About half of that is negative cost reduction, so the average for that level of cut would be substantially lower than $ 50 / ton. (dotearth.blogs.nytimes.com)
These «negative cost opportunities» would require little or no technology innovation, the report said. (scientificamerican.com)
I would argue that the sensible middle of the road position eight years ago was to start taking no or negative cost actions limiting greenhouse gas emissions. (realclimate.org)