Climate Dynamics

, Volume 40, Issue 1–2, pp 295–316 | Cite as

Asymmetries in tropical rainfall and circulation patterns in idealised CO2 removal experiments

  • Robin ChadwickEmail author
  • Peili Wu
  • Peter Good
  • Timothy Andrews


Atmospheric CO2 removal is currently receiving serious consideration as a supplement or even alternative to emissions reduction. However the possible consequences of such a strategy for the climate system, and particularly for regional changes to the hydrological cycle, are not well understood. Two idealised general circulation model experiments are described, where CO2 concentrations are steadily increased, then decreased along the same path. Global mean precipitation continues to increase for several decades after CO2 begins to decrease. The mean tropical circulation shows associated changes due to the constraint on the global circulation imposed by precipitation and water vapour. The patterns of precipitation and circulation change also exhibit asymmetries with regard to changes in both CO2 and global mean temperature, but while the lag in global precipitation can be ascribed to different levels of CO2 at the same temperature state, the regional changes cannot. Instead, ocean memory and heat transfer are important here. In particular the equatorial East Pacific continues to warm relative to the West Pacific during CO2 ramp-down, producing an anomalously large equatorial Pacific sea surface temperature gradient and associated rainfall anomalies. The mechanism is likely to be a lag in response to atmospheric forcing between mixed-layer water in the east Pacific and the sub-thermocline water below, due to transport through the ocean circulation. The implication of this study is that a CO2 pathway of increasing then decreasing atmospheric CO2 concentrations may lead us to climate states during CO2 decrease that have not been experienced during the increase.


CO2 removal Rainfall Tropical circulation Geoengineering 



The authors were supported by the Joint Department of Energy and Climate Change (DECC) and Department for Environment, Food and Rural Affairs (Defra) Met Office Hadley Centre Climate Programme, DECC/Defra (GA01101). We would like to thank Marie Boucher-Boucher for providing the HadGEM2-ES ramp-up/ramp-down data. Thanks also to Mark Ringer, Gill Martin and Graeme Stephens for useful discussions, and to two anonymous reviewers for helpful comments.


