Paul Brown* considers the complexities of climate change and the role of religion in communicated good stewardship.

Although the droughts in southern Europe in the first years of this century, and the extreme heat wave of 2003, have alerted many in this otherwise green continent to the potential spread of deserts, it is mostly in the developing world that loss of croplands has been causing alarm. One of the theoretical predictions of long-term climate change is that it will start to rain again in the Sahara but currently the world's largest desert is still expanding. It seems intent on crossing the Mediterranean to Spain, Italy and Greece. China is one of those countries where dust storms and desertification have been ringing alarm bells for years. A massive programme of tree planting is aiming to stem the tide.

But although natural forces change the boundaries of deserts, and in some cases dry areas can be reclaimed by irrigation and careful planting, man is also responsible for creating deserts and enlarging them. Cutting down forests, overgrazing of dry lands, and poor irrigation practices which cause salts to build up in the soil have increased massively the area of desert in China. Climate change adds to these pressures and makes rehabilitating deserts more difficult, pushing even greater numbers of people to seek employment in the cities because they can no longer feed themselves on the land. Population pressure is one of the taboo subjects in the environment debate. But how do you continue to feed this ever-increasing population in a warming world? It was one of the great rows at the Earth Summit in 1992, when the Roman Catholic Church threatened to withdraw support if birth control was discussed.

Those issues are discussed elsewhere but it is important to emphasise the relationship of climate change to other environmental problems; the role of air pollution in its various forms, for example. The public, and even sometimes scientists, have been slow to understand the links. Acid rain is a good example of this interlinking. In the 1970s in Europe there was a long battle to understand and then at a political level take action to combat acid rain. All over northern Europe life in lakes was dying, even though they looked crystal clear, and pine trees were losing their needles. Whole forests were denuded. The culprit was low quality coal being burned in power stations. The coal produced noxious fumes in the form of sulphur dioxide, which in dry weather was deposited directly onto the ground, but often mixed with the clouds and produced a weak solution of sulphuric acid. Smoke from British power stations drifted hundreds of miles to the north-east and fell as acid rain in southern Scandinavia. The pattern was being repeated all over Europe and the world. The damage was not just to fish and trees. Acid soils changed the type of plants able to survive in certain areas and damaged buildings; for example gargoyles on cathedrals carved of limestone literally dissolved. The problem of acid rain is solvable and rich communities like those in Europe and North America set about reducing sulphur emissions by filtering smoke before it was released. This had a surprising side effect. Unlike carbon dioxide, which effectively remains in the atmosphere for around 100 years, sulphur dioxide lasts only a few days or at most weeks. As soon as the smoke stacks began to be cleaned up, the air cleared and the temperature began to rise. It was studying the Mount Pinatubo eruption of 1991 and the 20 million tonnes of sulphur dioxide it put into the atmosphere that confirmed to scientists studying global warming that pollution had been holding down global temperatures by reflecting back sunlight. Some scientists now believe that the huge level of pollution between the 1940s and the 1970s held world temperatures down when they would otherwise have been rising in response to increased carbon dioxide levels. If this is true then it adds to the scariness of current climate change.

Some of the NASA pictures from space show massive pollution either side of the Himalayas. This is from the surging fossil fuel use in India and China, which has been accelerating over the last 30 years. This too must be limiting greatly the rise in temperatures which is already apparent. These two countries are both attempting to tackle the life-threatening pollution in their cities. If they succeed they will send the temperatures soaring over Asia.

Another complex interaction between two apparently unrelated environmental problems is the role of ozone depletion. The well-documented 'hole' in the ozone layer, caused by the release of man-made chemicals into the atmosphere, is a problem because it allowed larger quantities of harmful ultraviolet light to reach the earth. It also alters the balance in the amount of heat retained by the atmosphere. While greenhouse gases heat the lower layer, called the troposphere, ozone depletion caused the stratosphere to cool. While ground stations all measured the Earth heating up, satellites, which give more of a global average, showed virtually no warming. It provided a field day for the contrarians, throwing doubts on all of the science. Some scientists then worked out that the satellites had been averaging out the warming of one layer with the cooling of another. Discovering precisely what is happening remains elusive and this issue remains a hotly contested area.

