Chapter 2:
Mitigation pathways compatible
with 1.5°C in the context ofsustainable development
Joeri Rogelj
Coordinating Lead Author – IPCC SR1.5
Grantham Institute – Imperial College London
International Institute for Applied Systems Analysis (IIASA)

The remaining carbon budget

Image source: NASA blue marble

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The remaining carbon budget

Image source: NASA blue marble

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The remaining carbon budget

Image source: NASA blue marble

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The remaining carbon budget

Image source: NASA blue marble

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The remaining carbon budget

Image source: NASA blue marble

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The remaining 1.5°C carbon budget
Remaining carbon budget
580 GtCO2 left (50% chance of 1.5°C)
420 GtCO2 left (66% chance of 1.5°C)

REMAINING

2200 ±320 GtCO2
EMITTED
until 2017 byhuman activities± 400 GtCO2 geophysical uncertainty± 250 GtCO2 depends on non-CO2 reductions
Unrepresented Earth system feedbacks
reduce budget by 100 GtCO2 until
Currently: 42 ± 3 GtCO2/yr annually

Image background: NASA blue marble / Data: Chapter 2 IPCC SR1.5 for a global warming in GSAT

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

IAMC 1.5°C SCENARIO EXPLORER

https://data.ene.iiasa.ac.at/iamc-1.5c-explorer/

The emission reduction challenge
Global CO2 characteristics

Pathways limiting warming to 1.5°C
with no or limited overshoot (less than 0.1°C):a) Robust declining trend in next decadeb) Reach net-zero CO2 around mid-centuryc) Varying levels of carbon-dioxide removal (CDR)a.

High overshoot? Same net zero timing - More CDRb.
c.

Image source: IPCC SR1.5 SPM.3A

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

The emission reduction challenge
Global non-CO2 characteristics

Pathways limiting warming to 1.5°C
with no or limited overshoot (less than 0.1°C):a.

- Also strongly reduced- Do not reach zero globallyb.
c.

Image source: IPCC SR1.5 SPM.3A

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

Not all 1.5°C pathways are created equal

Image source: Natalie Behring (Aurora Photos) / IPCC SR1.5 SPM.3B

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

Where do we need to go?
Global greenhouse gas (GHG) in 2016:
about 52 GtCO2e/yr

2030 GHG emissions

Image source: www.vertic.ca

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

1.5°C pathways

2°C pathways

with no or limited
overshoot over 21st century

with at least 2/3rd chance
during 21st century

25-30 GtCO2e/yr

30-42 GtCO2e/yr

Where do we need to go?
Global greenhouse gas (GHG) in 2016:
about 52 GtCO2e/yr

2030 GHG emissions
1.5°C pathways

2°C pathways

with no or limited
overshoot over 21st century

with at least 2/3rd chance
during 21st century

25-30 GtCO2e/yr

30-42 GtCO2e/yr

Paris Agreement Pledges
NDC global GHG emissions in 2030
unconditional

conditional

52-58 GtCO2e/yr

50-54 GtCO2e/yr

From 2018-2030
400-560 GtCO2 projected to be emitted
Image source: www.vertic.ca

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5

Implications of where we are today
Implications of this mismatch:-Current NDCs on track for 3°C this century-Remaining 1.5°C carbon budget exhausted by2030 or due to steepest reductions
thereafter
Commitment to higher maximum warming
Commitment to large-scale carbon-dioxide
removal (CDR) for ambitious climate targets
Challenges increase, do not disappear,
but are pushed one decade into the future-Image source: www.vertic.ca

Joeri Rogelj - CLA Chapter 2 – IPCC SR1.5