The world spends about 0.7% of GDP on fossil fuel subsidies. The cost of curtailing carbon emissions to meet scientific goals by 2050 has been estimated at 1% of GDP. (The cost of not curtailing carbon emissions, measured in weather calamities, mass migrations and the like, could be 5-10% of GDP.
http://www.thedailygreen.com/environmental-news/blogs/shapley/fossil-fuel-subsidies-55082701
