Carbon budget for 1.5°C will run out in six years at current emissions levels – new research
(The Conversation, 30 Oct 2023) If humanity wants to have a 50-50 chance of limiting global warming to 1.5°C, we can only emit 250 another gigatonnes (billion metric tonnes) of CO₂. This effectively gives the world just six years to get to net zero, according to calculations in our new paper published in Nature Climate Change.
The global level of emissions is presently 40 gigatonnes of CO₂ per year. And, as this figure was calculated from the start of 2023, the time limit may be actually closer to five years.
Our estimate is consistent with an assessment published by 50 leading climate scientists in June and updates with new climate data many of the key figures reported by the Intergovernmental Panel on Climate Change (IPCC) in August 2021.
How much CO₂ can still be emitted while remaining under a certain level of warming is referred to as the “carbon budget”. The carbon budget concept works because the increase in Earth’s global mean surface temperature has increased in a linear fashion with the total amount of CO₂ people have emitted since the industrial revolution.
The other side of this equation is that, roughly speaking, warming stops when CO₂ emissions stop: in other words, at net zero CO₂. This explains why net zero is such an important concept and why so many countries, cities, and companies have adopted net zero targets.