Recent months have given the British plenty of opportunity to do what they like best - talk about the weather. Winds reached 116 mph and the mildest December for 330 years was rivalled by the warmest February for 221.
Not that Britain was the only country with problems. While Washington suffered its coldest December for 100 years and California its driest Christmas since 1950, Casablanca received six months' rainfall in one week and a cyclone hit the Bay of Bengal, killing 4,000 and destroying 2.5 million homes. Rome baked at 32 degrees Celsius, Sweden enjoyed its warmest February since records began and Alaska received a record 35 feet of snow, while some ski resorts had none. In April an area of Australia the size of west Europe was drowned by the worst floods this century.
Five of the warmest years on record occurred in the 1980s. In 1988 drought hit the American Mid-West and for the first time ever the USA - breadbasket for 100 countries - had to import food. James Hansen, Director of NASA's Goddard Institute for Space Studies, told Congress that he was '99 per cent certain' that the greenhouse effect was to blame.
Few climatologists would go so far. Recent events may be abnormal, but the trick is to distinguish long-term change from the natural variability of the climate. Many scientists say there is no firm evidence that the climate has yet begun to change - but that there are strong reasons to believe that it will. A Commonwealth group of experts who recently reviewed the research pointed to a scientific consensus that the world will warm by at least 1 to 2 degrees Celsius by 2030. 'Some estimates predict much bigger increases,' they state. 'A change of such magnitude over 50 years is in fact unprecedented in recorded human history. By 2030 the Earth is likely to be warmer than at any time in the past 120,000 years.'
The idea that carbon dioxide acts like a greenhouse roof over the Earth, letting the sun's heat in but not allowing it all to escape, has been around for 200 years. It was first aired by an eccentric eighteenth century French mathematician, Baron Jean Baptiste Joseph Fourier, who had served as Napoleon's governor in Egypt. His studies on the flow of heat gave him a pathological fear of cold which he fought with thick layers of clothing and by overheating his house, before he fell to his death down a staircase.
Fourier was talking about the carbon dioxide which is naturally present in the atmosphere. Without its insulating effect, the Earth would be a frozen desert. 200 billion tonnes of carbon circulate through the planet's systems every year, in a complex interchange between the oceans, living organisms and the skies.
It took a Swedish Nobel laureate, Svante Arrhenius, to raise the possibility that, with the additional carbon dioxide released by burning fossil fuels, the greenhouse effect could become too much of a good thing. Writing in 1896, he calculated that a doubling of carbon dioxide in the atmosphere could raise average temperatures by 5 degrees Celsius -a figure not far off the highest given by scientists today. In 1938 a British scientist, George Callender, went so far as to suggest it was already happening. He cited an apparent rise in surface temperatures between the 1880s and 1930s - but when these stabilized, interest in the greenhouse effect cooled.
Millions of meteorological observations and tons of hot air later, scientists agree on two points. First, in the last century, the average global temperature has risen by 0.5 degrees Celsius and sea level has risen by 10 to 15 cm. Secondly, the concentration in the atmosphere of the gases that can cause global warming has increased. The connection between these two facts cannot be proved, but, say the Commonwealth experts, both the warming and the sea level rise tally with the expected effects of increased concentrations of greenhouse gases.
Scientists are concerned about four main sorts of greenhouse gases. The first is carbon dioxide, whose concentration has risen by over 25 per cent since the Industrial Revolution. Human activities pump seven billion tons of carbon into the air every year - only a fraction of the natural 'carbon flux' but enough to disrupt the equilibrium of the atmosphere severely. Experts believe that some 65 to 90 per cent of the increased carbon in the atmosphere comes from the burning of coal, oil and gas (including petrol).
The rest comes from deforestation. Trees and other plants soak up carbon dioxide when they are growing, and release it when they are burned. So as the forests fall, the world not only adds more carbon dioxide to its problems but destroys one of the main natural sinks for its disposal.
The concentration of carbon dioxide in the atmosphere has been growing by 0.5 per cent a year and is thought to account for 56 per cent of the greenhouse effect that has been building up. The USA and USSR each emit over a billion tons of carbon a year. They are followed in the pollution stakes by China (600 million tons), Brazil (390 million) and Japan (250 million). Brazil's emissions come mainly from deforestation, the others' from fossil fuels. When the contribution is calculated on a per capita basis the responsibility falls squarely on the North - with the US, Canada, Australia and the Soviet Union leading the field.
