A new study titled “IMO2020 Regulations Accelerate Global Warming by up to 3 Years in UKESM1” finds that while IMO2020 aims to reduce harmful pollutants, it also accelerates warming.
In 2020, the International Maritime Organization (IMO) implemented new regulations to reduce the sulfur content in shipping emissions (IMO2020). While this initiative aims to enhance air quality and public health by lowering a significant pollutant, it also has implications for climate. Sulfur emissions contribute to the formation of sulfate aerosols, which brighten clouds and reflect sunlight, cooling the planet. Consequently, reducing these emissions is expected to lead to global warming, a topic of ongoing debate regarding its magnitude.
Using the UK Earth System Model (UKESM1), researchers conducted simulations to quantify the climatic impact of IMO2020. They estimated a global effective radiative forcing of 0.139 ± 0.019 Wm−2, primarily due to changes in cloud properties influenced by aerosols.
The simulations indicated that IMO2020 could increase global average surface temperatures by approximately 0.046 ± 0.010°C from 2020 to 2029, equivalent to about 2–3 years of global warming.
Notably, this regulation may help explain the exceptional warmth recorded in 2023, although other factors are also necessary for a complete understanding. The same year saw a significant decrease in reflected shortwave radiation, which was made more likely by the reductions in shipping emissions, highlighting the complex interactions at play.
To enhance understanding of the climatic impacts of IMO2020, the study suggests a model intercomparison project while waiting for a more comprehensive observational record.
To remind, another study, published in May 2024 and titled “Abrupt reduction in shipping emission as an inadvertent geoengineering termination shock produces substantial radiative warming” had also pointed out this phenomenon.
