LONDON — Naturalist and broadcaster Sir David Attenborough used to be skeptical about how far climate change could be ascribed to human actions. He has now declared he is convinced that what we are doing or failing to do has had seriously damaging effects on the climate, and he has been demonstrating through programs on British television how climate change will affect all of us. He is giving yet another wake-up call to world leaders.

We must all be deeply concerned about climate change. Global warming may seem far-fetched during the unusually cool spring we have had this year in Britain. The threat of drought may seem exaggerated when the rain pours down. Yet, the scientific evidence about how human behavior is causing climate change is now overwhelming except to those who do not want to see it because it does not coincide with their preconceived notions or is not in their immediate political interest.

American leaders delude themselves when they deny global warming, which was probably the cause of last year’s devastating Hurricane Katrina.

If current trends continue, much of the Netherlands will be inundated before the century is over, and island states such as Tuvalu in the Pacific will disappear under water. Deserts will expand and extremes of drought will alternate with flooding.

Although Britain’s winters could get colder if global warming leads to the diversion of the Gulf Stream, summers will probably get hotter to the extent that even Britons may want air conditioning. But will there be enough energy to run the power plants at that time?

The Kyoto protocol was only a first tentative step and needs to be reinforced soon by new measures. The refusal of U.S. President George W. Bush and congressional leaders to take effective action to reduce climate change, such as by raising gasoline prices through taxation to levels existing in other parts of the developed world, is at best myopic and at worst a betrayal of future generations.

We must also be aware that although hydrocarbon reserves will last for at least the larger part of this century, they are finite. Moreover, we have to be cautious about dependence on hydrocarbon imports. Supplies could be disrupted by wars or by deliberate manipulation by countries with surplus energy resources. Demand for hydrocarbons is rising faster than supplies can be augmented.

The industrialization of China has led to huge increases in demand. It seems certain that demand from India and other developing countries will also grow exponentially.

These countries are asking why they should take action on climate change when America does little except call for more work on alternative fuels. Developing countries need to be persuaded and helped to reduce demand for energy and to invest in clean energy sources.

Our governments must be pressed to think harder about the longer-term future rather than concentrating on the next political gimmick that will give them an electoral advantage. The U.S. government in particular must be shamed into doing much more.

Joint plans to deal both with climate change and with the likely future energy crisis must be developed. The main elements required of such plans are clear, but each element will arouse opposition from one or another section of the population. It will be difficult to strike the right balance and persuade those concerned to accept sacrifices for the general good.

No sane person will argue against energy conservation, but many motorists will shrug off objections to their gas-guzzling SUVs, arguing that their vehicle has no real effect on global warming.

Japanese hybrid vehicles that combine electric power with gasoline engines are increasing in popularity. In America efforts are being made to further develop engines that can be fueled by naturally grown biofuels. Research into the development of hydrogen as an alternative source of power needs to speed up, but this looks like a distant prospect.

All of these developments are welcome, but unless the prices of alternative fuels and of the engines that can use them are brought down soon, they will have only a marginal effect on pollution caused by automobile engines. Growth in air travel is causing a rapid rise in aircraft pollution, and no one has yet found a way to produce alternative fuels for aircraft.

Hydro-electric power is, in principle, a sensible way to generate electricity, but there is not much scope for expanding hydro-electric power plants so that the environment is not harmed. The Three Gorges project in China has disrupted the lives of more than a million people, and its general impact on the Chinese environment is likely to be huge.

The further development of wind power has many attractions, but windmills are not cheap to build and can be unsightly. As a result, new wind-power projects are attracting increasing criticism and opposition from local lobbies. And there is one fundamental problem with wind power: The wind may not blow at the right time or with the right strength. Wind power has to be backed up by other power sources.

Solar power has more advocates than wind power, but there are problems with it, too. Solar panels can be unsightly and do not work well in countries with cloudy climes. An alternative that finds favor with the green lobby is the use of heat pumps to draw heat from underground, but these are expensive to install and require space that may be difficult to find in urban areas.

Tidal and wave power are attractive alternatives, but are not easy to tap. More research is needed and the costs must be brought down.

Greater insulation can make a significant contribution to energy savings.

It may well not be possible to meet the energy needs of the developed and developing worlds through the various nonpolluting measures listed above. In that case, atomic power will get another serious look.

Finland has decided to build a new atomic power station. British Prime Minister Tony Blair has let it be known that in the government’s review of Britain’s energy needs, he does not rule out further development of atomic energy.

One of the main objections to building and replacing atomic power stations has been the total cost of nuclear energy compared with that of hydrocarbons such as oil, gas or coal. Another has been the fear of nuclear accidents. The biggest worry has been how to safely dispose of or store nuclear waste.

These objections can probably be overcome; thus no option should be ruled out that helps to reduce the threats to mankind from climate change.

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