Nearly a quarter of the greenhouse effect is caused by chlorofluorocarbons. Molecule for molecule some CFCs are 10,000 times more powerful as greenhouse gases than carbon dioxide, but there is much less of them in the atmosphere. In a completely separate process, CFCs also destroy the ozone layer, which screens out the most dangerous rays of the sun before they reach the Earth. This radiation causes skin cancer and cataracts and may kill the phytoplankton in the oceans, which - like the leaves of the forest - soak up carbon dioxide from the air.
CFCs are used in fridges, freezers and air conditioners and in solvents. They propel the spray out of some aerosols and puff up foams used in buildings, cars and fast food containers. They are already the subject of an international agreement, which comes up for tightening this month.
Concentrations of the third greenhouse gas, methane, have more than doubled since the mid-nineteenth century. Methane is credited with 14 per cent of the greenhouse effect and is 30 times as lethal to the atmosphere as carbon dioxide. It is produced by microbes in swamps, paddy fields and in the guts of the world's 1.3 billion cows. Methane is also released by burning plant matter and fossil fuels, and by fossil fuel extraction.
Vast quantities of methane are locked up in the frozen swamps of the Arctic tundra. The temperature rise caused by global warming is expected to be fiercest in the Arctic and there are fears that the permafrost could begin to thaw, releasing methane and thus reinforcing the greenhouse effect.
The final major greenhouse gas is nitrous oxide, released by fertilizers and the burning of fossil fuels and vegetation. The concentration of nitrous oxide in the atmosphere has also increased in the last 150 years, and accounts for some seven per cent of the effect. Ozone pollution near the Earth (as opposed to the protective layer miles above our heads) also adds to the greenhouse effect.
While you have been reading this article some 2,000 babies have been born, in all parts of the world. As they grow up, they will need qualities of courage, adaptability and generosity greater than any generation before. They will see pollution press the fast forward button on nature - packing the changes of 10,000 years into their short human span.
Scientists are hesitant about specifying exactly what these changes will amount to. No computer model is yet sophisticated enough to tell us for sure. At the same time, if planners wait until the forecasts are cast-iron, it will probably be too late to respond. So countries are being urged to make contingency plans on the basis of best-guess scenarios.
There is broad agreement that, as the Earth warms, mountain glaciers will melt and the waters of the oceans will expand, raising sea levels about 20 cm by 2030. The Antarctic ice sheets are not expected to melt in this period. But even if global warming screeches to a halt in 2030 -which is unlikely - sea levels will go on rising, because it takes a long time for heat to transfer from the atmosphere to the ocean. By 2100, according to the Intergovernmental Panel on Climate Change (IPCC), sea levels will be up by at least a metre. At the same time violent storms and surges will become more frequent.
Many of today's newborns could be driven from their homes by these forces before they are grandparents. Half the world's population lives by the sea. It is estimated that by 2030 the greenhouse effect will have given the world 60 to 300 million more refugees.
Most vulnerable of all are the children who have just been born on the 'endangered' coral atolls of the Pacific and Indian Oceans or in such delta states as Bangladesh and Egypt.
The little girl who has just opened her eyes in the Maldives will grow up less than two metres above sea level; her staple food, taro, grows in pits only 40 cm above sea level. As the climate changes, freak waves will regularly overwhelm her country's capital, Male, and its international airport, as they did three years ago.
At worst, this child - and those like her in six other Pacific and Indian Ocean island states - will see her country disappear altogether. 'If sea-level rises occur anywhere near the extreme projections which have been made we can write these nations off the map,' says the head of a recent study, John Pernetta of the University of Papua New Guinea.
In 1988 floods covered 85 per cent of Bangladesh and drove 30 million people from their homes. The country's 100 million inhabitants are at risk from all sides, as three mighty silt-swollen rivers crash down from the deforested Himalayas, annual cyclones send six-foot-high surges 200 kilometres inland, and the land itself sinks. The life expectancy of the baby who has just been born in Bangladesh is only 50 years. If he cheats the statistics and lives until he is 60, he may, according to one American study, have watched 18 per cent of his country vanish under water. By 2100 over a third of the country could have gone.
90 per cent of the inhabitants of Guyana in South America live in the coastal plains, below high tide level. Bangkok, Calcutta, Shanghai, Jakarta, Tokyo, Osaka, London, Rotterdam, Venice, Manhattan and New Orleans all lie too low for complacency.
