Add global emissions trajectories for concordia

[jkikstra]

Before being able to make a synthetic, comprehensive historical emissions dataset for concordia, we first still need to add global, total (no sectoral split), emissions trajectory data for HFC, C2F6, CF4, SF6.

Also, for CO2 AFOLU, we need global "Deforestation and other LUC" (gross emissions) and "Agriculture", as well as net CO2 AFOLU.

In addition, note that "Aircraft", and "International Shipping" (for all emissions species) will also only be processed at the global level.

[znichollscr]

@jkikstra do we have everything we need now or are we still missing things?

[jkikstra]

Almost, I think we have everything except 'gross emissions' (IAM: 'Gross Emissions|CO2|AFOLU') so far!

This just means updating/expanding the gcb notebook a bit.

I think we should do (taken from "Global_Carbon_Budget_2024_v1.0.xlsx", sheet: "Land-Use Change Emissions"):

'Gross Emissions|CO2|AFOLU' = "deforestation (total)" + "other transitions" + "peat drainage & peat fires" + "wood harvest & other forest management"

... and while we're at it, we could also add the gcb category "forest regrowth (total)", but I'm not yet sure what IAM variable that would relate to exactly.