Drought in the African Sahel: scientific research and societal implications Alessandra Giannini...
Transcript of Drought in the African Sahel: scientific research and societal implications Alessandra Giannini...
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Drought in the African Sahel:
scientific research and societal implications
Alessandra GianniniInternational Research Institute for Climate and Society
The Earth Institute at Columbia University
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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
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DJF
(1)
SO
N(0
)
RegCM3 25km resolutioncourtesy of J. Qian, H. Li (IRI) NOAA/GHCN station prcp
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http://www.pbs.org/wnet/africa/explore/sahel/sahel_overview.html
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Photos courtesy of USGS, UNESCO/D. Roger, UN
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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)
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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
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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
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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.)
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temporal signature and relation to surface temperature
Giannini et al., 2005 (Clim. Dyn.)
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decadal interannual
Giannini et al., 2003, 2005
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Giannini et al., 2003, 2005
decadal interannual
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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
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IPCC 4AR Multi-model average
Biasutti and Giannini, 2006 (GRL, in press)
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Biasutti and Giannini, 2006 (GRL, in press)
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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
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Top-down: stabilization
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Chiang and Sobel, J Climate 2002(Yulaeva and Wallace , J Climate 1994)
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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)
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Bottom-up: monsoon/moisture supply
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Rotstayn and Lohmann, J Climate 2002
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surface air temperature
(minus global mean)
precipitation
Haarsma et al., GRL 2005 2050-2080 minus 1950-1980
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Michela Biasutti, personal communication
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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
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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
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precipitation surface temperature
moisture convergence evaporation
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Sahel surface temperature variability (1930-2000)
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CMAP precipitation(66%)
NCEP/NCAR sfc temp(91%)
what constitutes a monsoon?
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Seasonal cycle of surface temperature/precipitation
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Lu and Delworth 2005 (Geophys. Res. Lett.)
The relative roles of Atlantic, Indian and Pacific SSTs
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