Back in 2015, nearly 200 countries came together to sign the Paris Agreement, committing to limit the global temperature rise to 1.5 degrees Celsius above pre-industrial levels. This threshold was identified because surpassing it would intensify the impacts of the climate crisis. However, new research suggests that the world only has a 50% probability of achieving this target by 2030, mainly due to persistently high greenhouse gas emissions.

This research represents the latest and most comprehensive analysis of the global carbon budget, which calculates the total greenhouse gases that can be emitted while maintaining temperature increases within desired limits. The remaining carbon budget is a vital tool for evaluating our progress towards meeting the objectives of the Paris Agreement.

For a 50% probability of limiting the temperature rise to 1.5°C, only about 250 gigatons of carbon dioxide remain in the global carbon budget. It might seem like a lot but it actually isn’t. Given the 2022 emission rates, which are approximately 40 gigatons per year, this budget is projected to be depleted by 2029.

The current budget estimate is notably lower than previous assessments, having been reduced by half since 2020. This sharp decline is primarily attributed to the ongoing surge in greenhouse gas emissions, predominantly from fossil fuel combustion. The planet’s average temperature has already risen by approximately 1.2 degrees Celsius, leading to extreme weather events like wildfires and hurricanes.

Estimating the remaining carbon budget is a complex task, fraught with uncertainties due to various factors, including the effects of gases other than carbon dioxide. In this study, the researchers utilized an updated dataset and enhanced climate models, providing a more refined estimate than those published earlier this year.

“Our finding confirms what we already know — we’re not doing nearly enough to keep warming below 1.5°C,” Robin Lamboll, study author at Imperial College London, said in a press release. The remaining budget is now so small that minor changes in our understanding of the world can result in large proportional changes to the budget.

All is not lost

Although the updated carbon budget is concerning, the overarching message remains consistent with previous evaluations: A significant reduction in greenhouse gas emissions is imperative to combat climate change. Achieving the 1.5°C target appears increasingly challenging, but it’s essential not to lose sight of the broader goal.

The researchers also revised the carbon budget for limiting warming to 2 degrees Celsius — the less ambitious target included in the Paris Agreement. Encouragingly, if nations fully implement their current climate strategies (a best-case scenario given some countries’ wavering commitments), we might be able to contain the temperature increase below this threshold.

With ambitious and coordinated global efforts, peak warming could be limited to around 1.6°C or 1.7°C. Moreover, with sustained efforts, it may be possible to bring temperatures back below the 1.5°C mark over a more extended period. The upcoming UN climate summit, COP28, will serve as a pivotal platform for nations to enhance their commitments in light of these findings.

The study was published in the journal Nature Climate Change.