Chapter 6 - Assessing transformation pathways

Clarke, L., Jiang, K., Akimoto, K., Babiker, M., Blanford, G., Fisher-Vanden, K., Hourcade, J.-C., Krey, V. ORCID:, et al. (2014). Chapter 6 - Assessing transformation pathways. In: Climate Change 2014: Mitigation of Climate Change. IPCC Working Group III Contribution to AR5. Cambridge University Press.

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Stabilizing greenhouse gas (GHG) concentrations at any level will require deep reductions in GHG emissions. Net global CO2 emissions, in particular, must eventually be brought to or below zero. Emissions reductions of this magnitude will require large-scale transformations in human societies, from the way that we produce and consume energy to how we use the land surface. The more ambitious the stabilization goal, the more rapid this transformation must occur. A natural question in this context is what will be the transformation pathway toward stabilization; that is, how do we get from here to there?

The topic of this chapter is transformation pathways. The chapter is motivated primarily by three questions. First, what are the near-term and future choices that define transformation pathways including, for example, the goal itself, the emissions pathway to the goal, the technologies used for and sectors contributing to mitigation, the nature of international coordination, and mitigation policies? Second, what are the key decision making outcomes of different transformation pathways, including the magnitude and international distribution of economic costs and the implications for other policy objectives such as those associated with sustainable development? Third, how will actions taken today influence the options that might be available in the future?

Two concepts are particularly important for framing any answers to these questions. The first is that there is no single pathway to stabilization of GHG concentrations at any level. Instead, the literature elucidates a wide range of transformation pathways. Choices will govern which pathway is followed. These choices include, among other things, the long-term stabilization goal, the emissions pathway to meet that goal, the degree to which concentrations might temporarily overshoot the goal, the technologies that will be deployed to reduce emissions, the degree to which mitigation is coordinated across countries, the policy approaches used to achieve these goals within and across countries, the treatment of land use, and the manner in which mitigation is meshed with other policy objectives such as sustainable development.

The second concept is that transformation pathways can be distinguished from one another in important ways. Weighing the characteristics of different pathways is the way in which deliberative decisions about transformation pathways would be made. Although measures of aggregate economic implications have often been put forward as key deliberative decision making factors, these are far from the only characteristics that matter for making good decisions. Transformation pathways inherently involve a range of tradeoffs that link to other national and policy objectives such as energy and food security, the distribution of economic costs, local air pollution, other environmental factors associated with different technology solutions (e.g., nuclear power, coal-fired carbon dioxide capture and storage (CCS)), and economic competitiveness. Many of these fall under the umbrella of sustainable development.

A question that is often raised about particular stabilization goals and transformation pathways to those goals is whether the goals or pathways are "feasible". In many circumstances, there are clear physical constraints that can render particular long-term goals physically impossible. For example, if additinional mitigation beyond that of today is delayed to a large enough degree and carbon dioxide removal (CDR) options are not available (see Section 6.9), a goal of reaching 450 ppm CO2eq by the end of the 21st century can be physically impossible. However, in many cases, statements about feasibility are bound up in subjective assessments of the degree to which other characteristics of particular transformation pathways might influence the ability or desire of human societies to follow them. Important characteristics include economic implications, social acceptance of new technologies that underpin particular transformation pathways, the rapidity at which social and technological systems would need to change to follow particular pathways, political feasibility, and linkages to other national objectives. A primary goal of this chapter is to illuminate these characteristics of transformation pathways.

Item Type: Book Section
Research Programs: Energy (ENE)
Transitions to New Technologies (TNT)
Bibliographic Reference: In:; Climate Change 2014: Mitigation of Climate Change. IPCC Working Group III Contribution to AR5; Cambridge University Press
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:51
Last Modified: 27 Aug 2021 17:24

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