Prospects for Detecting Accelerated Global Warming

With global temperatures approaching Paris climate agreement targets and a wide spread in modeled future warming, it is critical to rapidly identify any changes in warming rate. Here, I address the question of when we would be able to detect acceleration of warming in global‐mean temperature. Some standard techniques report significantly ( p < 0.05) accelerated warming over 1980–2020 in the latest versions of the three main data sets used in the The Intergovernmental Panel on Climate Change 5th Assessment Report, with a mean acceleration of 49 m°C/decade 2 , which would add about 0.5°C additional warming over 50 years compared with linear warming. Accounting for El Nino, volcanism, and solar activity using a published method, the acceleration is 36 ± 30m°C/decade 2 . Using large ensemble output, I show that statistical uncertainties are underestimated by several common approaches. I recommend a better‐performing method and show that with these techniques 49m°C/decade 2 acceleration would likely not be detectable with robust confidence until at least 2026.