If the predictions in yesterday's report by leading climate scientists proved correct, millions living in Britain and other northern climes would gain from milder winters and a longer growing season but, further south, people would suffer the consequences of intense heatwaves that would kill many unused to extreme temperatures.
Insect pests would proliferate and there would be an increase in malaria; sun-seekers would find the Mediterranean too hot for holidays in July and August.
As the intergovernmental panel on climate change set out yesterday, the Earth is warming faster than at any time in the last 10,000 years and man is causing the increase by burning fossil fuels, cutting down forests and making changes in agriculture.
The changes predicted would cause coastal areas to be inundated and lead to major population changes. They would end the ski industry in Europe, cause the disappearance of many of the world's glaciers on which communities rely for regular summer water supplies, and have serious effects on agriculture.
The growing season for many of the staple crops in Africa would be cut too short for a reliable harvest because of excess heat and lack of moisture, and in Europe the Mediterranean fringe would be too dry for cereal crops. Many of the world's forests would die because of changes in water supply and the increasing heat.
Night-time average temperatures would increasingly leave much larger areas frost-free, leading to increases in insect life. Heatwaves would increase over all northern land areas and droughts, already observed to be increasing in Africa and Asia, would become more severe.
According to the report, nearly all land areas, including northern Europe, Asia and the United States, will warm far faster than average, possibly by as much as 8C.
Climate models worked out by giant super-computers have become far more reliable since the last report in 1995. This, combined with the climate changes observed over two decades, has convinced scientists that something very serious is happening and that it cannot be a natural process. There is far greater unanimity among the world's scientists over the issue than among politicians.
The floods in Britain and other parts of northern Europe are entirely consistent with climate-change predictions. There has been an increase of 2% in cloud cover but it is the rise in rainfall during heavier storms that has caused the floods. This is expected to get worse each decade.
A reduction in snow cover and in the area of sea ice in the Arctic has been seen since the late 60s and is expected to accelerate. In the same period the remaining ice in the Arctic ice cap has become 40% less thick.
A fall of two weeks in the annual duration of lake and river ice-cover in mid and high latitudes of the northern hemisphere has already been observed.
A widespread retreat of mountain glaciers is expected to continue. Most of the sea-level rise observed in the last century has been caused by the melting of glaciers in places such as the Alps and because of the thermal expansion of the oceans. So far the giant ice caps on Greenland and Antarctica have been slow to react, but this will change.
Although the amount of sea-level rise in this century is slightly less than predicted in 1992, the report emphasises that the process will go on for thousands of years because of the time taken for the giant ice sheets of Greenland and Antarctica to react to increased temperatures.
Local warming over Greenland is likely to be one to three times the global average. If this warming were sustained, the complete melting of the Greenland ice cap would result in a rise in sea level of about seven metres (23ft), enough to drown all the major capitals of the world. A local warming of 5.5C would be likely to result in a contribution from Greenland of three metres to sea-level rise over 1,000 years.
If the West Antarctic ice sheet melted over the same period this would add another three metres to sea level.
One of the fears of scientists was that the flow of fresh water from the melting Greenland icecap would slow down or even halt the Gulf Stream, which warms Britain and the rest of Europe. The report says that while this may happen in the distant future, it is unlikely to have a serious effect this century.
The report says that the burning of fossil fuels is going to be "the dominant influence" on climate in the next century. As the carbon dioxide in the atmosphere increases, the ability of plant life on land and in the oceans to soak it up decreases. In 1750 the concentrations of carbon dioxide in the atmosphere were 280 ppm (parts per million). By 2000 the figure had increased 31%.
The report says the present carbon dioxide concentration has not been exceeded in the last 420,000 years and probably not for 20m years. It is now going up at the rate of 4% a decade and is expected to accelerate to reach 540ppm-970ppm by the end of the century. If it reaches the top of this range the temperature will rise up to 6C, two degrees higher than predicted five years ago.
The rate of warming is much higher than in the 20th century and at any time in the last 10,000 years since the ice age ended.
Methane concentrations have gone up 151% since 1750, partly due to fossil fuel burning, but also because of increase in rice culture and cattle, both of which generate methane from rotting vegetation. Landfill sites produce methane for the same reason but there are signs that these increases are levelling off.
Nitrous oxide, also a potent greenhouse gas, produced by industry, motor transport and agriculture continues to increase and concentrations have not been exceeded in 1,000 years.
Other attempts by man to reduce pollution for other reasons are now known to increase global warming. The complex atmospheric changes which cause the hole in the ozone layer also allow heat to escape from the Earth. If the ozone hole is mended, as scientists predict it will be, then the Earth will heat up faster than it otherwise would.
Stopping acid rain and reducing the burning of forests will also allow more heat to reach the Earth. This will partly be offset by an increase in tiny droplets of water from storms and spray but the net effect will be a warmer Earth.
© Guardian Newspapers Limited 2001