Sixty three people have been confirmed dead and 116 more are known to have been injured in a series of flash floods and landslides around the town of Katesh in the Manyara Region of northern Tanzania. The events happened when the annual rains arrived with exceptional ferocity, at the end of a months long draught. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. Around 5600 people are reported to have been displaced by the flooding, with about 1150 homes destroyed and several square kilometres of crops washed away.
The Manyara Region has a tropical climate with a dry season that typically runs from mid-May to mid-October, followed by a rainy season which runs from mid-October to mid-May, peaking in April. This year the rains were over a month late, and then exceptionally heavy, a pattern thought to be linked to the el Niño weather-system presently over the South Pacific; el Niño weather-systems typically being linked to more extreme weather patterns in East Africa.
The El Niño is the warm phase of a long-term climatic oscillation affecting the southern Pacific, which can influence the climate around the world. The onset of El Niño conditions is marked by a sharp rise in temperature and pressure over the southern Indian Ocean, which then moves eastward over the southern Pacific. This pulls rainfall with it, leading to higher rainfall over the Pacific and lower rainfall over South Asia. This reduced rainfall during the already hot and dry summer leads to soaring temperatures in southern Asia, followed by a rise in rainfall that often causes flooding in the Americas and sometimes Africa. Worryingly climatic predictions for the next century suggest that global warming could lead to more frequent and severe El Niño conditions, extreme weather conditions a common occurrence.
The development of an el Niño weather-system this year is considered particularly alarming by climate scientists, as the world has had several consecutive years in which average global sea-surface temperatures have equalled or slightly surpassed the hottest previous average temperatures recorded, despite the climate being in a la Niña phase. As sea surface temperatures are typically significantly warmer during an el Niño phase than a la Niña phase, the development of such a phase could push temperatures into areas not previously encountered on Earth since Modern Humans first appeared, potentially triggering or accelerating other climatic problems, such as glacial melting, droughts in tropical forests, and changes in ocean circulation, which might in turn take us further into unfamiliar climatic territory.
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