Future changes in coverage of 1.5 °C and 2 °C warming thresholds

The areas covered by 1.5 °C and 2.0 °C warming thresholds under RCP2.6, RCP4.5, and RCP8.5 were analyzed based on 22 CMIP5 models. More than 90% of the model runs are in agreement that by the end of the 21st century, near-surface air temperature changes over ∼5% (∼2%), ∼40% (∼18%), and ∼92% (∼86%) of the globe will cross the 1.5 °C (2.0 °C) threshold under RCP2.6, RCP4.5, and RCP8.5, respectively. Under RCP8.5, nearly the whole of North America, Europe + Russia, Africa, and Asia-Russia will cross the 1.5 °C (2.0 °C) threshold in ∼2050 (∼2060), while the coverage rates over South America and Oceania are ∼80% (∼75%) and ∼50% (∼30%), respectively. The threshold-onset time (TOT) for 2 °C warming is earliest over Europe + Russia and North America, followed by Africa, Asia-Russia, South America, and finally Oceania under the RCP4.5 and RCP8.5 scenarios. The TOT for 1.5 °C is ∼10-30 years ahead of that for 2.0 °C.