S

CIENCE has now become clear: most new evidence

confirms that global warming should be taken seriously. The report by the UN's Inter-governmental panel on Climate Change (IPCC) made up of world's top climate scientists concludes that man's actions have contributed substantially to the observed warming over the last 50 years. The warming trend exhibited by the build up of carbon dioxide and other green house gases in the atmosphere has caused serious climatic disruptions around the globe in recent time. The result according to scientists could be droughts, melting ice caps, rising sea levels, coastal flooding, severe storms and other climatic calamities.

Glaciers provide especially good ways to find out if our climate is changing. "Since they are typically formed as a response to cold climate, glaciers always reflect any change in climate", so says Gergan a glaciologist from the Wadia Institute of Himalayan Geology, Dehradun. After making numerous trips to the Dokriani Bamak glacier, a 5 km-long python of ice and mud that snakes through upper reaches of Garhwal, Himalays, Joseph Gergan is convinced that global warming trend has set in. After North India's freezing winter in 1998 and successive years, he expected the glacier to move forward. Instead it outran its annual average of about 16 m and retreated by an all time high of 20 m. Since 1998, Bangladesh and India have been experiencing hottest summers accompanied by extreme weather conditions surpassing all previous records. Mentionably, parts of India, including West Bengal, Bangladesh and China had the worst flood in a century. The prime explanation for

such freakish weather conditions is global warming, the heating up of the earth as forests are cut down crippling the earth's ability to absorb the rising clouds of carbon dioxide from its factories and vehicles.

No one disputes that the West is largely to blame for the existing greenhouse cover. But it is equally clear that the future trouble lies in Asia. South Korea already has the fastest growth rate for CO2 production in the industrial world. If the current trends continue, this nation of 45 million people will be the world's number - two CO2 producer by the year 2030, according to the Korean Federation of Environmental Movements. Canadian Sinologist and environmental expert Vaclav Smil predicts that by 2020 China will have displaced the United States as the

in the Indian Institute of Tropical Meteorology in Pune. This summer parts of India and Bangladesh was believed to be the earth's hottest ever. In consequence sea levels have also risen by about 0.5 m. The seas around India and Bangladesh have shown a 2.5 mm rise per year over the past few decades. With ocean waters becoming warmer, they tend to expand. Add to this ice melts and you have oceans rising. Seas rising by millimetres and lands warming by fractions of degrees might not sound like much but in the giant thermometers that is the earth, it is enough to change life forever. A half metre sea rise for instance, is enough to wipe out India's coastal areas.

These facts dovetail ominously well with the theory that carbon dioxide (CO2) released by burning

turn every house into its own electricity supplier.

Cars like NECAR4 housed in a lab near Stuttgart, could help make that happen. This experimental vehicle, being jointly developed by Ford, Daimler-Chrysler and Canada's Ballard Power Systems get its energy from hydrogenthe most abundant fuel in the entire universe. Hydrogen unlike fossil fuels contains no carbon atoms and thus generates zero carbon dioxide. However, it could produce some pollution since burning hydrogen taints the atmosphere by rearranging air molecules to form nitrogen oxides and ozone.

Mentionably, fuel cells invented in the 1800s were adopted by NASA for generating clean power in space in the 1960s. Only in the past

world's leading producer of greenhouse gases. According to National Institute for Environmental Studies in Japan, Asia now generates 25 percent of all CO2 emissions, but at current rates of growth that figure will rise to 50 percent over the next century.

That means around the globe from Asia to Europe to the U.S., human activity is heating up the planet. The signs seem to point that way: weather patterns have

become more erratic. As a general pattern we have been experiencing higher temperatures, says an expert

coal, oil and gasoline for heat, electricity and transportation is trapping excess energy from the sun. Carbon dioxide is produced when fossil fuels are used or when forests are burned. Agriculture releases other powerful green house gases (GHGS) such as methane and nitrous oxide. Industrial processes release chemicals known as halocarbons (including CFCs) and other long-lived gases some of which trap heat in the atmosphere. A study by a team led by James Hansen of America's space Agency, NASA, has looked in detail at the net effects of these factors. It distinguishes natural "forcings" from man-made ones, and works out the impact of each on temperature. Under natural conditions, the earth releases heat at the same rate at which it absorbs energy from the sun. But the researchers conclude that man's actions since 1850 have upset the balance. Man-made GHGs now cause a forcing of more than two watts per square metre, the equivalent of increasing the sun's brightness by around 1%. The study says that increasing GHGs are estimated to be the largest forcing and to result in a net positive forcing during the past few decades". Dr. Hansen stresses the big impact of GHGs other than CO2. Global warming as such is real and will probably get worse.

