A Year at 1.5°C: Have We Already Crossed the Paris Climate Threshold?

Hút Mật

26-03-2025 

“As time passes, news about the now hotter Earth buzzes through the bird village. Those kingfishers residing along the banks of the Red River often report drying riverbeds and skinny fish. As Kingfisher casts his gaze upon the events that have unfolded, he can’t help but feel a sense of unease creeping up within him.”

In “GHG Emissions”; Wild Wise Weird [1]

Over the 12-month span ending in June 2024, global surface temperatures remained at or above 1.5°C above pre-industrial levels—a milestone often associated with the upper limit set by the Paris Agreement. But does this signify that the world has already breached the long-term climate goal? A new study by climate scientist Alex J. Cannon, published in Nature Climate Change, addresses this pressing question with fresh insight from climate model projections [1].

The Paris Agreement’s 1.5°C target refers not to individual years or months but to a long-term average, typically defined over a 20-year period. Temporary spikes due to natural variability or unusual events—such as a strong El Niño or volcanic eruptions—do not, on their own, constitute failure to meet the goal [2]. However, Cannon [1]’s analysis of climate model data from the Coupled Model Intercomparison Project Phase 6 (CMIP6) suggests otherwise [3].

By examining when climate models first experience 12 consecutive months above 1.5°C and comparing that with when they actually cross the long-term threshold, the study finds that these brief spikes usually follow the long-term breach—by about 33 months on average. This indicates that our recent 12-month streak likely means the 1.5°C limit has already been surpassed in a sustained sense.

Even when accounting for the warming influence of the 2023–2024 El Niño or recent shifts in atmospheric conditions, such as reduced air pollution from shipping, the findings remain robust. Under CMIP6 simulations, there is a 76% chance the threshold has already been crossed.

In short, while a single year above 1.5°C does not seal our climate fate, a full year at that level strongly suggests we may have already entered a new, more dangerous phase of global warming. The findings underscore the urgent need for accelerated climate action and socio-cultural transitions [4,5].

References

[1] Vuong QH. (2024). Wild Wise Weird. https://www.amazon.com/dp/B0BG2NNHY6/

[2] Cannon AJ. (2025). Twelve months at 1.5 °C signals earlier than expected breach of Paris Agreement threshold. Nature Climate Change, 15, 266-269. https://www.nature.com/articles/s41558-025-02247-8 

[3] Esper J, et al. (2024). 2023 summer warmth unparalleled over the past 2,000 years. Nature, 631, 94-97. https://www.nature.com/articles/s41586-024-07512-y 

[4] O’Neil BC, et al. (2016). The Scenario Model Intercomparison Project (ScenarioMIP) for CMIP6. Geoscientific Model Development, 9(9), 3461–3482. https://doi.org/10.5194/gmd-9-3461-2016 

[5] Nguyen MH. (2024). How can satirical fables offer us a vision for sustainability? Visions for Sustainability. https://ojs.unito.it/index.php/visions/article/view/11267