billions of people depend directly or indirectly on these natural water storage facilities for drinking water, agriculture, industry and power generation during key parts of the year," said Mr Steiner. "There are many canaries emerging in the climate change coal mine. The glaciers are perhaps among those making the most noise and it is absolutely essential that everyone sits up and takes notice," he said. "To an important and significant extent that is already happening—indeed the elements of a Green Economy are already emerging from the more than $100 billion being invested in renewable energies to the responsible investment principles endorsed by 300 financial institutions with $13 trillion-worth of assets," said Mr Steiner. "The litmus test will come in late 2009 at the climate convention meeting in Copenhagen. Here governments must agree on a decisive new emissions reduction and adaptation-focused regime. Otherwise, and like the glaciers, our room for man oeuvre and the opportunity to act may simply melt away," he added. The WGMS findings also contain figures from around 100 glaciers, of which 30 form the core assessment, found in Antarctica, Asia, Europe, North America, Latin America and the Pacific. Some of the most dramatic shrinking has taken place in Europe with Norway's Breidalblikkbrea glacier thinning by close to 3.1 metres (2.9 metre water equivalent) during 2006 compared with a thinning of 0.3 metres (0.28 metres water equivalent) in the year 2005.
Other dramatic shrinking has been registered at Austria's Grosser Goldbergkees glacier, 1.2 metres in 2006 versus 0.3 in 2005; France's Ossoue glacier, nearly 3 metres versus around 2.7 metres in 2005; Italy's Malavalle glacier 1.4 metres versus around 0.9 metres in 2005; Spain's Maladeta glacier, nearly 2 metres versus 1.6 metres in 2005; Sweden's Storglaciaeren glacier, 1.8 metres versus close to 0.080 metres in 2005 and Switzerland's Findelen glacier, 1.3 metres versus 0.22 metres in 2005. Not all of the close to 100 glaciers monitored posted losses with some thickening during the same period including Chile's Echaurren Norte glacier while others, such as Bolivia's Chacaltaya glacier; Canada's Place glacier; India's Hamtah glacier and the Daniels and Yawning glaciers in the Untied States shrank less in 2006 than they did in 2005. However, for the close to 30 reference glaciers only one (Echaurren Norte in Chile) thickened over the same period.
Melting glaciers and water needs
Himalayan glaciers are receding in a similar way as glaciers in other mountain ranges at low latitudes. Many glaciers in these areas could, at current rates of global warming, disappear within the coming decades. Half a billion people in the Himalaya-Hindu-Kush region and a quarter billion downstream who rely on glacial melt waters could be seriously affected. The current trends in glacial melt suggest that the Ganga, Indus, Brahmaputra and other rivers that criss-cross the northern Indian plain may become seasonal rivers in the near future as a consequence of climate change with important ramifications for poverty and the economies in the region. North America: "Heavily-utilized water systems of the western US and Canada, such as the Columbia River, that rely on capturing snowmelt runoff will be especially vulnerable," says the Fourth report of IPCC Working Group II. A two degree C warming by the 2040s is likely to lead to sharply reduced summer flows coinciding with sharply rising demand. The report estimates that Portland, Oregon will by then require over 26 million additional cubic meters of water as a result of climate change and population growth. This will coincide with a fall in summer supplies from the Columbia River by an estimated five million cubic meters. Meanwhile, just over 40 per cent of the supply to southern California is likely to be vulnerable by the 2020s due to warming triggering losses of the Sierra Nevada and Colorado River basin snow pack. In Latin America, the IPCC warns of a melting of most tropical glaciers in the near future (2020-2030). The glacier retreat trend reported in the Third Assessment Report of the IPCC is continuing and reaching critical conditions in Bolivia, Peru, Colombia and Ecuador.

Recent studies indicate that most of the South American glaciers from Colombia to Chile and Argentina (up to 25ºS) are drastically reducing their volume at an accelerated rate. Changes in temperature and humidity are the primary cause for the observed glacier retreat during the 2nd half of the 20th century in the tropical Andes. In the next 15 years inter-tropical glaciers are very likely to disappear, affecting water availability and hydropower generation.
Adapted from materials provided by U.N. Environment Programme.

