Ok, so we have a long-term goal of keeping global warming below 2°C/1.5°C, but what does this mean in reality? Enter the IPCC AR5 cumulative emissions budgets! This is the maximum amount of tons of CO2 the atmosphere can take before crossing these limits.
According to the AR5, after 2010 we can only emit an additional 1,000 billion tons (Gt) of CO2 into our atmosphere if we want a higher than 66% likelihood of limiting global warming to below 2°C. To keep warming below 1.5°C the remaining carbon budget is consequently smaller.
Since 2010 we have already spent about a tenth of this budget. Oops! Freezing our annual global emissions to current levels would use up the remaining budget completely in just 25 years, and almost one third of it would be gone by 2020. With current growing emissions we’ll have used up our budget even sooner.
What does it mean? It means that peaking and starting the decline in emissions soon is fundamental for achieving the long-term goal.
It also means we’re no longer in the business of managing emissions. We have to phase them out to zero, and it needs to happen fast. If you thought we had time until the end of the century, you’ve misunderstood the IPCC’s conclusions.
What the IPCC carbon budgets imply, for CO2 emissions (most of which come from the burning of fossil fuels), is that we need to get to zero carbon by around 2050, if we want to have high certainty of keeping global warming below 2°C and some certainty of getting below 1.5°C. Also, if we don’t want to rely on technologies that only exist on paper and come with many risks.
It also means that looking for new fossil fuels – and spending billions in subsidies to support that exploration – makes no sense. We’ve already found too much and must leave about 80% of it in the ground.
Obviously, in the spirit of equity, which the IPCC finds is key to successful cooperation, the countries with the greatest responsibility and capability will need to phase out fossil emissions earlier, and provide support for the poorer countries.