The document discusses the challenges of limiting global warming to various temperature thresholds, emphasizing that while 2.5°C is achievable with advancements in clean technologies, reaching 1.5°C is 'hard' due to current CO2 levels. It highlights that significant policy changes are necessary to avoid escalating temperatures beyond 2°C, warning against reverting to fossil fuel dependencies. Overall, the message focuses on the importance of implementing effective climate policies to manage carbon budgets and mitigate climate risks.

1. If 2.5°C is easy, why is 2°C hard?
Glen Peters (CICERO Center for International Climate Research, Oslo, Norway)
Enovakonferansen 2020 (Trondheim, 29 January 2020)

2. Data: Global Carbon Project (2019)
CO2 emissions continue to grow

3. Data: Global Carbon Project (2019); Riahi et al. 2016; Rogelj et al. 2018; IIASA SSP Database;
The future is uncertain…

4. Data: Global Carbon Project (2019); Riahi et al. 2016; Rogelj et al. 2018; IIASA SSP Database;
What if we had no climate policy?
RCP8.5

5. Data: Global Carbon Project (2019); Riahi et al. 2016; Rogelj et al. 2018; IIASA SSP Database;
What if we had a little climate policy?

6. Data: Global Carbon Project (2019); Riahi et al. 2016; Rogelj et al. 2018; IIASA SSP Database;
What if we had maximum climate policy?

7. Data: Global Carbon Project (2019); Riahi et al. 2016; Rogelj et al. 2018; IIASA SSP Database;
Decision making under uncertainty…

8. The carbon budget

9. 1Gt CO2 equals 1 billion tonnes CO2
More CO2 emissions, higher temperature
Stylized figure

10. 1Gt CO2 equals 1 billion tonnes CO2
Carbon budget at zero CO2 emissions
Stylized figure
Carbon budgets
(from 2018, 50% probability)
~1.0°C ~2,000GtCO2
+0.5°C +600GtCO2
+1.0°C +1,500GtCO2
+3.0°C +>4,000GtCO2

11. • 5°C is really hard
…we would have to reverse policies & accelerate fossil fuel use
• 3°C is easy
…our weak policies may get us there already
• 2.5°C is not so hard
…clean technologies are getting cheap, attitudes changing (?)
…the challenge is to get to zero CO2 emissions
• 1.5°C is really hard (impossible)
…because we are almost there already!
Carbon budgets & temperatures

12. A risk approach…

13. Data: CICERO Climate Scenario Guide
Most likely
outcome
Transition Risk Physical Risk

14. Summary

15. • 5°C is really hard
…we would have to reverse policies & accelerate fossil fuel use
• 3°C is easy
…our weak policies may get us there already
• 2.5°C is not so hard
…clean technologies are getting cheap, attitudes changing (?)
…the challenge is to get to zero CO2 emissions
• 1.5°C is really hard (impossible)
…because we are almost there already!
Summary

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