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. 2024;5(1):281.
doi: 10.1038/s43247-024-01442-3. Epub 2024 May 30.

Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming

Tianle Yuan  1   2 , Hua Song  2   3 , Lazaros Oreopoulos  2 , Robert Wood  4 , Huisheng Bian  1   2 , Katherine Breen  2   5 , Mian Chin  2 , Hongbin Yu  2 , Donifan Barahona  2 , Kerry Meyer  2 , Steven Platnick  2
Affiliations

Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming

Tianle Yuan et al. Commun Earth Environ. 2024.

Abstract

Human activities affect the Earth's climate through modifying the composition of the atmosphere, which then creates radiative forcing that drives climate change. The warming effect of anthropogenic greenhouse gases has been partially balanced by the cooling effect of anthropogenic aerosols. In 2020, fuel regulations abruptly reduced the emission of sulfur dioxide from international shipping by about 80% and created an inadvertent geoengineering termination shock with global impact. Here we estimate the regulation leads to a radiative forcing of +0.2±0.11Wm-2 averaged over the global ocean. The amount of radiative forcing could lead to a doubling (or more) of the warming rate in the 2020 s compared with the rate since 1980 with strong spatiotemporal heterogeneity. The warming effect is consistent with the recent observed strong warming in 2023 and expected to make the 2020 s anomalously warm. The forcing is equivalent in magnitude to 80% of the measured increase in planetary heat uptake since 2020. The radiative forcing also has strong hemispheric contrast, which has important implications for precipitation pattern changes. Our result suggests marine cloud brightening may be a viable geoengineering method in temporarily cooling the climate that has its unique challenges due to inherent spatiotemporal heterogeneity.

Keywords: Atmospheric chemistry; Climate and Earth system modelling.

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Conflict of interest statement

Competing interestsThe authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Simulated impact of IMO2020 on AOD and Nd.
A simulated annual mean aerosol optical depth change induced by IMO2020 using NASA GOES-GOCART. B the ratio of aerosol optical depth changes between that induced by IMO2020 and that between 1750 and 2005. C map of simulated annual mean Nd change due to IMO2020. D) same as B, but for Nd change.
Fig. 2
Fig. 2. Calculated IMO2020 forcing maps from different components.
The spatial patterns of three components of forcing from cloud adjustments: A the Twomey effect, B LWP adjustment, and C cloud fraction adjustment.
Fig. 3
Fig. 3. Time series of global temperature anomaly since 1980 (Lensen et al., 2019).
The trend line is dashed. The expected warming trajectory from the combination of the linear trend and the calculated warming effect from IMO 2020 shock based on the energy balance model. The upper and lower bounds of the expected warming are shown in shades. The baseline period for temperature anomaly is between 1951 and 1980.
Fig. 4
Fig. 4. Sensitivity of forcing components to different cloud variables.
A The areal mean of forcing from IMO2020 in the North Atlantic (0o−80oW, 0o ~ 60oN) and its break down in three components. B–D sensitivity tests to gauge the impacts of seasonal variations in ΔNd, background Nd, and cloud fraction, respectively. In each test, we use an annual mean map instead of seasonally changing fields to calculate the radiative forcing and plot their difference from the baseline. Details in Methods section.
Fig. 5
Fig. 5. Observed time series of energy balance variables.
A the planetary heat uptake; B trailing 48-month mean of absorbed solar radiation for both hemispheres. The 48-month mean is applied to remove high-frequency noise. C Time series of Interhemispheric contrast in absorbed solar radiation. The vertical dotted line marks the Jan 2020—details in the Methods section.
See this image and copyright information in PMC

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