Paleohydrology

[5] Paleohydrological studies of sediments in the Fazzan Basin in Libya show that humid conditions once prevailed there that were capable of creating a lake with a surface area of around 76,250 km2 (29,400 sq mi).

[6] Before the abrupt desertification of North Africa about five thousand years ago, the Sahara was the home of Neolithic men and supported verdant vegetation and diverse wildlife.

Methods here include using radioactive isotopes, considering the geological development of the area, the presence or absence of certain organisms and the identification of fossil pollen.

[8] Direct data encompasses measured and historical information, including streamflow records, flood occurrences, and drought events.

In certain regions such as Egypt and China, direct data can extend back thousands of years, offering a rich historical perspective, while globally, it commonly spans approximately two centuries.

For example, variations in the water level of Lake Lisan correlates with data showing temperature fluctuations collected from polar ice core samples.

On a shorter time scale, minuscule climatic variations can have large hydrological effects as when excess rainwater entering the North Atlantic was linked with a serious drought in the eastern Mediterranean.

The Little Ice Age in northern Europe was linked with drought in East Africa, heavy rains in the African lakes, and persistent El Niño–Southern Oscillation conditions in the Pacific.