Carbon budgets and energy transition pathways

Detlef P Van Vuuren,Elmar Kriegler,Volker Krey,Leon Clarke,Michiel Schaeffer,Keywan Riahi,Heleen Van Soest,Massimo Tavoni,Joeri Rogelj

doi:10.1088/1748-9326/11/7/075002

Abstract

Scenarios from integrated assessment models can provide insights into how carbon budgets relate to other policy-relevant indicators by including information on how fast and by how much emissions can be reduced. Such indicators include the peak year of global emissions, the decarbonisation rate and the deployment of low-carbon technology. Here, we show typical values for these indicators for different carbon budgets, using the recently compiled IPCC scenario database, and discuss how these vary as a function of non-CO2 forcing, energy use and policy delay. For carbon budgets of 2000 GtCO2 and less over the 2010–2100 period, supply of low carbon technologies needs to be scaled up massively from today’s levels, unless energy use is relatively low. For the subgroup of scenarios with a budget below 1000 GtCO2 (consistent with >66% chance of limiting global warming to below 2 °C relative to preindustrial levels), the 2050 contribution of low-carbon technologies is generally around 50%–75%, compared to less than 20% today (range refers to the 10–90th interval of available data).

Highlights

Several publications have recently highlighted the relationship between cumulative CO2 emissions and long-term temperature change (Allen et al 2009, Matthews et al 2009, Meinshausen et al 2009, Zickfeld et al 2009, IPCC 2013, Friedlingstein et al 2014)
integrated assessment models (IAMs) information on carbon budgets Figure 1 shows—consistent with the carbon budget literature—that, for the scenarios included in the database, there is a very strong relationship between cumulative CO2 emissions and temperature and forcing outcomes
A range of different climate outcomes is associated with a specific carbon budget

Summary

Introduction

Several publications have recently highlighted the relationship between cumulative CO2 emissions and long-term temperature change (Allen et al 2009, Matthews et al 2009, Meinshausen et al 2009, Zickfeld et al 2009, IPCC 2013, Friedlingstein et al 2014). In defining emission pathways consistent with specific carbon budgets it is important to realise that these would require major changes in current energy and land-use systems (Clarke et al 2014, Kriegler et al 2014, Tavoni et al 2015) Such transitions will be constrained by socio-economic and technological inertia, manifested, among other things, in capital turnover rates, substitution dynamics, and limitations in implementation potential. For the recent IPCC Fifth Assessment Report (AR5), a large set of IAM-based scenarios has been compiled, based on different models and derived for different types of targets, including forcing targets, carbon budget constraints, emission targets and prescribed carbon taxes (Clarke et al 2014). The characteristics of these scenarios have been assessed in the IPCC AR5 report

Methods

Results

Conclusion