There Is No 1.5°C Climate Cliff

Dubai, United Arab Emirates—"The North Star of the COP28 Presidency is to keep 1.5°C within reach," has been the frequent refrain of Sultan Ahmed Al Jaber, the COP28 president overseeing the current U.N. climate change negotiations in Dubai. Al Jaber is reflecting the oft-chanted activist slogan "Keep 1.5 Alive!" The idea is that humanity must reduce its emissions of globe-warming greenhouse gases from burning fossil fuels sufficiently to keep the planet from warming more than 1.5 degrees Celsius above the pre-industrial baseline (1850-1900).

It is worth tracing the history of...