As environment ministers from around the world gather in the Mexican resort of Cancun for another round of fruitless bickering over what to do about climate change, Hong Kong's officials are feeling pretty smug. The city's government came out with its own plan for reducing greenhouse gas emissions back in September. It is proposing to cut Hong Kong's carbon dioxide output by at least 19 per cent over the next 10 years, which equates to a 26 per cent reduction compared to a 'business as usual' scenario (see the first chart below). The reduction will be achieved mainly by phasing out Hong Kong's existing coal-fired power plants and buying in more nuclear-generated electricity from the mainland. This plan is so flawed that even Hong Kong's head-in-the-sand officials should be able to spot its obvious failing. It is true that closing down our coal-fired power stations and importing nuclear power from the mainland will reduce the amount of locally-produced carbon dioxide. But if Hong Kong buys nuclear power from the mainland, that power cannot be consumed at home. This is a problem because the mainland doesn't exactly have nuclear power to spare. With demand for energy rising, the mainland is building nuclear plants as fast as it possibly can. Some 25 are under construction now, with more than another 100 planned over the next 10 years - and those plants will be built whether Hong Kong buys more nuclear-generated electricity or not. As result, if Hong Kong buys nuclear-generated electricity from the mainland, then the mainland will have to find another source of power to make up for what it sells. In energy-short China, that source will inevitably be the only one the country has in abundance: coal. In other words, the plan will not result in any net reduction in greenhouse gas emissions. It will merely displace those emissions from Hong Kong to the mainland. In the worst case it could even cause an increase in overall emissions if the mainland substitutes the electricity it sells us with power generated in inefficient or older coal plants. The real problem here is that Hong Kong's officials are trying to cut emissions by imposing a top-down solution: outsourcing the city's energy production to the mainland. It would make far more sense to concentrate instead on a bottom-up solution: encouraging the city's businesses to use energy more efficiently, which would reduce greenhouse gas emissions by reducing overall energy use. Happily, this would neither be especially difficult nor expensive. According to the Environmental Protection Department, 67 per cent of Hong Kong's greenhouse gas emissions are produced by generating electricity. And 66 per cent of that electricity is consumed by the city's commercial buildings - offices, shops and the like. Yet our commercial buildings are desperately inefficient users of energy. A local supermarket, for example, uses 50 per cent more electricity than an equivalent supermarket in Britain, and 66 per cent more than one in the United States. A good place to start would be with air-conditioning. As the second chart below shows, Hong Kong's electricity consumption rises by 70 per cent or more in summer as we crank up the air-con. Yet the vast majority of our air-conditioners are old-fashioned and inefficient. Modern cooling plants eat up 30 to 40 per cent less power. Similarly, we could use 40 per cent less energy if we updated our lighting, and save 50 per cent by modernising our lifts and escalators. Overall, engineers estimate that by enforcing more rigorous efficiency standards we could reduce the energy consumed by Hong Kong's commercial buildings by 30 per cent. That would cut the city's greenhouse gas emissions by around 13 per cent - roughly as much as the government says it will cut by buying in more nuclear power. What's more, although the upfront costs of compliance would be heavy, the resulting energy savings would be great enough to pay for themselves within eight to 10 years. Yet the government has baulked at introducing tough efficiency standards. The mandatory building energy codes approved last week are less demanding even than India's. And they apply only to new buildings, which means their effect on our greenhouse gas emissions will be minimal. In short, the government's proposals for cutting emissions will be ineffective and expensive. Our officials have nothing to be smug about.