Meeting the 1.5 degree target from the Paris climate agreement could be even more difficult than previously assumed. Calculations using new data and improved models come to an unfavorable conclusion: In order not to miss this goal, humanity must emit significantly less carbon dioxide (CO2) than estimated in the United Nations’ sixth global climate report in 2021. With global CO2 emissions at the 2022 level, this amount would be used up in about six years, writes a research group led by Robin Lamboll from Imperial College London in the journal “Nature Climate Change”.
The Paris Climate Agreement of 2015 aims to curb global warming: Limiting greenhouse gas emissions is intended to limit the rise in temperature to 1.5 degrees Celsius above pre-industrial levels, if possible. In recent years, climate researchers have repeatedly used computer models and calculations to estimate the amount of CO2 that will lead to a maximum warming of 1.5 degrees. In the sixth global climate report from 2021, this estimate was 494 billion tons of CO2.
In a recalculation, Lamboll and colleagues now came to a remaining amount of CO2 of 247 billion tons of CO2 – half of the previous estimate. However, in the world climate report, the remaining amount referred to the period from the beginning of 2020, while the current study refers to the period from the beginning of 2023.
A large part of the difference from the previous estimate is the use of a new computer model that simulates climate change caused by greenhouse gases. The research team also used more current data on actual CO2 emissions and thawing permafrost. After the decline in emissions in the first year of the corona pandemic – i.e. 2020 – the amount of global CO2 emissions in 2022 was back to the pre-corona level at around 40 billion tons per year.
If humanity does not emit more than 247 billion tons of CO2 in the next few years, then there is a 50 percent chance that global warming will not rise above 1.5 degrees. According to Lamboll and colleagues’ estimate, there would still be 1,220 billion tons to meet the two-degree target with a probability of 50 percent.
In a commentary, also in “Nature Climate Change,” Benjamin Sanderson of the Center for International Climate and Environmental Research in Oslo writes: “The work of Lamboll and colleagues makes uncomfortable reading for policymakers.” According to him, the study results make it clear that any calculation, no matter how strict, can change with revised data and findings.
Climate researcher Tatiana Ilyina from the University of Hamburg considers the results of Lamboll’s team to be serious and reliable. The study shows once again how urgent it is to quickly reduce greenhouse gas emissions. “We are expected to have the highest CO2 emissions ever again this year. I don’t know what else we as scientists should do to get global policymakers to really make an effort.” There are fewer and fewer climate change deniers; But it is increasingly being said that we cannot prevent climate change anyway, so we can continue to live as before. “Climate change won’t leave things as usual,” emphasizes Ilyina.
Niklas Höhne, head of the New Climate Institute in Cologne, says that the study results should in no way be interpreted as meaning that efforts to reduce greenhouse gas emissions could be abandoned. On the contrary: “Even if the multi-year average exceeds 1.5 degrees, it is good to have saved as many emissions as possible beforehand, as every ton saved leads to a smaller global temperature increase and thus to less damage.”
