Predicted chance that global warming will temporarily exceed 1.5 °C

However, natural internal variability may exacerbate anthropogenic warming to produce temporary excursions above 1.5 degrees C. Such excursions would not necessarily exceed the Paris Agreement, but would provide a warning that the threshold is being approached. Here we develop a new capability to predict the probability that global temperature will exceed 1.5 degrees C above preindustrial levels in the coming 5 years.

For the period 2017 to 2021 we predict a 38% and 10% chance, respectively, of monthly or yearly temperatures exceeding 1.5 degrees C, with virtually no chance of the 5-year mean being above the threshold. Our forecasts will be updated annually to provide policy makers with advanced warning of the evolving probability and duration of future warming events.