A critical review of global decarbonization scenarios: what do they tell us about feasibility?

Abstract

Dozens of scenarios are published each year outlining paths to a low carbon global energy system. To provide insight into the relative feasibility of these global decarbonization scenarios, we examine 17 scenarios constructed using a diverse range of techniques and introduce a set of empirical benchmarks that can be applied to compare and assess the pace of energy system transformation entailed by each scenario. In particular, we quantify the implied rate of change in energy and carbon intensity and low-carbon technology deployment rates for each scenario and benchmark each against historical experience and industry projections, where available. In addition, we examine how each study addresses the key technical, economic, and societal factors that may constrain the pace of low-carbon energy transformation. We find that all of the scenarios envision historically unprecedented improvements in energy intensity, while normalized low-carbon capacity deployment rates are broadly consistent with historical experience. Three scenarios that constrain the available portfolio of low-carbon options by excluding some technologies (nuclear and carbon capture and storage) a priori are outliers, requiring much faster low-carbon capacity deployment and energy intensity improvements. Finally, all of the studies present comparatively little detail on strategies to decarbonize the industrial and transportation sectors, and most give superficial treatment to relevant constraints on energy system transformations. To be reliable guides for policymaking, scenarios such as these need to be supplemented by more detailed analyses realistically addressing the key constraints on energy system transformation.

Comparing future patterns of energy system change in 2 °C scenarios with historically observed rates of change

“…A similar analysis has been done by Loftus et al (2014), who normalized electricity capacity deployment rates in various global decarbonization scenarios using global GDP. In their study they found that the rates of change are broadly consistent with historical experience.…”

“…In their study they found that the rates of change are broadly consistent with historical experience. Only specific decarbonization scenarios with imposed restrictions on the implementation of clean and carbon sequestration technologies would lead to unprecedented rates of change for the remaining eligable low-carbon energy technologies (Loftus et al, 2014).…”

“…Historically observed rates of change can be important reference points for assessing the difficulty associated with future rates of change -providing possibly also insights in real world factors not covered in the models. In fact, several studies have already tried to compare model results and historical data using different indicators (Kramer and Haigh, 2009;Loftus et al, 2014;Riahi et al, 2015;Tavoni and van der Zwaan, 2009;van der Zwaan et al, 2013;Van Vuuren and Stehfest, 2013;Wilson et al, 2012). In these studies different methods and data sets have been used to confront existing scenarios with historical evidence, meaning that their results and conclusions cannot be easily compared.…”

Implications of Australia's Population Policy for Future Greenhouse Gas Emissions Targets

“…Thus, even a complete decarbonization of the nation's electricity production would not be enough to meet a 2050 target of 80 per cent reduction. Most of the transport industry would have to be decarbonized as well (Loftus et al 2015), fuelled by a mix of synthetic products from a nuclear-derived surplus of heat and electricity and battery electric 'plug-in' vehicles (Brook 2012b), and current domestic gas use would have to be electrified (Heard 2013). Massive gains in efficiency might also be needed, depending on deployment rates.…”

The Implications for Renewable Energy Innovation of Doubling the Share of Renewables in the Global Energy Mix between 2010 and 2030

“…A recent review by Reference [44] categorize decarbonization scenario studies into four types of methodologies (the low-carbon technology options considered in some of these studies include carbon capture and storage and nuclear), namely (i) top-down, scenario based back-casting; (ii) top-down integrated assessment modeling; (iii) bottom-up energy system modeling; and (iv) bottom-up technical or techno-economic assessments. These methodologies typically apply cost as a cut-off criteria, otherwise the models stop with technology deployment once its desired objective (e.g., emission reduction) is reached.…”