Potential impacts of rapidly changing European use of fossil fuels on global warming

The balance of primary energy sources for Europe has been changing rapidly over recent decades, shifting towards more renewables and using fossil fuels with lower carbon emissions. However, the latter is being impacted by the Russia-Ukraine conflict. Here, we determine the potential bounds of how this may affect global warming, based on whether the European use of Russian gas and oil is replaced with either less efficient burning of coal (with and without the gas and oil then used in new markets elsewhere) or with renewables. We perform calculations as perturbations from a baseline carbon dioxide (CO2) trajectory associated with 'middle range' and 'low' Shared Socioeconomic Pathways (SSP), SSP2-45 and SSP1-26. We calculate the CO2 perturbations as a simulated step change in emissions for the year 2023, which then decays linearly to zero by 2043. The emission profiles drive the FaIR simple climate model. FaIR links greenhouse gas emissions to global warming levels and includes a representation of warming uncertainty based on projections made using more complex Earth system models. We find that the direct impact of the conflict on the global mean temperature is likely to be relatively small, amounting to the worst case of nearly one-hundredth of a degree. This warming is equivalent to approximately an extra half year of current global CO2 emissions. However, we suggest that it is important to consider the implications of the precedents set by the European response to the reduced availability of Russian gas and oil. Such action may reveal the potential for faster uptake of low-carbon energy sources or the converse of backtracking on current Nationally Determined Contributions (NDCs).