The document discusses the concept of net-zero emissions, emphasizing that achieving zero CO2 emissions is critical to halting global temperature rise, as CO2 is a cumulative pollutant. It highlights the challenges of eliminating emissions in hard-to-decarbonize sectors and the potential need for carbon dioxide removal (CDR) to achieve net-zero, while cautioning against over-reliance on offsets. Furthermore, it stresses the urgency of drastically reducing fossil fuel emissions in the short term to effectively address climate change.

1. Net-zero or zero, or perhaps offsets?
Glen Peters (CICERO Center for International Climate Research, Oslo, Norway)
#Klimafrokost: Hva betyr «netto nullutslipp» i 2050? (17/03/2021)

2. 1Gt CO2 equals 1 billion tonnes CO2
Stylized figure
Temperature rise versus total CO2 emissions

3. 1Gt CO2 equals 1 billion tonnes CO2
Stylized figure
More CO2 emissions, higher temperature

4. 1Gt CO2 equals 1 billion tonnes CO2
Zero CO2 emissions, temperature rise stops
Stylized figure

5. 1Gt CO2 equals 1 billion tonnes CO2
Stylized figure
Zero CO2 emissions, temperature rise stops

6. • Science says that the global temperature will stop rising
when CO2 emissions reach zero
– This essentially defines the ‘carbon budget’
– CO2 is a cumulative pollutant
– Any emissions of CO2 causes permanent damage
• Non-CO2 emissions play an important, but smaller role
– Declining CH4 (methane) emissions leads to declining temperature
– N2O behaves more like CO2, but emissions are much smaller
The need for (net)-zero

7. Distributing a carbon budget over time

8. 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

9. 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 brown area is a carbon budget of 580GtCO2 (consistent with 1.5°C in 2100).
1Gt CO2 equals 1 billion tonnes CO2
Emission pathways – zero emissions

10. There are likely sectors where it is too hard (or expensive) to get emissions to zero (leads to ‘residual emissions’)
Carbon dioxide removal (e.g., afforestation) can offset those emissions leading to ‘net-zero’ emissions
1Gt CO2 equals 1 billion tonnes CO2
Emission pathways with net-zero

11. If we (deliberately) allow CO2 emissions to decline slower in the short-term, we can ‘overshoot’ the carbon budget,
but then we 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
This scenario reaches the same
temperature in 2100 as the
others, but first exceeds the
temperature reaching a maximum
at the point of net-zero
Net-zero
Net-negative

12. A problem with ‘net-zero’ is that it is still necessarily to radically reduce fossil emissions in the short term…
It is not possible to ‘offset’ by emitting just as much (or a little less) and buying some Carbon Dioxide Removal
Emissions pathways to avoid

13. Positives and negatives

14. Some parts of the energy system are particularly difficult to decarbonize, including aviation, long-distance transport,
steel & cement production, and provision of a reliable electricity supply
Source: Davis et al (2018)
Can all emissions be eliminated?

15. Many sources of agricultural emissions are hard-to-mitigate, and short-lived pollutants can warm or cool
Most mitigation scenarios suggest that non-CO2 emissions will cause a warming to 2050 and then a cooling effect
Non-CO2 emissions
Sources: Unsplash, Unsplash, Pixabay, Shuttershock

16. Because of hard-to-mitigate (or too expensive-to-mitigate) sectors, Carbon Dioxide Removal (CDR) is likely needed
Thus, net-zero emissions are probably unavoidable…though the required scale of CDR is an important discussion
Source: MCC Berlin
Carbon Dioxide Removal

17. Net-zero GHG emissions occur 10-20 years after net-zero CO2 emissions for 1.5°C pathways
Net-zero years are about 20 years later for likely below 2°C.
Source: Rogelj et al (2021)
Net-zero GHG versus CO2 emissions
Positive (residual)
Negative (CDR)

18. Net-zero, balance, carbon neutral, climate neutral, CO2, and GHG are all common terms.
Sometimes they mean the same, sometime they don’t… Best to use net-zero and not carbon / climate neutral.
Source: Eve Tamme
Terminology – Take care

19. Is it possible to offset out of the problem?

20. • Offsets are reductions or removals done by others
• Companies (even big ones) have limited jurisdiction
• If a company is ‘net-zero’ now, or in the next decade, it is
likely via offsets….
Companies, net-zero, and offsets

21. Think of a big company that sells books. It has cars and trucks, computers, heating, storage, etc
The books are produced externally and electricity is needed to run the business
Consider a company that sells books

22. The company gets climate conscious and wants to reduce its emissions
Consider a company that sells books

23. In the short-term, it can reduce but not eliminate direct emissions. It can buy renewable electricity (perhaps on paper).
It is a big company, with lots of money, so it buys even more electricity that it uses, and it buys a forest or two.
Consider a company that sells books

24. In the short-term, it can reduce but not eliminate direct emissions. It can buy renewable electricity (perhaps on paper).
It is a big company, with lots of money, so it buys even more electricity that it uses, and it buys a forest or two.
Consider a company that sells books
The company claims net-zero!
The CEO does lots of interviews and
becomes famous. Other CEOs think
this is how to solve the climate
problem. They do the same.

25. A problem with ‘net-zero’ is that it is still necessarily to radically reduce fossil emissions in the short term…
It is not possible to ‘offset’ by emitting just as much (or a little less) and buying some Carbon Dioxide Removal
Emissions pathways to avoid

26. • Scale: The scale is limited and so offsets (and removals)
need to be prioritised to where it is absolutely needed
• Equity: The richest companies and countries in the world
buy offsets instead of investing in the difficult solutions
• Timing: We have a climate emergency, but globally we
want net-zero ~2050. Pathways matter (2025, 2030, …).
‘Offsets’ all have problems

27. The climate problem is solved when
everyone
stops burning fossil fuels

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