  1. Andrews T, Forster PM, Gregory JM (2009) A surface energy perspective on climate change. J Climate 22(10):2557–2570CrossRefGoogle Scholar
  2. Andrews T, Forster PM, Boucher O, Bellouin N, Jones A (2010) Precipitation, radiative forcing and global temperature change. Geophys Res Lett 37(L14701)Google Scholar
  3. Bain CL, De Paz J, Kramer J, Magnusdottir G, Smyth P, Stern H, Wang C-C (2011) Detecting the ITCZ in instantaneous satellite data using spatiotemporal statistical modeling: ITCZ climatology in the East Pacific. J Climate 24(1):216–230CrossRefGoogle Scholar
  4. Bala G, Duffy PB, Taylor KE (2008) Impact of geoengineering schemes on the global hydrological cycle. PNAS 105(22):7664–7669CrossRefGoogle Scholar
  5. Bala G, Caldeira K, Nemani R (2010) Fast versus slow response in climate change: implications for the global hydrological cycle. Clim Dyn 35(2–3):423–434CrossRefGoogle Scholar
  6. Barsugli JJ, Shin SI, Sardeshmukh PD (2006) Sensitivity of global warming to the pattern of tropical ocean warming. Clim Dyn 27(5):483–492CrossRefGoogle Scholar
  7. Boucher O, Burke E, Doutriaux-Boucher M, Halloran P, Jones CD, Lowe J, Ringer MA, Wu P (2011) Is the Earth System reversible to climate change? (submitted)Google Scholar
  8. Cao L, Bala G, Caldeira K (2011) Why is there a short-term increase in global precipitation in response to diminished CO2 forcing? Geophys Res Lett 38(L06703)Google Scholar
  9. Chiang JC, Bitz CM (2005) Influence of high latitude ice cover on the marine intertropical convergence zone. Clim Dyn 25:477–496CrossRefGoogle Scholar
  10. Chiang JC, Fang Y, Chang P (2008) Interhemispheric thermal gradient and tropical Pacific climate. Geophys Res Lett 35(L14704)Google Scholar
  11. Chou C, Neelin J (2004) Mechanisms of global warming impacts on regional tropical precipitation. J Climate 17(13):2688–2701CrossRefGoogle Scholar
  12. Chou C, Neelin JD, Chen CA, Tu JY (2009) Evaluating the “Rich-Get-Richer” mechanism in tropical precipitation change under global warming. J Climate 22(8):1982–2005CrossRefGoogle Scholar
  13. Clement A, Seager R, Cane M, Zebiak S (1996) An ocean dynamical thermostat. J Climate 9(9):2190–2196CrossRefGoogle Scholar
  14. Collins M, An SI, Cai W, Ganachaud A, Guilyardi E, Jin FF, Jochum M, Lengaigne M, Power S, Timmermann A, Vecchi G, Wittenberg A (2010) The impact of global warming on the tropical Pacific ocean and El Nino. Nat Geosci 3(6):391–397CrossRefGoogle Scholar
  15. Collins W, Bellouin N, Doutriaux-Boucher M, Gedney N, Halloran P, Hinton T, Hughes J, Jones C, Joshi M, Liddicoat S, Martin G, O’Connor F, Rae J, Senior C, Sitch S, Totterdell I, Wiltshire A, Woodward S (2011) Development and evaluation of an earth-system model—HadGEM2 (submitted to Geosci Model Dev)Google Scholar
  16. DiNezio PN, Clement AC, Vecchi GA, Soden BJ, Kirtman BP (2009) Climate response of the equatorial pacific to global warming. J Climate 22(18):4873–4892CrossRefGoogle Scholar
  17. Gastineau G, Le Treut H, Li L (2008) Hadley circulation changes under global warming conditions indicated by coupled climate models. Tellus ser A- Dyn Meteorol Oceanogr 60(5):863–884CrossRefGoogle Scholar
  18. Gastineau G, Li L, Le Treut H (2009) The Hadley and Walker circulation changes in global warming conditions described by idealized atmospheric simulations. J Climate 22(14):3993–4013CrossRefGoogle Scholar
  19. Good P, Gregory JM, Lowe JA (2011a) A step-response simple climate model to reconstruct and interpret AOGCM projections. Geophys Res Lett 38(L01703)Google Scholar
  20. Good P, Ingram W, Lambert FH, Lowe JA, Gregory JM, Webb MJ, Ringer MA, Wu P (2011b) A step-response simple climate model for predicting and understanding precipitation from global to regional scales (submitted)Google Scholar
  21. Gordon C, Cooper C, Senior C, Banks H, Gregory J, Johns T, Mitchell J, Wood R (2000) The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Clim Dyn 16(2–3):147–168CrossRefGoogle Scholar
  22. Hansen J, Sato M, Ruedy R, Nazarenko L, Lacis A, Schmidt G, Russell G, Aleinov I, Bauer M, Bauer S, Bell N, Cairns B, Canuto V, Chandler M, Cheng Y, Del-Genio A, Faluvegi G, Fleming E, Friend A, Hall T, Jackman C, Kelley M, Kiang N, Koch D, Lean J, Lerner J, Lo K, Menon S, Miller R, Minnis P, Novakov T, Oinas V, Perlwitz J, Perlwitz J, Rind D, Romanou A, Shindell D, Stone P, Sun S, Tausnev N, Thresher D, Wielicki B, Wong T, Yao M, Zhang S (2005) Efficacy of climate forcings. J Geophys Res Atmos 110(D18104)Google Scholar
  23. Held IM, Soden BJ (2006) Robust responses of the hydrological cycle to global warming. J Climate 19(21):5686–5699CrossRefGoogle Scholar
  24. Held IM, Winton M, Takahashi K, Delworth T, Zeng F, Vallis GK (2010) Probing the fast and slow components of global warming by returning abruptly to preindustrial forcing. J Climate 23(9):2418–2427CrossRefGoogle Scholar
  25. Jones A, Haywood J, Boucher O, Kravitz B, Robock A (2010) Geoengineering by stratospheric SO(2) injection: results from the Met Office HadGEM(2) climate model and comparison with the Goddard Institute for Space Studies ModelE. Atmos Chem Phys 10(13):5999–6006CrossRefGoogle Scholar
