Updating Tier classification: the emissions input for climate-assessment is Tier 1

[jkikstra]

The climate-assessment post-processing module takes a specific set of variables as input.

These are described here, and in this excel file: minimum_variables_climaterun_scenarioexplorer_v2.xlsx (sheet: "Maximum emissions (option B)").
P.S. note that this is based on the AR6 template. The workflow assumes, in line with AR6, that if "Emissions|CO2|Other" and "Emissions|CO2|Waste" are reported, they are additive to "Emissions|CO2|Energy Industrial Processes" and "Emissions|CO2|AFOLU". The four together should sum up to "Emissions|CO2".

These variables should thus be reported by all models, as much as possible, to get an accurate climate assessment.

Currently, they're not assigned any tier.

Modelling teams might therefore perceive this to be lower priority, which is incorrect.

Possible solutions
End-state: define tiers comprehensively.
Temporary: communicate that tiers should be disregarded if not used for a project (e.g., currently with ScenarioMIP), or delete the tier column.

FYI @danielhuppmann @phackstock