How did a sudden reduction in shipping pollution inadvertently stoke global warming?
A major shift in global shipping regulations intended to improve air quality may have temporarily — and inadvertently — set off a geoengineering reaction that is warming the planet, new research has found.
In January 2020, the International Maritime Organization instituted a change in the way goods are transported, substantially reducing the upper limit of harmful sulfur dioxide content in ships’ fuel from 3.5% to 0.5%. The move was part of a broad strategy to improve public health, including reductions in strokes, asthma, lung cancer, and cardiovascular and pulmonary diseases for people who live in and around ports.
But while the shift amounted to a roughly 80% reduction in sulfur dioxide emissions, experts say it also had the unintended consequence of dimming clouds across global oceans and allowing more sunlight to reach the planet.
The added energy gain from all that sunlight, sometimes referred to as climate forcing, contributed to anomalously high global temperatures in 2023 — the planet’s hottest year on record — and the current 12-month streak of record-hot months, according to a study published recently in the journal Communications Earth & Environment.
