A reduction in sulfur dioxide emissions may have caused “80% of the measured increase in planetary heat uptake since 2020.” The shipping industry’s efforts to cut air pollution have inadvertently accelerated global warming and contributed to record-breaking sea temperatures, according to a new climate model.
Recent global shipping regulations slashed sulfur dioxide emissions from cargo ships by 80%. This rapid reduction in sulfur pollution may have “created an inadvertent geoengineering termination shock with global impact,” according to a new study. The warming effect aligns with the strong warming observed in 2023 and is expected to make the 2020s anomalously warm, with the warming equivalent to “80% of the measured increase in planetary heat uptake since 2020.”
The new shipping regulations, implemented in 2020 by the International Maritime Organization (IMO), reduced the maximum sulfur content in shipping fuel from 3.5% to 0.5%, aiming to improve air quality and prevent 30,000 premature deaths annually. However, sulfur dioxide particles are highly reflective, acting as a planetary sunblock by bouncing the sun’s rays back into space. The reduction in pollution, therefore, removed this sunblock, inadvertently increasing solar energy entering Earth’s atmosphere.
Since March 2023, the loss of sulfurous fog, combined with factors like global warming, the El Niño climate pattern, and the 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano, has led to record-high sea surface temperatures. Some climate scientists, however, dispute the study’s conclusions. Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, acknowledges the accuracy of increased solar energy estimates but believes the temperature response is overstated.
Schmidt referred to an analysis by Zeke Hausfather, a climate scientist at the Breakthrough Institute, which argues that the study’s model oversimplifies ocean heat uptake, thus overestimating the warming impact of sulfur reduction. Ongoing analyses related to other factors like the Hunga Tonga-Hunga Ha’apai volcano, other aerosol emissions, and internal variability are still awaited.
The findings come as governments consider controversial solar radiation management (SRM) techniques, proposing to intentionally release aerosols like sulfur dioxide to dim sunlight and combat climate change. However, Schmidt doubts the viability of SRM due to governance and geopolitical uncertainties rather than scientific issues.
