Integrated Assessment Models (IAMs) play a central role for the assessment of mitigation pathways by the IPCC and are frequently used to inform national and international climate policy considerations. In NAVIGATE, the next generation of IAMs was developed and made more accessible to users in order to provide more targeted advice for the climate policy process in a post-Paris world. To achieve this, NAVIGATE successfully advanced IAM capabilities in the following key areas:
Structural and technological change: Macroeconomic and structural change scenarios including the impact of the COVID-19 pandemic were developed. The impact of climate mitigation policies on structural changes at the macroeconomic level were shown to be small compared to the uncertainty about future structural transformations. Employment effects of the net zero transitions in the EU are generally positive, but there are winners and losers in terms of sectors and regions.
Behavioural change: NAVIGATE developed an open-source lifestyle typology with global universality for low-carbon research which was soft-coupled with a global IAM as a first-of-its-kind demonstration of endogenous modelling of lifestyle change. The main insight is that low-carbon lifestyle change interacts with - and can potentially amplify - the mitigation benefits of technological change. However, lifestyle change is highly variable across different population segments and ‘disengaged’ groups risk being marginalised in the absence of strong social learning on climate action.
Sector transformations: Models now represent a broader range of green technologies for industry and an extended portfolio of land-based mitigation options including technical mitigation options for non-CO2 emissions from agriculture and terrestrial carbon storage options with lower land demand. The modelling of the building sector was refined, e.g. with regard to energy demand scenarios or different types of building types and household preferences for deep renovation. In the transport sector, an improved understanding of the implications of infrastructure development and the transformation of consumer preferences was reached. The advancements were applied in model comparison studies which showed that the energy supply sector can reach net negative CO2 emissions by 2050 and the full portfolio of mitigation options can reduce emissions and limit energy demand simultaneously.
Distributional impacts: NAVIGATE analysed inequality and poverty implications of climate policies and climate impacts, household heterogeneity and revenue recycling, within-country inequality, and interaction of inequality and carbon pricing. It was shown that strong climate action will benefit poorer households in the long term, while in the near-term additional redistributive policies may be required to cushion regressive outcomes. However, there may be a trade-off between using carbon pricing revenues for reducing distortive labour taxes leading to higher economic growth, or for redistribution which is more conducive for equity.
NAVIGATE developed a methodology to downscale emissions and energy projections in IAM scenarios to the country level. The downscaling tool was applied in the development of climate transition scenarios for the Network for Greening the Financial System (NGFS).
Mitigation benefits: In order to assess benefits of avoided impacts, the modelling of climate change impacts was improved and related to an assessment of regional/sectoral adaptation and adaptive capacity. In addition, an assessment to achieve nexus SDG objectives (climate-land-energy-water) including climate feedbacks was conducted, pointing towards clear synergies in near-term action to achieve the SDGs and climate mitigation.
Model transparency: The common IAM documentation (IAMC wiki) has been continuously used as the main platform to provide transparent and harmonised model documentation, e.g. for the AR6 WG III Annex C on Scenarios and Modelling Methods. In NAVIGATE, several model comparison functions (e.g. search filters), data export options, a diagnostic assessment of the models’ key behaviour in response to climate policy incentives, and a linkage to the AR6 Scenario Explorer and Database have been added. This directly provides quantitative information on key input assumptions for the models. A primer on IAMs is available as an introductory resource for those less familiar with IAMs.
A synthesis model comparison study showed that the simultaneous and immediate use of all advanced mitigation measures across sectors can substantially accelerate action and close the gap between a pathway limiting warming to well below 2°C and a pathway compatible with limiting warming to 1.5°C by 2100. Results from the project were synthesised in a final report (
https://www.navigate-h2020.eu/wp-content/uploads/2023/11/NAVIGATE-synthesis-report-compressed.pdf(öffnet in neuem Fenster)) and presented during a final event at the EC in Brussels and at a side event at COP28 in Dubai. All modelling tools, scenarios and information material that were developed during the course of the project are available on the NAVIGATOR platform:
https://www.navigate-h2020.eu/navigator/(öffnet in neuem Fenster).
