A presentation I gave for the Energy System Analysis course at the Yale School of Forestry and Environmental Studies (led by Edgar Hertwich). I cover recent emission trends and a variety of aspects of energy system transitions in 2°C emission pathways.

1. Mitigation pathways, emissions
scenarios, & stabilizing temperature
Glen Peters (CICERO)
Energy System Analysis (20/02/2018, Yale – remote)

2. • Trends in carbon dioxide emissions up to 2017
• A ‘typical’ 2°C pathway
• Emission scenarios (Shared Socioeconomic Pathways)
• Transition risk (energy systems for 2°C)
• Key characteristics of 2°C pathways
• Carbon budgets
• Interpreting the Paris Agreement
Outline

3. Emission trends to 2017

4. Land-use change was the dominant source of annual CO2 emissions until around 1950
Others: Emissions from cement production and gas flaring
Source: CDIAC; Houghton and Nassikas 2017; Hansis et al 2015; Le Quéré et al 2017; Global Carbon Budget 2017
Total global emissions by source

5. Total global emissions: 40.8 ± 2.7 GtCO2 in 2016, 52% over 1990
Percentage land-use change: 42% in 1960, 12% averaged 2007-2016
Land-use change estimates from two bookkeeping models, using fire-based variability from 1997
Source: CDIAC; Houghton and Nassikas 2017; Hansis et al 2015; van der Werf et al. 2017;
Le Quéré et al 2017; Global Carbon Budget 2017
Total global emissions

6. Global emissions from fossil fuel and industry: 36.2 ± 2 GtCO2 in 2016, 62% over 1990
Projection for 2017: 36.8 ± 2 GtCO2, 2.0% higher than 2016
Estimates for 2015 and 2016 are preliminary. Growth rate is adjusted for the leap year in 2016.
Source: CDIAC; Le Quéré et al 2017; Global Carbon Budget 2017
Emissions from fossil fuel use and industry
Uncertainty is ±5% for
one standard deviation
(IPCC “likely” range)

7. Global emissions from fossil fuels and industry are projected to rise by 2.0% in 2017
The global projection has a large uncertainty, ranging from +0.8% to +3.0%
Source: CDIAC; Jackson et al 2017; Le Quéré et al 2017; Global Carbon Budget 2017
Emissions Projections for 2017

8. Share of global emissions in 2016: coal (40%), oil (34%), gas (19%), cement (6%), flaring (1%, not shown)
Source: CDIAC; Le Quéré et al 2017; Global Carbon Budget 2017
Emissions from coal, oil, gas, cement

9. A ‘typical’ 2°C pathways

10. Net emissions = CO2 emissions from fossil fuels, industrial processes, land-use change, and bioenergy with CCS
Source: Anderson & Peters (2016)
A ‘typical’ 2°C pathway

11. Net emissions = CO2 emissions from fossil fuels, industrial processes, land-use change, and bioenergy with CCS
Source: Anderson & Peters (2016)
Negative emissions: gross versus net

12. Less CO2 removal requires more rapid reductions in fossil fuel and industry emissions
Source: Anderson & Peters (2016)
Are negative emissions a moral hazard?
With BECCS
Without
BECCS

13. Source: MCC 2016
Negative emission technologies

14. • It is hard to see a pathway to 2°C without CO2 removal
– That means CO2 is actively removed from the atmosphere and
global emissions are net negative
– It is worth pondering the implications of this point!
Key characteristic of 2°C pathways

15. The SSPs will be the basis for the next IPCC assessment report (up to 2022)
Share Socioeconomic Pathways (SSPs)

16. The IPCC AR5 scenarios have served their purpose, and it is time to move onto a new generation of scenarios…
The IPCC Fifth Assessment Report assessed about 1200 scenarios with detailed climate modelling on four Representative Concentration Pathways (RCPs)
Source: Fuss et al 2014; CDIAC; IIASA AR5 Scenario Database; Global Carbon Budget 2016
Goodbye IPCC AR5 scenarios…

17. 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)

18. 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

19. We are uncertain about the future, so we use emission scenarios to explore the key uncertainties
IPCC Sixth Assessment Report will be based on a new generation of scenarios
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

20. Physical climate risks require resource intensive calculations and can only be performed on a selection of scenarios
The climate modelling community will investigate climate outcomes for a subset of marker scenarios
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
Selected marker scenarios

21. We are uncertain about the future, so we use emission scenarios to explore the key uncertainties
IPCC Sixth Assessment Report will be based on a new generation of scenarios
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

22. The “baseline” scenarios assume no climate policy, a world which no long exists
The emission pledges submitted to the Paris Agreement move away from the baselines of >3.5°C in 2100
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
Baseline with no climate policy
Emission pledges

23. Most studies suggest, depending on post-2030 assumptions, the
emission pledges will lead to 2.5°C to 3.5°C warming
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
Nationally Determined Contributions
Emission pledges

24. There is generally a large gap between emission pledges and what is required in the Paris Agreement
The size of the gap depends on what “well below 2°C” means
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
Keeping “well below 2°C”
Emission pledges

25. 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

26. What are key changes in the energy system?
Transition risk

27. 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

28. 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

29. … 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

30. 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

31. • 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)

32. Different scenarios have very different levels of CCS, hence very different risks on fossil resources
IEA World Energy Outlook has relatively low CCS (about 1500 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)
Building block: Carbon capture & storage

