``We see changes in climate, we believe we humans are involved and we're projecting future climate changes much more significant over the next 100 years than the last 100 years,'' said Robert Watson of the U.N.'s Intergovernmental Panel on Climate Change.

Robert Watson, left, chairman of the Intergovernmental Panel on Climate Change (IPCC), answers questions Monday, Jan. 22, 2001 at a news conference. In the most emphatic warning yet about the danger of global warming, a meeting of scientists from 99 nations issued a report Monday that sharply increased projected climate change blamed on air pollution and warned of drought and other disasters. Persons next to Watson are Sir John Houghton, center, and Yihui Ding, right. (AP Photo/Eugene Hoshiko)

A warmer climate would raise sea levels as ice caps recede and could force tens of millions of people to flee low lying areas like China's Pearl River Delta, Bangladesh and Egypt, the IPCC chairman told a news conference in Shanghai.

Klaus Toepfer, the head of the United Nations Environment Program which part sponsors the IPCC, said the report should ring alarm bells everywhere.

``The scientific consensus presented in this comprehensive report about human-induced climate change should sound alarm bells in every national capital and in every local community,'' he said in a statement.

``We must move ahead boldly with clean energy technologies and we should start preparing ourselves for the rising sea levels, changing rain patterns and other impacts of global warming.''

Global warming is a highly controversial subject with many respected scientists arguing that the earth undergoes periodic climatic changes with or without contributions from humanity.

The IPCC report, which runs to more than 1,000 pages, was written by 123 lead authors around the world who drew on 516 contributing experts and is one of the most comprehensive produced on global warming.

A draft summary for policy makers, issued on Monday, said the report projects the earth's average surface temperature will rise 1.4 to 5.8 degrees Celsius (2.5 to 10.4 degrees Fahrenheit) between 1990 and 2100, higher than its 1995 estimate of a one to 3.5 degree C rise (1.8 to 6.3 degrees F).

Sea levels were likely to rise between nine and 88 cm (3.54 and 34.64 inches) over the same period, it said.

``The decade of the 1990s was the hottest decade of the last century and the warming in this century is warmer than anything in the last 1,000 years in the Northern Hemisphere,'' Watson said.

``We will see a drier summer in arid and semi-arid areas which will make water management much more difficult in the future,'' he said. Ecosystems such as coral and forests will suffer.

The earth's temperature had already risen 0.6 degrees C (1.08 degrees F) over the last 100 years and it has seen more floods and droughts around the world in the last decade. Land areas had warmed close to one degree, more than oceans, the IPCC said.

Disease, Less Water

Watson said the main reason behind expectations of faster global warming is an anticipated fall in cooling agents such as sulfur dioxide. Sulfur emissions are expected to ease due to concerns they cause acid rain and deposits, he said.

Greenhouse gases such as carbon dioxide prevent heat from leaving the earth, therefore warming the earth's atmosphere, whereas sulfur dioxide tends to cool it.

Watson said the implications of global warming on human health included increases in heat stress mortality in the summer and diseases such as malaria and dengue fever.

It could also hit agriculture and water resources, which many experts believe will be a major issue in coming years.

Watson said industrialized nations had to help curb global warming, but developing countries must become more energy efficient and getting the right technologies in place everywhere was critical.

``Governments can play a critical role in placing the right enabling framework to facilitate the transfers of technology,'' he said. ``It's not just hardware, it's information and knowledge.''

Copyright © 2001 Reuters Limited

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