[Bolincentret-at-su.se] RT3 Seminar | Prof. Martin Claussen on "Green Sahara Riddles" (8 June 2023 at 2 pm)

[Frederik Schenk]

Dear colleagues,

we're very happy to have Martin Claussen visiting us. Please join his seminar lecture where he will talk about one of the key topics in (paleo-)climate research: The Green Sahara, proxy evidence and challenges in climate modelling to simulate and explain the rise and collapse of a Green Sahara. The involved research has implications far beyond paleoclimate as it provides fundamental insights into the dynamics and feedbacks of how the Earth system responds to climate change and how well our models manage to represent these processes.

RT3 | Research Theme 3 Seminar
EVENT
Date: 08 June 2023, 2.00 PM - 3.00 PM
Venue: Högbomsalen, Geoscience building, Hus U, Plan 3, SU
Speaker: Martin Claussen, Professor emeritus of Physical Meteorology at Universität Hamburg and former Director at the Max Planck Institute for Meteorology (MPI-M) in Hamburg, Germany
Green Sahara Riddles
[cid:c4997003-425a-4eff-a66a-d665cb0763fe]

Abstract
Several thousand years ago, Sahara and Sahel were much wetter and greener than today. Subtle and steady variations in the Earth’s orbit are supposed to have triggered changes in the West African monsoon which were amplified by feedbacks between climate, ocean and primarily the land surface. While these processes are understood in principle, reconstructions and simulations differ. Some missing feedbacks are generally blamed for the deviation of model results from reconstruction. But the issue might be simpler: most models do not capture the steep and high mountains in the Sahara. High-resolution simulations help to solve the riddle of deep crater lakes in the Tibesti, the highest and steepest mountain in the central Sahara. Lakes were presumably abundant in the Sahara, but it is not yet known, how widespread lakes were and what their effect on the climate was. First attempts to predict the interaction between climate, dynamic lakes and vegetation are presented. Some 25 years ago, we predicted a “collapse” of the “green Sahara” that should have occurred some 5.5000 years ago. New, more details predictions and reconstructions of abrupt changes in the Sahara are shown, and a suggestion is made to answer the question of what “abrupt” really means. Reconstructions indicate that a greening of the Sahara had occurred rather regularly in the more distant past. A tentative answer to the question of why the past green Saharas differed in their amplitude and extent is given including a prediction for Saharan greening of the last 800,000 years.

[cid:c1f384ca-9ef3-4adb-91d7-2f348ddeb336]


Coffee & tea will be served after the seminar.

If you want to hear even more about the West African Monsoon and Green Sahara, please attend the Thesis Defence by Ellen Berntell on Friday, 9 June 2023: https://www.su.se/department-of-physical-geography/calendar/dissertation-ellen-berntell-1.657167


Best wishes from the RT3 "Past Climates" co-leaders,

Frederik, Fredrik, Natasha & Margret


Climate Researcher, Paleoclimate Modelling and Statistics &
Research Area Leader "Past Climates"
Bolin Centre for Climate Research &
Department of Geological Sciences
Stockholm University
Svante Arrhenius väg 8 C
106 91 Stockholm
Phone +46 8 16 47 41
https://www.mech.kth.se/~fsche/
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