Global biodiversity loss: Increasing numbers of plant and animal species at high extinction risk . The transition from non-detectable risk to moderate risk was based on the observed documentation of hundreds of local population extinctions, major declines in many sub-species and two to 92 global species extinctions that are attributable to climate change . The transition from moderate risk to high risk of biodiversity loss is centred around 1.5℃, based on a few taxa that are known from their basic biology and habitat requirements to be at high risk of extinction  at 1.5ºC, and on the increasing number of taxa that are projected to have a high extinction risk affecting >10% of the species in that taxa . The transition to very high risk of biodiversity loss comes from the increasing number of taxa projected to have >20% of species at a high risk of extinction. In the worst-case scenario , some of the taxa show >50% of the species at a high risk of extinction. These assessments are also weighted by role the species in the taxa play in performing ecosystem services . There is high confidence for the moderate risk threshold because it is based on observed trends attributed to climate change. There is medium confidence for future projections since, for the purpose of developing this burning embers diagram, these risk thresholds are based on one large study  for which there were multiple warming scenarios considered, and primarily on the loss of suitable climate. Based on Sections 2.4.2, 2.5.1, 2.6.1, 2.6.6, Table 2.3, Figure 2.6, Table SM2.1 and Table SM2.2.
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report