A presentation I gave at the International Energy Agency (IEA) 6 September 2018. I focussed on carbon budget and the diverse array of scenarios consistent with the same temperature level.

1. Beyond carbon budgets and back to
emission scenarios
Glen Peters (CICERO Center for International Climate Research, Oslo, Norway)
IEA lunch seminar (6/09/2018)

2. • Carbon budgets
– Simple version
– Complex (real) version
• Shared Socioeconomic Pathways (SSPs)
– IPCC assessments versus IEA
– Diversity versus detail
• The role of oil in a 2°C world (maybe)
Overview

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

4. Every new molecule of CO2 added to the atmosphere will cause temperatures to keep rising…
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

5. From carbon budgets to pathways
The “carbon budget” is too abstract, it needs to be distributed over time

6. 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

7. 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 1.5°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)

8. 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)

9. 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)

10. 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

11. Our methods takes the cumulative positive and negative emissions from 2017 to 2100 & distributes over time
We distribute positive emissions using an exponential (with short-term inertia), negative emissions with a cosine
1Gt CO2 equals 1 billion tonnes CO2
Aside: How good are IAMs?

12. Our methods takes the cumulative positive and negative emissions from 2017 to 2100 & distributes over time
We distribute positive emissions using an exponential (with short-term inertia), negative emissions with a cosine
1Gt CO2 equals 1 billion tonnes CO2
Aside: How good are IAMs?

13. 1Gt CO2 equals 1 billion tonnes CO2
RCP1.9, ~1.4°C

14. 1Gt CO2 equals 1 billion tonnes CO2
RCP2.6, ~1.7°C

15. 1Gt CO2 equals 1 billion tonnes CO2
RCP3.4, ~2.2°C

16. Beyond carbon budgets

17. Big range in estimates, from -200 to +800GtCO2, with methods and definitions important factors
Source: Carbon Brief (2018)
Remaining budget for 1.5°C (66%)

18. These are the “core” 1.5°C scenarios assessed by the IPCC SR15 (SSP1.9).
All scenarios cross 1.5°C, and then drop back down with negative emissions.
Source: Peters (2018)
Pathway & definition matters
Carbon budgets

19. Exceedance Budget (when 1.5°C is crossed), Peak Budget when zero emissions is reached (~peak temperature),
Avoidance Budget cumulative emissions to 2100 in a scenario that avoids 1.5°C in 2100 (multiple definitions)
Source: Peters (2018)
Definitions are important

20. Cumulative net-negative emissions are a key factor describing the variation in the budget, but why?
Source: Peters (2018)
Negative emissions play a big role

21. Strong relationship between non-CO2 and cumulative net (top) and cumulative net-negative emissions (bottom)
This figure is for 66% 2°C scenarios, but the general result applies for other temperature levels
Source: Peters (2018)
Non-CO2 is actually rather important…

23. • The total amount we can emit depends on
– The temperature level we would like (Millar: 0.9°C vs 1.2°C)
– Uncertainties in the climate system (50%, 66%, etc, chance)
– How much non-CO2 is emitted (explains much of the range)
– How much ‘overshoot’ is accepted (changes pathway)
• For 1.5°C, CO2 emissions from 2016 to 2100 range from
−100 to +475 GtCO2 (median: +250 GtCO2)
Cumulative emissions to emission pathways
Source: Rogelj et al (2018)

24. Exploring climate, technical, social, political uncertainties
Stylized pathways to emission scenarios

25. Emission scenarios are used to explore the consequences of key uncertainties (climate, technical, social, political)
Scenarios are not projections or predictions, but tools to assess risks…
Source: Riahi et al. 2016; IIASA SSP Database; Rogelj et al (2018); Global Carbon Budget 2017
Scenarios used to explore uncertainties

26. In the lead up to the IPCC’s Sixth Assessment Report new scenarios have been developed to more systematically
explore key uncertainties in future socioeconomic developments
Five Shared Socioeconomic Pathways (SSPs) have been developed to explore challenges to adaptation and mitigation.
Shared Policy Assumptions (SPAs) are used to achieve target forcing levels (W/m2). Marker Scenarios are indicated.
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
New generation of emissions scenarios

27. The IEA has two sets of scenarios: Energy Technology Perspectives (ETP) & World Energy Outlook (WEO)
New Policies: Builds planned & changed policy onto the Current Policies. Sustainable Development ≈ 2°C.
IEA does not include emissions from non-energy sectors (e.g. cement) or land-use change
Source: World Energy Outlook (2017)
IEA World Energy Outlook (WEO)

28. IPCC assessments versus IEA

29. • Frequency
– IPCC every 5-7 years
– IEA annually (familiarity)
• Model diversity
– ~6 core, plus many others
– 1 (or 2 with ETP)
• Socioeconomic diversity
– IPCC: 5 SSPs
– IEA: 1 set of population, GDP
IPCC assessments versus IEA
• Volume
– IPCC: ~100 pages 5-7 years
– IEA: ~1000 pages annually
• Detail
– IPCC better non-CO2, climate
– IEA reports much more detail
• Consistency
– IPCC assesses mix of scenarios
– IEA builds on a narrative
• Method of communication

30. SDS is at the low end of the 2°C pathways, but need to take into account cement and post-2040
The SDS is consistent with ~1.75°C (in 2100) scenarios, but would the energy system be different in 1.5°C vs 2°C?
CO2 pathways

31. IEA SDS has relatively flat energy use compared to 2°C scenarios (left); & relatively low fossil fuel use (right)
IEA World Energy Outlook: Current Policy Scenario; New Policy Scenario; Sustainable Development Scenario
Source: Riahi et al. 2016; IIASA SSP Database
Energy & fossil fuel use

