create mapping for historical data

[eahoegner]

creates the mapping for aggregating the historical data from countries to to the common definitions regions for the IAMs

• create mapping file History.yaml
• check for missing countries (see #30)
• do the aggregation per species and sector to IAM regions
  this may include more sub-points, but I haven't gotten around to figuring out how exactly this is done
• resolve minor data inconsistencies
  • differences in countries available in CEDS, GFED, and the common definitions (see #30)
  • available time frames; 1997 onwards for GFED, until we use gridded data
  • unify units (GFED did not include /yr)

[eahoegner]

so far I've only done this for CEDS alone, but GFED should work similarly. both can be added together in a next step. is there any need down the line to keep track of whether specific data came from CEDS or GFED?

[chrisroadmap]

so far I've only done this for CEDS alone, but GFED should work similarly. both can be added together in a next step. is there any need down the line to keep track of whether specific data came from CEDS or GFED?

My feeling is that if it's not a pain to do, it might save us a lot of headaches in the future when we come to update these datasets; so inclined to say yes

[jkikstra]

I've put an example of roughly what I had in mind for this in #37 (it was a lot simpler than what you started here)