A. Such is our dependence on fossil fuels, and such the volume of carbon dioxide we have already released into the atmosphere, that most climate scientists agree that significant global warming is now inevitable – the best we can hope to do is keep it at a reasonable level, and even that going to be an uphill task.

At present, the only serious option on the table for doing this is cutting back on our carbon emissions, but a few countries are making major strides in this regard, the majority are having great difficulty even stemming the rate of increase, let alone reversing Consequently, an increasing number of scientists are beginning to explore the alternatives. They under the banner of geoengineering generally defined as the intentional large-scale manipulation of the environment.

B. Geoengineering has been shown to work, at least on a small, localised scale, for decades. May Day parades in Moscow have taken place under clear blue skies, aircraft having deposited dry ice, silver iodide (m $1) and cement powder to disperse clouds. Many of the schemes now suggested look to do the opposite, and reduce the amount of sunlight reaching the planet.

One scheme focuses on achieving a general cooling of the Earth and involves the concept of releasing aerosol sprays into the stratosphere above the Arctic to create clouds of sulphur dioxide, which would, in turn, lead to a global dimming. The idea is modelled on historical volcanic explosions, such as that of Mount Pinatubo in the Philippines in 1991; which led to a short-term cooling of global temperatures by 0.5°c. The aerosols could be delivered by artillery, high-flying aircraft or balloons.

C. Instead of concentrating on global cooling, other schemes look specifically at reversing the melting at the poles. One idea is to bolster an ice cap by spraying it with water. Using pumps to carry water from below the sea ice the spray would come out as snow or ice particles, producing thicker sea ice with a higher albedo (the ratio of sunlight reflected from a surface) to reflect summer radiation. Scientists have also scrutinised whether it is possible to block iceflow in Greenland with cables which have been reinforced, preventing icebergs from moving into the sea.

Veil Albert Kallio, a Finnish scientist, says that such an idea is impractical, because the force of the ice would ultimately snap the cables and rapidly release a large quantity of frozen ice into the sea. However, Kallio believes that the sort of cables used in suspension bridges could potentially be used to divert, rather than halt, the southward movement of ice from Spitsbergen. It would stop the ice moving south, and local currents would see them float northwards’ he says.

D. A number of geoengineering ideas are currently being examined in the Russian Arctic. These include planting millions of birch trees: the thinking, according to Kallio, is that their white bark would increase the amount of reflected sunlight. The loss of their leaves in winter would also enable the snow to reflect radiation. In contrast, the native evergreen pines tend to shade the snow and absorb radiation.

Using ice-breaking vessels to deliberately break up and scatter coastal sea ice in both Arctic and Antarctic waters in their respective autumns, and diverting Russian rivers to increase cold-water flow to ice-forming areas, could also be used to slow down warming, Kallio says. 1 You would need the wind to blow the right way, but in the right conditions, by letting ice float free and head north, you would enhance ice growth.’

E. But will such ideas ever be implemented? The major counter-arguments to geoengineering schemes are, first, that they are a ‘cop-out’ that allow US to continue living the way we do, rather than reducing carbon emissions; and, second, even if they do work, would the side-effects outweigh the advantages? Then there’s the daunting prospect of upkeep and repair of any scheme as well as the consequences of a technical failure. ‘I think all of US agree that if we were to end geoengineering on a given day, then the planet would return to its pre-engineered condition very rapidly, and probably within 10 to 20 years’ says Dr Phil Rasch, chief scientist for climate change at the US-based Pacific Northwest National Laboratory.

That’s certainly something to worry about. I would consider geoengineering as a strategy to employ only we manage the conversion to a non-fossil- fuel economy. ‘The risk with geoengineering projects is that you can “overshoot”,’ says Dr Dan hunt, from the University of Bristol. ‘You may bring global temperatures back to pre-industrial levels, but the risk is that the poles will still be warmer than they should be and the tropics be cooler than before industrialization.’

F. The main reason why geoengineering is countenanced by the mainstream scientific community is that most researchers have little faith in the of politicians to agree – and then bring in the necessary carbon cuts. Even leading conservation organisations believe the subject worth exploring. As Dr Martin Sommerkorn, a climate change advisor says.’

But human-induced climate change has brought humanity to a position where it important not to exclude thinking thoroughly about this topic and its possibilities despite the potential drawbacks. If, over the coming years, the science US about an ever-increased climate sensitivity of the planet and this isn’t unrealistic – then we may be best served by not having to start our thinking from scratch.

For two years southern Sri Lanka suffered a prolonged drought, described by locals as “the worst in 50 years”. Some areas didn’t see a successful crop for four or five consecutive seasons. Livestock died, water in wells dropped to dangerously low levels, children were increasingly malnourished and school attendance has fallen. An estimated 1.6 million people were affected.

