Climate Dynamics

, Volume 50, Issue 11–12, pp 4561–4581 | Cite as

Atmospheric feedbacks in North Africa from an irrigated, afforested Sahara

  • Tronje Peer KemenaEmail author
  • Katja Matthes
  • Thomas Martin
  • Sebastian Wahl
  • Andreas Oschlies


Afforestation of the Sahara has been proposed as a climate engineering method to sequester a substantial amount of carbon dioxide, potentially effective to mitigate climate change. Earlier studies predicted changes in the atmospheric circulation system. These atmospheric feedbacks raise questions about the self-sustainability of such an intervention, but have not been investigated in detail. Here, we investigate changes in precipitation and circulation in response to Saharan large-scale afforestation and irrigation with NCAR’s CESM-WACCM Earth system model. Our model results show a Saharan temperature reduction by 6 K and weak precipitation enhancement by 267 mm/year over the Sahara. Only 26% of the evapotranspirated water re-precipitates over the Saharan Desert, considerably large amounts are advected southward to the Sahel zone and enhance the West African monsoon (WAM). Different processes cause circulation and precipitation changes over North Africa. The increase in atmospheric moisture leads to radiative cooling above the Sahara and increased high-level cloud coverage as well as atmospheric warming above the Sahel zone. Both lead to a circulation anomaly with descending air over the Sahara and ascending air over the Sahel zone. Together with changes in the meridional temperature gradient, this results in a southward shift of the inner-tropical front. The strengthening of the Tropical easterly jet and the northward displacement of the African easterly jet is associated with a northward displacement and strengthening of the WAM precipitation. Our results suggest complex atmospheric circulation feedbacks, which reduce the precipitation potential over an afforested Sahara and enhance WAM precipitation.


Afforestation Climate engineering Circulation Irrigation West African monsoon 



This work is a contribution to the DFG-funded Priority Program SPP 1689 and was partly performed within the Helmholtz-University Young Investigators Group NATHAN, funded by the Helmholtz-Association and GEOMAR, the Helmholtz Centre for Ocean Research Kiel. The CESM-WACCM simulations have been performed at the Deutsche Klimarechenzentrum (DKRZ) in Hamburg, Germany. We thank two anonymous reviewers for their helpful comments.


