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In Paris, all governments solemnly promised to come to COP26 with more ambitious 2030 commitments to close the massive 2030 emissions gap that was already evident in 2015. Three years later the IPCC Special Report on 1.5°C reinforced the scientific imperative, and earlier this year it called a climate “code red.” Now, at the midpoint of Glasgow, it is clear there is a massive credibility, action and commitment gap that casts a long and dark shadow of doubt over the net zero goals put forward by more than 140 countries, covering 90% of global emissions.

In December 2020, 50 of the world’s leading biodiversity and climate experts, selected by a 12-person Scientific Steering Committee assembled by IPBES and IPCC, participated in a four-day virtual workshop to examine the synergies and trade-offs between biodiversity protection and climate change mitigation and adaptation.

An extensive new multi-proxy database of paleo-temperature time series (Temperature 12k) enables a more robust analysis of global mean surface temperature (GMST) and associated uncertainties than was previously available. We applied five different statistical methods to reconstruct the GMST of the past 12,000 years (Holocene). Each method used different approaches to averaging the globally distributed time series and to characterizing various sources of uncertainty, including proxy temperature, chronology and methodological choices. The results were aggregated to generate a multi-method ensemble of plausible GMST and latitudinal-zone temperature reconstructions with a realistic range of uncertainties. The warmest 200-year-long interval took place around 6500 years ago when GMST was 0.7 °C (0.3, 1.8) warmer than the 19th Century (median, 5th, 95th percentiles). Following the Holocene global thermal maximum, GMST cooled at an average rate −0.08 °C per 1000 years (−0.24, −0.05). The multi-method ensembles and th