The Air we cannot see: Why Ghana must start taking its atmosphere seriously

There is something strange about the air we breathe. We cannot see it, yet it surrounds us. We cannot hold it in our hands, yet without it we would not survive for more than a few minutes. It carries heat, moisture, gases and tiny particles across cities, countries and continents. It interacts with sunlight; controls part of the Earth’s energy balance and helps determine the weather we experience every day. As a physicist, I have learned to look at the atmosphere differently. To many of us, the sky is simply the space above our heads. To physics, however, the atmosphere is not empty space. It is a dynamic physical system governed by the same fundamental principles that govern the movement of matter and energy throughout nature. And this is where our conversation about air pollution should begin. Not with the smoke we see. Not even with the health problems we fear.

But with the physics of the air itself. THE ATMOSPHERE IS A PHYSICAL SYSTEM The Earth’s atmosphere is a thin layer of gases held around the planet by gravity. Nitrogen and oxygen make up most of it, with smaller quantities of argon, carbon dioxide, water vapour and other gases. But the atmosphere is far more than a mixture of gases. It is constantly moving. The Sun supplies energy to the Earth. The Earth’s surface absorbs part of that energy and releases energy back into the atmosphere and space. Differences in temperature create differences in pressure. Differences in pressure drive winds. Water evaporates, condenses and falls as precipitation. Heat is transported from one region to another. In other words, the atmosphere is a giant energy and mass transfer system. The air above Accra is not necessarily the same air that was there yesterday. Air masses move. They mix. They rise and descend. They carry…