So it seems that although air pollution, acid rain and the ozone depletion are all serious problems, which must be solved because each one has detrimental effects on human health and the environment, their cure will also have a bearing on how fast the Earth heats up. In some heavily-polluted areas in Asia the effect could be large. Although the net result of civilisation's attempts to solve these various environmental problems on climate change is still not quantified, there have been some more recent attempts to discover how much the climate will warm. But there is an emerging consensus that anything above two degrees Celsius risks disaster. It is also a tall order for many long-lived species like trees to adapt to a rapid rise in temperature. A one degree Celsius rise is equivalent to moving 150 miles south in Europe and a similar rise would move the tree-line 150 metres up a mountain.

An important aside here is that throughout, the amount of carbon dioxide in the air has been central to the scientific and political argument. Methane has also been mentioned as a key greenhouse gas. There are other greenhouse gases including chlorofluorocarbons, or CFCs, which are being phased out  because they are the major cause of the destruction of the ozone layer. As has been mentioned earlier, there were six greenhouse gases, or groups of gases, mentioned in the Kyoto Protocol, the reduction of all of them counting towards any country's target. Apart from carbon dioxide and methane these are nitrous oxide, otherwise known as laughing gas, and two groups of chemicals called hydrofluorocarbons and perfluorocarbons, which are produced in chemical manufacture, and sulphur hexafluoride. All of them have a far greater heat-trapping effect in the atmosphere, per kilogramme emitted, than carbon dioxide but are in such tiny quantities that, controlled properly, they will not be a problem. Nitrous oxide is released with the production of nylon and is produced naturally in the soil but excessive fertiliser use is a major human cause. Extensive efforts are being made by industry to control the other industrial gases and find non-damaging substitutes.

Methane is very significant because it has 23 times the global warming potential of carbon dioxide per kilogramme emitted and is produced in large quantities both naturally and because of human activities. Natural sources include rotting vegetation in wetland. Even termites burp 20 million tonnes of methane a year, more than is released from the oceans. Man-made sources, coal mining in particular, natural gas and oil exploitation, release far more - about 100 million tonnes. Troublesome quantities also come from rice paddies and the digestive systems of cows and sheep. One large source in Britain is landfill sites; a new industry has been developed to capture and burn the gas as it is released to produce electricity. Power from landfill gas is one of the cheapest forms of electricity and has been one of the key examples of the benefits of tackling climate change. Although burning the gas produces carbon dioxide, this has far less global warming potential than the original methane.

Although methane remains an important greenhouse gas, direct man-made emissions of the gas are being reduced successfully in many countries. The most important problem remains carbon dioxide simply because it is the gas we are pumping out in the largest quantities and seem politically unable to tackle. Potentially, however, it is the easiest problem to deal with. All we have to do is stop using fossil fuels. Man's rapid development over the last 200 years, which brought the industrial revolution and a population explosion to the planet, has also brought society to this crisis. Science and politics have intertwined and clashed. Alongside this there has been a long argument, which still runs through most religions, about man's dominion over nature verses the responsibility for stewardship of God's creation. It has important political implications both in the Muslim world and in the influence of the religious right on the Republican party. Both the Orthodox Christians and the Roman Catholic Church have started taking the environment seriously, and protecting the environment has become part of both churches' teaching.

But as far as most of mankind is concerned, the forests and fields and the animal and fish stocks have always been treated as natural resources which are infinite, even if there is plain evidence to the contrary. If the clean water runs out, pipe some from over the hill. If you chop down a forest, import timber from elsewhere. No matter that north Africa was once forested until the Romans cut down the trees to grow grain or that most civilisations that have disintegrated have done so because of misuse or lack of natural resources. The magnificent but lonely statues
of Easter Island are a classic example of a civilisation which became impoverished because it cut down all the trees, could no longer build canoes to hunt food, and simply
ran out of the ability to sustain itself.

All that was a long time ago, but it is obvious that so far few lessons have been learned. But with the aid of constant monitoring from space mankind can clearly see on a daily basis how its activities are affecting every part of the globe, often disastrously. Forest fires, droughts, even the progress of new logging roads through the Amazon can be seen from satellites. It is also clear that none of these things are happening in isolation. The logs cut in tropical forests, mostly illegally, end up as furniture or expensive building materials in the rich world. The pollution emitted in India or China is to power factories, which export cheap goods to Europe and America. The pollution in those far-off places and in Europe and America caused by our profligate lifestyles chokes both our and their citizens. At the same time it keeps the temperature lower than it would otherwise be.

* Paul Brown is Environmental Correspondent for The Guardian.  This is an edited excerpt from his book Global Warning, The Last Chance for Change.