The effects of relentlessly rising global temperatures in the coming century are likely to be catastrophic for the world, the second volume of the new IPCC report spells out with more chilling confidence than ever before.

The key point to grasp from Impacts, Adaptation and Vulnerability is that so many terrible things might happen at once to a planet already under severe stress from rapid population growth, poverty and pollution.

Water supplies, agriculture, human health, wildlife, coastal cities, towns and villages and even whole national economies are all likely to be knocked off balance by climate change, the report predicts. Its 1,000-plus pages go into enormous detail about every continent.

Billions of people will to be affected directly. Societies may be able to bring about some limited adaptation, but the least able to adapt will be the poor developing countries in Africa, Asia, Latin America and the Pacific, who will be hit hardest. Their future is grim.

But do not just think of this as the future. The effects of a warming world are already vividly visible all around us and have been widely documented, the report says: across the globe now glaciers are shrinking, permafrost is thawing, ice on the sea, lakes and rivers is freezing later and melting earlier, and plant and animal behaviour is changing, with some species extending their ranges towards the poles and others declining. There are earlier dates for trees coming into leaf, insects emerging, and birds laying their eggs.

George W. Bush take note:  in its sober scientific language, the report insists that these phenomena are not accidental. "The observed changes in these systems are consistent in direction and coherent across diverse localities and/or regions... there is high confidence that recent regional changes in temperature have had discernible impacts on many physical and biological systems."

Yet the future that the report predicts is far worse. In the natural world, glaciers, coral reefs and atolls, mangrove swamps, northern and tropical forests, polar and alpine ecosystems, wetlands and grasslands may not just change, but "undergo significant and irreversible damage". Rare and endangered species will generally move close to extinction, and more will disappear, despite conservationists' efforts to save them.

For the human world the outlook is equally dire, not least for the fact that climate change will be imposing new interlocking stresses on human society -- in an era of soaring population growth, falling incomes and rising pollution -- all at the same time.

Among the most significant points are:

Global warming threatens the world with a double whammy over water, the report predicts. Where there is currently enough, there is likely to be too much, in the shape of floods from increased rainfall; where it is badly needed, there is likely to be less, in the shape of droughts. The supercomputer models indicate that there will be heavier rainfall over areas such as northern Europe, including Britain, and lower rainfall over areas such as northern Africa or Australia.

"Flood magnitude and frequency could increase in many regions as a consequence of increased frequency of heavy precipitation events," the report says. It adds:  "River flood hazard will increase across much of Europe" -- a line that will be resonant to anyone driven out of their home by the floods following last winter's rains in Britain, the heaviest in southern England since at least 1727, and by some calculations, for 500 years or more.

But water shortage may be an even heavier burden to bear. Approximately 1.7 billion people, one-third of the world's population, already live in countries that are water-stressed, the report points out, and this figure is predicted to increase to five billion by 2025. In many of these countries, especially those in central Asia, north Africa and southern Africa, rainfall is likely to decrease further, and water quality is likely to become degraded through higher temperatures and pollutant run-off.

The implication of water shortage is simple: the failure of food supplies. The report predicts "a general reduction in crop yields in most tropical and sub-tropical regions for most projected increases in temperature, and a general reduction, with some variation, in potential crop yields in most regions in mid-latitudes, for increases in annual temperature of more than a few degrees C".

Across Africa, grain yields are expected to fall in many areas, with deserts growing; many countries of southern Asia are likely to see their yields fall also. In Latin America, yields may decrease to such an extent that "subsistence farming may be threatened".

The models predict some agricultural benefit from a warmer world. Timber-growing in some areas may for a time be more productive, and crops may be able to flourish in unaccustomed areas, such as northern Canada, but the report gives a warning at reading too much into this: "Benefits for crops would decline at an increasing rate and possibly become a net loss with further warming."

As if flooding and the failure of food supplies were not enough, a greatly increased danger of disease will accompany them. There is likely to be a significant rise in the numbers of people exposed to vector-borne diseases such as malaria and dengue fever, and water-borne diseases such as cholera, which already impinge on up to 50 per cent of the world's population, the report says.

"Within their present ranges, these and many other infectious diseases would tend to increase in incidence and seasonality -- although regional decreases would occur in some infectious diseases."

Disease itself is not the only health threat. "Projected climate change will be accompanied by an increase in heatwaves, often exacerbated by increased humidity and urban air pollution, which would cause an increase in heat-related deaths and illness episodes. The evidence indicates that the impact would be greatest in urban populations, affecting particularly the elderly, sick, and those without access to air-conditioning."

But the lack of food and water and health are not the only threats: the places where people live may be at risk directly. Climate change presents another bleak threat from water, the destructive power of the sea. Combine two expected phenomena, sea-level rise and the increase in violent storms, and you have a recipe for disaster on an unthinkable scale, especially in countries such as Bangladesh or Egypt where millions of people are living on land below sea level.

With a mid-range sea-level rise of 40cm, the report says, the mean annual number of people who would be flooded by coastal storm surges would increase by 2080 by between 75 and 200 million, depending on the preventive measures taken.

Landslides may be as big a threat as flooding in some parts of the world.

Plants and animals, of course, will be every bit as affected as humans, and the resultant stresses will result in some of them going extinct. Modelling studies "continue to show the potential for significant disruption of ecosystems under climate change," the report says.

