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The sulfur emissions of the ships have caused the records of global warming of 2023

In 2020, the IMO has cut the sulfur emissions of the ships lowering of 80% the sulfur content in the fuels

It was probably right to point the finger at sulphur emissions from ships. The global warming record of 2023 (+1.48 according to Copernicus) and its long tail that we are seeing in 2024 (with May we will be at the 11th consecutive month above the threshold of 1.5 degrees) received a “substantial” contribution from the new rules on marine pollution that from 2020 have reduced from 3.5 to 0.5% the sulfur content in marine fuels, and therefore the emissions of SO2.


The role of this greenhouse gas in the evolution of global temperature in recent years is one of the most debated issues today by climate scientists. And it’s crucial. Global warming, especially in 2023, has moved a long way from the most reliable forecasting models. Understanding why it happened is crucial to deciding whether we need to change models because they don’t capture structural dynamics or if it’s a transient phenomenon. In the first case, we will also have to recalibrate – make them more ambitious – our climate policies.

A part of the scientific community immediately looked at sulphur dioxide. This greenhouse gas can trap heat in the atmosphere, but it is also one of the components of aerosols, suspended particles that create a “screen” capable of bouncing part of the incoming solar radiation on Earth. In addition, they contribute to the formation of clouds, an additional shielding. To diminish the marine pollution reducing the sulfur emissions of the ships has made to stop, in a short time, this screen. So far, the scientific consensus is rather compact. The positions differ, instead, on the weight that this factor can have on global warming.

Halving ships emissions 7 years is possible and convenient

The sulfur emissions of the ships and the leap of the global warming from 2023

A study coordinated by the University of Maryland and published in Communications Earth & Environment puts a first anchor. The reduction in sulphur emissions from ships, the authors calculate, has increased the solar radiation absorbed by the global oceans by 0.2 0.11 Wm2. An amount that “is consistent with the strong warming observed recently in 2023″ and contributed 80% to the increase in heat measured globally since 2020.

Not only. The amount of radiative forcing “could lead to a doubling (or more) of the heating rate in the 2020’s compared to the rate since 1980” and consequently make this decade “unusually hot“. In fact, the study summarizes, the new regulation on naval fuels was a kind of involuntary experiment in geoengineering, which provoked a “cessation shock” with global impacts.

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