32. Coal has rapid declines in all 2°C scenarios (left); maybe place for a little new oil depending on decline rates (right)
Gas is more complex (not shown), with a wide variety of pathways in 2°C scenarios
IEA World Energy Outlook: Current Policy Scenario; New Policy Scenario; Sustainable Development Scenario
Source: Riahi et al. 2016; IIASA SSP Database
Fossil fuels decline rapidly

33. Solar and wind grow rapidly in 2°C scenarios, as does bioenergy (though not with IEA)
Modest growth in hydro and nuclear, though some scenarios have rapid growth in nuclear
IEA World Energy Outlook: Current Policy Scenario; New Policy Scenario; Sustainable Development Scenario
Source: Riahi et al. 2016; IIASA SSP Database
Non-fossil sources need to grow rapidly

34. Different scenarios have very different levels of CCS, hence very different risks on fossil resources
IEA World Energy Outlook has relatively low CCS (about 3000 facilities in 2040), others can have 15,000!
3.0GtCO2//yr is approximately 150 Sleipner size fields per year, or 3 fields per week
CCS volumes are estimated on energy consumption data and a capture rate of 90%
Source: IIASA SSP Database; World Energy Outlook (2017)
Carbon capture & storage

35. North America and Europe have the largest historical responsibility for current climate change, but
to keep “well below 2°C” all have to contribute, particularly Asia
IEA World Energy Outlook: Current Policy Scenario; New Policy Scenario; Sustainable Development Scenario
Source: Riahi et al. 2016; IIASA SSP Database
All countries need to reduce emissions

36. Electricity generation dominates emissions, then industry, transport, and residential & commercial
Transport emissions persist the longest, and electricity generation removes carbon from the atmosphere
Source: IIASA AR5 Scenario Database (own calculations)
All sectors go down, electricity negative

37. Assume the world does not work as in a model
But, we are not in an “optimal” world

38. The slow time-scales in the climate system means that a) a certain level of climate change is unavoidable (physical
risk), and b) rapid transitions are needed now to make small changes in decades ahead (transition risk)
Physical versus transition risk

39. There are many ways to get to 2°C, depending on socioeconomic and modelling assumptions
All 2°C scenarios require rapid decarbonization, zero emissions around 2070, and negative emissions thereafter
Source: IIASA SSP Database
Carbon dioxide pathways to 2°C

40. While there is little flexibility in the carbon dioxide pathways to 2°C, there is a big variation in energy consumption
Here are 18 scenarios consistent with 2°C, the “missing scenarios” are assumptions that could not keep below 2°C
SSPs represent different socioeconomic pathways (five in total), different models are abbreviated in brackets)
Source: IIASA SSP Database
Energy system pathways to 2°C
IEA in 2040

41. … and very different energy mixes. It is possible to have high energy consumption with no fossil fuels, low energy
consumption with lots of fossil fuels, and everything in between. There is no single pathway to 2100.
SSPs represent different socioeconomic pathways (five in total), different models are abbreviated in brackets)
Source: IIASA SSP Database
Energy system pathways to 2°C

42. At the detailed level, there are many different energy systems that can be consistent with 2°C. E.g., it is not possible
to categorically say 2°C is consistent with low fossil fuel consumption, as it depends on CCS assumptions
SSPs represent different socioeconomic pathways (five in total), different models are abbreviated in brackets)
Source: IIASA SSP Database
Energy system pathways to 2°C

43. Different models & socioeconomic assumptions lead to different pathways, and a different role for oil and gas.
Here are four alternative models (AIM, MESSAGE, REMIND, GCAM) with three socioeconomic inputs (SSP1, 2, 5)
Source: Riahi et al. 2016; IIASA SSP Database; own calculations
2°C pathways depend on model & assumptions

44. • There are many energy systems that are consistent with
the same climate target
– Each energy system (scenario) is coherent
– If you take out one “building block” coherency is lost
• Transition risk:
– It is critical to perform analysis across a range of scenarios &
models, and weigh up different risks
– Can always find a scenario that suits your needs…
Building blocks and coherency
Source: CICERO Scenario Guide (2018)

45. Assume the world works as in a model…
The “optimal” role of oil in a 2°C world

46. Emission scenarios are used to explore the consequences of key uncertainties (climate, technical, social, political)
Scenarios are not projections or predictions, but tools to assess risks…
Source: Riahi et al. 2016; IIASA SSP Database; Rogelj et al (2018); Global Carbon Budget 2017
Scenarios used to explore uncertainties

47. I will only show the median of each scenario “group” to focus on core characteristics, not specific model details
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
Simplified “stylised” scenarios

48. In an average 2°C pathway oil demand/supply peaks in the 2020-2030s and declines towards zero in 2100
Source: Riahi et al. 2016; IIASA SSP Database; own calculations
Oil demand in different pathways

49. In an average 2°C pathway oil demand/supply peaks in the 2020-2030s and declines towards zero in 2100
Oil supply in existing fields is lower than a 2°C pathway (if no new additional supply is added)
Source: Riahi et al. 2016; IIASA SSP Database; own calculations
Oil demand in different pathways
Potential
supply gap
The exact size of the “supply gap”
will depend on many assumptions

50. The additional supply in an average 2°C pathway is greater than the oil in existing fields
Source: Riahi et al. 2016; IIASA SSP Database; own calculations
Additional supply in different pathways
2°C world
Reference

51. Discussion / Conclusion

52. • The use of stylized scenarios to explain mechanisms
• Carbon budgets have limited use, & highly uncertain
• Pathways more relevant, but vary by model, socioeconomics, …
• IPCC versus IEA
Talking points

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