Tropical Africa - Recent News: History of Tropical Africa

Recent News: History of Tropical Africa

In early 2007, scientists created an entirely new proxy to determine annual mean air temperature on land-- based on molecules from the cell membrane of soil inhabiting bacteria. Recently, Scientists from the NIOZ Royal Netherlands Institute for Sea Research conducted a temperature record dating back to 25,000 years ago. In concord with the German colleague of the University of Bremen, this detailed record shows the history of land temperatures based on the molecular fossils of soil bacteria. When applying this to the outflow core of the Congo River, the core contained eroded land material and microfossils from marine algae. That concluded that the land environment of tropical Africa was cooled more than the bordering Atlantic Ocean during the last ice-age. Since the Congo River drains a large part of tropical central Africa, the land derived material gives an integrated signal for a very large area. These findings further enlighten in natural disparities in climate and the possible costs of a warming earth on precipitation in central Africa!

Scientists discovered a way to measure sea temperature-- based on organic molecules from algae growing off the surface layer of the Ocean. These organisms acclimatize the molecular composition of their cell membranes to ambient temperature to sustain regular physiological properties. If such molecules sink to the sea floor and are buried in sediments where oxygen does not go through, they can be preserved for thousands of years. The ratios between the different molecules from the algal cell membrane can approximate the past temperature of the sea surface. The new “proxy” used in this sediment core obtained both a continental and a sea surface temperature record. In comparison both records shows that ocean surface and land temperatures behaved differently during the past 25,000 years. During the last ice age, African temperatures were 21 °C, about 4 °C lower than today, while the tropical Atlantic Ocean was only about 2.5 °C cooler. Lead author Johan Weijers and his colleagues arrived that the land-sea temperature difference has by far the largest influence on continental rainfall. The relation of air pressure to temperature strongly determines this factor. During the last ice age, the land climate in tropical Africa was drier than it is now, whereas it favors the growth of a lush rainforest.