Analysis: How low-sulphur shipping rules are affecting global warming

Jul 6, 2023

The International Maritime Organization (IMO) implemented new regulations in 2020 that require ships to use low-sulphur fuel.

Low-sulphur shipping fuel: '...unlikely to be sufficient to explain the spike in global sea surface temperature in recent weeks' Image: Pexels/Martin Damboldt

Dr Zeke Hausfather

Climate Science Contributor, Carbon Brief

Prof Piers Forster

Professor of Climate Physics, University of Leeds

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Global SO2 emissions from international shipping from the global aerosol dataset (CEDS) (1970-2019). Estimates thereafter by Leon Simons based on projected effects of low-sulphur fuel regulations introduced in 2020. Image: by Zeke Hausfather for Carbon Brief, using Highcharts.

lobal daily sea surface temperature (SST) between 60S and 60N from NOAA’s OISST dataset for each year since 1981. The current year is shown in black. Image: Climate Reanalyzer.

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Global emissions of SO2 from shipping prior to IMO regulations limiting sulphur content of marine fuel (left) and the pattern of natural dimethyl sulphide (DMS) emissions (right). Image: Jin et al 2018.

Global SO2 emissions from a middle-of-the-road SSP2-4.5 scenario (grey) and the same scenario with a reduction in SO2 emissions of 8.5MtSO2 per year after 2020 (yellow). Black squares represent observational estimates of SO2 emissions in 2019 and 2022 from Forster et al 2023. Image: by Zeke Hausfather for Carbon Brief, using Highcharts.

Estimates of global average radiative forcing due to the shift to low-sulphur marine fuel from Carbon Brief, Yuan et al 2022, Bilsback et al 2020, Jin et al 2018, Sofiev et al 2018, Partanen et al 2013, Fuglestvedt et al 2009, and Lauer et al 2007. Forster et al 2023 considers a generic reduction of 9MtSO2 per year and is not specific to marine low-sulphur fuel. Image: by Zeke Hausfather for Carbon Brief, using Highcharts.

Global mean temperature change from the FaIR model simulating the effects of a reduction in SO2 emissions equivalent to 8.5MtSO2 per year after 2020, relative to the SSP2-4.5 scenario across 66 different CMIP6 models. The solid line shows the average of all model runs, while the shaded area shows the 5th to 95th percentile range. Image: by Zeke Hausfather for Carbon Brief.

Global mean temperature change from the FaIR model for SSP2-4.5, both with the 8.5 MtSO2 reduction implied by 2020 IMO regulations (blue) and without (orange). Image: by Zeke Hausfather for Carbon Brief, using Highcharts.

Global mean temperature change from the FaIR model simulating the effects ten years and thirty years after a change in forcing of between 0 and 0.3 watts per square metre in 2020, relative to the SSP2-4.5 scenario across 66 different CMIP6 models. The solid lines show the average of all model runs, while the shaded areas show the 5th to 95th percentile range. Image: by Zeke Hausfather for Carbon Brief, using Highcharts.

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