  26. Karnauskas KB, Seager R, Kaplan A, Kushnir Y, Cane MA (2009) Observed strengthening of the zonal sea surface temperature gradient across the Equatorial Pacific Ocean. J Climate 22(16):4316–4321CrossRefGoogle Scholar
  27. Knutson T, Manabe S (1995) Time-mean response over the tropical Pacific to increased CO2 in a coupled ocean-atmosphere model. J Climate 8(9):2181–2199CrossRefGoogle Scholar
  28. Liu Z, Vavrus S, He F, Wen N, Zhong Y (2005) Rethinking tropical ocean response to global warming: the enhanced equatorial warming. J Climate 18(22):4684–4700CrossRefGoogle Scholar
  29. Lloyd J, Guilyardi E, Weller H, Slingo J (2009) The role of atmosphere feedbacks during ENSO in the CMIP3 models. Atmos Sci Lett 10(3, SI):170–176CrossRefGoogle Scholar
  30. Martin GM, Bellouin N, Collins WJ, Culverwell ID, Halloran PR, Hardiman SC, Hinton TJ, Jones CD, McDonald RE, McLaren AJ, O’Connor FM, Roberts MJ, Rodriguez JM, Woodward S, Best MJ, Brooks ME, Brown AR, Butchart N, Dearden C, Derbyshire SH, Dharssi I, Doutriaux-Boucher M, Edwards JM, Falloon PD, Gedney N, Gray LJ, Hewitt HT, Hobson M, Huddleston MR, Hughes J, Ineson S, Ingram WJ, James PM, Johns TC, Johnson CE, Jones A, Jones CP, Joshi MM, Keen AB, Liddicoat S, Lock AP, Maidens AV, Manners JC, Milton SF, Rae JGL, Ridley JK, Sellar A, Senior CA, Totterdell IJ, Verhoef A, Vidale PL, Wiltshire A (2011) The HadGEM2 family of Met Office unified model climate configurations (to Geosci Model Dev)Google Scholar
  31. Matei D, Keenlyside N, Latif M, Jungclaus J (2008) Subtropical forcing of tropical Pacific climate and decadal ENSO modulation. J Climate 21(18):4691–4709CrossRefGoogle Scholar
  32. McCreary J, Lu P (1994) Interaction between the subtropical and equatorial ocean circulations—the subtropical cell. J Phys Oceanogr 24(2):466–497Google Scholar
  33. McPhaden M, Zhang D (2002) Slowdown of the meridional overturning circulation in the upper Pacific Ocean. Nat 415(6872):603–608CrossRefGoogle Scholar
  34. Mitchell J, Wilson C, Cunnington W (1987) On CO2 climate sensitivity and model dependence of results. QJRMS 113(475):293–322CrossRefGoogle Scholar
  35. Pennell C, Reichler T (2011) On the effective number of climate models. J Climate 24(9):2358–2367CrossRefGoogle Scholar
  36. Ricke KL, Morgan G, Allen MR (2010) Regional climate response to solar-radiation management. Nat Geosci 3(8):537–541CrossRefGoogle Scholar
  37. Robock A, Oman L, Stenchikov GL (2008) Regional climate responses to geoengineering with tropical and Arctic SO2 injections. J Geophys Res-Atmospheres 113(D16101)Google Scholar
  38. Schubert S, Suarez M, Pegion P, Koster R, Bacmeister J (2004) On the cause of the 1930s Dust Bowl. Sci 303(5665):1855–1859CrossRefGoogle Scholar
  39. Seager R, Murtugudde R (1997) Ocean dynamics, thermocline adjustment, and regulation of tropical SST. J Climate 10(3):521–534CrossRefGoogle Scholar
  40. Seager R, Naik N, Vecchi GA (2010) Thermodynamic and dynamic mechanisms for large-scale changes in the hydrological cycle in response to global warming. J Climate 23(17):4651–4668CrossRefGoogle Scholar
  41. Stouffer R (2004) Time scales of climate response. J Climate 17(1):209–217CrossRefGoogle Scholar
  42. Sugi M, Yoshimura J (2004) A mechanism of tropical precipitation change due to CO2 increase. J Climate 17(1):238–243CrossRefGoogle Scholar
  43. Trenberth K, Stepaniak D, Caron J (2000) The global monsoon as seen through the divergent atmospheric circulation. J Climate 13(22):3969–3993CrossRefGoogle Scholar
  44. Vecchi G, Soden B, Wittenberg A, Held I, Leetmaa A, Harrison M (2006) Weakening of tropical Pacific atmospheric circulation due to anthropogenic forcing. Nat 441(7089):73–76CrossRefGoogle Scholar
  45. Vecchi GA, Soden BJ (2007) Global warming and the weakening of the tropical circulation. J Climate 20(17):4316–4340CrossRefGoogle Scholar
  46. Wu L, Liu Z, Gallimore R, Jacob R, Lee D, Zhong Y (2003) Pacific decadal variability: The tropical Pacific mode and the North Pacific mode. J Climate 16(8):1101–1120CrossRefGoogle Scholar
  47. Wu P, Wood R, Ridley J, Lowe J (2010) Temporary acceleration of the hydrological cycle in response to a CO2 rampdown. Geophys Res Lett 37(L12705)Google Scholar
  48. Xie SP, Deser C, Vecchi GA, Ma J, Teng H, Wittenberg AT (2010) Global warming pattern formation: sea surface temperature and rainfall. J Climate 23(4):966–986CrossRefGoogle Scholar
  49. Yang H, Zhu J (2011) Equilibrium thermal response timescale of global oceans. Geophys Res Lett 38(L14711)Google Scholar
  50. Zhang M, Song H (2006) Evidence of deceleration of atmospheric vertical overturning circulation over the tropical Pacific. Geophys Res Lett 33(12)Google Scholar

Copyright information

© Crown Copyright 2012

Authors and Affiliations

  • Robin Chadwick
    • 1
    Email author
  • Peili Wu
    • 1
  • Peter Good
    • 1
  • Timothy Andrews
    • 1
  1. 1.Met Office Hadley CentreExeterUK

Personalised recommendations