Recent observations from two satellites have consistently shown emissions of between 1 and 1.5 billion tonnes of carbon each year over northern tropical Africa. The data suggest that stored carbon has been released from degraded soils – those subject to prolonged or repeated drought or land-use change – in western Ethiopia and western tropical Africa, but scientists say that further study is needed to provide a definitive explanation for the emissions.
According to a team of researchers at the University of Edinburgh, Scotland, who carried out the research, the carbon source might have gone undiscovered with land-based surveys alone.
Their findings are aimed to improve understanding of greenhouse gas sources and aid efforts to meet the terms of the Paris Agreement, which aims to limit the average global temperature to a level below 2 degrees centigrade.
Researchers examined data gathered by two NASA satellite missions: the Japanese Greenhouse Gases Observing Satellite (GOSAT) and the Orbiting Carbon Observatory (OCO-2). They compared readings with three atmospheric models, showing changes in vegetation and a host of other measurements of groundwater, fire and levels of photosynthesis.
Although the study reveals the unusual growth of carbon dioxide in the northern tropical region of Africa, the continent still remains one of the lowest contributors to global greenhouse gas. The chart below shows annual global carbon dioxide emissions by country and region. Most African countries produce less than 100 million tonnes of carbon dioxide emissions yearly.
Professor Paul Palmer of the University of Edinburgh’s School of Geosciences, who led the study, said: “The tropics are home to one-third of Earth’s three billion trees and their stored carbon, and yet we are only scratching the surface of understanding how they are responding to changes in climate. We anticipate that satellite data will continue to improve that situation.”
The study, published in Nature Communications, was funded by the Natural Environment Research Council’s National Centre for Earth Observation. It also involved researchers from the University of Leicester, Laboratoire des Sciences du Climat et de l’Environnement (LSCE) in France, and Colorado State University in the U.S.A.
According to the United Nations, “Africa is the continent most vulnerable to the adverse effect of climate change. The continent is already experiencing temperature increases of approximately 0.7°C across vast areas, and with predictions that temperatures will rise further, Africa is facing a wide range of impacts, including increased drought and floods. In the near future, climate change will contribute to decreases in food production, floods and inundation of its coastal zones and deltas, the spread of waterborne diseases and risk of malaria, and changes in natural ecosystems and loss of biodiversity”.
As part of a nation-wide reforestation campaign, Ethiopia recently planted over 350 million trees within 12 hours on 29 July 2019 to reduce the effect of climate change and land degradation.