By Roger Diamond

According to a recent news article in the Guardian (UK), parts of the Nile Delta are being flooded by rising sea levels. The rising sea levels are, of course, being blamed on climate change. Indeed, sea levels are apparently rising and it is almost certain that most of this rise is caused by climate change, most of which is probably being caused by the anthropogenic increase in CO2. So, surely this is the end of the story then?

Not at all. The Nile Delta is there because of two reasons, which work hand in hand. Subsidence and sediment supply. Subsidence is the sinking of land due to geological setting and can result in water flowing towards that sinking area. Rivers of water on land generally carry sediment with them and when the water velocity slows down, as happens when the river reaches the sea, the sediment will drop out and be left behind. So the Nile River flowed towards the subsiding low point and then the sediment dropped out to form a delta at the edge of the sea. This is exactly how the Nile Delta has worked for millions of years, until 1970 AD, when the Aswan High Dam was finished, thereby blocking the flow of sediment to the Mediterranean Sea.

Subsidence is encouraged by the extra weight of sediment. However, stopping sediment supply for a few decades, or even centuries, will not suddenly stop the subsidence, which operates on geological time scales of thousands and millions of years. So the Nile Delta is continuing to sink, but has no new sediment to keep piling up and keep the land above sea level. This is undoubtedly a reason that the Delta is being eroded by waves at the sea front and being swamped by the sea in low lying areas. Attributing all the erosion and flooding to a climate change-induced rise in sea level is simply wrong and shows ignorance of simple geology or even high school level geography lessons.

That’s really all I have to say, but I will add a perspective to this insight: that is, we are potentially at the mercy of the media, who bring us information and interpret this information, often to fit into a paradigm. The “climate-change-is-the-cause-of-all-ills” paradigm is very strong at the moment. The media use it at every possible opportunity.

This is not wrong if it really is the cause of something, but when it is only a part of the full picture, we should try to see the rest of the picture, and for this we either have to rely on the media to report comprehensively, or we have to educate ourselves more. Although I’d like the former, I think I’ll trust the latter.

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