The Honest Broker

Bibliography

The primary sources behind this site.

With thanks

This site rests on the CMIP7 marker scenarios, and on the ScenarioMIP Explorer that IIASA hosts. The scenarios come from years of work by the ScenarioMIP team and the integrated assessment modelling groups behind them.

Without both, this tool could not exist. Thanks to everyone who played a role in building them and making them available. Open science is good science.

Van Vuuren, D. P., O’Neill, B. C., Tebaldi, C., Sanderson, B. M., Chini, L. P., Friedlingstein, P., Hasegawa, T., Riahi, K., et al. (2026). The Scenario Model Intercomparison Project for CMIP7 (ScenarioMIP-CMIP7). Geoscientific Model Development, 19, 2627–2656. doi:10.5194/gmd-19-2627-2026

Thanks also to Justin Ritchie, whose pathbreaking work on scenarios inspired my intensive work in this area over the past decade, along with Matt Burgess and others.

Ritchie, J., & Dowlatabadi, H. (2017). Why do climate change scenarios return to coal? Energy, 140, 1276–1291. doi:10.1016/j.energy.2017.08.083

The book

  • Pielke Jr., R. (2010). The Climate Fix: What Scientists and Politicians Won't Tell You About Global Warming. Basic Books. thehonestbroker.org/books

    Sets out the argument behind this tool: that emissions follow from a small number of measurable and projectable quantities.

Our work on scenarios

  • Pielke Jr., R., Burgess, M. G., & Ritchie, J. (2022). Plausible 2005–2050 emissions scenarios project between 2 °C and 3 °C of warming by 2100. Environmental Research Letters, 17, 024027. doi:10.1088/1748-9326/ac4ebf

    Screens the scenario set against the observed record and reports which paths remain plausible. The nearest published work to this tool.

  • Burgess, M. G., Ritchie, J., Shapland, J., & Pielke Jr., R. (2021). IPCC baseline scenarios have over-projected CO₂ emissions and economic growth. Environmental Research Letters, 16, 014016. doi:10.1088/1748-9326/abcdd2

    Compares baseline scenario projections of the emissions drivers against observations, and finds most of them running high.

  • Pielke Jr., R., & Ritchie, J. (2021). Distorting the view of our climate future: The misuse and abuse of climate pathways and scenarios. Energy Research & Social Science, 72, 101890. doi:10.1016/j.erss.2020.101890

    How scenarios built as exploratory tools acquired the standing of predictions, and how that reading spread through the literature.

  • Pielke Jr., R., & Ritchie, J. (2021). How climate scenarios lost touch with reality. Issues in Science and Technology, 37(4), 74–83. issues.org

    The non-technical version of the argument, written for readers outside the field.

  • Pielke Jr., R. (2018). Opening up the climate policy envelope. Issues in Science and Technology, 34(4), 30–36. jstor.org

    On widening the range of futures that policy discussion takes seriously, rather than narrowing it to a handful of published paths.

  • Stevenson, S., & Pielke Jr., R. (2015). Assumptions of spontaneous decarbonization in the IPCC AR5 baseline scenarios. Center for Science and Technology Policy Research, University of Colorado Boulder. PDF

    Separates out the energy and carbon intensity assumptions inside the AR5 baselines, the two sliders in the middle of this page.

  • Pielke Jr., R., Wigley, T., & Green, C. (2008). Dangerous assumptions. Nature, 452(7187), 531–532. doi:10.1038/452531a

    The earliest statement of the problem: the amount of decarbonization the scenarios assume in advance of any policy.

The two technology bounds

  • Ausubel, J. H. (1995). Technical progress and climatic change. Energy Policy, 23(4–5), 411–416. doi:10.1016/0301-4215(95)90166-5

    The argument behind the two bound presets: that technological trajectories move at rates steady enough to bound the future, and that a scenario halting them describes technical regression rather than business as usual.

  • Ausubel, J. H., Grübler, A., & Nakicenovic, N. (1988). Carbon dioxide emissions in a methane economy. Climatic Change, 12(3), 245–263. doi:10.1007/BF00139432

    The published trajectory behind the Ausubel methane economy preset, which takes carbon in primary energy to 0.06 tonnes of carbon per kilowatt-year by 2100.

Behind the Learn More pages

    Where the numbers come from

    • Energy Institute. Statistical Review of World Energy, 2026 edition. energyinst.org

      CO₂ from energy and total energy supply, world, 1965–2024.

    • World Bank. GDP at purchasing power parity, constant 2021 international dollars (NY.GDP.MKTP.PP.KD), and population (SP.POP.TOTL). data.worldbank.org

      Income per person and the denominator for energy per dollar, 1990–2024. Also the country comparison.

    • Global Carbon Project. Global Carbon Budget, via Our World in Data. globalcarbonbudget.org

      Fossil and industrial CO₂ for the base year, cement included, so the four factors count what the CMIP7 scenarios count.

    • IIASA. SSP database, version 3.2, June 2025 release. data.ece.iiasa.ac.at/ssp

      The SSP1, SSP2 and SSP3 world population trajectories the population slider interpolates between.

    • ScenarioMIP CMIP7 marker scenarios. wcrp-cmip.org

      The seven paths drawn behind your path, and the Kaya factors behind each calibration mark.

    • Smith, C. J., et al. FaIR, the Finite-amplitude Impulse Response model, version 2.2, with the fair-calibrate v1.4.1 constrained ensemble. docs.fairmodel.net

      The runs behind the warming curve on this page. An indicative fit rather than a model result.

    The project's DATA.md sets out every series, its vintage and its units; METHODS.md sets out the calculation and its limits.