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DDC: 500 × Subject: Atmospheric thermodynamics ×

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    Non-linear intensification of Sahel rainfall as a possible dynamic response to future warming
    (München : European Geopyhsical Union, 2017) Schewe, Jacob; Levermann, Anders
    Projections of the response of Sahel rainfall to future global warming diverge significantly. Meanwhile, paleoclimatic records suggest that Sahel rainfall is capable of abrupt transitions in response to gradual forcing. Here we present climate modeling evidence for the possibility of an abrupt intensification of Sahel rainfall under future climate change. Analyzing 30 coupled global climate model simulations, we identify seven models where central Sahel rainfall increases by 40 to 300% over the 21st century, owing to a northward expansion of the West African monsoon domain. Rainfall in these models is non-linearly related to sea surface temperature (SST) in the tropical Atlantic and Mediterranean moisture source regions, intensifying abruptly beyond a certain SST warming level. We argue that this behavior is consistent with a self-amplifying dynamic–thermodynamical feedback, implying that the gradual increase in oceanic moisture availability under warming could trigger a sudden intensification of monsoon rainfall far inland of today's core monsoon region.
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    Agreement between reconstructed and modeled boreal precipitation of the Last Interglacial
    (Washington, DC [u.a.] : Assoc., 2019) Scussolini, Paolo; Bakker, Pepijn; Guo, Chuncheng; Stepanek, Christian; Zhang, Qiong; Braconnot, Pascale; Cao, Jian; Guarino, Maria-Vittoria; Coumou, Dim; Prange, Matthias; Ward, Philip J.; Renssen, Hans; Kageyama, Masa; Otto-Bliesner, Bette; Aerts, Jeroen C. J. H.
    The last extended time period when climate may have been warmer than today was during the Last Interglacial (LIG; ca. 129 to 120 thousand years ago). However, a global view of LIG precipitation is lacking. Here, seven new LIG climate models are compared to the first global database of proxies for LIG precipitation. In this way, models are assessed in their ability to capture important hydroclimatic processes during a different climate. The models can reproduce the proxy-based positive precipitation anomalies from the preindustrial period over much of the boreal continents. Over the Southern Hemisphere, proxy-model agreement is partial. In models, LIG boreal monsoons have 42% wider area than in the preindustrial and produce 55% more precipitation and 50% more extreme precipitation. Austral monsoons are weaker. The mechanisms behind these changes are consistent with stronger summer radiative forcing over boreal high latitudes and with the associated higher temperatures during the LIG.