In that context, I think about "lowering your carbon footprint" It refers to becoming more eco-friendly or more "green." http://green.wikia.com/wiki/How_to_reduce_your_carbon_footprint

low carbon? You mean carbon dioxide? If I wanted to end it, I would think low carbon dioxide was a bad thing. :P If I wanted so save someone sitting in their car, who had turned on the engine in the garage, I would think it was a good thing. :P