The IPCC's Special Report, Global Warming of 1.5℃

The details of the IPCC’s Special Report, Global Warming of 1.5℃, if thoughtfully read, should oblige policy makers to conclude that the obstacles to limiting global warming to this level, and indeed even to higher temperatures, are not just arbitrary blockages, rocks in the road to be removed, but fundamental and structural problems with the policy options currently available, which are almost certainly more harmful than the climate change they set out to mitigate.Most of the press coverage of the IPCC’s Special Report, Global Warming of 1.5℃ (henceforth SR1.5),has so far focused on the threats posed by climate change at higher temperature levels, and very little on what is required to contain warming below 1.5℃. But in fact the UNFCC request to the IPCC was quite specifically that “the report […] should not only assess what a 1.5°C warmer world would look like but also the different pathways by which global temperature rise could be limited to 1.5°C” (IPCC SR1.5, 1-43, “FAQ 1.1 “Why are talking about 1.5℃?”).Even a glance at the Summary for Policy Makers (SPM) will show that the authors have not neglected their duty, and much of the study is consequently concerned with these pathways, as well as the hazards. From a reader’s point of view these two elements have to be considered together if the study is to have any significance. It is not, after all, remotely surprising that SR1.5 finds that a 1.5℃ increase is less hazardous than an increase of 2℃. That is obviously and trivially true, and we did not need an IPCC Special Report to reach such a conclusion.The crucial consideration is whether the cost of that reduction is proportional to the benefit, and the answer to that question is most certainly neither obvious nor trivial. Steps toward such an answer are the core payload of SR1.5. However, it is precisely this issue that is conspicuously evaded in general publicity around the IPCC’s findings.What then does SR1.5 actually say about the measures, the emissions pathways needed to limit temperature increase to 1.5℃ above pre-industrial levels? Professor Jim Skea of Imperial College, one of the Report’s authors, and Co-Chair of IPCC Working Group III, is quoted in the Press Release as follows:

"Limiting warming to 1.5℃ is possible within the laws of chemistry and physics but doing so would require unprecedented changes."

This is not too difficult to decode. It is “within the laws of chemistry and physics” for the computer on which I am writing to suddenly pass through the library table on which it is currently resting, thanks to a fortunate coincidence of empty spaces in their respective atomic structures, but experience and theory tells us that this is vanishingly unlikely and consequently empirically “unprecedented”. By the same token, Professor Skea is saying that the emissions pathway required to restrain temperature increases to 1.5℃ is theoretically possible, but would require a synchronised transformation of technology, economy, and society of a scale and character that has never occurred in human history. Bluntly, it’s possible but it won't happen.This point is in fact also clearly implied in Section C of the Summary for Policy Makers (SPM), “Emission Pathways and System Transitions Consistent with 1.5℃ Global Warming”, particularly in sections C2 to C2.7, which consider the various sectoral transformations required.In overview, C2 notes that the pathways required to deliver the limit “would require rapid and far-reaching transitions in energy, land, urban infrastructure (including transport and buildings), and industrial systems (high confidence)”. No area is untouched, and “deep emissions reductions” in “all sectors” are necessary. Translation: This a tall order.C2.1 observes in addition that the 1.5℃limit requires “changes that are more rapid and pronounced over the next two decades than in 2℃ pathways (high confidence)”. The authors furthermore note that while rapid change of the kind required has been observed in “specific sectors, technologies and spatial contexts”, “there is no documented historic precedent for their scale (medium confidence)”. Translation: The overall transition required appears to be improbable.C2.2 notes that significant energy demand reduction is required, “including through enhanced energy efficiency”, implying that some straightforwardly coerced conservation of energy will be needed. In addition, not only would a “faster electrification of energy end use” than that needed for a 2℃ limit be required for 1.5℃, but renewables would have to rise to supply 70–85% of global electricity in 2050, with gas fuelled electricity generation, equipped with Carbon Capture and Sequestration, limited to 8% in 2050, and coal falling away to nothing. On this remarkable vision the authors comment:

"While acknowledging the challenges, and differences between the options and national circumstances, political, economic, social and technical feasibility of solar energy, wind energy and electricity storage technologies have substantially improved over the past few years (high confidence). These improvements signal a potential system transition in electricity generation."

Translation:Even assuming the best for renewables and energy storage, the required global electricity sector transition is still no more than a theoretical possibility.C2.3 reports that industrial emissions must be 75–90% lower in 2050, relative to 2010, “as compared to 50–80% for global warming of 2℃”. The options for these very major reductions are “technically proven at various scales but their large-scale deployment may be limited by economic, financial, human capacity and institutional constraints”. Translation: Industrial emissions reductions at the magnitude required are very unlikely.C2.4 summarises the required changes in urban and infrastructural systems, including an increase in the electrification of buildings, and a dramatic increase in the share of low emission transport, which would have to rise from 5% in 2020 to 35–65% in 2050, as compared to 25–45% for a 2℃ limit. The authors conclude: “Economic, institutional and socio-cultural barriers may inhibit these urban and infrastructure system transitions, depending on national, regional and local circumstances, capabilities and the availability of capital (high confidence)”. Translation: Urban and infrastructural transition on the scale required is improbable.C2.5 discusses global and regional land use changes that would be required, and projects the conversion of up to 8 million km² of pasture and up to 5 million km² of non-pasture agricultural land currently devoted to food and feed crops to up 7 million km² of energy crops. Forests might have to be reduced by 1 million km²  or increased by up 10 million km² in 2050 relative to 2010. Interestingly, these changes are similar to those required for a 2℃ target. The authors candidly grant that “Such large transitions pose profound challenges for sustainable management of the various demands on land for human settlements, food, livestock, seed, fibre, bioenergy, carbon storage, biodiversity and other ecosystem services”. It is no wonder at all then, that the section concludes that “The implementation of land-based mitigation options would require overcoming socio-economic, institutional, technological, financing and environmental barriers”. Translation: The land use changes required for 1.5℃ (and actually for 2℃) are very unlikely to be either societally or environmentally acceptable.C2.6 examines the scale of energy-related investment to deliver the 1.5℃ limit.  The authors suggest energy-related mitigation investment would have to be reach an average annual total over the period 2015 to 2050 of around 900 billion USD in 2015 prices, with a range of 180 billion to 1,800 billion. This implies an increase of about 12% over and above that required for the 2℃ target, but could be as much as 23% more. Reference to the main study itself, see 2-84, provides the relevant gloss: “Estimates and assumptions from modelling frameworks suggest a major shift in investment patterns and entail a financial system effectively aligned with mitigation challenges (high confidence)”.Translation: The entire world’s finances must be dedicated to climate mitigation, and this is unlikely.Finally, C2.7 draws these various points together in the single observation that the global average discounted marginal abatement costs (i.e. $/tCO2) for a 1.5 ℃ scenario are “roughly 3–4 times higher than in pathways limiting global warming to below 2℃ (high confidence)”.Translation: The additional effort required to deliver a 1.5℃ target, as opposed to a 2℃, is very large, and clearly unlikely to be realised.Cumulatively, the effect is quite clear, and although SR1.5 carefully avoids making any explicit Cost-Benefit Assessment of the 1.5℃ limit, tactfully leaving this to policy makers, the conclusions presented in C2.1 to C2.7, and in the main text, imply that the difficulties, the costs, the sacrifices required to deliver the necessary policies are very high indeed, and consequently that the world’s peoples will probably decide, through their actions, that these economic and other harms exceed those of climate change resulting from a temperature increase of 0.5℃ over current levels. Consequently, this target is unrealistic (and, sotto voce, so is the 2℃ target).