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Unextractable fossil fuels in a 1.5°C world

Dan Welsby, James Price, Steve Pye, and Paul Ekins (2021)

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The article uses a global energy systems model (TIMES Integrated Assessment Model, UCL) to assess the amount of fossil fuels needed to be left in the ground to allow for a 50 per cent probability of limiting warming to 1.5°C. 


The model provides a representation of the global energy system, capturing primary energy sources (oil, fossil methane gas [also known as “natural gas”], coal, nuclear, biomass and renewables) from production through to their conversion (electricity production, hydrogen and biofuel production, oil refining), transport and distribution, and their eventual use to meet energy demands across a range of economic sectors. Using a scenario-based approach, the evolution of the system over time to meet future energy service demands can be simulated, driven by a least-cost objective. 


The model findings show the vast majority of yet-to-be-developed fossil fuel resources remain unused. Nearly 60 per cent of oil and fossil methane gas reserves and 90 per cent of coal reserves remain unextracted by 2050 to keep within a 1.5°C carbon budget. The research estimates that oil and gas production must decline globally by 3 per cent each year until 2050, with most regions having either peaked their production today, or reaching that peak within a decade. Importantly, it notes that these findings reflect a likely underestimate of the changes required because they do not account for Earth system feedbacks and uncertainties as to the feasibility of deploying negative emissions technologies at scale, suggesting the required rate of fossil fuel decline is even greater.  


The article contains a table showing unextractable reserves of fossil fuels under a 1.5°C scenario globally and by region (Africa, Australia and other OCED Pacific, Canada, China and India, Russia and former Soviet states, Central and South America, Europe, the Middle East, USA, Other Developing Asia). It also highlights that specific types of resources should also remain unextracted. For example, 99% of unconventional oils, such as tar sands, should remain unextracted, and 86% of unconventional gas. Arctic oil and fossil methane gas resources, across all regions where these are located, also remain undeveloped. 


The article suggests country producers, fossil fuel companies and their investors need to seriously reassess their production outlooks, particularly those countries reliant on fossil fuels. The article can be used to show the need for extraction projects to be limited / denied in order to meet Paris Agreement targets (the 'carbon budget’ approach). Crucially, it also provides insights on rates of reduction in specific geographies and in relation to types of oil and gas. It can also be used to argue that rapid reductions are required despite the offsetting role of Carbon Dioxide Removal (CDR), the deployment of which is associated with large uncertainties.  


The article challenges arguments that individual country producers can continue producing and still be Paris-aligned. It highlights that there is a global carbon budget, which requires much reduced extraction in future years - and that while all producers will have to reduce production, some will have to do so at faster rates than others.  


The article can also be used indirectly to challenge market substitution and carbon leakage arguments that suggest that rejecting a proposed new fossil fuel development will not result in emissions reductions because demand will be met by overseas supply. The article shows the worldwide need to limit extraction, indicating that it cannot be assumed these countries will not also limit production, reinforcing the power of rejecting each extraction proposal. 

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