33. Key characteristics of “well below 2°C”

34. To drive emission reductions, models need a strong carbon price…
Uniform, global, all countries, all sectors, no exceptions!
Source: Riahi et al. 2016; IIASA SSP Database
Strong, sustained climate policy

35. 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

36. 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

37. Many 2°C scenarios have large scale carbon capture and storage (left), some as much as we currently emit today!
Carbon dioxide removal is a key technology in many scenarios (right), removing
IEA World Energy Outlook: Current Policy Scenario; New Policy Scenario; Sustainable Development Scenario
Source: Riahi et al. 2016; IIASA SSP Database
New technologies emerge

38. To stabilize global average temperature must have net-zero emissions, which means negative emissions.
Why? a) some sectors hard to mitigation, b) may allow some to emit longer, c) easier to shift problem later
Source: Riahi et al. 2016; IIASA SSP Database
Negative emissions for stabilization?

39. 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

40. 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

41. • Need global, coordinated, and strong climate policy
• Need to grow non-fossil energy sources
• Need to shut down existing fossil infrastructure
• Need carbon capture and storage
• Need carbon dioxide removal
• Need all countries/sectors to contribute
• Misjudge the challenges, then underinvest in adaptation?
Key characteristics of 2°C pathways

42. Carbon budgets

43. Many nuances, but put simply integrate these pathways from the red dot to a point in the future
(e.g., time peak warming is reached or 2100)
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
Carbon budget for 2°C of warming

44. <2.0°C, >66%
Typical phrases: “We have already used two-thirds of the carbon budget”, “no space for more fossil fuels”
Historical emissions 1870-2016: 2100GtCO2. All values rounded to the nearest 50 GtCO2
The remaining quotas are indicative and vary depending on definition and methodology (Rogelj et al 2016).
Source: IPCC AR5 SYR (Table 2.2); Le Quéré et al 2016; Global Carbon Budget 2016
One number to save the world!
2100
GtCO2
Indicative range
450-1050GtCO2
800
GtCO2

45. Non-CO2 pathways are important, and can lead to a large range in cumulative emissions
A 0.1°C change in non-CO2 temperature contribution, changes budget about 200GtCO2
Source: Rogelj et al (2016); Peters (2017), Avoid/Exceed Blog
Non-CO2 emissions have big impact

46. Negative emissions allows “carbon debt”: Emit more than allowed, as long as paid back with negative emissions
Add about 150GtCO2 for 2016-2020. Need to deduct cement, what to use?
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
Carbon budget for 2°C of warming (66%)

47. Add about 150GtCO2 for 2016-2020. Need to deduct cement, what to use?
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
Carbon budget for 2°C of warming (66%)
Remainingcarbonbudget(GtCO2)
(from2020)
300 GtCO2
1300 GtCO2

48. Summing the 2°C emission scenarios gives the carbon budget (66% chance), with large uncertainty ranges
Carbon Capture and Storage (CCS) and “Negative Emissions” allows the use of more fossil fuels
Note: Totals are not always consistent because medians are not additive, and some columns have different numbers of scenarios
Source: Peters (2016)
Carbon budget ≠ Fossil fuels
Non-CO2
emissions
No CCS
New study

49. • Simple way to communicate challenges
– …“simple” means trade-off with complexity
– Main message: emissions need to go to zero!
• Be aware it is uncertain, no single magic number
– Climate uncertainty
– Non-CO2 uncertainty
• Conceptual challenges
– Carbon capture and storage, and carbon dioxide removal
– Carbon dioxide budget, not a fossil fuel budget
Using the carbon budget

50. “Well below 2°C” and balance of GHGs

51. • Article 2: “Holding the increase … to well below 2°C …
pursue efforts to limit … to 1.5 °C …”
• Article 4: “global peaking … as soon as possible …
undertake rapid reductions … achieve a balance between
… sources and … sinks … in the second half of this
century”
The Paris Agreement
Source: Peters (2017)

52. A 66% chance of staying below 2°C (used often in IPCC ARs) gives a likely temperature increase of 1.6-1.7°C in 2100
There is strong argument to define 2°C, pursue 1.5°C, as “66% chance of 2°C” as this was studied in IPCC AR5.
Source: Peters (2017)
What does “well below 2°C” mean?

53. The “balance of source and sinks” is problematic: CO2 versus GHG & IPCC versus UNFCCC (similar results with SSPs)
Problem is that half 1.5/2°C scenarios do not go net-zero before 2100, particularly for GHGs (Paris Agreement)
Source: Peters (2017), based on IPCC AR5 scenarios
Net-zero, balance of sources and sinks

54. • Possible to defend “well below 2°C” and the “balance” as
scenarios with a 66% probability of staying below 2°C
– This gives a median temperature of 1.6-1.8°C
– IEA 450 scenario is a 50% probability of below 2°C (median 2°C)
• Small changes, big consequences
– Changing from 50% to 66% allows ~800GtCO2 extra
– Changing from 2°C to 2.5°C allows ~900GtCO2 extra
– (both assume the same non-CO2 emissions)
Translating the Paris Agreement
Source: Peters (2017), Peters(2017)

55. Summary

56. • Global emissions may have plateaued, but a long way
from declining
• Global emissions need to get to zero about 2050-2100
– Rich countries to zero earlier, poor countries later
• Most likely that carbon dioxide removal is needed
• Many different energy systems can give the same
emission pathway
Summary

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