he Residual carbon budget (RCB) It is the net amount Carbon dioxide (CO2) Which humans can still emit by keeping global warming below a certain limit, taking into account the influence of others Human climate factors. This concept is key when considering the speed of decarbonization needed to achieve the Paris Agreement target Keep global warming well below 2°C compared to pre-industrial levels and continue efforts to limit it to less than 1.5°C.
Now a study conducted by researchers from Imperial College London It has just been published in The nature of climate changebecomes the most up-to-date and complete analysis of the global carbon budget, an estimate of the amount of emissions that could be accounted for by keeping global warming below certain temperature limits.
The Paris Agreement aims to limit the rise in global temperature and continue efforts to limit it to 1.5 degrees Celsius. The remaining carbon budget is commonly used to evaluate overall progress toward these goals.
The new study estimates that l 50% chance of limiting temperature rise to 1.5°C, less than 250 Gt remaining Carbon dioxide in the global budget
The researchers warn that if carbon dioxide emissions remain at 2022 levels of around 40 gigatonnes per year, the budget allowance will be exhausted by around 2029, committing the world to a temperature rise of 1.5 degrees Celsius above pre-industrial levels.
This result means that the budget is lower than previously estimated and has been reduced by almost half since 2020 due to the continued rise in global greenhouse gas emissions, mainly caused by the burning of fossil fuels, as well as an improved estimate. The cooling effect of aerosols, which continues to decline globally due to measures to improve air quality and reduce emissions.
“Our results confirm what we already know: We are not doing enough to keep the temperature rise below 1.5 degrees Celsius – explained Robin Lambole, researcher at the Center for Environmental Policy at Imperial College London and lead author of the study. The remaining budget is now so small that small changes in our understanding of the world can lead to large proportionate changes in the budget. but, Estimates indicate less than a decade of emissions at current levels. The lack of progress in reducing emissions means that we can confirm that the window for keeping temperatures at safe levels is closing quickly.
“This carbon budget update is expected and fully consistent with the latest UN climate report,” concluded Professor Guerri Rogelj, Director of Research at the Grantham Institute and Professor of Climate Science and Policy at the Center for Environmental Policy at Imperial College London. The 2021 report has already highlighted that there is a one in three chance of this happening The remaining carbon budget at 1.5°C could be small, as our study now indicates. “This shows the importance of not just looking at central estimates, but also looking at the uncertainty surrounding them.”
The newspaper found that too The carbon budget for a 50% chance of limiting temperature rise to 2°C is about 1,200 gigatonnes. This means that if CO2 emissions continue at current levels, the central 2°C budget will be exhausted in 2046.
There was significant uncertainty in this estimate due to the influence of other factors, including warming caused by gases other than carbon dioxide and the ongoing effects of emissions that were not taken into account in the models.
The new research used an updated data set and improved climate models compared to other recent estimates, distinguishing these uncertainties and increasing confidence around estimates of the remaining carbon budget.
The enhanced methodology also provided new insights The importance of potential responses to the climate system To achieve net zero, which refers to achieving a general balance between global emissions produced and those removed from the atmosphere.
According to the study’s modeling results, there are still significant uncertainties about how different parts of the climate system will respond in the years before net zero is reached. The climate may continue to warm due to effects such as melting ice, methane emissions, and changes in ocean circulation. However, carbon sinks, such as increased vegetation growth, can also absorb large amounts of carbon dioxide, causing global temperatures to fall before reaching net zero.
Lambole says these doubts further highlight the urgent need to cut emissions quickly. “At this point, our best guess is that the opposing warming and cooling will roughly cancel each other out after we reach net zero. However, only when we reduce emissions and get closer to net zero will we be able to see what the long-term heating and cooling adjustments will look like.” Every fraction of a degree of warming will make life more difficult for people and ecosystems. This study is another warning from the scientific community. “It is now up to governments to act,” he concluded.