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
Drought in the African Sahel:
scientific research and societal implications
Alessandra GianniniInternational Research Institute for Climate and Society
The Earth Institute at Columbia University
IRI Asia-Pacific Regional Program project on:“Climate forecast applications for disaster mitigation in Indonesia, Philippines and Vietnam”
NASA/GPCP 1979-2004warm ENSO – neutral anomalies
BUT ...- seasonality (e.g. Haylock and McBride 2001; Naylor et al. 2001)- spatial scales
DJF
(1)
SO
N(0
)
RegCM3 25km resolutioncourtesy of J. Qian, H. Li (IRI) NOAA/GHCN station prcp
http://www.pbs.org/wnet/africa/explore/sahel/sahel_overview.html
Photos courtesy of USGS, UNESCO/D. Roger, UN
r = 0.60A. Giannini, R. Saravanan and P. Chang, 2003. Science, 302, 1027-1030Also see e.g. Bader and Latif, 2003 (GRL); Lu and Delworth, 2005 (GRL)
Outline
1. Simulations of Sahel drought with climate modelsa. atmospheric models forced with historical sea surface temperature
Giannini, Saravanan and Chang 2003, 2005b. 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 2002b. monsoon/moisture supply – bottom-up
e.g. Lindzen and Nigam 1987
3. Climate and society interactionsreflections on the role of science and scientists
Outline
1. Simulations of Sahel droughta. atmospheric models forced with historical sea surface temperature
Giannini, Saravanan and Chang 2003, 2005b. 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 2002b. monsoon/moisture supply – bottom-up
e.g. Lindzen and Nigam 1987
3. Climate and society interactionsreflections on the role of science and scientists
spatial signature of July-September African rainfall variabilityG
ulf
of G
uine
a pa
tter
nS
ahel
pat
tern
Giannini et al., 2005 (Clim. Dyn.)
temporal signature and relation to surface temperature
Giannini et al., 2005 (Clim. Dyn.)
decadal interannual
Giannini et al., 2003, 2005
Giannini et al., 2003, 2005
decadal interannual
NASA/GISS analysis of surface temp – linear trend 1950-2000Hansen et al. 1999 (J. Geophys. Res.)
regression of NASA/NSIPP1 Sahel PC and sfc tempGiannini et al. 2003, 2005
IPCC 4AR Multi-model averageBiasutti and Giannini 2006
IPCC 4AR Multi-model average
Biasutti and Giannini, 2006 (GRL, in press)
Biasutti and Giannini, 2006 (GRL, in press)
Outline
1. Simulations of Sahel droughta. atmospheric models forced with historical sea surface temperature
Giannini, Saravanan and Chang 2003, 2005b. 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 2002b. monsoon/moisture supply – bottom-up
e.g. Lindzen and Nigam 1987
3. Climate and society interactionsreflections on the role of science and scientists
Top-down: stabilization
Chiang and Sobel, J Climate 2002(Yulaeva and Wallace , J Climate 1994)
El Nino – central equatorial Pacificglobal warming – global tropical oceans(e.g. Neelin et al., GRL 2003)
atmosphericadjustment:net surfaceheat fluxes
What role for theland surface??
(e.g. Chiang and Lintner, J. Climate 2005)
Bottom-up: monsoon/moisture supply
Rotstayn and Lohmann, J Climate 2002
surface air temperature
(minus global mean)
precipitation
Haarsma et al., GRL 2005 2050-2080 minus 1950-1980
Michela Biasutti, personal communication
Outline
1. Simulations of Sahel droughta. atmospheric models forced with historical sea surface temperature
Giannini, Saravanan and Chang 2003, 2005b. 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 2002b. monsoon/moisture supply – bottom-up
e.g. Lindzen and Nigam 1987
3. Climate and society interactionsreflections on the role of science and scientists
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
precipitation surface temperature
moisture convergence evaporation
Sahel surface temperature variability (1930-2000)
CMAP precipitation(66%)
NCEP/NCAR sfc temp(91%)
what constitutes a monsoon?
Seasonal cycle of surface temperature/precipitation
Lu and Delworth 2005 (Geophys. Res. Lett.)
The relative roles of Atlantic, Indian and Pacific SSTs