The change will happen too quickly for ecosystems to migrate, so the species composition within them will alter. As species are adapted to their ecosystems, this means big trouble for many of them.

"Many species and populations are already at high risk, and are expected to be placed at greater risk by the synergy between climate change rendering portions of current habitat unsuitable for many species, and land-use change fragmenting habitats and raising obstacles to species migration," says the report. "These pressures will cause some species currently classified as 'critically endangered' to become extinct and the majority of those labelled 'endangered or vulnerable' to become rarer, and thereby close to extinction, in the 21st century."

Throughout the 1,000 pages of predictions one theme is constant: it will be the poor of the world who will be hardest hit. Not only will climate disruption be greatest in the countries with lowest incomes -- in water and food shortages, disease and natural disasters -- the people who live there are those who can least afford adaptation and mitigation measures. Will the rich countries be able to sit back and watch it all happen? Or is this coming collection of stresses on a battered planet be something with the power to overwhelm us all?

Planet Earth is warming faster than at any time in the past one thousand years and there is little doubt that human activity is to blame, according to the latest and most definitive scientific assessment of climate change.

An exhaustive analysis of global temperature and weather measurements on land, sea and air has found that we are living through an unprecedented period of climatic instability that is almost certainly the result of industrial pollution.
In a report published today by the United Nations Intergovernmental Panel on Climate Change (IPCC), hundreds of the world's leading scientists give their unqualified support to the view that global warming is real and that the release of man-made greenhouse gases is largely responsible. Since their previous report was published five years ago, the IPCC scientists found that they had vastly underestimated the extent to which average global temperatures were rising. They now believe they will rise by as much as 5.8C by the end of this century, almost twice the increase predicted in their 1996 report.

The latest three-volume report, amounting to 2,600 pages of detailed analysis, leaves the reader in little doubt that the scientific uncertainties of the previous decade are being resolved in favour of an emerging, and increasingly pessimistic consensus.

"There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities," the report says. The conclusion replaces the view of the previous IPCC report of 1996, which stated:  "The balance of evidence suggests a discernible human influence on global climate."

Although many uncertainties still remain, the latest report, Climate Change 2001, The Scientific Basis, says that more recent analysis of an "enormous body of observations of all parts of the climate system" has justified the updated view of a world that is getting progressively warmer. "Both temperature and sea level are projected to continue to rise throughout the 21st century for all scenarios studied," the report says. "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system."

Average global temperatures taken over the Earth's surface show a pattern that has worsened consistently since records began in 1861. Over the 20th century the increase has been about 0.6C, with records showing two distinct periods of warming: one between 1910 and 1945, and the other between 1976 and 2000.

Although the scientists believe that natural variability in the climate may have contributed to the warming seen in the first half of the past century, they believe it cannot fully account for that seen in more recent decades. "The warming over the last 50 years due to anthropogenic [man-made] greenhouse gases can be identified despite [other] uncertainties," the scientists say.

Globally, it is very likely that the 1990s was the warmest decade and that 1998 was the warmest year since readings began in 1861. If more historical records, estimated from studies of tree rings, corals and ice cores, are taken into account then the increases in temperature seen at the end of the 20th century are likely to be the highest of any century in the past millennium.

Other observations relating to snow and ice, sea levels and rainfall also show a clear trend, suggesting that a warmer world is having a drastic impact on global weather patterns. Satellite data shows it is "very likely" that snow cover has decreased by about 10 per cent over the past 40 years. Other data supports the view that ice on lakes and rivers in the northern hemisphere now disappears at least two weeks earlier at the end of each winter than it did a century ago.

Mountain glaciers are rapidly melting in non-polar regions and the area covered by sea ice in the Arctic has retreated by between 10 and 15 per cent since the 1950s. The thickness of Arctic ice has suffered an even more catastrophic decline, thinning by about 40 per cent over a similar period.

As the oceans warm up, then the sea levels rise, mainly because of thermal expansion. "Tidal gauge data shows that global average sea level rose between 0.1 and 0.2 metres during the 20th century," the scientists say.

Global warming is also causing more rainfall in some parts of the world, mainly the temperate regions of the north, and increased cloud cover as a warmer world means more water evaporates from the oceans. In some parts of Asia and Africa, the frequency and intensity of droughts have increased in recent decades.

The IPCC scientists are in little doubt over what they believe to be largely responsible for such severe changes to the climate. Emissions of greenhouse gases and aerosols are altering the atmosphere and affecting climate, they say.

Levels of carbon dioxide (CO2), the principal greenhouse gas produced by burning fossil fuels, have increased in the atmosphere by 31 per cent since 1750, when the Industrial Revolution began.

"The present CO2 concentration has not been exceeded during the past 420,000 years and likely not during the past 20 million years. The current rate of increase is unprecedented during at least the past 20,000 years," the IPCC says.

About three quarters of the increase in man-made CO2 since about 1980 is due to burning fossil fuel. The rest is due to changes in land use, mostly caused by deforestation.

Other important greenhouse gases -- which help to trap solar heat in the atmosphere -- have also increased. Methane, produced by cattle ranching, rice production and landfills, has more than doubled since 1750. Nitrous oxide has increased by 17 per cent over the same period, a concentration not seen at least in the past 1,000 years.

"In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations," the IPCC concludes.