Leading climate scientists now agree that human pollution mainly caused by burning fossil fuels has contributed substantially to global warming in the past 50 years and that the Earth is likely to get far hotter than previously predicted with immense consequences for people and wildlife everywhere.
A leaked summary of the final draft of 1,000 pages of new research carried out by the Intergovernmental Panel on Climate Change, a UN-sponsored group of hundreds of the world's leading atmosphere scientists, has been sent to governments this week.
It is expected to add urgency to the global climate change talks in The Hague next month where Britain intends to take an international lead in persuading countries to set targets and timetables to reduce emissions.
The report suggests that the upper range of warming over the next 100 years could be far higher than estimated in 1995. Its worst-case scenario now raises the average global temperature 11 degrees F from its 1990 levels.
Average temperatures today are 9 V F warmer than they were at the end of the last Ice Age. In its 1995 analysis the panel concluded that a worst case would raise temperatures a conservative 6.3 degrees. The leaked document is the first major update of climate science since 1995 when the same UN panel concluded merely that there was "a discernible human influence" on climate because of the greenhouse effect, from build-up of heat-trapping chemicals in the atmosphere.
The panel has now concluded that the burning of fossil fuels and emissions of man-made chemicals have "contributed substantially to the observed warming over the last 50 years". The scientists believe, too, that temperatures could go far higher and faster than previously predicted if emissions are not curtailed. The human influence on the Earth's climate has long been debated, but this is the first time such an authoritative group of scientists has gone so far.
While there are still uncertainties, the scientists say there is "an increasing body of observations that provide a collective picture of a warming world that cannot be solely explained by natural forces. Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that affect the climate system," the report says.
Many panel members in the US say the summary represents the closest thing to a consensus possible in science.
Global warming is expected to impact most deeply on poor countries, leading to huge numbers of environmental refugees, crop failures and extreme weather. The US is responsible for 23 per cent of carbon emissions, with Britain the same as the whole of Africa at 3 per cent.