From 1920 to the present day, the Sahara desert has increased its area by 10 percent. This is indicated by the data collected by scientists at the University of Maryland (United States), who have made the first research on the evolution of the limits of this African region on a time scale as long as a century.
His work, published in the Journal of Climate, suggests that other deserts on the planet could be expanding as well, and he attributes this situation to a combination of two factors: climate change caused by human activity and certain natural cycles of the climate that decrease rainfall. .
To consider a place as desert, it is used as a measuring stick for the level of rainfall, which must be less than 100 milliliters per square meter per year. Researchers at the University of Maryland analyzed rainfall data collected in Africa between 1920 and 2013 and found that the Sahara had grown by 10 percent in that period, keeping in mind the amount of rain that fell on its changing borders.
Why is it happening?
The Sahara is the largest hot desert in the world, with an area of more than 9 million square kilometers, almost the same as that of the United States. Its dimensions fluctuate with the seasons, so that they grow during dry winters and diminish with the summer rains typical of sub-Saharan Africa, with which it borders to the south.
Why has it grown so much in the last hundred years? According to Sumant Nigam, lead author of the research, it is due in part to human-caused climate change, which in addition to warming the planet, alters phenomena such as the Atlantic Multidecadal Oscillation (AMO), a phenomenon that occurs in the North Atlantic and causes ocean temperatures to fluctuate in cycles of 50 to 70 years duration.
Scientists have long known that AMO affects rainfall over the Sahara and the Sahel, the transition zone between the North African desert and the savannah. The notable lack of rainfall in the Sahel between 1950 and 1980, for example, was due to a cold phase of the AMO. There is another analogous phenomenon that also affects the expansion of the Sahara: the Pacific Decadal Oscillation (PDO), which changes the temperatures of that ocean in cycles of 40 to 60 years.
Seas and atmosphere influence each other and change the climate of land masses, for better or for worse, as in this case.
The hand of man
To find out how far the Sahara grows due to man-made climate change, researchers at the University of Maryland used statistical methods that eliminated the influence of AMO and PDO on Saharan rainfall between 1920 and 2013. They concluded that these climate cycles Natural sources were to blame for two thirds of the Saharan expansion, and that the rest could be attributed to our polluting emissions, although they warn that more research is needed to reach irrefutable results.
However, this work on the Sahara is important because it is the first to cover such a long period of time, and because it offers clues about the possible future of this and other subtropical deserts. An increase in the arid lands of the African continent would have disastrous results for its inhabitants, who depend to a great extent on agriculture and are seeing how the summers lengthen and intensify as the rains decrease.
