1. Drought in the African Sahel: scientific research and societal implications Alessandra Giannini International Research Institute for Climate and Society The Earth Institute at Columbia University

3. IRI Asia-Pacific Regional Program project on: “Climate forecast applications for disaster mitigation in Indonesia, Philippines and Vietnam” NASA/GPCP 1979-2004 warm ENSO – neutral anomalies BUT... - seasonality (e.g. Haylock and McBride 2001; Naylor et al. 2001) - spatial scales

4. DJF(1)SON(0) RegCM3 25km resolution courtesy of J. Qian, H. Li (IRI) NOAA/GHCN station prcp

6. http://www.pbs.org/wnet/africa/explore/sahel/sahel_overview.html

7. Photos courtesy of USGS, UNESCO/D. Roger, UN

8. r = 0.60 A. Giannini, R. Saravanan and P. Chang, 2003. Science, 302, 1027-1030 Also see e.g. Bader and Latif, 2003 (GRL); Lu and Delworth, 2005 (GRL)

9. Outline 1. Simulations of Sahel drought with climate models a. atmospheric models forced with historical sea surface temperature Giannini, Saravanan and Chang 2003, 2005 b. coupled ocean-atmosphere models (IPCC 4AR) Biasutti and Giannini 2006 2. Mechanisms of Sahel drought/African climate variability and change (Giannini, Biasutti, Held and Sobel, in preparation) a. stabilization – top-down e.g. Chiang and Sobel 2002 b. monsoon/moisture supply – bottom-up e.g. Lindzen and Nigam 1987 3. Climate and society interactions reflections on the role of science and scientists

10. Outline 1. Simulations of Sahel drought a. atmospheric models forced with historical sea surface temperature Giannini, Saravanan and Chang 2003, 2005 b. coupled ocean-atmosphere models (IPCC 4AR) Biasutti and Giannini 2006 2. Mechanisms of Sahel drought/African climate variability and change (Giannini, Biasutti, Held and Sobel, in preparation) a. stabilization – top-down e.g. Chiang and Sobel 2002 b. monsoon/moisture supply – bottom-up e.g. Lindzen and Nigam 1987 3. Climate and society interactions reflections on the role of science and scientists

11. spatial signature of July-September African rainfall variability Gulf of Guinea patternSahel pattern Giannini et al., 2005 (Clim. Dyn.)

12. temporal signature and relation to surface temperature Giannini et al., 2005 (Clim. Dyn.)

13. decadalinterannual Giannini et al., 2003, 2005

14. decadalinterannual

15. NASA/GISS analysis of surface temp – linear trend 1950-2000 Hansen et al. 1999 (J. Geophys. Res.) regression of NASA/NSIPP1 Sahel PC and sfc temp Giannini et al. 2003, 2005 IPCC 4AR Multi-model average Biasutti and Giannini 2006

16. IPCC 4AR Multi-model average Biasutti and Giannini, 2006 (GRL, in press)

18. Outline 1. Simulations of Sahel drought a. atmospheric models forced with historical sea surface temperature Giannini, Saravanan and Chang 2003, 2005 b. coupled ocean-atmosphere models (IPCC 4AR) Biasutti and Giannini 2006 2. Mechanisms of Sahel drought/African climate variability and change (Giannini, Biasutti, Held and Sobel, in preparation) a. stabilization – top-down e.g. Chiang and Sobel 2002 b. monsoon/moisture supply – bottom-up e.g. Lindzen and Nigam 1987 3. Climate and society interactions reflections on the role of science and scientists

20. Top-down: stabilization

21. Chiang and Sobel, J Climate 2002 (Yulaeva and Wallace, J Climate 1994)

22. El Nino – central equatorial Pacific global warming – global tropical oceans (e.g. Neelin et al., GRL 2003) atmospheric adjustment: net surface heat fluxes What role for the land surface?? (e.g. Chiang and Lintner, J. Climate 2005)

23. Bottom-up: monsoon/moisture supply

24. Rotstayn and Lohmann, J Climate 2002

25. surface air temperature (minus global mean) precipitation Haarsma et al., GRL 2005 2050-2080 minus 1950-1980

26. Michela Biasutti, personal communication

27. Outline 1. Simulations of Sahel drought a. atmospheric models forced with historical sea surface temperature Giannini, Saravanan and Chang 2003, 2005 b. coupled ocean-atmosphere models (IPCC 4AR) Biasutti and Giannini 2006 2. Mechanisms of Sahel drought/African climate variability and change (Giannini, Biasutti, Held and Sobel, in preparation) a. stabilization – top-down e.g. Chiang and Sobel 2002 b. monsoon/moisture supply – bottom-up e.g. Lindzen and Nigam 1987 3. Climate and society interactions reflections on the role of science and scientists

28. Reflections on: desertification - “Farmers freed of blame in Sahel drought” (SciDev.net) - multidisciplinary studies, linking climate and environmental/ecological sciences global warming - social/environmental equity

31. precipitationsurface temperature moisture convergenceevaporation

32. Sahel surface temperature variability (1930-2000)

33. CMAP precipitation (66%) NCEP/NCAR sfc temp (91%) what constitutes a monsoon?

34. Seasonal cycle of surface temperature/precipitation

35. Lu and Delworth 2005 (Geophys. Res. Lett.) The relative roles of Atlantic, Indian and Pacific SSTs