At the global level, scenarios reaching 450 ppm CO2eq are also characterized by more rapid improvements of energy efficiency, a tripling to nearly a quadrupling of the share of zero ‐ and low ‐ carbon energy supply from renewables, nuclear energy and fossil energy with carbon dioxide capture and storage (CCS), or bioenergy with CCS (BECCS) by the year 2050 (Figure SPM.4, lower panel).
This is a scenario that keeps temperature rise below 2 degrees centigrade – in fact, it overreaches if we take the following as the goal.
Mitigation scenarios reaching concentration levels of about 500 ppm CO2eq by 2100 are more likely than not to limit temperature change to less than 2°C relative to pre‐industrial levels, unless they temporarily ‘overshoot’ concentration levels of roughly 530 ppm CO2eq before 2100, in which case they are about as likely as not to achieve that goal.
That’s a lot of caveats, but clear enough. Strikingly, nuclear energy is always a part of the solution to achieve carbon emission goals, yet the report is not remotely partisan in its discussion of energy types. It simply looks at what’s there and what could be there (coal with ccs, for example). The idea, I think, is that policymakers will take it from there. This makes sense, as the United Nations needs to keep in mind an extraordinarily broad set of policy options across its membership.
This is how the report puts it:
Well‐designed systemic and cross-sectoral mitigation strategies are more cost-effective in cutting emissions than a focus on individual technologies and sectors. At the energy system level these include reductions in the GHG emission intensity of the energy supply sector, a switch to low carbon energy carriers (including low‐carbon electricity) and reductions in energy demand in the end‐use sectors without compromising development.
That last bit seems especially important, as it will be the developing world that makes these goals plausible, for while the developed world has numerous energy options, the developing world has significantly fewer type of energy it can implement – at least with current resources – and without help from the developed world.
But none of this means the report isn’t fairly explicit on what not using nuclear energy entails. Look at Table SPM.2 on page 18 of the summary. The orange section details the implication of not having a particular energy type available has on reduction goals (as a percent change.) Obviously, not having carbon capture is huge, but a nuclear phase-out is also shown as having a sizeable negative impact. Again, remember that the report is not taking any view on no CCS or no nuclear – it is saying that doing without would lead to poor outcomes.
We’ll take a look at the full report and some of the press coverage of it later this week.
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