  1. Allaway WG, Mansfield TA (1967) Stomatal responses to changes in carbon dioxide concentration in leaves treated. New Phytol 66:57–63CrossRefGoogle Scholar
  2. Ayars JE, Christen EW, Hornbuckle JW (2006) Controlled drainage for improved water management in arid regions irrigated agriculture. Agric Water Manag 86:128–139. doi: 10.1016/j.agwat.2006.07.004 CrossRefGoogle Scholar
  3. Bathiany S, Claussen M, Brovkin V, Raddatz T, Gayler V (2010) Combined biogeophysical and biogeochemical effects of large-scale forest cover changes in the MPI earth system model. Biogeosciences 7:1383–1399. doi: 10.5194/bg-7-1383-2010 CrossRefGoogle Scholar
  4. Betts RA (2011) Climate science: afforestation cools more or less. Nat Geosci 4:504–505. doi: 10.1038/ngeo1223 CrossRefGoogle Scholar
  5. Bowring SPK, Miller LM, Ganzeveld L, Kleidon A (2014) Applying the concept of “energy return on investment” to desert greening of the Sahara/Sahel using a global climate model. Earth Syst Dyn 5:43–53. doi: 10.5194/esd-5-43-2014 CrossRefGoogle Scholar
  6. Broccoli AJ, Dahl KA, Stouffer RJ (2006) Response of the ITCZ to Northern Hemisphere cooling. Geophys Res Lett 33:1–4. doi: 10.1029/2005GL024546 CrossRefGoogle Scholar
  7. Charney JG (1975) Dynamics of deserts and drought in the Sahel. Q J R Meteorol Soc 101:193–202. doi: 10.1002/qj.49710142802 CrossRefGoogle Scholar
  8. Claussen M, Kubatzki C, Brovkin V, Ganopolski A, Hoelzmann P, Pachur H-J (1999) Simulation of an abrupt change in Saharan vegetation in the mid-Holocene. Geophys Res Lett 26:2037–2040. doi: 10.1029/1999GL900494 CrossRefGoogle Scholar
  9. Cook KH (1999) Generation of the African easterly jet and its role in determining West African precipitation. J Clim 12:1165–1184. doi: 10.1175/1520-0442(1999)012<1165:GOTAEJ>2.0.CO;2 Google Scholar
  10. Cook KH, Vizy EK (2006) Coupled model simulations of the West African monsoon system: twentieth- and twenty-first-Century simulations. J Clim 19:3681–3703. doi: 10.1175/JCLI3814.1 CrossRefGoogle Scholar
  11. Cook K, Meehl G a, Arblaster JM (2012) Monsoon Regime and processes in CCSM4. Part II: African and American monsoon systems. J Clim 25:2609–2621. doi: 10.1175/JCLI-D-11-00185.1 CrossRefGoogle Scholar
  12. Danabasoglu G, Bates SC, Briegleb BP, Jayne SR, Jochum M, Large WG, Peacock S, Yeager SG (2012) The CCSM4 ocean component. J Clim 25:1361–1389. doi: 10.1175/JCLI-D-11-00091.1 CrossRefGoogle Scholar
  13. DeMott PJ, Sassen K, Poellot MR, Baumgardner D, Rogers DC, Brooks SD, Prenni AJ, Kreidenweis SM (2003) African dust aerosols as atmospheric ice nuclei. Geophys Res Lett 30:26–29. doi: 10.1029/2003GL017410 CrossRefGoogle Scholar
  14. Devaraju N, Bala G, Modak A (2015) Effects of large-scale deforestation on precipitation in the monsoon regions: remote versus local effects. Proc Natl Acad Sci 112:201423439. doi: 10.1073/pnas.1423439112 CrossRefGoogle Scholar
  15. Diongue A, Lafore J-P, Redelsperger J-L, Roca R (2002) Numerical study of a Sahelian synoptic weather system: Initiation and mature stages of convection and its interactions with the large-scale dynamics. Q J R Meteorol Soc 128:1899–1927. doi: 10.1256/003590002320603467 CrossRefGoogle Scholar
  16. Garcia RR, Marsh DR, Kinnison DE, Boville BA, Sassi F (2007) Simulation of secular trends in the middle atmosphere, 1950–2003. J Geophys Res Atmos 112:1–23. doi: 10.1029/2006JD007485 Google Scholar
  17. Grist JP, Nicholson SE (2001) A study of the dynamic factors influencing the rainfall variability in the West African Sahel. J Clim 14:1337–1359. doi: 10.1175/1520-0442(2001)014<1337:ASOTDF>2.0.CO;2 CrossRefGoogle Scholar
  18. Harlaß J, Latif M, Park W (2015) Improving climate model simulation of tropical Atlantic sea surface temperature: The importance of enhanced vertical atmosphere model resolution. doi: 10.1002/2015GL063310.Received
  19. Harrison SP, Bartlein PJ, Izumi K, Li G, Annan J, Hargreaves J, Braconnot P, Kageyama M (2015) Evaluation of CMIP5 palaeo-simulations to improve climate projections. Nat Clim Chang 5:735–743. doi: 10.1038/nclimate2649 CrossRefGoogle Scholar
  20. Holland MM, Bailey D a., Briegleb BP, Light B, Hunke E (2012) Improved sea ice shortwave radiation physics in CCSM4: the impact of melt ponds and aerosols on Arctic Sea Ice*. J Clim 25:1413–1430. doi: 10.1175/JCLI-D-11-00078.1 CrossRefGoogle Scholar
