Improved air quality found to have accelerated global warming in recent decades

An international team of researchers led by the University of Leipzig has used satellite data to show that the concentrations of pollutant particles have fallen significantly since the year 2000. This is necessary because of their health effects. But it is also of great importance because it has reduced the cooling effect of the particles on the climate. The study results were published in the journal Atmospheric chemistry and physics.

Global warming is caused by the emission of greenhouse gases. According to the Intergovernmental Panel on Climate Change (IPCC), the temperature rose by 1.1 degrees Celsius by 2019 compared to pre-industrial levels. At the same time, however, the combustion of fossil fuels releases aerosols in the form of pollutant particles such as soot or sulfuric acid, which cool our climate.

They reflect sunlight and also increase the reflectivity of clouds. According to the IPCC, the presence of aerosols in the atmosphere meant that the climate in 2019 was 0.5 degrees Celsius cooler than without them. Other effects such as land use changes also play a role.

The study documents widespread evidence for this reduced cooling climate effect

In a new international analysis, Professor Johannes Quaas, meteorologist at the University of Leipzig, and colleagues from across Europe, China and the USA have now documented robust evidence of the effect that improved air quality has on the climate.

“We analyzed data from NASA’s Terra and Aqua satellites. They have been providing comprehensive satellite observations of the earth since the year 2000 and measure incoming and outgoing radiation, but also clouds and aerosol pollution. The latter has decreased significantly in North America, Europe and East Asia since 2000,” says Professor Johannes Quaas, first author of the study, which was initiated at a meeting of the two European research projects CONSTRAIN and FORCES.

Reducing aerosol-induced cooling increases warming from CO₂ by up to 50% since 2000

This has also reduced the cooling effect of aerosols. Compared to the year 2000, this has led to an increase in the warming effect of up to 50% that of CO₂ increases over the same period. This means an acceleration in the drivers of global warming compared to the previous period.

“Our study should not be interpreted in such a way that we should now emit more aerosols to cool the climate. On the contrary: aerosols are harmful to human health and the environment, which is why we have to further reduce emissions,” concludes Quaas. Because of this, air quality laws have become increasingly stringent since the 1970s and are being implemented by more and more countries.

In the new study, Professor Quaas and his colleagues emphasize the increasingly urgent need for rapid and deep reductions in greenhouse gas emissions.