A Muthukandiya is a village in Moneragala district, one of the drought-stricken areas in the “dry zone” of southern Sri Lanka, where half the country’s population of 18 million lives. Rainfall in the area varies greatly from year to year, often bringing extreme dry spells in between monsoons. But this drought was much worse than usual. Despite some rain in November, only half of Moneragala’s 1,400 tube wells were in working order by March. The drought devastated supplies of rice and freshwater fish, the staple diet of inland villages. Many local industries closed down and villagers headed for the towns in search of work.

B The villaers of muthukandiya arrived in the 1970s as part of a government resettlement scheme. Each family was given six acres of land, with no irrigation system. Because crop production, which relies entirely on rainfall, is insufficient to support most families, the village economy relies on men and women working as day-laborers in nearby sugar-cane plantations. Three wells have been dug to provide domestic water, but these run dry for much of the year. Women and children may spend several hours each day walking up to three miles (five kilometers) to fetch water for drinking, washing, and cooking.

C n 1998, communities in the district discussed water problems with Practical Action South Asia. What followed was a drought mitigation initiative based on a low-cost “rainwater harvesting” technology already used in Sri Lanka and elsewhere in the region. It uses tanks to collect and store rain channeled by gutters and pipes as it runs off the roofs of houses.

D  Despite an indigenous tradition of rain-water harvesting and irrigation systems going back to the third century BC, policy-makers in modern times have often overlooked the value of such technologies, and it is only recently that officials have taken much interest in household-level structures. Government and other programmes have, however, been top-down in their conception and application, installing tanks free of charge without providing training in the skills needed to build and maintain them properly. Practical Action South Asia’s project deliberately took a different approach, aiming to build up a local skills base among builders and users of the tanks, and to create structures and systems so that communities can manage their own rainwater harvesting schemes.

E The community of Muthukandiya was involved throughout. Two meetings were held where villagers analysed their water problems, developed a mitigation plan and selected the rainwater harvesting technology. Two local masons received several days’ on-the-job training in building the 5,000-litre household storage tanks: surface tanks out of Ferro-cement and underground tanks out of brick. Each system, including tank, pipes, gutters and filters, cost US$195 – equivalent to a month’s income for an average village family. Just over half the cost was provided by the community, in the form of materials and unskilled labour. Practical Action South Asia contributed the rest, including cement, transport and payment for the skilled labour. Households learned how to use and maintain the tanks, and the whole community was trained to keep domestic water supplies clean. A village rainwater harvesting society was set up to run the project. To date, 37 families in and around Muthukandiya have storage tanks. Evaluations show clearly that households with rainwater storage tanks have considerably more water for domestic needs than households relying entirely on wells and ponds. During the driest months, households with tanks may have up to twice as much water available. Their water is much cleaner, too.

F Nandawathie, a widow in the village, has taken full advantage of the opportunities that rainwater harvesting has brought her family. With a better water supply now close at hand, she began by growing a few vegetables. The income from selling these helped her to open a small shop on her doorstep. This increased her earnings still further, enabling her to apply for a loan to install solar power in her house. She is now thinking of building another tank in her garden so that she can grow more vegetables. Nandawathie also feels safer now that she no longer has to fetch water from the village well in the early morning or late evening. She says that her children no longer complain so much of diarrhoea. And her daughter Sandamalee has more time for school work.

G In the short term, and on a small scale, the project has clearly been a success. The challenge lies in making such initiatives sustainable and expanding their coverage. At a purely technical level, rainwater harvesting is evidently sustainable. In Muthukandiya, the skills required to build and maintain storage tanks were taught fairly easily and can be shared by the two trained masons, who are now finding work with other development agencies in the district.

H  The non-structural elements of the work, especially it’s financial and organizational, present a bigger challenge. A revolving fund was set up, with households that had already benefited agreeing to contribute a small monthly amount to pay for maintenance, repairs and new tanks. However, it appears that the revolving fund concept was not fully understood and it has proved difficult to get households to contribute. Recovering costs from interventions that do not generate income directly will always be a difficult proposition, although this can be overcome if the process is explained more fully at the outset.

I The Muthkandiya initiative was planned as a demonstration project, to show that community-based drought mitigation through rainwater harvesting was feasible. Several other organizations have begun their own projects using the same approach. The feasibility of introducing larger tanks is being investigated.

J However, a lot of effort and patience are needed to generate the interest, develop the skills and organize the management structures needed to implement sustainable community-based projects. It will probably be some time before rainwater harvesting technologies can spread rapidly and spontaneously across the district’s villages, without external support.