Copenhagen Climate Deal - how to close the gap?

Globally business as usual emissions for 2020 of 57 GtCO2e are projected. To have a good chance at limiting global warming to 2°C or 1.5°C, 2020 emissions would need to be below 44 and 40 GtCO2e respectively. Hence the Copenhagen Climate Deal needs reductions of around 13-17 GtCO2e by 2020.