Source: http://www.sciencedaily.com/releases/2008/03/080317154235.htm

Will Global Warming Increase Plant Frost Damage?

ScienceDaily (Mar. 4, 2008) — Widespread damage to plants from a sudden freeze that occurred across the Eastern United States from 5 April to 9 April 2007 was made worse because it had been preceded by two weeks of unusual warmth, according to an analysis published in the March 2008 issue of BioScience. The authors of the report, Lianhong Gu and his colleagues at the Oak Ridge National Laboratory and collaborators at NASA, the University of Missouri, and the National Oceanic and Atmospheric Administration, found that the freeze killed new leaves, shoots, flowers, and fruit of natural vegetation, caused crown dieback of trees, and led to severe damage to crops in an area encompassing Nebraska,Maryland,SouthCarolina,andTexas.

Subsequent drought limited

regrowth.Valentia orange tree damaged

by frost. Global warming may result in

increased plant frost damage.

(Credit:Stockphoto/Loretta Hostettler)

Rising levels of atmospheric carbon dioxide are believed to reduce the ability of some plants to withstand freezing, and the authors of the BioScience study suggest that global warming could lead to more freeze and thaw fluctuations in future winters. This pattern is potentially dangerous for plants because many species must acclimate to cold over a sustained period. Acclimation enables them to better withstand freezes, but unusual warmth early in the year prevents the process. A cold spring in 1996, in contrast to the 2007 event, caused little enduring damage because it was not preceded by unusual warmth.
The 2007 freeze is likely to have lasting effects on carbon balance in the region. Plants cannot resorb nutrients from dead tissue that would normally be remobilized within the plants during autumnal senescence, so many nutrients became less available for plants in 2008. Wildlife is expected to have suffered harm from lack of food, and changes to plant architecture could have long-term implications.
Gu and his colleagues propose that the 2007 spring freeze should not be viewed as an isolated event, but as a realistic climate-change scenario. Further study of its long-term consequences could help refine scenarios for ecosystem changes as carbon dioxide levels increase and the climate warms.
Reference: The 2007 Eastern US Spring Freeze: Increased Cold Damage in a Warming World. Lianhong Gu, Paul J. Hanson, W. Mac Post, Dale P. Kaiser, Bai Yang, Ramakrishna Nemani, Stephen G. Pallardy, and Tilden Meyers
Adapted from materials provided by American Institute of Biological Sciences.

Source: http://www.sciencedaily.com/releases/2008/03/080303072651.htm

Promising New Material For Capturing Carbon Dioxide From Smokestacks

ScienceDaily (Mar. 4, 2008) — Scientists and engineers in Georgia and Pennsylvania are reporting development of a new, low-cost material for capturing carbon dioxide from the smokestacks of coal-fired electric power plants and other industrial sources before the notorious greenhouse gas enters the atmosphere.

In the new study, Christopher W. Jones and colleagues point out that existing carbon capture technology is unsuitable for wide use. Absorbent liquids, for instance, are energy intensive and expensive. Current solid adsorbents show promise, but many suffer from low absorption capacities and lack stability after extended use. Stronger, longer-lasting materials are needed, scientists say.
The scientists describe development of a new solid adsorbent coined a hyperbranched aminosilica (HAS) that avoids those problems. When compared to traditional solid adsorbents under simulated emissions from industrial smokestacks, the new material captured up to seven times more carbon dioxide than conventional solid materials, including some of the best carbon dioxide adsorbents currently available, the researchers say. The material also shows greater stability under different temperature extremes, allowing it to be recycled numerous times.
The article "Designing Adsorbents for CO2 Capture from Flue Gas-Hyperbranched Aminosilicas Capable of Capturing CO2 Reversibly" is scheduled for the March 19 issue of the ACS' Journal of the American Chemical Society.
Adapted from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Source: http://www.sciencedaily.com/releases/2008/03/080303163804.htm

Increased Hurricane Losses Due To More People, Wealth Along Coastlines, Not Stronger Storms

