A presentation to some members of the Swedish Parliament on the carbon cycle, carbon budget, and emission pathways consistent with "well below 2°C". Hosted by Future Earth.

1. How much carbon can we emit?
Glen Peters (CICERO)
Climate Seminar with Swedish Parliament (15/03/2018, Stockholm)

2. C Le Quéré UK | RM Andrew Norway | GP Peters Norway | JG Canadell Australia | P Friedlingstein UK |
R Jackson USA | S Sitch UK | JI Korsbakken Norway | J Pongratz Germany | AC Manning UK
Thomas A. Boden USA | Pieter P. Tans USA | Oliver D. Andrews UK | Vivek K. Arora Canada | Dorothee C. E. Bakker UK |
Leticia Barbero USA | Meike Becker Norway | Richard A. Betts UK | Laurent Bopp France | Frédéric Chevallier France |
Louise P. Chini USA | Philippe Ciais France | Catherine E. Cosca USA | Jessica Cross USA | Kim Currie New Zealand |
Thomas Gasser Austria | Ian Harris UK | Judith Hauck Germany | Vanessa Haverd Australia | Richard A. Houghton USA |
Christopher W. Hunt USA | George Hurtt USA | Tatiana Ilyina Germany | Atul K. Jain USA | Etsushi Kato Japan | Markus
Kautz Germany | Ralph F. Keeling USA | Kees Klein Goldewijk The Netherlands | Arne Körtzinger Germany | Peter
Landschützer Germany | Nathalie Lefèvre France | Andrew Lenton Australia | Sebastian Lienert Switzerland | Ivan Lima
USA | Danica Lombardozzi USA | Galen McKinley USA | Nicolas Metzl France | Frank Millero USA | Pedro M. S.
Monteiro South Africa | David R. Munro USA | Julia E. M. S. Nabel Germany | Shin-ichiro Nakaoka Japan | Yukihiro
Nojiri Japan | X. Antonio Padín Spain | Anna Peregon France | Benjamin Pfeil Norway | Denis Pierrot USA | Benjamin
Poulter USA | Gregor Rehder Germany | Janet Reimer USA | Christian Rödenbeck Germany | Joyashree Roy India | Jörg
Schwinger Norway | Roland Séférian France | Ingunn Skjelvan Norway | Benjamin D. Stocker Spain | Hanqin Tian USA |
Bronte Tilbrook Australia | Ingrid T. van der Laan-Luijkx The Netherlands | Guido R. van der Werf The Netherlands |
Libo Wu China | Steven van Heuven The Netherlands | Nicolas Viovy France | Nicolas Vuichard France | Anthony P.
Walker USA | Andrew J. Watson UK | Andrew J. Wiltshire UK | Sönke Zaehle Germany | Dan Zhu France
Atlas Team Members at LSCE, France
P Ciais | A Peregon | P Peylin | P Brockmann | V Maigné | P Evano | C Nangini
Communications Team
O Gaffney | A Minns | A Scrutton
Contributors 77 people | 57 organisations | 15 countries

3. Global Carbon Cycle

4. 30%
11.2 GtCO2/yr
Global Carbon Cycle (2007–2016)
Source: CDIAC; NOAA-ESRL; Houghton and Nassikas 2017; Hansis et al 2015; Le Quéré et al 2017; Global Carbon Budget 2017
23%
8.7 GtCO2/yr
34.3 GtCO2/yr
88%
12%
4.9 GtCO2/yr 17.3 GtCO2/yr
47%
Sources = Sinks
6%
2.1 GtCO2/yr
Budget Imbalance:
(the difference between estimated sources & sinks; knowledge gaps)

5. Popularized recently as the “carbon budget”
Temperature and cumulative emissions

6. 1Gt CO2 equals 1 billion tonnes CO2
Temperature versus cumulative emissions

7. 1Gt CO2 equals 1 billion tonnes CO2
Temperature versus cumulative emissions
Stylized figure

8. Continued emissions lead to continued temperature increase
1Gt CO2 equals 1 billion tonnes CO2
Temperature versus cumulative emissions
Stylized figure
Continued carbon emissions
leads to higher temperatures

9. Continued emissions lead to continued temperature increase: CO2 emissions must go to zero!
1Gt CO2 equals 1 billion tonnes CO2
Temperature versus cumulative emissions
Stylized figure

10. Cumulative emissions to emission pathways

11. • We have already emitted a lot of CO2 and we can only
emit a little more
• The total amount we can emit depends on
– The temperature level we would like
– Uncertainties in the climate system
– How much non-CO2 we emit
– How much ‘overshoot’ we can accept
• For 1.5°C, CO2 emissions from 2016 to 2100 range from
−200 to +500 GtCO2 (median: +250 GtCO2)
Cumulative emissions to emission pathways
Source: Rogelj et al (2018)

12. We have already emitted a lot of CO2, and thus we can only emit a little more to stay under 1.5°C or 2°C.
1Gt CO2 equals 1 billion tonnes CO2
Emission pathways

13. We have already emitted a lot of CO2, and thus we can only emit a little more to stay under 1.5°C or 2°C.
The dark grey area is an approximate carbon budget of 250GtCO2 from 2017 (consistent with “well below 2°C”).
1Gt CO2 equals 1 billion tonnes CO2
Emission pathways
Illustrative pathway consistent
with the Paris Agreement’s
“well below 2°C” (~1.5°C)

14. If we (deliberately) allow CO2 emissions to decline slower in the short-term, then we ‘overshoot’ the carbon budget,
and then must repay that ‘carbon debt’ by removing carbon from the atmosphere at a planetary scale.
1Gt CO2 equals 1 billion tonnes CO2
Emission pathways with overshoot
Illustrative pathway consistent
with the Paris Agreement’s
“well below 2°C” (~1.5°C)

15. To reach zero emissions in 2050, we need to start planetary-scale carbon dioxide removal (negative emissions) now!
It is likely that we cannot get positive emissions to zero, thus, we will always need some level of negative emissions
1Gt CO2 equals 1 billion tonnes CO2
‘Negative’ emissions
Illustrative pathway consistent
with the Paris Agreement’s
“well below 2°C” (~1.5°C)

16. To stabilize global average temperature (at any level) requires global net emissions to be zero.
Because of equity, one would expect rich countries to be zero first and poor countries later (but still zero).
Everyone needs net-zero emissions
Zero-year for
a rich country
Zero-year for
a poor country
Illustrative pathway consistent
with the Paris Agreement’s
“well below 2°C” (~1.5°C)

17. Summary

18. • As little as possible!
– The ultimate carbon budget will depend on climate
uncertainties and political choices (e.g., non-CO2, carbon debt)
– The required emission reductions are unprecedented,
regardless of the uncertainties and choices
• Are we making progress?
– Emissions have been flat for three years (better than rising)
– The flat emissions are a delicate balance, and unlikely a peak
How much carbon can we emit?

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