Integrated assessment models

Integrated assessment models
Name	Integrated assessment models
Purpose	Assess interactions among human and Earth systems for decision support

Integrated assessment models are computational frameworks that combine representations of physical, chemical, biological, and social systems to analyze policy-relevant questions about climate change, energy transitions, and sustainability. They synthesize data and theory from multiple domains to project pathways, compare mitigation and adaptation options, and quantify trade-offs under uncertainty. Practitioners use them to inform international negotiations, national planning, and scientific assessments.

Overview and purpose

Integrated assessment models bring together modules for the Intergovernmental Panel on Climate Change, United Nations Framework Convention on Climate Change, Organisation for Economic Co-operation and Development, International Energy Agency, and World Bank users to explore scenarios that link emissions, climate response, impacts, and socioeconomic outcomes. They are designed to support decision-making by governments such as the European Commission, United States Department of Energy, Ministry of Environment (Japan), and agencies like the National Aeronautics and Space Administration and National Oceanic and Atmospheric Administration. Core purposes include providing input to reports by the IPCC, informing targets discussed at Conference of the Parties, underpinning analyses by the World Resources Institute and Rocky Mountain Institute, and offering quantitative bases for laws such as the Energy Independence and Security Act and initiatives of the Green Climate Fund.

Historical development

The development lineage traces through institutional and disciplinary milestones involving the RAND Corporation studies, early work at Massachusetts Institute of Technology, and projects funded by the Ford Foundation and National Science Foundation. Influential moments include contributions from research groups at Stanford University, Princeton University, Carnegie Mellon University, and Pacific Northwest National Laboratory. Integration accelerated after global events like the 1970s energy crisis and the negotiation of the United Nations Framework Convention on Climate Change, with synthesis efforts culminating in model intercomparison projects coordinated by the IPCC and collaborative networks such as the Model Intercomparison Project on the climatic response and regional initiatives supported by the Asian Development Bank.

Model structure and components

Typical models couple modules for carbon and greenhouse gas cycles developed in the tradition of NOAA and Hadley Centre climate science, energy system modules comparable to analyses from the International Energy Agency and Lawrence Berkeley National Laboratory, land‑use modules informed by work at NASA and European Space Agency, and damage or impact modules referencing studies from Resources for the Future and Stockholm Environment Institute. Economic components draw on approaches from Harvard University, London School of Economics, University of Chicago, and Yale University to represent production, consumption, and technological change. Social and demographic inputs often incorporate datasets and projections from the United Nations Department of Economic and Social Affairs and World Health Organization. Numerical methods and uncertainty quantification have benefited from collaborations with institutions like Los Alamos National Laboratory and Argonne National Laboratory.

Applications and policy use

Integrated assessment models have been applied to assess pathways aligned with targets considered at Paris Agreement negotiations, to estimate social cost metrics used in regulatory analysis by the U.S. Environmental Protection Agency, and to support national commitments submitted as Nationally Determined Contributions. They inform infrastructure investment choices evaluated by entities such as Asian Infrastructure Investment Bank and European Investment Bank, guide subsidy reform debates in legislatures like the United States Congress and European Parliament, and underpin carbon pricing proposals considered by the World Bank and International Monetary Fund. Sectoral applications include electricity planning referenced by California Energy Commission, aviation assessments involving the International Civil Aviation Organization, and land‑use policy interactions with the Food and Agriculture Organization.

Criticisms and limitations

Critiques have been raised by scholars affiliated with Columbia University, University of Oxford, Princeton University, and advocacy organizations such as Friends of the Earth and Greenpeace about structural assumptions, treatment of uncertainty, and representation of technological innovation. Concerns highlight reliance on damage functions debated in literature tied to Stern Review and contested cost–benefit approaches originating in analyses by William Nordhaus. Other limitations include regional resolution constraints noted by researchers at Australian National University, potential biases in scenario ensembles used by the IPCC, and transparency issues emphasized by groups like the Open Knowledge Foundation.

Key models and examples

Prominent models and modeling families developed or hosted at institutions include frameworks associated with IIASA and the MESSAGE family, models emerging from MIT including the lineage of the Integrated Global System Model tradition, the approaches linked to FUND and work by Nordhaus at Yale University, the models coordinated by Potsdam Institute for Climate Impact Research, and large multi‑institution efforts such as those participating in the Coupled Model Intercomparison Project. Regional and sectoral examples span tools used by National Renewable Energy Laboratory, TERI in India, and models employed in analyses by McKinsey & Company and BloombergNEF.

Category:Climate models