Additional land use forcing option

[chrisroadmap]

Some IAMs, especially those running the SSPs, provide total global areas of land types (pasture, cropland, forest) in future projections. These could be used to drive land-use ERF, rather than cumulative land-use related CO2 emissions, by assigning an albedo value to each land cover type. This could further be broken down by region (R5, and native IAM region groupings) to more specifically assign contributions to SW reflected radiation based on latitude and dominant plant type in each region. More of a "nice to have" than a genuine issue, this one, as it is assumed that the large majority of IAM pathways will still just report CO2 AFOLU emissions and not the land cover types.