Scientists have warned in a report released today (30 January) that the effects of climate change could be far worse than already predicted, and that developing countries face the biggest threats.
In the introduction to the report, UK prime minister Tony Blair said it is now clear that human activities are "causing global warming at a rate that is unsustainable".
The report, published by the British government, brings together research on climate change presented at an international conference held at the UK Meteorological Office in February 2005.
It warns that developing countries could face reduced crop yields, increased desertification, more water shortages, and a possible increase in malaria in Africa.
The report repeats earlier warnings that rising sea levels are likely to cause major flooding in low-lying coastal areas and islands.
Research published in the journal Geophysical Research Letters this month shows that sea levels are rising at an increasing rate. It says sea levels could rise by a global average of 30 centimetres by 2100 if the current trends do not change.
The authors say their study is the first to use historical data to confirm predictions made by computer models.
John Church and Neil White of the Commonwealth Scientific and Industrial Research Organisation, Australia, studied tidal records going back to 1870. They say sea levels rose by an average of 1.44 millimetres a year since then, but that since 1950 this figure increased to 1.75 millimetres a year.
The authors attribute the acceleration in sea-level rise to melting glaciers and polar ice caused by global warming. They call for greenhouse gas emissions to be halved by 2050.