Climatic zones will shift towards the poles, taking species and rainfall patterns with them. The babies born today in the far north will see the greatest temperature rises. As rains increase, they could grow up to man a farming boom in Norway, Sweden, Iceland and Siberia. By contrast the babies of the North American Mid-West could see the wheat-lands turn to a dust-bowl and find that soils further north in Canada are not rich enough to make up. By and large, a warmer world will be a wetter world -but dry areas could get drier. The world's poorest farmers, tilling arid marginal land in North Africa, Ethiopia, Somalia, Namibia, Botswana, Eastern Brazil, India and Pakistan are likely to be worst hit.
Overall, experts reckon, world food production will bear up - and some of the world's staple crops may even flourish as a result of the extra carbon dioxide in the air. But everything will depend on the speed with which local communities and governments are able to adapt.
Greenhouse gases know no frontiers. No country can fence off its own patch of sky - and unilateral decisions to phase out coal burning, for instance, would probably just push down coal prices elsewhere. Only a global solution has a chance.
This penny has already dropped when it comes to the similar-but simpler-issue of the ozone layer. Spurred by the discovery of the Antarctic ozone hole, countries representing over half of the world's population have agreed to cut back on the chemicals, including CFCs, which damage the protective filter in the sky. This month they meet in London in an attempt to agree to phase out these chemicals altogether.
Protecting the ozone layer is easier than preventing global warming because there are alternatives to most uses of CFCs. But these substitutes are expensive, both to buy and manufacture. The make-or-break issue this month will be whether developed nations agree to set up a fund to help developing nations do without CFCs. It is a chance to relaunch the North-South dialogue on a more equal basis - for there is no question, when it comes to the atmosphere, that the North needs the South.
The same issue will be the crux in any attempt to slow the greenhouse effect. How an the North, which developed by cutting own its forests and burning fossil fuels, persuade the South not to follow its example? Certainly not by denying their right to growth and development.
After all the rich world created the problem in the first place - and still produces the lion's share of greenhouse gases. An American releases 56 times more carbon into the skies every year than a Nigerian; a Briton lets loose 91 times as much as a Zaire. But some developing nations are catching up. China, now the world's largest producer of coal, already emits a tenth of the world's carbon and plans to double its coal consumption by the end of the century. Compared to Western nations, Brazil, Indonesia and Colombia don't use much coal. But deforestation puts them into the top ten emitters of carbon.
So how can the Third World's need for growth be reconciled with the whole world's need to check global warming? In the short term, developing countries' use of fossil fuels will have to go on increasing - and, to make this possible, developed countries will have to cut back all the more dramatically.
Energy efficiency alone - in both developed and developing nations - could cut the annual weight of carbon pollution by three billion tons early next century. It is reckoned that, with energy efficiency, developing countries would only need to raise their per capita energy use by a fifth to meet their basic needs. Without it, they would have to double their energy use.
Drafts leaked to the British press suggest that the IPCC, set up to pave the way for a global climate convention, will recommend that carbon dioxide emissions should be halved by 2050. As means cf doing this they will propose dramatic improvements in the fuel efficiency of cars, a carbon tax to discourage the use of coal, an expansion of renewable energy and - in the medium term - increased use of nuclear power, an end to deforestation by the year 2000 and the planting of 2.5 billion acres of trees. They will also urge countries to phase out CFCs altogether by the year 2000.
To achieve this, money will have to pass from North to South, and from West to East. These funds cannot be taken from existing aid budgets - they will have to be in addition to them. They could be raised, perhaps, by a tax on fossil fuel use.
No-one is saying that saving the planet will be cheap. Some experts, governments, see this as a reason to wait for further research. Voters disagree. Recent polls revealed that 74 per cent of Americans want their government to curb pollution regardless of cost and four out of five Britons think their government is doing too little about the greenhouse effect.
What are we waiting for?
How to cool it? Switch it off. Seventeen per cent of the world's electricity - responsible for 250 million tons of carbon pollution a year - is used for lighting. Better still, replace your light bulbs with low-energy fluorescent bulbs.
Is your journey really necessary? The world's 400 million cars discharge some 550 million tons of carbon every year - a tenth of the total pollution from fossil fuels. Walk, bike, bus or train - and make sure that your car is as energy efficient and well tuned as possible.
Insulate your home. Put on - or take off - a jersey instead of turning up the heat or the cooling system.
Make sure your household appliances use as little energy as possible.
Plant a tree - the American Forestry Association aims to encourage local communities to plant 100 million trees by 1992. They will soak up five million tons of carbon a year. Recycle paper.
Don't use CFC-propelled aerosol cans; don't accept foam food packaging; don't use air-conditioning in your car. If you get a new fridge find out whether the manufacturers of your old one can recover its CFCs for recycling.
Cultivate attitudes of generosity and adaptability in yourself and your family - you're going to need them!
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