ScienceDaily (Mar. 1, 2008) — A team of scientists have found that the economic damages from hurricanes have increased in the U.S. over time due to greater population, infrastructure, and wealth on the U.S. coastlines, and not to any spike in the number or intensity of hurricanes

“We found that although some decades were quieter and less damaging in the U.S. and others had more land-falling hurricanes and more damage, the economic costs of land-falling hurricanes have steadily increased over time,” said Chris Landsea, one of the researchers as well as the science and operations officer at NOAA’s National Hurricane Center in Miami. “There is nothing in the U.S. hurricane damage record that indicates global warming has caused a significant increase in destruction along our coasts.”
In a newly published paper in Natural Hazards Review, the researchers also found that economic hurricane damage in the U.S. has been doubling every 10 to 15 years. If more people continue to move to the hurricane-prone coastline, future economic hurricane losses may be far greater than previously thought.
“Unless action is taken to address the growing concentration of people and property in coastal hurricane areas, the damage will increase by a great deal as more people and infrastructure inhabit these coastal locations,” said Landsea.
The Natural Hazards Review paper, “Normalized Hurricane Damage in the United States: 1900-2005,” was written by Roger A. Pielke Jr. (University of Colorado), Joel Gratz (ICAT Managers, Inc.), Chris Landsea, Douglas Collins (Tillinghast-Towers Perrin), Mark A. Saunders (University College London), and Rade Musulin (Aon Re Australia).
The team used two different approaches, which gave similar results, to estimate the economic damages of historical hurricanes if they were to strike today, building upon the work published originally by Landsea and Pielke in 1998, and by Collins and Lowe in 2001. Both methods used changes in inflation and wealth at the national level. The first method utilized population increases at the county coastal level, while the second used changes in housing units at the county coastal level.
The results illustrate the effects of the tremendous pace of growth in vulnerable hurricane areas. If the 1926 Great Miami Hurricane were to hit today, the study estimated it would cause the largest losses at $140 billion to $157 billion, with Hurricane Katrina second on the list at $81 billion.
The team concludes that potential damage from storms – currently about $10 billion yearly – is growing at a rate that may place severe burdens on exposed communities, and that avoiding huge losses will require a change in the rate of population growth in coastal areas, major improvements in construction standards, or other mitigation actions.
Adapted from materials provided by National Oceanic And Atmospheric Administration.

Source:http://www.sciencedaily.com/releases/2008/02/080228074324.htm

12 simple things you can do... for combating Climate Change

Source: UNDP India

Human Development Report (HDR) 2007-2008

2007/2008 Human Development Report tackles climate change27 November - The report warns that the world should focus on the development impact of climate change, which could bring unprecedented reversals in poverty reduction, nutrition, health and education.
Download the HDR here
http://www.undp.org.in/index.php?option=com_content&task=view&id=312&Itemid=481

New Materials Can Selectively Capture Carbon Dioxide, Chemists Report

ScienceDaily (Feb. 17, 2008) — UCLA chemists report a major advance in reducing heat-trapping carbon dioxide emissions in the Feb. 15 issue of the journal Science.

