Connection between the climate of the Mediterranean and tropical Africa
The study which was led by Hendrik Vogel and Bernd Wagner from the University of Cologne was published in the prestigious scientific journal Nature. It is entitled „Mediterranean winter rainfall in phase with African monsoon during past 1.36 million years“. By providing an unprecedented understanding of the factors that have driven the Mediterranean region's climate in the past, the collected data will help scientists to model more accurately the region's future climate under global warming. Geochemical data and the pollen record show that winter rainfall increased in the north-central Mediterranean region during warm, interglacial periods. During these intervals, climate model simulations indicate increased cyclogenesis (the development and strengthening of low-pressure areas in the atmosphere) over the Mediterranean Sea particularly during late autumn leading to considerably higher rainfall.
The Mediterranean climate is characterised by dry summers and wet winters so winter rainfall is vital for the region's population and agriculture. "We discovered a positive phase relationship between the African monsoon and winter precipitation in the Mediterranean region, so between tropical climate systems and rainfall in the mid-latitudes thousands of kilometres away," said Hendrik Vogel. "Whenever incoming solar radiation from the sun is enhanced in the northern hemisphere during summer you have this northward migration of the tropical climate system and we see increased rainfall in winter at Lake Ohrid. We see this mechanism consistently over the past 1.3 million years."
(Source: University of Wollongong, University of Cologne)