Since 1993, the IEA has provided medium- to long-term energy projections using a continually evolving set ofdetailed, world-leading modelling tools. First, the World Energy Model (WEM) – a large-scale simulation modeldesigned to replicate how energy markets function – was developed. A decade later, the Energy TechnologyPerspectives (ETP) model – a technology-rich bottom-up model – was developed for use in parallel to the WEM.In 2021, the IEA adopted for the first time a new hybrid modelling approach relying on the strengths of bothmodels to develop the world’s first comprehensive study of how to transition to an energy system at net zero CO2 emissions by 2050; this analysis has been updated in 2023.