The latest set of non-IPCC scenarios are out at last. The data are here.
Recall that the governments that ultimately rule the IPCC, find it difficult to sign off on scenarios showing that the promises they made to their electorates may not materialize. Scenario-builders therefore created a consortium that cross-my-heart-and-hope-to-die has nothing to do with the IPCC — they just happen to be much the same crowd.
These are the previous scenarios, SSPs, for carbon dioxide emissions, decomposed according to the Kaya Identity:
And here are the new ones, let’s call them MIPs:
The scenarios for population, per capita income, and energy intensity are much the same. They just ditched SSP4 and SSP5, the two scenarios with really high average income in 2100.
The scenarios for carbon intensity are very different. The much-critized, return-to-coal scenario has been retired. This was just about not-implausible when the SSPs were conceived but already untenable when published. Instead of the two no-renewables SSPs, we now have three MIPs with very rapid decarbonization. Very rapid. Very, very rapid.
At the moment, nothing beats wind and solar. I do not think this will change. Electrification of private transport is gaining pace. Developments in heating, transportation, and industry are promising. Decarbonisation will continue and may well accelerate.
Two of the scenarios go negative — that is, bioenergy with carbon capture and storage at scale. I have previously expressed my scepticism. The market for carbon dioxide is saturated. No one will capture CO2 unless subsidized. Those subsidies are substantial in scenarios of rapid decarbonization: They are comparable in size to public spending on defense, education, or even health care. Bioenergy need not cost much if you do it in large, mechanized monoplantations on cheap soils. It is hard to see this work out politically.
In a follow-up paper, I discuss the implications for the host countries. Some of that is illustrated in this graph for Latin America:
In one of the scenario/model combinations, 37% of economic output in Latin America is in carbon capture and removal.
This is same graph for the so-called Reforming Economies
That is, the average Russian will earn 19 out of every 20 rubles in CCR. I see a bad moon rising. Local economies can hyperspecialize. Continental economies do not. Most of the CCR credits would be for export. Dutch disease and corruption would swamp these economies.
There is an underlying worry. The large integrated assessment models keep growing by adding more detail on energy technologies, which now includes agriculture. Unfortunately, they do not add to the economics and politics. Indeed, the difference between SSPs and MIPs is energy supply — as if we didn’t have 15 years of additional data and insights into demographics, economic growth, and energy demand. As Chris Bateille noted, I’m “not sure whether to comment seriously or laugh hysterically”.
People got bent out of shape over the unrealism of SSP585, but seem happy with equally unlikely scenarios if they project massive negative emissions.
Scenarios have multiple purposes. One purpose is to say what would happen if emissions were much higher or much lower than anticipated. Scenarios should therefore bracket expectations. If we do not have unrealistic scenarios, the suite of scenarios are not doing their job.