The scientists have demonstrated that they can successfully isolate and capture carbon dioxide, which contributes to global warming, rising sea levels and the increased acidity of oceans. Their findings could lead to power plants efficiently capturing carbon dioxide without using toxic materials. "The technical challenge of selectively removing carbon dioxide has been overcome," said Omar M. Yaghi, UCLA's Christopher S. Foote Professor of Chemistry and co-author of the Science paper. "Now we have structures that can be tailored precisely to capture carbon dioxide and store it like a reservoir, as we have demonstrated. No carbon dioxide escapes. Nothing escapes -- unless you want it to do so. We believe this to be a turning point in capturing carbon dioxide before it reaches the atmosphere." The carbon dioxide is captured using a new class of materials designed by Yaghi and his group called zeolitic imidazolate frameworks, or ZIFs. These are porous and chemically robust structures, with large surface areas, that can be heated to high temperatures without decomposition and boiled in water or organic solvents for a week and still remain stable. Rahul Banerjee, a UCLA postdoctoral research scholar in chemistry and Anh Phan, a UCLA graduate student in chemistry, both of whom work in Yaghi's laboratory, synthesized 25 ZIF crystal structures and demonstrated that three of them have high selectivity for capturing carbon dioxide (ZIF-68, ZIF-69, ZIF-70). "The selectivity of ZIFs to carbon dioxide is unparalleled by any other material," said Yaghi, who directs of UCLA's Center for Reticular Chemistry and is a member of the California NanoSystems Institute at UCLA. "Rahul and Anh were so successful at making new ZIFs that, for the purposes of reporting the results, I had to ask them to stop." The inside of a ZIF can store gas molecules. Flaps that behave like the chemical equivalent of a revolving door allow certain molecules -- in this case, carbon dioxide -- to pass through and enter the reservoir while blocking larger molecules or molecules of different shapes. "We can screen and select the one type of molecule we want to capture," Phan said. "The beauty of the chemistry is that we have the freedom to choose what kind of door we want and to control what goes through the door." "The capture of carbon dioxide creates cleaner energy," Yaghi said. "ZIFs in a smokestack would trap carbon dioxide in the pores prior to its delivery to its geologic storage space." In ZIFs 68, 69 and 70, Banerjee and Phan emptied the pores, creating an open framework. They then subjected the material to streams of gases -- carbon dioxide and carbon monoxide, for example, and another stream of carbon dioxide and nitrogen -- and were able to capture only the carbon dioxide. They are testing other ZIFs for various applications. Carbon dioxide is killing corral reefs and marine life, damage that will be irreversible, at least for many centuries, Yaghi noted. Currently, the process of capturing carbon dioxide emissions from power plants involves the use of toxic materials and requires 20 to 30 percent of the plant's energy output, Yaghi said. By contrast, ZIFs can pluck carbon dioxide from other gases that are emitted and can store five times more carbon dioxide than the porous carbon materials that represent the current state-of-art. "For each liter of ZIF, you can hold 83 liters of carbon dioxide," Banerjee said. The word zif, Yaghi noted, is used in the Bible to describe a region of splendor. It also means comeliness and brightness. This name is fitting for this new class of materials, he said, because its members are many and of quite beautiful constructions. On a fundamental level, the invention of ZIFs has also addressed two major challenges in zeolite science. Zeolites are stable, porous minerals made of aluminum, silicon and oxygen that are employed in petroleum refining and are used in detergents and other products. Yaghi's group has succeeded in replacing what would have been aluminum or silicon with metal ions like zinc and cobalt, and the bridging oxygen with imidazolate to yield ZIF materials, whose structures can now be designed in functionality and metrics. Banerjee and Anh automated the process of synthesis. Instead of mixing the chemicals one reaction at a time and achieving perhaps several reactions per day, they were able to perform 200 reactions in less than an hour. The pair ran 9,600 microreactions and from those reactions uncovered 25 new structures. "We keep producing new crystals of ZIFs every day," Banerjee said. "These reactions produce crystals that look as beautiful as diamonds." Co-authors are Bo Wang, a UCLA graduate student in chemistry in Yaghi's laboratory; Carolyn Knobler and Hiroyasu Furukawa of the Center for Reticular Chemistry at the UCLA's California NanoSystems Institute; and Michael O'Keeffe of Arizona State University's department of chemistry and biochemistry. In the early 1990s, Yaghi invented another class of materials called metal-organic frameworks (MOFs), which have been described as crystal sponges and which also have implications for cleaner energy. Yaghi can change the components of MOFs nearly at will. Like ZIFs, MOFs have pores -- openings on the nanoscale in which Yaghi and his colleagues can store gases that are usually difficult to store and transport. Yaghi's laboratory has made several hundred MOFs, with a variety of properties and structures. Molecules can pass in and out of them unobstructed. BASF, a global chemical company based in Germany, funded the synthesis of the materials, and the U.S. Department of Energy funded the absorption and separation studies of carbon dioxide.
Adapted from materials provided by University of California - Los Angeles.

Source: http://www.sciencedaily.com/releases/2008/02/080214144344.htm