Methods
Our global public interface focuses on inter-model differences regarding emissions projections.
We carry out projections across numerous Integrated Assessment Models with a specific focus on policy representation and harmonisation methods.
We used four different scenarios for representing policies: Two scenarios for up to 2030, corresponding to Current Policies and Nationally Determined Contributions, and two different ways of extrapolating after 2030 accordingly (to represent possible interpretations of continued ambition). NDC scenarios were modelled on top of Current Policies. The first post-2030 extension method takes the equivalent carbon price in 2030, increasing it with GDP per capita; the second method takes the rate of emissions intensity reductions implied between 2020 and 2030 and applies it after 2030.
Harmonisation Methods: Harmonisation efforts have been undertaken as a novelty in multi model comparison bearing in mind differences across model features and heterogeneity. Expert users of models within the PR modelling consortium have conducted a coordinated effort on whether variables have been fully, partially or not harmonized and/or checked for consistency across models.
The models that have been used for the global interface are the following global models:
| Model | World regions |
|---|---|
| FortyTwo(42) | 50 |
| E3ME | 61 |
| GCAM | 32 |
| Gemini-E3 | 11 |
| ICES | 45 |
| MUSE | 28 |
| TIAM | 15 |
Where is the world headed towards based on current policies?
Current Policies are broken down into two projection scenarios, one based on emissions intensity and the other on carbon price.
| Scenario | 2030 target | Post-2030 assumption | Description |
|---|---|---|---|
| CP_Intensity | Current policy | Constant rate of emissions intensity | Scenario exploring where emissions are headed assuming current policy to 2030 and constant rates of emissions intensity reductions thereafter |
| CP_Price | Current policy | Carbon price increasing with per capita GDP | Scenario exploring where emissions are headed assuming current policy to 2030 and carbon prices increasing with per capita GDP thereafter |
This graph illustrates global energy related CO2 emissions until the year 2050 across several of the IAMs. Current policy constrained scenarios reach levels of emissions between 32-36 GtCO2 in 2030 and 26-40 GtCO2 in 2050. Current policy estimations of energy related CO2 emissions are higher than Nationally Determined Contributions pledges because not all regions are on track to meet their targets.
Shaded areas show emissions spanned by CP_Price and CP_Intensity scenarios for each model and colored bars show 2050 ranges (2045 value for FortyTwo, which only has intensity scenarios). Markers above bars show baseline values in 2050 (in 2045 for FortyTwo). GEMINI baseline value in 2050, 47.25 Gt CO2, is outside the range shown in the figure. Black lines show historical emissions.
Where is the world headed towards based on Nationally Determined Contributions (NDCs) policies?
Similarly, Nationally Determined Contributions (NDCs) scenarios are also broken down into two projection scenarios, one based on emissions intensity and the other on carbon price.
| Scenario | 2030 target | Post-2030 assumption | Description |
|---|---|---|---|
| NDC_Intensity | NDCs | Constant rate of emissions intensity | Scenario exploring where emissions are headed assuming NDCs to 2030 and constant rates of emissions intensity reductions thereafter |
| NDC_Price | NDCs | Carbon price increasing with per capita GDP | Scenario exploring where emissions are headed assuming NDCs to 2030 and carbon prices increasing with per capita GDP thereafter |
Different to the previous, this graph illustrates NDC constrained scenarios of global energy related CO2 emissions until 2050 across the IAMs. Levels of emissions vary between 30-34 GtCO2 in 2030 and 23-38 GtCO2 in 2050. These ranges are slightly lower than the Current Policy scenarios based on countries’ efforts to align emission policies with NDC targets, planning and implementation processes.
Shaded areas show emissions spanned by NDC_Price and NDC_Intensity scenarios for each model and colored bars show 2050 ranges (2045 value for FortyTwo, which only has intensity scenarios). Markers above bars show baseline values in 2050 (in 2045 for FortyTwo). GEMINI baseline value in 2050, 47.25 Gt CO2, is outside the range shown in the figure. Black lines show historical emissions.
What are the global temperature estimates across models until 2100?
This figure shows global temperature estimates until the year 2100. (The bars show ranges including all scenarios runs.). Across the range of scenarios considered, median 2100 temperature results at around 2.2-2.9°C. NDC constrained scenarios give lower 2100 temperatures than current policy constrained scenarios, reflecting their greater ambition by 2030 and beyond at a global level. Intensity scenarios - based on greater optimism in terms of effort - also give lower 2100 temperature estimates than price scenarios.
Note: Our temperature range considers all emissions intensity scenarios but only three (of six) carbon price scenarios. The low end of our temperature range is more robust than the high end.
What is the global final energy use by fuel type?
Over time, electricity, is expected to dominate electricity production, characterised by a low share of fossil fuels (and higher shares of renewables) displacing gases and solids. These figures show the final energy consumption by fuel type across 2020-2050. Different columns for the same model represent different scenarios and their results for final energy by fuel type.
What is the global final energy use by sector?
Global final energy increases in almost all sectors over time with industry, residential and commercial sectors, and the transport sector leading the increase. These figures show the final energy consumption by sector in industry, transport, residential and commercial (buildings), other sectors (such as agriculture, forestry, fishing, and livestock) and in non-energy across models and scenarios over time. Different columns for the same model represent different scenarios and their results for final energy by sector.
What is the role of CCS in global emissions reduction?
Here, we investigate the role of CCS potential up till 2030 and 2100. The use of CCS is found to be significantly higher in scenarios using economy-wide carbon prices to represent current policies than in scenarios representing current policies explicitly. By 2100, the levels of CCS in our scenarios (for the models that run to 2100) rival the levels seen in some deep mitigation scenarios.
