New research reveals that the sudden rise in temperatures recorded in 2023 was caused by the reduction in sulfur missions from shipping routes.
In the summer of 2023, global temperatures unexpectedly rose, leaving climate scientists perplexed. The dramatic increase, described as “crazy” by some researchers, it has raised concerns about the acceleration of climate change.
However, a new study by researchers at Cornell University clarifies the phenomenon, attributing it in part to reducing sulfur emissions of international maritime routes.
The study, published in Earth System Dynamics by Assistant Professor Daniele Visioni and postdoctoral researcher Ilaria Quaglia, analyzed the effects of stricter sulfur regulations applied by the International Maritime Organization (IMO) in 2020. These rules forced a reduction in sulfur content in ship fuels from 3.5% to 0.5%, leading to a decrease of 80% in sulfur oxide emissions.
Although this change improved air quality, it also reduced the formation of sulfate aerosols, which play a crucial role in cloud formation. Fewer aerosols mean fewer clouds to reflect solar radiation back into space, contributing to warming, explains .
Visioni Earth System Model simulations revealed that this reduction is likely increased global temperatures by 0.08°C between 2020 and 2023, a significant factor behind recent temperature anomalies.
The results highlight the complex trade-offs of environmental policy. Although reducing air pollution brings immediate health benefits, Visioni highlights the need to take into account unintended consequences. “We are reducing air pollution more than predicted 10 years ago, so a much more open debate is needed,” he said.
Despite the warming effect, Visioni is clear that efforts to reduce pollution must continue. The study highlights the urgency of reducing greenhouse gas emissions to mitigate climate change. “THE improvement in air quality is immediateand everyone will always choose that”, explained Visioni. “But we have to fill the gap and prevent warming by other means.”
The shipping industry is exploring alternative fuels such as methanol, hydrogen and ammonia, along with wind-assisted propulsion systems, to become align with decarbonization objectivesthe. Meanwhile, Visioni suggests investigating geoengineering solutions, such as increasing cloud luminosity, to temporarily offset the effects of warming.
