The science paper URL:http://www.sciencemag.org/content/346/6214/1223.full

New research demonstrates for the first time what was the key factor in causing substantially more rainfall in two major regions of Africa, in the period called African Humidity Period (AHP). The joint study, led by the National Center for Atmospheric Research (NCAR) in USA, in which researchers from School of Physics, Peking University in China participated,was published last week in Science.

Proxy records suggest an abrupt climate change happened in Afirca about 14,700 years before present, when climate in southeastern equatorial and northern Afirca was much wetter than today. The transient simulation with a climate model shows that melt-water-induced reduction in the Atlantic meridional overturning circulation (AMOC) during the early deglaciation suppressed precipitation in both regions. Once the AMOC reestablished, wetter conditions developed north of the equator in response to high summer insolation and increasing greenhouse gas (GHG) concentrations, whereas wetter conditions south of the equator were a response primarily to the GHG increase.

The simulation shows good agreement with individual proxy records. The finding provides new evidence that the current increase in greenhouse gases will have an important impact on Africa’s future climate by improving our mechanistic understanding of the past climate. It is also important in the socio-economic perspective, with implications for water resources, agriculture and potential conflict.

Professor Zhengyu Liu and Phd student Zhengyao Lu of the Lab. Climate, Atmospherie and Ocean studies, School of Physics, Peking University are among the co-authors of this paper. The lead author is Bette L. Otto-Bliesner from NCAR, USA. It is another achievement in paleoclimate researh since the research group of Prof. Liu published a letter in Nature discussing the mechnism of ENSO change of the last 21,000 years in Nov 2014.

Model variables are plotted as decadal means (light red) and as sampledat temporal resolution of data (darker red). (A) 231Pa/230Th ratio at Bermuda rise as a proxy for AMOC export (black) and modelmaximum AMOC (Sv). (B) GeoB7920-2 continental humidity index (black) and model NA precipitation (millimeters per year). (C) Ocean Drilling Program site 658Cterrigenous percentage (black) (8) and model NA total leaf area index (TLAI) (square meters per square meters). (D) Lake Tanganyika hydrogen isotopic composition of leaf waxes (dDwax) (permil versus Vienna standard mean ocean water, black), Lake Challa branched and isoprenoidtetraether (BIT) index (blue), andmodel SEA precipitation (millimeters per year). (E) GeoB6518 dDwax (black) (25) and Congo Basinmodel precipitation (millimetersper year). Green shading delineates AHP.

Lakes and other water features, such as the Ubari Oasis in southern Libya, were more prevalent across now-dry parts of Africa during past periods of more-plentiful precipitation.

Source (photo by Sfivat)：http://commons.wikimedia.org/wiki/File:Oasis_in_Libya.jpg

ABOUT THE ARTICLE

Title: Coherent changes of southeastern equatorial and northern African rainfall during the last deglaciation

Authors: Bette L. Otto-Bliesner, James M. Russell, Peter U. Clark, Zhengyu Liu, Jonathan T. Overpeck, Bronwen Konecky, Peter deMenocal, Sharon E. Nicholson, Feng He, Zhengyao Lu

Publication: Science, doi: 10.1126/science.1259531