MAGICC: A reduced complexity Earth system model

MAGICC is a reduced complexity Earth system model that has been widely used in climate science for over three decades, most notably in multiple IPCC reports. It is most often used in a probabilistic setup, providing information not only about our best-estimate of future climate change but also the uncertainty that arises from interactions between the Earth system’s many components. MAGICC is also as the climate component in multiple integrated assessment models (IAMs).

MAGICC represents the Earth with four boxes: one for land and one for the ocean, in each hemisphere. The ocean component is an upwelling-diffusion model with multiple layers. The atmospheric component is based on the energy balance equation, modified to support MAGICC’s four box structure. In addition to its core energy balance components, MAGICC includes models of the carbon cycle, methane cycle, impact of anthropogenic aerosol emissions and sea-level rise.

MAGICC’s key input is emissions of anthropogenic emissions that impact the climate system, primarily greenhouse gases but also aerosol precursors and emissions that influence other gas cycles such as carbon monoxide. Based on these inputs, MAGICC provides projections of a number of key quantities, including atmospheric greenhouse gas concentrations, effective radiative forcing for different species, temperature change, Earth system heat uptake and sea-level rise. Global-mean quantities are the key output, but outputs at the hemispheric level can also be used in more specialised applications.

MAGICC was used as part of the IPCC’s Sixth Assessment Report to assess the climate implications of the Working Group 3 (WG3) scenario database. It was used alongside other reduced complexity models, all of which were run as part of the WG3 climate assessment workflow. This tool is the next step in standardised climate assessment and provides a base for further developments into the future.

MAGICC’s development is led by Prof. Malte Meinshausen at the University of Melbourne, Australia and is available from magicc.org. As part of the ESM2025 project, Zebedee Nicholls and Jared Lewis are working at IIASA to refactor MAGICC and update its carbon cycle modules alongside updates to the OSCAR reduced complexity model. As part of the ESM2025 project, MAGICC will be made open-source in 2023.

Click here to access the MAGICC website

Selected publications:

Meinshausen, M., Lewis, J., McGlade, C. et al. Realization of Paris Agreement pledges may limit warming just below 2 °C. Nature, 604, 304–309 (2022).
Nicholls, Z., Meinshausen, M., Lewis, J., Smith, C. J., Forster, P. M., Fuglestvedt, J. S., et al. Changes in IPCC scenario assessment emulators between SR1.5 and AR6 unraveled. Geophysical Research Letters, 49, e2022GL099788 (2022).
Brecha, R.J., Ganti, G., Lamboll, R.D. et al. Institutional decarbonization scenarios evaluated against the Paris Agreement 1.5 °C goal. Nat. Commun., 13, 4304 (2022).
Kate Dooley, Zebedee Nicholls, Malte Meinshausen, Carbon removals from nature restoration are no substitute for steep emission reductions, One Earth, 5(7), 812-824 (2022).
Kikstra, J. S., Nicholls, Z. R. J., Smith, C. J., Lewis, J., Lamboll, R. D., Byers, E., Sandstad, M., Meinshausen, M., Gidden, M. J., Rogelj, J., Kriegler, E., Peters, G. P., Fuglestvedt, J. S., Skeie, R. B., Samset, B. H., Wienpahl, L., van Vuuren, D. P., van der Wijst, K.-I., Al Khourdajie, A., Forster, P. M., Reisinger, A., Schaeffer, R., and Riahi, K.: The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways: from emissions to global temperatures, Geosci. Model Dev., 15, 9075–9109 (2022).
Meinshausen, M., Meinshausen, N., Hare, W., Raper, S. C. B., Frieler, K., Knutti, R., Frame, D. J., & Allen, M. R. Greenhouse-gas emission targets for limiting global warming to 2°C. Nature, 458(7242), 1158–1162 (2009).
Meinshausen, M., Raper, S. C. B., & Wigley, T. M. L. Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6 – Part 1: Model description and calibration. Atmospheric Chemistry and Physics, 11(4), 1417–1456 (2011).
Meinshausen, M., Nicholls, Z. R. J., Lewis, J., Gidden, M. J., Vogel, E., Freund, M., Beyerle, U., Gessner, C., Nauels, A., Bauer, N., Canadell, J. G., Daniel, J. S., John, A., Krummel, P. B., Luderer, G., Meinshausen, N., Montzka, S. A., Rayner, P. J., Reimann, S., Wang, R. H. J. The shared socio-economic pathway (SSP) greenhouse gas concentrations and their extensions to 2500. Geoscientific Model Development, 13(8), 3571–3605 (2020).

Selected publications:

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