scientists say that making predictions about greenhouse gas emissions in the next century is not going to be easy. By the year 2010, emissions could be five times as high as today's, twice the level previously predicted, or just possibly, they could be slightly lower than today's. The biggest hurdle in their predictions is the unknown factor: how technology develops to reduce emissions, they ask.

A draft special report on emissions scenarios by the United Nations Intergovernmental Panel on Climate Change ( ipcc ), which will be published in March next year, represents the consensus view of hundreds of scientists and economists.

Earlier reports from the ipcc have come up with a "business-as-usual' scenario, which project likely emissions of greenhouse gases in the next millennium if governments do not cut them. Many scientists believe that this scenario would double the concentration of greenhouse gases in the atmosphere and increase global temperatures by between 2-4