The idea that there is a certain amount of carbon dioxide, that we can release by burning more coal, gas and oil, and still keep the global temperature increase to under 2°C is a dangerous illusion. This so called “carbon budget” is based on unrealistic, high-risk, assumptions.
The most frequently advocated carbon budget declares that we can emit 275 billion tons of carbon (which is 1000 billion tons of CO2) giving a 33% risk of exceeding the target of 2°C. Is it reasonable that this budget gives a 33% change of failure, when engineers design bridges so the risk of failure is less than one in a million or 0.01%.
If we demand a 90% chance of staying below the 2°C target, there is simply no carbon budget available. We have already burned too much fossil fuel.
Also, this 2°C of warming is not a safe target. It is the boundary between dangerous and very dangerous temperature increase. It would take the temperature to 1°C higher than experienced during the whole period of human civilisation …. The last time greenhouse gas levels were as high as they are today, modern humans did not exist, so we are conducting a dangerous experiment on the climate of our planet.
Decades of procrastination mean there is no longer sufficient time for an incremental and non-disruptive reduction in emissions. Only a whole-of-society rescue plan, understood as action at emergency speed outside of the business-as-usual political mode, can provide hope of retaining a liveable planet for ourselves and future generations.
“Recount: It’s time to do the math again”
(David Spratt, 23 April 2015)