An advantage of the carbon budget is the ability to transparently share emissions to countries, for the purpose of comparability. Negative emissions makes that harder, and in this presentation we explore ways to allocate negative emissions to countries.

1. Allocating negative emissions to
countries
Glen Peters, Robbie Andrew (CICERO) Oliver Geden (SWP, MPI-M), Detlef van Vuuren (PBL, Uni Utrecht)
Negative CO2 Emissions (22-24/05/2018, Gothenburg)

2. • One nice feature of carbon budget approaches is to
“allocate” the budget to countries
– Allocation is useful for comparing, not prescribing!
• Negative emissions make allocation more difficult
• Simple and transparent approaches can play an important
niche and help users to understand mechanisms
Background

3. Source: Robbie Andrew
Simple approach, easy communication

4. We earlier allocated a carbon budget to countries to compare if their emission pledges were fair and ambitious
We did not allow net-negative emissions, which greatly restricted the applicability of the method
Source: Peters et al 2015; Global Carbon Budget 2016
A fair and ambitious agreement

5. Allocating negative emissions

6. Global CO2 emissions (fossil fuels, industry, & land-use change) in a “well below 2°C” scenario from MESSAGE
It is possible to split the net emissions (black line) into gross positive and gross negative emissions.
Source: Rockström et al (2017)
Gross versus net emission pathways

7. It is then possible to derive a carbon budget for gross positive and gross negative emissions.
The gross positive and negative budgets are always monotonically increasing / decreasing making “sharing” easier.
Source: Rockström et al (2017)
Gross versus net emission pathways

8. The gross positive and negative budgets can be distributed over time with stylized functions
Positive: exponential decay with inertia based on current growth rate; Negative: S-curve (cosine)
Source: Rockström et al (2017); own calculations
Gross versus net emission pathways

9. The same function fit results from the IMAGE model, but IMAGE has a more rapid deployment of negative emissions
Source: van Vuuren et al (2018); own calculations
Gross versus net emission pathways

10. An advantage of stylized functions is the ability to quickly experiment with different configurations
Here, pathways with different levels of CO2 removal show how CO2 removal reduces short-term mitigation rates
Source: own calculations
Gross versus net emission pathways

11. Distributing positive & negative emissions

12. • Allocate budget first, allocate pathway second
• Point is not to discuss ethics, but to test the method
• We use two methods of allocation
– Current population (per capita)
– Current emissions (grand fathering)
• Other options will be included later
– Positives: Historical responsibility, wealth, capacity, etc…
– Negatives: bioenergy potential, CCS availability, etc…
Allocating to countries

13. • We allocate positive and negatives asymmetrically
– If positives by population, then negative by emissions
– If positives by emissions, then negative by population
• Low per capita emissions
– Larger positive quota, smaller negative quota
• High per capita emissions
– Smaller positive quota, larger negative quota
• Overly stylized, will be improved later
Allocating positives & negatives

14. Blue: range of emission pathways with no net negative emissions; Grey: Range of positive emission pathways;
Yellow: Range of negative emissions; Solid/Dotted: Net emission pathways
China (high per capita emissions)
Positives by population
Negatives by emissions
Positives by emissions
Negatives by population

15. Blue: range of emission pathways with no net negative emissions; Grey: Range of positive emission pathways;
Yellow: Range of negative emissions; Solid/Dotted: Net emission pathways
USA (very high per capita emissions)
Positives by population
Negatives by emissions
Positives by emissions
Negatives by population

16. Blue: range of emission pathways with no net negative emissions; Grey: Range of positive emission pathways;
Yellow: Range of negative emissions; Solid/Dotted: Net emission pathways
Europe (high per capita emissions)
Positives by population
Negatives by emissions
Positives by emissions
Negatives by population

17. Blue: range of emission pathways with no net negative emissions; Grey: Range of positive emission pathways;
Yellow: Range of negative emissions; Solid/Dotted: Net emission pathways
India (low per capita emissions)
Positives by population
Negatives by emissions
Positives by emissions
Negatives by population

18. Given the use of stylized pathways, the pathways compare reasonably with IAMs (IMAGE shown here)
Parameter choices: country budget allocation (positive, negative), residual positive emissions, initial mitigation rate, …
Source: van Vuuren et al (2018); own calculations
Model comparisons

19. Why does the UK have a net-zero year after the global average? Methodological issue or reality?
Factors: Allocation method, initial mitigation rate, stylized functions, etc. Can these be addressed?
UK example

20. Summary

21. • Positive and negative carbon budgets used with stylized
functions to approximate output of IAMs
– Quick and flexible method to understand processes
• Possible to share emissions using different methods and
approximate expected behavior
• Next steps
– Broader range of methods to allocate carbon budgets
– Broader comparison with other results
Allocating emissions to countries

22. Peters_Glen
cicero.oslo.no
cicerosenterforklimaforskning
glen.peters@cicero.oslo.no
Glen Peters