The Earth's atmosphere is a dynamic physical system governed by fundamental principles that govern the movement of matter and energy throughout nature. As a physicist, Petras Anaab Ali notes that the atmosphere is not empty space, but a thin layer of gases held around the planet by gravity, comprising mostly nitrogen and oxygen, with smaller quantities of argon, carbon dioxide, water vapour, and other gases. The atmosphere is constantly moving, with the Sun supplying energy to the Earth, and the Earth's surface absorbing part of that energy and releasing energy back into the atmosphere and space.
The atmosphere is a giant energy and mass transfer system, with differences in temperature creating differences in pressure, driving winds, and water evaporating, condensing, and falling as precipitation. Heat is transported from one region to another, and air masses move, mix, rise, and descend, carrying moisture, dust, smoke, and other particles with them. This physical reality has an important consequence: what we release into the atmosphere does not necessarily remain where we release it, as a particle emitted in one location can be transported somewhere else by wind and atmospheric circulation.
Aerosols, tiny solid and liquid particles suspended in the atmosphere, play a crucial role in atmospheric physics. Some aerosols come from natural processes, such as dust lifted from dry soils, sea spray, volcanic eruptions, and vegetation, while others are produced or influenced by human activity, including vehicle exhaust, industrial processes, construction, agricultural activities, combustion, and open waste burning. These particles interact with radiation, scattering or absorbing sunlight, and influencing clouds, with some aerosols exerting a cooling influence and others warming the atmosphere.
Ghana's air quality is a significant concern, with the 2024 World Air Quality Report estimating the country's population-weighted annual average PM 2.5 concentration at 35.8 micrograms per cubic metre, more than seven times the World Health Organization's annual guideline of 5 micrograms per cubic metre. Accra's estimated annual average was approximately 36.3 micrograms per cubic metre, highlighting the need for careful interpretation of these numbers, as air-quality monitoring coverage remains uneven, particularly across Africa.
The lack of measurement should never be mistaken for a lack of pollution, and insufficient measurement may be one of Africa's greatest environmental challenges. Africa cannot manage an atmosphere it does not adequately measure, with the monitoring gap striking, and IQAir's 2024 assessment reporting roughly one air-quality monitoring station for every 3.7 million people in Africa, compared to the scientific infrastructure available in many wealthier parts of the world.
The atmosphere does not recognise borders, and Ghana's air quality is connected to the West African atmosphere, a connected system where mineral dust from the Sahara and Sahel can be transported southward during the dry season, causing hazy conditions in parts of Ghana. To address air pollution, Ghana needs measurements, atmospheric models, meteorological observations, satellite observations, and scientists who can bring these different sources of information together.
Understanding the physics of the atmosphere is crucial to addressing environmental questions, and Ghana must start taking its atmosphere seriously, recognising the importance of atmospheric physics in mitigating air pollution. By acknowledging the connected nature of the atmosphere and addressing the measurement gap, Ghana can work towards a better understanding of its air quality and develop effective strategies to manage its atmosphere.
Key points
- Ghana's atmosphere is a connected system that requires careful consideration and management to mitigate air pollution.
- The country's air quality is a significant concern, with high levels of PM 2.5 concentration.
- Africa's lack of air-quality monitoring infrastructure is a major environmental challenge.
