The document discusses whether 1.5°C global warming can be avoided according to the Paris Agreement goals. It summarizes that emission scenarios consistent with limiting warming to 2°C show a median temperature rise of 1.7-1.8°C. Nationally determined contributions are currently insufficient and would lead to around 2.5-3.5°C warming. Avoiding over 2°C of warming would require rapid declines in fossil fuel use, rapid growth of non-fossil sources like solar and wind, deployment of carbon capture and storage, and net-negative emissions globally by mid-century with participation from all countries and sectors.

1. Can we avoid 1.5°C warming?
Glen Peters (CICERO)
CenSES energi- og klimakonferanse 2017, 7-8/12/2017 (Oslo)

2. Paris Agreement

3. • “Holding the increase … to well below 2°C … pursue
efforts to limit … to 1.5 °C …”
• “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)

4. Emission scenarios consistent with a “66% chance” of staying below 2°C have a median temperature of 1.7-1.8°C.
Only half of the scenarios are below zero in the second half of the century.
Only scenarios with a radiative forcing of 2.6Watts/m2 shown in this figure, with weighting based on a Global Warming Potential (100yrs)
Source: Riahi et al. 2016; IIASA SSP Database
Defining “well below 2°C”…

5. • What about 90% below 1.5°C, or 66% below, etc?
– Because that is not what the Paris Agreement says
• A good case for using existing scenarios, 66% below 2°C,
as a reference for “purse efforts to limit … to 1.5°C”
– “66% chance” relates to uncertainties in the climate system
The Paris Agreement
Source: Peters (2017)

6. The future is uncertain, and we use the future to explore these uncertainties
Emission scenarios

7. 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

8. 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

9. 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

10. 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

11. To avoid 2°C of warming, global CO2 emissions need to decline rapidly and cross zero emissions after 2050
Rich countries would need to reach zero earlier (e.g., 2040), and electricity generation even earlier (e.g., 2030)
Source: Riahi et al. 2016; IIASA SSP Database; Global Carbon Budget 2017
Pathways that avoid 2°C of warming
Emission pledges

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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. Can we avoid 1.5°C warming?

20. • No
– If you don’t understand the obstacles, 1.5°C is not an option!
• Why?
– Need global, relatively coordinated action
– Growing non-fossil sources is not enough
– Need to shut down existing fossil infrastructure
– Need carbon capture and storage, and carbon dioxide removal
– All countries/sectors need to contribute, irrespective of wealth
• Misjudge the challenges, then underinvest in adaptation?
Can we avoid 1.5°C warming?

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