Cleaner air linked to unexpected surge in global warming
Theories are emerging suggesting that a decrease in aerosols accelerates the climate disaster. Does cleaner air accelerate global warming?
James Hansen, a well-known climatologist who warned the U.S. Congress about global warming in the 1980s, once again emphasizes that we may be underestimating the impact of decreasing air pollution on the climate. In January 2025, a record temperature rose, sparking a debate about the pace of global warming.
However, other scientists argue that these conclusions are based on uncertain grounds, and we still do not know to what extent air pollution reduction contributes to global warming.
Hansen's research team previously linked the increasing pace of global warming with decreasing air pollution levels. They are presenting a new analysis suggesting that reducing pollution might be a key factor in the rise in temperature over the last two years. Aerosols in pollution can directly reflect solar radiation and simultaneously affect clouds' light-reflecting ability.
The 2020 experiment
Researchers focused on a 2020 regulation effect that drastically reduced the amount of harmful sulphur compounds in shipping fuels. This sudden decrease in pollution over the oceans provided scientists with data to more precisely determine aerosols' climate effects.
Climate warming is progressing faster than expected
Hansen and his team studied shipping lanes in the Pacific to estimate this effect by measuring changes in solar radiation absorption by the planet in these areas. Their studies indicate that the decrease in shipping aerosols increased the heat reaching the Earth by about 4.5 megajoules per square metre. This is roughly equivalent to the warming effect of a decade of carbon dioxide emissions at the current level.
This additional warming could explain part of the unexplained temperature increase over the last two years. However, the implications are broader: It would mean that the cooling effect of air pollution masked the full impact of greenhouse gas warming. Hansen and his colleagues warn that this means the climate is more sensitive to rising greenhouse gas levels than expected.
Potential solutions
Scientists suggest considering methods of cooling the planet, such as solar geoengineering. However, not all scientists agree with these conclusions. More data is needed to explain the temperature increase in 2023, and further studies on the warming effects of aerosols are necessary.
