From Mark Gilkey
We are not, as your article implies, limited to an “either/or” choice between per-capita emissions and per-unit-of-GDP emissions of carbon (25 May, p 12). A blended system could start with levels similar to current emissions and move towards a per-capita system. That prevents abrupt changes in existing high-emissions economies, but forces the overall system to move towards a fair long-term per-capita limit.
Since a pure per-capita limit could encourage population growth in countries with low per-capita emissions (the larger population would allow those countries more emissions rights, which they could sell), the population component of the limit would be based on population as of a certain date (which must be in the past, not the future).
The sum of all nations’ emissions would be based on a total global cap that would never be expanded, regardless of population growth or GDP growth.
Palo Alto, California, US
