The path to net-zero emissions
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The document discusses the path to achieving net-zero emissions, emphasizing that global temperature rise will cease only when CO2 emissions reach zero, thus defining the 'carbon budget.' It outlines the balance between CO2 emissions from sources and removals by sinks, highlighting complicating factors like hard-to-mitigate sectors and the need for Carbon Dioxide Removal (CDR) to offset residual emissions. Many countries have committed to net-zero emissions by various target years, but the document notes potential loopholes in these commitments.
The path to net-zero emissions
- 1. The path to net-zero emissions Glen Peters (CICERO Center for International Climate Research, Oslo, Norway) Third Annual Conference of the Transatlantic University Collaboration for Climate and Energy Law (Remote from Oslo, 28/04/2021)
- 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. • The global temperature will stop rising when CO2 emissions reach zero (emissions & removals balance) – 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 emissions
- 7. 1) Positive: Emissions by sources (e.g., burning fossil fuels, cutting down forests) 2) Negative: Removals by sinks (e.g., growing new forests, engineered removal of CO2 from the atmosphere) Net: 1 + 2: Emissions by sources plus removals by sinks What are ‘net-zero’ emissions?
- 8. Distributing a carbon budget over time
- 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). 1Gt CO2 equals 1 billion tonnes CO2 Emission pathways
- 10. 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
- 11. 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
- 12. 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
- 13. 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
- 15. 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?
- 16. 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
- 17. Because of hard-to-mitigate (or too expensive-to-mitigate) sectors, Carbon Dioxide Removal (CDR) is likely needed Some removals are needed to balanced with residual emissions, the required scale of CDR is an important discussion Source: MCC Berlin Carbon Dioxide Removal
- 18. 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 CO2 versus GHG emissions Positive (residual) Negative (CDR)
- 19. • Many countries are pledging for ‘net-zero’ emissions – US, EU27 have pledged net-zero GHG emissions by 2050 – China has pledged net-zero CO2 emissions by 2060 • Rich countries should reach net-zero before the global average: – ~2075: Net-zero GHG emissions – ~2050: Net-zero CO2 emissions • Many loopholes in definitions ‘Net-zero’ at the country level
- 20. Solving global warming the easy way!
- 21. The climate problem is solved when everyone stops burning fossil fuels (& stops cutting down forests)