Ecological macroeconomic assessment of meeting a carbon budget without negative emissions

Abstract

Non-technical summary This paper expands the range of scenarios usually explored in integrated assessment models by exploring unconventional economic scenarios (steady-state and degrowth) and assuming no use of negative emissions. It is shown, using a mathematical model of climate and economy, that keeping cumulative emissions within the 1.5 degree carbon budget is possible under all growth assumptions, assuming a rapid electrification of end use and an immediate upscaling of renewable energy investments. Under business-as-usual investment assumptions no economic trajectory corresponds with emissions reductions consistent with the 1.5 degree carbon budget. Technical summary This paper presents a stock-flow consistent input–output integrated assessment model designed to explore the dual dynamics of transitioning to renewable energy while electrifying end use subject a carbon budget constraint. Unlike the majority of conventional integrated assessment model analyses, this paper does not assume the deployment of carbon dioxide removal and examines the role that alternative economic pathways (steady-states and degrowth) may play in achieving 1.5°C consistent emissions pathways. The model is internally calibrated based on a life-cycle energy return on investment scheme and the energy transition dynamics are captured via a dynamic input–output formulation. Renewable energy investment as a fraction of gross domestic product for successful emissions pathways reaches 5%. In terms of new capital requirements and investments, degrowth trajectories impose lower transition requirements than steady-state and growth trajectories. Social media summary We explore the role that steady-state and degrowth economic trajectories may play in emissions reductions consistent with a 1.5 degree world..

Emerging consensus on net energy paves the way for improved integrated assessment modeling

“…A considerable exception to current IAMs is the MEDEAS model 5,118,119 -now developed as the WILIAM model in the scope of the LOCOMOTION project–which appears to be the sole multi-scale¶¶The SFCIO-IAM 204 and WORLD7 235 are for instance only global models. IAM that explores, from a heterodox perspective, 120 the implications that the energy required for the transition may have on the energy system and the economy. 121 Unlike other IAMs, MEDEAS includes an energy-economy feedback that allows energy availability to limit GDP growth in the event that it falls short of demand.…”

“…6. the exploration of new mitigation pathways achieving high wellbeing levels with low resource use, 203 limiting the deployment of energy intensive carbon dioxide removal, 204–208 and equitable low-growth 209 and post-growth scenarios. 210–217…”

“…176,177 In an attempt to bridge the gap § In this regard, it is worth noting that it has been estimated that, due to residual fossil emissions, 640-950 GtCO 2 carbon dioxide removal (CDR), i.e., BECCS, DACCS and afforestation, will be required for a likely chance of limiting end-ofcentury warming to 1.5 1C, when strengthened pre-2030 mitigation action is combined with very stringent long-term policies. 234 ¶ The SFCIO-IAM 204 and WORLD7 235 are for instance only global models.…”

“…3. the use of an ecological macroeconomic framework (as in HARMONEY 195,196 or TranSim 46 ) or ESM which deal with environmental and biophysical indicators 197 in a more comprehensive way, such as ENBIOS, 198 EnergyScope 199 or the one developed by Crownshaw;200 4. a common reporting template to include the energy consumption of the energy sector as well as useful energy in mitigation scenarios; 8,201,202 5. an explicit modelling of energy-economy feedbacks (including rebound effects) using net energy, at least with the aim of understanding how a net energy feedback would affect IAMs results to assess to what extent energy and economic feedbacks are internally (in)consistent across mitigation pathways; 202 6. the exploration of new mitigation pathways achieving high wellbeing levels with low resource use, 203 limiting the deployment of energy intensive carbon dioxide removal, [204][205][206][207][208] and equitable low-growth 209 and post-growth scenarios. [210][211][212][213][214][215][216][217] However, if these measures are to be properly implemented, they must be carried out simultaneously and without neoclassical economics theories, 218,219 which we see as incompatible.…”

Systemwide energy return on investment in a sustainable transition towards net zero power systems

“…The pioneering EROI studies present diverse concepts due to methodological inconsistencies 7 , 8 , with some deriving varieties of EROI concepts 9 – 12 , implementing different boundary conditions 13 – 15 , comparing fossil fuel and RE technologies with or without enabling technologies 16 – 19 . However, recent studies 20 – 23 diverted this attention towards EROI analysis for ETs 24 , 25 to foresee the feasibility of 100% RE systems 26 . Some of these studies questioned the plausibility of 100% RE in terms of net energy production 20 , 22 .…”