  21. Huffman GJ, Bolvin DT, Nelkin EJ, Wolff DB, Adler RF, Gu G, Hong Y, Bowman KP, Stocker EF (2007) The TRMM multisatellite precipitation analysis (TMPA): quasi-global, multiyear, combined-sensor precipitation estimates at fine scales. J Hydrometeorol 8:38–55. doi: 10.1175/JHM560.1 CrossRefGoogle Scholar
  22. Irizarry-Ortiz MM, Wang G, Eltahir EAB (2003) Role of the biosphere in the mid-Holocene climate of West Africa. J Geophys Res D Atmos 108:ACL 5-1–ACL 5-15. Artn 4042. doi: 10.1029/2001jd000989 Google Scholar
  23. Kafando P, Chane-Ming F, Petitdidier M (2015) Stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the West African monsoon. Clim Dyn. doi: 10.1007/s00382-015-2764-1
  24. Keller DP, Feng EY, Oschlies A (2014) Potential climate engineering effectiveness and side effects during a high carbon dioxide-emission scenario. Nat Commun 5:3304. doi: 10.1038/ncomms4304 Google Scholar
  25. Kojima T, Kakubari Y, Komiyama H (1995) Significance of afforestation of desert and its evaluation as a countermeasure against carbon dioxide problem. Energy Convers Manag 36:923–926. doi: 10.1016/0196-8904(95)00154-6 CrossRefGoogle Scholar
  26. Kraus EB (1977) Subtropical droughts and cross-equatorial energy transports. Mon Weather Rev 105:1009–1018CrossRefGoogle Scholar
  27. Lawrence DM, Oleson KW, Flanner MG, Fletcher CG, Lawrence PJ, Levis S, Swenson SC, Bonan GB (2012) The CCSM4 land simulation, 1850–2005: assessment of surface climate and new capabilities. J Clim 25:2240–2260. doi: 10.1175/JCLI-D-11-00103.1 CrossRefGoogle Scholar
  28. Leng G, Huang M, Tang Q, Sacks WJ, Lei H, Leung LR (2013) Modeling the effects of irrigation on land surface fluxes and states over the conterminous United States: sensitivity to input data and model parameters. J Geophys Res Atmos 118:9789–9803. doi: 10.1002/jgrd.50792 CrossRefGoogle Scholar
  29. Liou KN (2002) An introduction of atmospheric radiation, 2nd edn. Academic Press, Chap. 8Google Scholar
  30. Marsh DR, Mills MJ, Kinnison DE, Lamarque JF, Calvo N, Polvani LM (2013) Climate change from 1850 to 2005 simulated in CESM1(WACCM). J Clim 26:7372–7391. doi: 10.1175/JCLI-D-12-00558.1 CrossRefGoogle Scholar
  31. Nicholson SE (2009) A revised picture of the structure of the “monsoon” and land ITCZ over West Africa. Clim Dyn 32:1155–1171. doi: 10.1007/s00382-008-0514-3 CrossRefGoogle Scholar
  32. Nicholson SE (2013) The West African Sahel: a review of recent studies on the rainfall regime and its interannual variability. ISRN Meteorol 2013:32. doi: 10.1155/2013/453521
  33. Nicholson SE, Grist JP (2001) A conceptual model for understanding rainfall variability in the West African Sahel on interannual and interdecadal timescales. Int J Climatol 21:1733–1757. doi: 10.1002/joc.648 CrossRefGoogle Scholar
  34. Oleson KW, Lawrence DM, Gordon B, Flanner MG, Kluzek E, Peter LJ, Levis S, Swenson SC, Thornton PE (2010) Technical description of version 4.0 of the community land model (CLM). NCAR/TN-478 + STR NCAR Tech Note 266Google Scholar
  35. Ornstein L, Aleinov I, Rind D (2009) Irrigated afforestation of the Sahara and Australian Outback to end global warming. Clim Change 97:409–437. doi: 10.1007/s10584-009-9626-y CrossRefGoogle Scholar
  36. Ozawa H, Okabayashi T, Komiyama H, Kaya Y (1995) Research of arid land afforestation technologies for carbon dioxide fixation. Energy Convers Manag 36:911–914CrossRefGoogle Scholar
  37. Parajuli SP, Yang Z-L, Lawrence DM (2016) Diagnostic evaluation of the Community Earth System Model in simulating mineral dust emission with insight into large-scale dust storm mobilization in the Middle East and North Africa (MENA). Aeolian Res 21:21–35. doi: 10.1016/j.aeolia.2016.02.002 CrossRefGoogle Scholar
  38. Park J-Y, Bader J, Matei D (2015) Northern-hemispheric differential warming is the key to understanding the discrepancies in the projected Sahel rainfall. Nat Commun 6:5985. doi: 10.1038/ncomms6985 CrossRefGoogle Scholar
  39. Park J, Bader J, Matei D (2016) Anthropogenic Mediterranean warming essential driver for present and future Sahel rainfall. Nat Clim Chang 6:1–6. doi: 10.1038/nclimate3065 CrossRefGoogle Scholar
  40. Patricola CM, Cook KH (2008) Atmosphere/vegetation feedbacks: A mechanism for abrupt climate change over northern Africa. J Geophys Res 113:D18102. doi: 10.1029/2007JD009608 CrossRefGoogle Scholar
