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What does net-zero emissions mean?

What does net-zero emissions mean?

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A presentation on net-zero CO2 and GHG emissions. I focus mainly on the conceptual background, discussing also the role of Carbon Dioxide Removal and offsets... Details https://klimastiftelsen.no/arrangement/klimafrokost-hva-betyr-netto-nullutslipp-i-2050-for-beslutninger-og-investeringer-i-dag/

A presentation on net-zero CO2 and GHG emissions. I focus mainly on the conceptual background, discussing also the role of Carbon Dioxide Removal and offsets... Details https://klimastiftelsen.no/arrangement/klimafrokost-hva-betyr-netto-nullutslipp-i-2050-for-beslutninger-og-investeringer-i-dag/

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What does net-zero emissions mean?

  1. 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. 2. 1Gt CO2 equals 1 billion tonnes CO2 Stylized figure Temperature rise versus total CO2 emissions
  3. 3. 1Gt CO2 equals 1 billion tonnes CO2 Stylized figure More CO2 emissions, higher temperature
  4. 4. 1Gt CO2 equals 1 billion tonnes CO2 Zero CO2 emissions, temperature rise stops Stylized figure
  5. 5. 1Gt CO2 equals 1 billion tonnes CO2 Stylized figure Zero CO2 emissions, temperature rise stops
  6. 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. 7. Distributing a carbon budget over time
  8. 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. 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. 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. 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. 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. 13. Positives and negatives
  14. 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. 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. 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. 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. 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. 19. Is it possible to offset out of the problem?
  20. 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. 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. 22. The company gets climate conscious and wants to reduce its emissions Consider a company that sells books
  23. 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. 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. 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. 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. 27. The climate problem is solved when everyone stops burning fossil fuels
  28. 28. Peters_Glen cicero.oslo.no cicerosenterforklimaforskning glen.peters@cicero.oslo.no Glen Peters

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