Almost all of climate change is due to human activities

Since the middle of the 19th century, the planet has gained more than 1 ° C. Researchers wanted to determine how much of this warming was caused by greenhouse gas emissions from human activities and how much was linked to "natural forcings", natural factors such as large volcanic eruptions or fluctuations in solar radiation.

Unmistakable results

Scientists, therefore, reviewed 13 different climate models to simulate temperature changes under three scenarios. In the first, aerosols are the only contributors to warming, in the second, only natural forcings are considered, and in the third, greenhouse gas emissions are taken into account.

Conclusion: human activity has contributed to the warming by 0.9 to 1.3 ° C, an estimate in line with the current warming. “Our results clearly show that global warming is caused primarily by humans,” commented Nathan Gillet, co-author of the study.

Ambitiously reducing emissions

The 2015 Paris agreement aims to keep global warming below + 2 ° C if possible + 1.5 ° C. But to achieve the latter goal, emissions would have to be reduced by 7.6% per year between 2020 and 2030, according to the UN. A figure similar to the drop measured in 2020 due to the coronavirus pandemic.

Given the magnitude of the estimate of this latest study, human warming "could already be close to the limit of 1.5 ° C". "If warming […] is at the bottom of the range, the 1.5 ° C target is still achievable with ambitious and rapid reductions in emissions," notes Nathan Gillet. But at the top of the estimate, "the 1.5 ° C target could be practically impossible."