Whenever you read a media story about how we’re heading toward catastrophe if we continue operating “business as usual” — i.e., if we don’t slash carbon emissions — the reports are almost always referring to a model simulation using RCP8.5. And you can bet that nowhere in the story will they explain that RCP8.5 is an implausible worst-case scenario that was never meant to represent a likely base case outcome, or that scientists have begun castigating its usage as a prediction of a doomed business-as-usual future.
The term RCP8.5 refers to a greenhouse gas emissions scenario often used by scientists for climate model projections. You might never have heard of RCP8.5 but you have definitely heard of forecasts based on it. Listening to the politicians who make the strongest pleas for radical climate action, it is clear that their fears for the future are driven by RCP8.5 scenarios, yet it is also clear that they have no idea what it is or what is wrong with it.
RCP stands for “Representative Concentration Pathways,” or projections of how much carbon dioxide (CO2) will accumulate in the atmosphere due to fossil fuel use over the coming century. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) generated a set of four RCP scenarios a decade ago, attaching to each a number indicating how much “radiative forcing” (a measure of global warming potential) each one generates. RCP2.6 refers to a benign, low-end emission scenario with correspondingly minimal radiative forcing. In the middle are RCP4.5 and RCP6.0, and at the top end is RCP8.5, a scorcher that predicts historically unprecedented increases in global CO2 emissions.
To appreciate how implausible RCP8.5 is, consider its coal use trajectory. From the 1920s to the year 2000, global coal consumption stayed between 15 and 20 gigajoules per capita, peaking at 20 in 1960, falling back to 15 by 2000, then rising to about 23 earlier this decade with the sudden industrialization of China and India. Groups like the International Energy Agency expect it will gradually return to the 15-20 gigajoule per capita range by 2040.
The RCP8.5 scenario offers a different outcome. Instead of a return to normal, it projects coal use will rise to about 30 gigajoules by 2040, 45 gigajoules by 2060 and 70 gigajoules by 2100. No one seriously believes this is even possible, including people who use RCP8.5 in their climate simulations.
The term RCP8.5 refers to a greenhouse gas emissions scenario often used by scientists for climate model projections. You might never have heard of RCP8.5 but you have definitely heard of forecasts based on it. Listening to the politicians who make the strongest pleas for radical climate action, it is clear that their fears for the future are driven by RCP8.5 scenarios, yet it is also clear that they have no idea what it is or what is wrong with it.
RCP stands for “Representative Concentration Pathways,” or projections of how much carbon dioxide (CO2) will accumulate in the atmosphere due to fossil fuel use over the coming century. The United Nations’ Intergovernmental Panel on Climate Change (IPCC) generated a set of four RCP scenarios a decade ago, attaching to each a number indicating how much “radiative forcing” (a measure of global warming potential) each one generates. RCP2.6 refers to a benign, low-end emission scenario with correspondingly minimal radiative forcing. In the middle are RCP4.5 and RCP6.0, and at the top end is RCP8.5, a scorcher that predicts historically unprecedented increases in global CO2 emissions.
To appreciate how implausible RCP8.5 is, consider its coal use trajectory. From the 1920s to the year 2000, global coal consumption stayed between 15 and 20 gigajoules per capita, peaking at 20 in 1960, falling back to 15 by 2000, then rising to about 23 earlier this decade with the sudden industrialization of China and India. Groups like the International Energy Agency expect it will gradually return to the 15-20 gigajoule per capita range by 2040.
The RCP8.5 scenario offers a different outcome. Instead of a return to normal, it projects coal use will rise to about 30 gigajoules by 2040, 45 gigajoules by 2060 and 70 gigajoules by 2100. No one seriously believes this is even possible, including people who use RCP8.5 in their climate simulations.
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