Gross CO2 removals missing in emission variables

[flohump]

There are variables for gross CO2 emission and carbon dioxide removal but gross CO2 removals are currently missing in emission variables. I discussed with @merfort that it would be of high value to add gross CO2 removals including sub-categories espcially for AFOLU.
This would allow to analyze how gross CO2 emissions and gross CO2 removals add-up to net CO2 emissions. With the CDR variables this is not possible for two reasons:

• not all negative CO2 emissions are considered as CDR, e.g. regrowth of vegetation on abandoned land or regrowth of timber plantations for wood production
• the CDR variables are defined as positive

@jkikstra @IAMconsortium/common-definitions-emissions @IAMconsortium/common-definitions-land
What do you think about this proposal?

Releated to #222

[strefler]

Agree! We prioritized net removals for the first step, but I think it would be valuable to disaggregate those into net removals and remaining emissions associated with CDR technologies. We should probably discuss the concrete structure, and also clear definitions to avoid confusion as to where emissions should be reported.