How much CO2 can humanity still emit if it wants to survive? goals of the Paris agreement? A new study shows there may be less time than expected to limit emissions and warming, while highlighting the uncertainties surrounding the issue. According to this analysis published this Monday in Nature Climate Changethere are about six years left before the 1.5°C warming mark is crossed, at the current rate of carbon emissions (i.e. around 40 billion tonnes each year).
Based on reassessed data and methodology compared to previous estimates, including the latest IPCC report, Robin Lamboll of Imperial College and his team recalculated the remaining “carbon budget”. That is to say the net quantity of CO2 which can still be emitted without exceeding a given warming threshold. Conclusion: “the window to avoid 1.5 degrees is narrowing,” underlines Robin Lamboll. Joeri Rogelj, one of the other contributors, is even more radical: “It is clear that the likely options for limiting warming to 1.5°C are gone, and have been for some time,” he said. .
Fateful consequences
Since the industrial era, the planet has already warmed by 1.2°C on average. And the latest estimates from the European Copernicus Observatory show that +1.5°C could occur by 2034, and not in the middle of the century as climate policies around the world predict.
To be effectively reached, this limit will have to be measured over several decades, but its crossing could be observed occasionally much earlier, opening the way to cascading harmful consequences such as the melting of ice caps, the dieback of forests, etc. It is thus “ highly likely that 2023 will exceed 1.5 degrees,” estimates Robin Lamboll. To stay below 2 degrees, a “last resort” according to scientists, the room for maneuver is hardly higher.
Not to give up
However, many uncertainties remain, other factors such as warming by other greenhouse gases such as methane or the cooling effect of aerosols (fine particles), could also intervene, underline the authors. “It’s like playing Russian roulette with two balls. Few people will be surprised if someone gets shot with such odds,” warns Joeri Rogelj. However, the authors insist that we must not give up.
“Even if we don’t limit warming to 1.5 degrees, sticking to limited emissions will give us a better chance of staying at 1.6 or 1.7 degrees, which would be a very good result given the direction in which we are currently heading. The latest scientific reports show that we are currently on a trajectory of warming to +2.4 degrees or more by the end of the century.
The authors urge governments to act quickly, one month before COP28 in Dubai where the rapid reduction of emissions, and the means to achieve it, will be one of the most difficult negotiating themes.