Simulera gröna Sahara med en jordsystemmodell

As described in the novel The English Patient, what is now the world’s largest Sahara Desert was extensively covered by shrubland and grassland 5,000 to 11,000 years ago. Marine sediments indicate that during that period Sahara was about 10 times as wet as today, dotted with large and small lakes and the vegetated area extended as north as 31°N, thus created a “Green Sahara”.

The Green Sahara was a direct result of African monsoonal climate responses to periodic variations in the Earth´s orbit around the Sun. During the green Sahara period the dust emissions were 70 to 80% lower than today. More interestingly, paleoclimate data also show that the beginning and termination of the Green Sahara period were abrupt, occurring within decades to centuries.The project aims to use an Earth System Model (ESM) to investigate how do the local and global climate response to the greening of Sahara. We will assess the different role played by vegetation and dust in climate change. We will simulate a 2000 years’ evolution of mid-Holocene climate driven by slowly changed insolation in the ESM and to observe if the climate-vegetation interaction would cause an abrupt change in Sahara as suggested by the paleoclimate data. These simulations on one hand will enhance our understanding on the dramatic change in ecosystem happened in the past and on the other hand will provide a very useful test for the ESM during a transient climate like future climate projections.