Africa is on fire. It has been for thousands of years. The continent contains more than 50% of the total area on Earth that is burning, on average, and there is no sign of it stopping; indeed, the migrating hemisphere-hopping African wildfire season is steadily increasing.
The fire is essentially feeding itself in a vicious cycle involving aerosols, tiny particles that have a large impact on Earth's climate. Their interaction with the climate is intricate; they reinforce regulations of African ecosystems and pave the way for evolving wildfire patterns each year.
But human-induced air pollution adds complexity to this already intricate dance between fire and atmosphere. The brown-hued aerosol particles visible in satellite imagery underscore this interaction - an ominous testament to humanity's contribution to these everlasting fires.
How Aerosols Fuel the Fire
(Photo : FADEL SENNA/AFP via Getty Images)
Aerosols are produced by both natural and human sources, such as dust, sea salt, volcanic eruptions, biomass burning, and fossil fuel combustion.
They can affect the climate in two ways: directly, by scattering and absorbing solar radiation, and indirectly, by acting as cloud condensation nuclei (CCN) and modifying cloud properties.
In Africa, aerosols from biomass burning are the dominant source of atmospheric particles. These aerosols can have both warming and cooling effects, depending on their size, composition, and location.
For example, black carbon aerosols, which are strongly absorbing, can warm the atmosphere and reduce cloud formation, while organic carbon aerosols, which are more scattering, can cool the atmosphere and enhance cloud formation.
The net effect of aerosols on the climate is still uncertain, but some studies suggest that they may have a significant impact on the regional and global circulation patterns, especially over Africa. Aerosols can alter the temperature gradient between the land and the ocean, affecting the strength and location of the monsoon winds.
They can also influence the formation and distribution of the Saharan Air Layer (SAL), a hot and dry air mass that originates over the Sahara desert and travels across the Atlantic Ocean.
The SAL can suppress the development of tropical cyclones, which are a major source of rainfall for West Africa. It can also transport aerosols from Africa to other regions, such as South America and the Caribbean, where they can affect the local climate and ecosystems.
Also Read: Africa's Little-Known Struggles with Climate Crisis Over the Past Months
How the Climate Feeds the Fire
The feedback loop between aerosols and climate is not only one-way; the climate can also affect the production and distribution of aerosols. For instance, changes in temperature, humidity, and precipitation can alter the frequency and intensity of wildfires, which in turn can emit more aerosols into the atmosphere.
According to a recent study by researchers from the Georgia Institute of Technology, the aerosol feedback loop is responsible for about 70% of the interannual variability of the African fire season.
The study used satellite observations and climate models to investigate how aerosols affect the precipitation and fire patterns over Africa.
The researchers found that aerosols from biomass burning can reduce the rainfall over the continent by increasing the CCN and reducing the cloud droplet size.
This makes the clouds less efficient at producing rain and more likely to evaporate before reaching the ground. The reduced rainfall then creates drier conditions that favor more fire activity, which in turn emits more aerosols and completes the cycle.
The study also showed that the aerosol feedback loop can have a hemispheric effect, as the smoke from the African fires can cross the equator and affect the precipitation and fire patterns in the Southern Hemisphere.
The researchers estimated that the aerosol feedback loop can account for about 30% of the variability of the fire season in South America.
The study highlights the importance of considering the aerosol feedback loop in predicting and managing the African fire season, as well as its implications for the global climate and ecosystems.
The researchers suggest that reducing the human-induced air pollution could help mitigate the aerosol feedback loop and its negative consequences.
Related Article: African Wildfires: 'Everlasting' Blaze in the Continent Caused by Aerosol Feedback Loop [Study]
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