Carbon in Atmosphere

Did you know that the largest sources of greenhouse gas emissions in the United States are electricity, heat, and transportation? Transport is the largest contributor of greenhouse gases in the UK. It's hard to imagine how our actions can be linked to an increase in atmospheric carbon, something we can't even physically see! One thing we can see, however, are the effects. The concentration of atmospheric carbon strongly influences the natural greenhouse effect, which in turn determines the distribution of temperature and precipitation. The balance of atmospheric carbon regulates the temperature of the Earth, but this balance is being pushed as human activity has released more carbon into the atmosphere.

The effect of carbon dioxide in the atmosphere

Have you ever seen a greenhouse, brimming with bright green plants even in the middle of winter? Greenhouses work by trapping solar energy. Sunlight enters the greenhouse through the clear glass panels. The glass and the plants convert the sunlight into heat, which is then physically trapped inside the greenhouse. This keeps the greenhouse warm, even if the weather surrounding the greenhouse is relatively cold.

Our atmosphere functions in much the same way as a greenhouse, but with greenhouse gases instead of glass windows. We call this process the greenhouse effect, and it is a fundamental aspect of our planet's climate.

Greenhouse gases in the atmosphere cause the Earth to retain some of the solar energy from the sun that would have otherwise dissipated. The more greenhouse gases that are present in the atmosphere, the more amplified the greenhouse effect becomes. Among these gases is carbon dioxide (CO₂). Gases such as CO₂ and methane (CH₄) are naturally emitted through respiration and outgassing.

The importance of carbon dioxide in the atmosphere

Solar radiation enters the earth's atmosphere and passes through the greenhouse gas layer. Some solar radiation is absorbed by the Earth's surface, while some is reflected back into space. The greenhouse gas layer acts as a blanket, warming our planet to a high enough temperature to support life on Earth.

Impacts of atmospheric carbon on the greenhouse effect

The greenhouse effect impacts temperature distribution and precipitation on Earth.

Temperature distribution

Depending on the angle of the sun's rays, different locations of the Earth receive different levels of solar energy. The equator receives the most concentrated radiation, whilst the same radiation is dispersed over a greater distance at the poles.

Precipitation distribution

The heating of the Earth's surface leads to warm air rising, cooling and condensing to create clouds. This movement of air is called atmospheric circulation. Along with ocean circulation, it redistributes thermal energy across the surface of the Earth.

Diagram showing global atmospheric circulation, NASA/Wikimedia, Public Domain

The intense radiation on the equator leads to warm air rising, causing high levels of rainfall all year long. This is called the Inter-Tropical Convergence Zone.

At 30 degrees north and 30 degrees south, the air cools and sinks again resulting in high surface pressure where rainfall is rare. This is unlike the high pressure which builds at high altitudes, which usually results in condensation leading to rainfall.

At 60 degrees north and 60 degrees south, different air masses meeting results in frontal rainfall. Finally, at the poles, the air sinks due to the cold, causing little rainfall.

Seasonal changes

Depending on the season, there are periods of cooler weather and reduced hours of sunlight. This means fewer plants are photosynthesising, so plants take up less CO₂. The global atmospheric carbon is higher in the winter than in the summer.

The albedo effect

The albedo effect describes the ability of a surface to reflect solar radiation. A surface's ability to reflect solar radiation is correlated with its colour. For example, the white snow atop glaciers and ice caps reflects the majority of incoming radiation, while dark oceans and forests absorb the majority of incoming radiation. This heat is then redistributed to air circulations and ocean currents.

Three ways carbon dioxide is removed from the atmosphere

We can reduce the amount of CO₂ we are adding to the atmosphere by cutting back on the activities that release greenhouse gases, such as burning fossil fuels. But how do we remove some of the CO₂ that is already there? Dozens of ideas have been put forward, including constructing complex machines that are capable of sequestering carbon. For now, however, the most straightforward and practical method is to invest in natural carbon sinks: things that absorb more CO₂ than they release.

Forestry

Like all plants, trees use carbon dioxide in their photosynthetic processes. Trees can sequester an incredible amount of CO₂ depending on their size and age. Together as large-scale, old-growth forests, trees act as significant carbon sinks.

In order to allow this natural system to continue, we have to decrease deforestation while also increasing or enabling reforestation or afforestation. Put simply, more trees on the ground means less CO₂ in the atmosphere.

Blue carbon

Blue carbon is carbon that is stored in the Earth's oceans and wetlands. This includes the great variety of plant life associated with water, but also includes an unlikely hero: phytoplankton. Phytoplankton, which are tiny protists, photosynthesise like plants. Phytoplankton are now thought to absorb far more carbon than originally assumed.

In order to enable this process to continue, wetlands and oceans should be protected, or even restored in areas where they have been disrupted- especially in aquatic ecosystems that are known to house large quantities of phytoplankton and the animals that eat them.

Carbon farming

When forests are cleared to make way for agriculture, the carbon that had been stored within the trees- and in the soil- is released into the atmosphere. Land that has already been farmed for a long time may experience soil erosion and lose its ability to store carbon.

When soil is healthy, it can store carbon. When it is unhealthy, soil fails to store hardly any carbon and can scarcely even absorb water. This can even lead to flooding events.

There are methods farmers can use to keep soil healthy and to replicate the carbon sequestration that would have been performed by wild plants, including planting cover crops when the field is not in use; charring and burying unwanted plants as biochar; and composting. Livestock farmers can also use rotational grazing to allow their soil to remain healthy so that their pastures can continue to sequester carbon.