Human activity causes the emission of small particles such as soot from combustion into the atmosphere. These particles, also called aerosols, have a growing impact on the climate system and negative effects on human health. Our industries, transport systems, agriculture and heating all emit aerosols into the air. These anthropogenic aerosols have a different origin than naturally occurring aerosol particles like dust and sea salt. Typical anthropogenic particles include soot from combustion and aerosols containing sulfur and nitrogen from transport and agriculture. They differ in particle size and chemical composition, and that affects their water solubility in clouds.

Aerosols affect the Earth’s radiation budget. Depending on their characteristics and the conditions under which they occur, they reflect incoming solar radiation back into space. This has a cooling effect on Earth’s climate. But some particles can absorb radiation, which warms the air. Since they also serve as nuclei for condensation, aerosols also directly affect Earth’s water cycle. Water vapor can condense onto aerosol particles to form cloud droplets; this has a significant influence on the characteristics of clouds and the distribution of precipitation, and thus on our weather and climate.

In addition to its effects on human health, exceeding the planetary boundary for air pollution in the long term will also strain the climate system and the weather. This is because the particles that act as condensation nuclei change the process of cloud formation and the hydrological balance, especially at the regional level. Overall, the global concentration of aerosols has doubled since pre-industrial times.

A specific factsheet including Belgian situation will be available for download June 24.

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