There has been some occasional chatter about the use of relative baselines in setting targets for greenhouse gas emissions, with some folks arguing for using a 1990 baseline and others suggesting 2005. How silly. How about just using absolute baselines? The following examples use carbon dioxide emissions.
If the world wants to achieve an 80% reduction in carbon dioxide emissions below 1990 levels this really means returning to 1939 levels of emissions.
For the US, a 17% reduction in carbon dioxide emissions below 2005 levels (such as in the Waxman-Markey Bill) represents a return to about 1990 levels. An 80% reduction represents a return to 1905 levels.
For the United Kingdom, a reduction of 34% from 1990-(its 2022 interim target) represents a return to carbon dioxide emissions of 1896 and an 80% reduction (its 2050 target) represents a return to emissions of 1849. (Wow!)
You can calculate other absolute baselines with the dataset here.