Kevin Anderson, of the Tyndall Centre for Climate Change Research in Manchester, has shown that the carbon emissions budget for avoiding 2 °C warming is due to be used up by 2034.[1] 

Climate scientists recognise that the global temperature depends directly on the cumulative amount of carbon dioxide emitted into the atmosphere. 

Last year the Intergovernmental Panel on Climate Change (IPCC) said that humanity would have a 66% chance of avoiding 2 °C warming if it kept within a budget of 1000 billion tonnes (Gt) of CO2 starting from 2011. Anderson applied simple arithmetic to this budget (see figure).

graph of emissionsFirst, he subtracted 140 Gt that have already been emitted from burning fossil fuels between 2011 and 2014. Next he subtracted conservative estimates of the emissions from deforestation (60 Gt) and cement production (150 Gt) up to 2100.

This left a budget of 650 Gt for energy production. In 2013 global emissions from energy production were 34.2 Gt.[2] 

This leads to the inevitable conclusion that the world will hit the 2°Cwarming threshold within 650/34.2 = 19 years time or around 2034. Anderson’s paper concludes “… the carbon budgets associated with a 2 °C threshold demand profound and immediate changes to the consumption and production of energy”.

[1] Anderson, Kevin. “Duality in Climate Science.” Nature Geoscience, October 12, 2015, pp.2. doi:10.1038/ngeo2559.