Indicates whether gross FFI emissions surpass the upper limiting case of
SSP baseline. Assumes zero CDR emissions if cdr-emissions-curve not supplied.
Returns true if gross FFI emissions are feasible; false, otherwise

Indicates whether cumulative net amount of CO2 realised to the atmosphere
exceeds remaining emissions quota. Returns true if net FFI emissions is
feasible; false, otherwise

Remaining emissions quota, measured in GtCO2, is taken from Friedlingstein et
al. (2014) for 50% probability of global-mean warming below 3 °C.

[1] Friedlingstein, P., Andrew, R., Rogelj, J., Peters, G., Canadell, J.,
Knutti, R., Luderer, G., Raupach, M., Schaeffer, M., van Vuuren, D., &
Le Quere, C. (2014). Persistent Growth of CO2 Emissions and Implications for
Reaching Climate Targets. Nature Geoscience, Advanced Online Publication.
https://doi.org/10.1038/ngeo2248

Indicates whether net FFI emissions exceed the lower limiting case of minimum
gross FFI emissions in deep mitigation pathways and maximum capacity in massive
CDR deployment (Kriegler et al. 2018). Returns true if net FFI emissions is
feasible; false, otherwise

[1] Kriegler, E., Luderer, G., Bauer, N., Baumstark, L., Fujimori, S., Popp, A.,
Rogelj, J., Strefler, J., & van Vuuren, D. (2018). Pathways Limiting Warming To
1.5°C: A Tale Of Turning Around In No Time?. Philosophical Transactions A, 376:
20160457. https://doi.org/10.1098/rsta.2016.0457

Indicates whether gross GDP series is feasible. Returns true if series is
non-negative; false, otherwise