Impact du changement climatique sur la mousson d'Afrique de l'Ouest Philippe Quirion CNRS CIRED et LMD
Le Sahel est la région qui a connu la plus forte baisse des précipitations au 20 e siècle Source : GIEC 2007, Groupe 1, ch. 3, p
Pluies au Sahel Source : GIEC 2007 ch. 3 p. 299
La sécheresse au Sahel semble liée à la hausse de la température des océans "The recent drying trend in the semiarid Sahel is attributed to warmer- than-average low-latitude waters around Africa" Giannini, Saravanan & Chang, Science 2005
Le 21 e siècle en Afrique de l'Ouest: +2 à +6°C Source : GIEC 2007 groupe 1, ch. 11
Les modèles divergent quant aux précipitations Source : GIEC 2007 Groupe I ch. 11, p. 869
La divergence persiste même si l'on se limite aux "meilleurs" modèles Cook & Vizy, Journal of Climate 2006
La paléoclimatologie : les moussons sont des systèmes fragiles "Paleoclimatic observations indicate that abrupt decadal- to centennial-scale changes in the regional frequency of tropical cyclones, floods, decadal droughts and the intensity of the African- Asian summer monsoon very likely occurred during the past yr. However, the mechanisms behind these abrupt shifts are not well understood, nor have they been thoroughly investigated using current climate models." GIEC 2007 Groupe 1 p. 436 "Lake sediment and historical documentary evidence indicate that northern Africa and the Sahel region have for a long time experienced substantial droughts lasting from decades to centuries. Although there have been attempts to link these dry periods to solar variations, the evidence is not conclusive." GIEC 2007 Groupe 1 p. 483
Conclusion : comment s'adapter à un changement inconnu ? New studies confirm that Africa is one of the most vulnerable continents to climate variability and change because of multiple stresses and low adaptive capacity. Some adaptation to current climate variability is taking place, however, this may be insufficient for future changes in climate. (GIEC 2007 groupe 2, SPM, p. 8)