The revised figure comes from the Scenario Model Intercomparison Project (ScenarioMIP), an international collaboration whose findings will feed into future UN Intergovernmental Panel on Climate Change (IPCC) assessments [1].
Under current policies, ScenarioMIP's analysis projects approximately 2.5°C of warming by 2100. A scenario in which net-zero is achieved by the end of the century would result in roughly 2°C [1]. Both figures exceed the 2015 Paris Agreement's ceiling of 1.5°C.