Although there is great uncertainty about exactly what will happen, climate researchers who have prepared reports for the Intergovernmental Panel on Climate Change (IPCC) have pointed to some thought-provoking implications.

Sea level rises

At present some 46 million people live in areas at risk of flooding due to storm surges. Scientists estimate that a 50cm rise in sea level would increase this number to 92 million and a one-metre rise would put 118 million in peril. The figures are based on current population density and present levels of sea defence measures.

Floods like these in Bangladesh could become more common if sea levels continues to rise at the predicted rate

If the global ocean level went up by one metre, Egypt would lose 1% of its land area, the Netherlands would lose 6%, Bangladesh would lose 17.5%, and on the Majuro Atoll in the Pacific Marshall Islands some 80% of the land would disappear under water.

Crops and productivity

It is thought that total global crop production would be unchanged but regional effects of climate change would vary widely.

Those most at risk from famine would be peoples who rely on isolated agricultural systems in arid and semi-arid regions.

Populations particularly under threat live in sub-Saharan Africa, south east Asia and tropical areas of Latin America.

Climate change could also alter market conditions and the range of agricultural pests.

Disease

Extensions of the geographical range and season for some organisms could result in increases of diseases like malaria, dengue fever and yellow fever.

If the temperature increases by 3-5C the number of people potentially exposed to malaria could go up from 45% to 60% of the world population and result in an extra 50-80 million cases a year.

Air pollution and exposure to greater extremes in temperature could lead to a greater frequency of asthma and respiratory diseases.

Ecosystems

Scientists predict that composition and range of many ecosystems will shift as species respond to climate change.

Research models project that a substantial fraction of the world's forests, and possibly up to two thirds, will undergo major changes. They say the species composiiton will change and some forest may disappear all together.

Deserts are likely to become more extreme and result in increased soil erosion.

Mountain glaciers could retreat and inland wetlands would be affected by global warming with resultant changes in habitat for the current species.

Ice in northern latitudes will melt if the global climate warms as predicted

Researchers suggest that there will be a myriad of other changes and even a few surprises.

But both the scientists and environment campaigners say human impact on the climate can be reduced by a number of measures.

Alternatives

We could reduce energy consumption by making fewer journeys and using better insulation in our homes. This would lessen the need to burn coal and oil, and lead to reduced emissions of carbon dioxide and nitrous oxide.

The last IPCC report in 1995 said advances in technology could result in fossil fuels being burned more efficiently. It also said emissions could be reduced by making wider use of low carbon fossil fuels like natural gas, and decarbonising exhaust gases from power plants.

Environmental groups like Greenpeace and Friends of the Earth would like to see a switch to renewable and clean sources of energy such as solar, wind and hydro-electric power.

Sustaining existing forest cover, planting new trees and better management of land use is also suggested as a means to slow global warming.

More controversial is the use of nuclear power. Nuclear fission avoids using large quantities of fossil fuel for energy but is very contentious because it produces radioactive waste.

Nuclear fusion, a theoretical way of harnessing power by fusing atoms which is still under development, may one day provide a cleaner alternative to the world's energy problem.