The Reason for Sahara’s Expanding

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Sahara is the largest hot desert in the world. During the last century, it has expanded by about 10%. The scientists believe that the main reason for such an expanding is climate change. More facts we can find in a new research by University of Maryland scientists.

Research of Sahara: details

The study results suggest that human-caused climate change, as well as natural climate cycles such as the Atlantic Multidecadal Oscillation (AMO), caused the desert’s expansion. The geographical pattern of expansion varied from season to season, with the most notable differences occurring along the Sahara’s northern and southern boundaries.

“Deserts generally form in the subtropics because of the Hadley circulation, through which air rises at the equator and descends in the subtropics,” University of Maryland professor and study senior author Sumant Nigam said. “Climate change is likely to widen the Hadley circulation, causing northward advance of the subtropical deserts.”

Deserts are typically defined by low average annual rainfall—usually 100 millimetres of rain per year or less.

The research was based on analyzing over 90 years worth of rainfall data for the region.

“The trends in Africa of hot summers getting hotter and rainy seasons drying out are linked with factors that include increasing greenhouse gases and aerosols in the atmosphere,” said Ming Cai with the National Science Foundation, which funded the research. “These trends also have a devastating effect on the lives of African people, who depend on agriculture-based economies.”

Yet that is when the greatest southward advance of the Sahara occurred, he said. A season of rain was being replaced by the expansion of a desert, without the affected governments, Chad and Sudan mostly, noticing.

Results of the study

The future implications for countries already affected by lack of rain and drought could be dire, Nigam said. “Water resource planning, water use and long-term planning are important.”

“With this study, our priority was to document the long-term trends in rainfall and temperature in the Sahara. Our next step will be to look at what is driving these trends, for the Sahara and elsewhere,” Natalie Thomas said, a graduate student in atmospheric and oceanic science at UMD and lead author of the research paper.

“We have already started looking at seasonal temperature trends over North America, for example. Here, winters are getting warmer but summers are about the same. In Africa, it’s the opposite—winters are holding steady but summers are getting warmer. So the stresses in Africa are already more severe.”- Thomas added.

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