Those attending hope to finalise a report on how the world can mitigate rising levels of greenhouse gases. A draft version of the report, seen by the BBC, says it is possible to make a real difference, but that countries need to implement policies immediately.
Environmentalists argue that while massive investment is needed to put these policies into practice, the eventual consequences of doing nothing far outweigh the cost of tackling global climate change now.
Two reports issued earlier this year by the IPCC, the leading United Nations panel on global warming, warned that the earth was already warming considerably, and that mankind was almost certainly to blame.
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