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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.
Model projections of global temperature change from the 1990 Intergovernmental Panel on Climate Change (IPCC) First Assessment Report (FAR) (blue) compared to the NASA GISTEMP dataset of measured average global surface temperature (red). Results from the IPCC FAR "best estimate" scenario (2.5°C equilibrium climate sensitivity for doubled CO2) were adjusted to reflect the actual observed greenhouse gas (GHG) emissions since 1990 rather than the predicted GHG emissions used in the FAR. Contrary to the myth that climate models are unreliable, even in 1990 the IPCC FAR accurately predicted the next two decades of global warming even using climate models that are much simpler than today's models.