Fighting global warming will be inexpensive but governments have little time left to avert big, damaging temperature rises, a draft United Nations report shows.
The draft, due for release in Bangkok on May 4th, indicates warming is on track to exceed a 2 Celsius (3.6 F) rise over pre-industrial times, regarded by the European Union as a threshold for "dangerous" change to nature.
Two scenarios highlighted in the report, the third in a UN series in 2007 that will guide policymakers, say the costs of limiting emissions of greenhouse gases could mean a loss of 0.2 or 0.6 per cent of global gross domestic product (GDP) in 2030.
Some models show that measures such as greater efficiency in burning fossil fuels such as oil and coal could even mean a small net boost to the world economy, it said.
The most stringent scenario assessed, demanding that governments ensure that global greenhouse gas emissions start falling within 15 years, would cost 3 per cent of GDP by 2030.
The conclusions broadly support those in a report last year by former World Bank chief economist Nicholas Stern, who estimated that costs of acting now to slow global warming were about one percent of global output, against a far larger 5 to 20 per cent if the world delayed action.
The UN draft says there is "significant economic potential" for cuts in greenhouse gas emissions, mainly from burning fossil fuels, "sufficient to offset growth of global emissions or to reduce emissions below current levels."
Last week, the latest published report by the Intergovernmental Panel on Climate Change (IPCC) predicted that hundreds of millions of people in the poorest regions of the world will face water shortages, flooding, hunger and disease because of global warming over the coming century.
The report predicts that millions of people in coastal areas, especially small islands and large river deltas, could lose their homes due to flooding.
This will be prompted by increases in sea level due to ice melting in polar regions and other glacial fields and more intense storms.