Future-proofing interpretations of the Paris Agreement’s limit of well below 2 °C

Abstract

The Paris Agreement’s ‘well below 2 °C’ target is often interpreted as holding warming below 2 °C with a probability in the 66–90% range. We argue that such interpretations are not future-proof as decreasing uncertainties with time will allow temperatures to approach 2 °C later in the century. We show how referring to median warming can resolve this issue and illustrate how past probabilistic target interpretations would translate to a median 1.65–1.8 °C warming limit range. Here the authors show that a common interpretation of the Paris Agreement’s ‘well below 2° C’ target is changing with time, which could lead to higher overall warming. They propose that using median temperatures instead of probability ranges is more robust.