A history of the 1.5°C target

The 1.5°C target is now widely considered as the maximum acceptable limit for global warming. However, it is at once recent and, as it appears increasingly unreachable, already almost obsolete. Adopted as an aspirational target in the Paris Agreement in 2015, the 1.5°C objective originated with a political impetus within UNFCCC negotiations. The Intergovernmental Panel on Climate Change (IPCC) endorsed this policy‐driven target when it produced the Special Report on 1.5°C. This article highlights the continuity of the history of the 1.5°C target with that of the 2°C target, but also the differences between the two. Because the 1.5°C target considerably raises the bar on mitigation efforts, it exacerbates political tensions and ambiguities that were already latent in the 2°C target. This article retraces the emergence of the 1.5°C in diplomatic negotiations, the preparation of the IPCC Special report on 1.5°C, and the new kinds of debates they provoked among climate scientists and experts. To explain how an unreachable target became the reference for climate action, we analyze the “political calibration” of climate science and politics, which can also be described as a codependency between climate science and politics.