World economy could suffer a $20 trillion hit by century's end if governments fail to address global warming. The figure, equal to six to eight percent of projected global economic output in 2100.
It is likely an underestimate because it does not account for the cost of bio-diversity loss or of unpredictable events such as extreme weather or the collapse of the Gulf Stream.
According to sources, here on Saturday, these findings were made by two American economists in their report 'Climate Change the Costs of Inaction', which was compiled by economists at Tufts University's Global Development and Environment Institute. The study brings together the very latest scientific and economic thinking on climate change.
The report says that the climate system has enormous momentum, as does the economic system that emits so much carbon dioxide and thus we have to start turning off greenhouse gas emissions now in order to avoid catastrophe in decades to come.
The authors contend the true costs of climate change are incalculable, but argue that relatively small amounts of money are needed to keep temperatures in check.
Action to limit temperature increases to two degrees centigrade could avoid US $12 trillion in annual damages at a quarter of the cost, mentioned the report.
'The world, as a whole, could just barely, cope with the impacts of the first 2 degrees of warming, but only if there are immediate, large-scale, and creative approaches to international equity and co-operation,' the report added.
According to the report, the world faces serious economic and environmental problems if the burning of fossil fuels is not greatly curtailed.
Global temperatures have already risen by 0.6 degrees centigrade above pre-industrial levels. If emissions continue to rise unchecked global temperatures could increase by more than four degrees centigrade by 2100.
The world is very likely to hit a 2 degree increase without rapid action, with an array of costly environmental impacts, including decreased crop yields in the developing world, as well as from widespread drought and water shortages.
The report said that other impacts include a near total loss of coral reefs, the expanded northward spread of tropical diseases such as malaria, and the potential extinction of arctic species including the polar bear.
The study warns that a 3 degree temperature increase would have further impacts on world food supplies, spread diseases and potentially cause the wholesale collapse of the Amazon ecosystem as well as the complete loss of all boreal and alpine ecosystems.
If temperatures rise 4 degrees by century's end, sea levels will rise five to six meters, putting vast tracks of land underwater and producing millions of environmental refugees.
Elsewhere, entire regions would have no agricultural production whatsoever as a result of the changing climate. A temperature increase of more than 4 degrees, the report said, would bring a 50 percent chance that the ocean's circulation system would shut down, removing the crucial currents that warm and stabilise the climate of Northern Europe.