Incredible: scientists have solved the mystery of the 2023 climate

The year 2023 was marked by an unusually high temperature spike, revealing the increasing impact of human activity on the climate. Scientists at Cornell University in the US warn that there is no time to delay - not only do we need to make decisive cuts in emissions, but we must also consider bold climate interventions to tackle global warming.

Global temperature rise exceeds forecasts

Global temperatures rose sharply in the summer of 2023, exceeding forecasts. Many scientists were surprised that their models did not show such a spike in temperatures.

"Climate scientists said it was virtually impossible; that it was crazy to see such a sharp rise at the same time," said Daniele Visioni, associate professor in the Department of Earth and Atmospheric Sciences at Cornell University.

The study by Cornell University scientists reveals the reasons for this anomaly.

The cause is the shipping industry

The researchers found that mandatory measures to reduce sulphur dioxide emissions from international shipping routes in 2020 contributed in part to the record temperatures. 

Fewer aerosol particles in the atmosphere have reduced cloud cover, weakening the ability of clouds to reflect solar radiation back into space. 

Future policy decisions on the rapid reduction of tropospheric aerosols should take into account their effect on surface temperatures, the researchers say.

Undermined by updated regulations

Previously, it was thought that reducing sulphur emissions from the shipping industry would only marginally increase global temperatures through a reduction in cloud formation. 

In 2014, the International Maritime Organisation decided to introduce stricter emission limits from 2020, forcing ships to use fuel with no more than 0.5% sulphur (the previous limit was 3.5%), which has led to a reduction of more than 80% in sulphur oxide emissions.

While this has been talked about in the industry, the potential climate impact of these changes has not been widely addressed.

Changes in the shipping industry alone are not enough 

Researchers at Cornell University looked at global temperature anomalies between 2020 and 2023 and found that removing sulphur dioxide from shipping fuels was likely to increase the planet's temperature by 0.08 °C. 

The researchers noted that while improving air quality is an important and quickly achievable outcome, more discussion is needed on the trade-offs of reducing emissions

The shipping industry is already switching to alternative fuels. But other measures, such as cloud brightening or geoengineering, would be needed to prevent further warming, the researchers said.

However, researchers at Cornell University have shown that the sharp drop in sulphur dioxide emissions had a more significant effect.