  41. Pausata FSR, Messori G, Zhang Q (2016) Impacts of dust reduction on the northward expansion of the African monsoon during the Green Sahara period. Earth Planet Sci Lett 434:298–307. doi: 10.1016/j.epsl.2015.11.049 CrossRefGoogle Scholar
  42. Prentice IC, Jolly D (2000) Mid-Holocene and glacial-maximum vegetation geography of the northern continents and Africa. J Biogeogr 27:507–519. doi: 10.1046/j.1365-2699.2000.00425.x CrossRefGoogle Scholar
  43. Rachmayani R, Prange M, Schulz M (2015) North African vegetation-precipitation feedback in early and mid-Holocene climate simulations with CCSM3-DGVM. Clim Past 11:175–185. doi: 10.5194/cp-11-175-2015 CrossRefGoogle Scholar
  44. Richter I, Xie SP (2008) On the origin of equatorial Atlantic biases in coupled general circulation models. Clim Dyn 31:587–598. doi: 10.1007/s00382-008-0364-z CrossRefGoogle Scholar
  45. Richter JH, Sassi F, Garcia RR (2010) Toward a physically based gravity wave source parameterization in a general circulation model. J Atmos Sci 67:136–156. doi: 10.1175/2009JAS3112.1 CrossRefGoogle Scholar
  46. Rienecker MM, Suarez MJ, Gelaro R, Todling R, Bacmeister J, Liu E, Bosilovich MG, Schubert SD, Takacs L, Kim GK, Bloom S, Chen J, Collins D, Conaty A, Da Silva A, Gu W, Joiner J, Koster RD, Lucchesi R, Molod A, Owens T, Pawson S, Pegion P, Redder CR, Reichle R, Robertson FR, Ruddick AG, Sienkiewicz M, Woollen J (2011) MERRA: NASA’s modern-era retrospective analysis for research and applications. J Clim 24:3624–3648. doi: 10.1175/JCLI-D-11-00015.1 CrossRefGoogle Scholar
  47. Shepherd JG (2012) Geoengineering the climate: an overview and update. Philos Trans R Soc A Math Phys Eng Sci 370:4166–4175. doi: 10.1098/rsta.2012.0186 CrossRefGoogle Scholar
  48. Smith LJ, Torn MS (2013) Ecological limits to terrestrial biological carbon dioxide removal. Clim Change 118:89–103. doi: 10.1007/s10584-012-0682-3 CrossRefGoogle Scholar
  49. Smith P, Davis SJ, Creutzig F, Fuss S, Minx J, Gabrielle B, Kato E, Jackson RB, Cowie A, Kriegler E, van Vuuren DP, Rogelj J, Ciais P, Milne J, Canadell JG, McCollum D, Peters G, Andrew R, Krey V, Shrestha G, Friedlingstein P, Gasser T, Grübler A, Heidug WK, Jonas M, Jones CD, Kraxner F, Littleton E, Lowe J, Moreira JR, Nakicenovic N, Obersteiner M, Patwardhan A, Rogner M, Rubin E, Sharifi A, Torvanger A, Yamagata Y, Edmonds J, Yongsung C (2015) Biophysical and economic limits to negative CO2 emissions. Nat Clim Chang 6:42–50. doi: 10.1038/nclimate2870 CrossRefGoogle Scholar
  50. Swann ALS, Fung IY, Chiang JCH (2012) Mid-latitude afforestation shifts general circulation and tropical precipitation. Proc Natl Acad Sci USA 109:712–716. doi: 10.1073/pnas.1116706108 CrossRefGoogle Scholar
  51. Swann ALS, Fung IY, Liu Y, Chiang JCH (2014) Remote Vegetation Feedbacks and the Mid-Holocene Green Sahara. J Clim 27:4857–4870. doi: 10.1175/JCLI-D-13-00690.1 CrossRefGoogle Scholar
  52. Thiéblemont R, Matthes K, Omrani N-E, Kodera K, Hansen F (2015) Solar forcing synchronizes decadal North Atlantic climate variability. Nat Commun 6:8268. doi: 10.1038/ncomms9268 CrossRefGoogle Scholar
  53. Thorncroft CD, Nguyen H, Zhang C, Peyrille P (2011) Annual cycle of the West African monsoon: Regional circulations and associated water vapour transport. Q J R Meteorol Soc 137:129–147. doi: 10.1002/qj.728 CrossRefGoogle Scholar
  54. Tierney JE, Pausata FSR, deMenocal PB (2017) Rainfall regimes of the Green Sahara. Sci Adv 3:1–9. doi: 10.1126/sciadv.1601503 CrossRefGoogle Scholar
  55. Wang Y, Notaro M, Liu Z, Gallimore R, Levis S, Kutzbach JE (2008) Detecting vegetation-precipitation feedbacks in mid-Holocene North Africa from two climate models. 59–67. doi: 10.5194/cp-4-59-2008
  56. Wu M-LC, Reale O, Schubert SD, Suarez MJ, Koster RD, Pegion PJ (2009) African easterly jet: structure and maintenance. J Clim 22:4459–4480. doi: 10.1175/2009JCLI2584.1 CrossRefGoogle Scholar
  57. Yu K, D’Odorico P, Bhattachan A, Okin GS, Evan AT (2015) Dust-rainfall feedback in West African Sahel. Geophys Res Lett 42:7563–7571. doi: 10.1002/2015GL065533 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Tronje Peer Kemena
    • 1
    Email author
  • Katja Matthes
    • 1
    • 2
  • Thomas Martin
    • 1
  • Sebastian Wahl
    • 1
  • Andreas Oschlies
    • 1
    • 2
  1. 1.GEOMAR Helmholtz Centre for Ocean Research KielKielGermany
  2. 2.Christian-Albrechts Universität zu KielKielGermany

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