The only way to slow it down is to restructure the way we produce energy. Such stop-gap measures as insulation, carpooling and energy efficient light bulbs are all useful ways to begin curbing the burning of carbon rich fossil fuels. But in the long run as the world's population continues to increase and living standards rise these measures will not be enough. Experiments now going on in laboratories around the world are not only important but encouraging too. At a research centre outside Stuttgart, Germany engineers at Daimler Chrysler have created a high performance car whose tail pipe emits nothing but water vapour. In a giant wind tunnel at NASA's Ames Research Centre in California engineers are set to analyse air turbulence in order to make super efficient wind power turbines. In Japan scientists are perfecting paper-thin solar cells that will be cheap to produce and could

decade they have been made small enough to fit in inside a car. The NECAR4 based on a Mercedes -Benz A class sedan accommodates five people plus luggage reaches speeds of 90 m.p.h. (145 km/h) and goes about 280 miles (450 km) between fill-ups. By 2004, DaimlerChrysler and Ford as well as GM, Toyota and other companies expect to be selling fuel cell cars directly to consumers.

In an ideal situation the hydrogen may be produced sustainably with renewable electricity from the sun or wind. But till now the electricity required to split H2O (Water) into H (Hydrogen) and O (Oxygen) would be prohibitively expensive. So the first large-scale plants will probably wrest hydrogen from old-fashioned fossil fuels. That's very much a good news for China, whose gigantic-size rapid industrialisation and huge domestic coal reserves threaten to pump cataclysmic amounts of carbon dioxide into the air over the next century. While scaling fuel cells down to fit inside cars and trucks is a challenge, but scaling them up or linking them together to run factories and power plants should be no problem at all.

There is still some untoward effect in pulling hydrogen from fossil fuels in the sense that it leaves carbon dioxide behind. If the carbon dioxide is vented into the atmosphere, global warming will be as big a problem as ever. Engineers are thinking of an alternative to pump it into the ground. In Norway, for example, the energy company Norsk Hydro is building a power plant that will be fueled with hydrogen drawn from natural gas. The CO2 that's left over will be reinjected into an oil field on the continental shelf. Not only will this take the carbon dioxide out of circulation but it will also pressurize the field and make the remaining oil easier to pump out. In Europe and the U.S., pumping CO2 into underground aquifers has proved an effective way of keeping it out of the atmosphere.

Fossil fuels will remain an important energy source for the foreseeable future, but they will eventually run out and the world will have to switch to what environmental visionaries have been dreaming about since the original Earth Day: endlessly renewable power from wind

and sun.

Wind has the edge. It's fast catching up with oil and gas in cost efficiency with the help of experiments such as the one at Ames Research Center. By comparing what they learn from the wind tunnel's smooth airflow with data from the turbulent breezes at the National Renewable Energy Laboratory's test range near Golden, Colorado, engineers expect to build a new generation of super-efficient wind turbines with blades well over 200 ft. (60 m) across.

Efficiency doesn't help when the wind isn't blowing; as such it would be necessary to store energy generated during gales for use when the air is still. The best way to do that, says Robert Williams, of Princeton University's Center for Energy and Environmental Studies, is to use the excess to compress air and force it into subterranean aquifers, caves or salt domes.

Then, when the wind dies, the compressed air can be pulled out to help drive the turbines. "The technology was originally developed in the 1960s," says Williams, "to let nuclear power plants store excess electricity during off-peak hours." Now it could permit countries rich in wind resourcesincluding China, the U.S., Denmark and Germanyto take advantage of a free, unlimited and nearly pollution-less source of electricity.

On the solar-power front, the visions of 1970s-era environmentalists can still be realized, at least in part, if manufacturers could find a way to produce silicon-based photovoltaic cells more efficiently and thus drive down their high cost. One strategy is to reduce the thickness of a solar cell from the current standardabout that of a piece of cardboardto onehundredth of that size. Such thin-film cells, whose development is furthest along in Japan, will use less raw material and will be far easier to manufacture with the extraordinary purity required to make them efficient enough to be economical.

Beyond that, their light weight will make installation easy, permitting them over windows. Because a given solar cell is sensitive to just a few colors of the many that make up sunlight, researchers are working on multilayered cells, which will trap most of the colours of the rainbow.

Since the sun doesn't shine with equal power everywhere, even a building slathered with solar cells will need another source of electricity. One possibility: a system that uses both solar cells and a two-way fuel cell. During daylight, when the solar cells are operating, excess electricity could be run through a fuel cell to produce hydrogen from water. At night, the fuel cell could use the hydrogen to produce electricity again.

Ideally, every factory, building, home and vehicle would have its own clear, renewable power source, eliminating oil wells, coal mines, power plants and power lines--and all the environmental disruption they cause. For now, the world has a more urgent mission: to stop the planet from overheating, and to do it in a hurry. Thanks to the fuel-cell cars and more advanced wind turbines and solar cells that are close to fruition, the global-warming challenge seems a little less daunting than it did just a few years ago.

Md. Asadullah Khan is Controller of Examinations, BUET

***Ideally, every factory, building, home and vehicle would have its own clear, renewable power source, eliminating oil wells, coal mines, power plants and power lines--and all the environmental disruption they cause. For now, the world has a more urgent mission: to stop the planet from overheating, and to do it in a hurry. Thanks to the fuel-cell cars and more advanced wind turbines and solar cells that are close to fruition, the global-warming challenge seems a little less daunting than it did just a few years ago.***