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Enhanced land–sea warming contrast elevates aerosol pollution in a warmer world


Many climate models simulate an increase in anthropogenic aerosol species in response to warming1, particularly over the Northern Hemisphere mid-latitudes during June, July and August. Recently, it has been argued that this increase in anthropogenic aerosols can be linked to a decrease in wet removal associated with reduced precipitation2, but the mechanisms remain uncertain. Here, using a state-of-the-art climate model (the Community Atmosphere Model version 5), we expand on this notion to demonstrate that the enhanced aerosol burden and hydrological changes are related to a robust climate change phenomenon—the land–sea warming contrast3,4. Enhanced land warming is associated with continental reductions in lower-tropospheric humidity that drive decreases in low clouds—particularly large scale (stratus) clouds—which, in turn, lead to reduced large-scale precipitation and aerosol wet removal. Idealized model simulations further show that muting the land–sea warming contrast weakens these hydrological changes, thereby suppressing the aerosol increase. Moreover, idealized simulations that only feature land warming yield enhanced continental aridity and an increase in aerosol burden. Thus, unless anthropogenic emission reductions occur, our results add confidence that a warmer world will be associated with enhanced aerosol pollution.

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Fig. 1: CAM5 seasonal and annual mean aerosol burden and wet deposition response to climate change.
Fig. 2: CAM5 seasonal mean hydrology response for default warming and muted land warming simulations.
Fig. 3: CAM5 seasonal mean response of aerosol burden and wet deposition due to LSP for default warming and muted land warming simulations.
Fig. 4: CAM5 seasonal mean response of aerosol burden and wet deposition due to LSP for enhanced land warming simulations.

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Code availability

The codes used to process the CAM5 simulations are available from R.J.A.

Data availability

CAM5 data and simulations are available from R.J.A.


  1. Westervelt, D. et al. Quantifying PM2.5-meteorology sensitivities in a global climate model. Atmos. Environ. 142, 43–56 (2016).

    Article  CAS  Google Scholar 

  2. Allen, R. J., Landuyt, W. & Rumbold, S. T. An increase in aerosol burden and radiative effects in a warmer world. Nat. Clim. Change 6, 269–274 (2016).

    Article  CAS  Google Scholar 

  3. Sutton, R. T., Dong, B. & Gregory, J. M.Land/sea warming ratio in response to climate change: IPCC AR4 model results and comparison with observations.Geophys. Res. Lett. 34, L02701 (2007).

    Article  Google Scholar 

  4. Boer, G. The ratio of land to ocean temperature change under global warming. Clim. Dynam. 37, 2253–2270 (2011).

    Article  Google Scholar 

  5. Bond, T. C. et al. Historical emissions of black and organic carbon aerosol from energy-related combustion, 1850–2000. Glob. Biogeochem. Cycles 21, GB2018 (2007).

    Article  Google Scholar 

  6. Boucher, O. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 571–657 (IPCC, Cambridge Univ. Press, 2013).

  7. Ramanathan, V., Crutzen, P., Kiehl, J. & Rosenfeld, D. Aerosols, climate, and the hydrological cycle. Science 294, 2119–2124 (2001).

    Article  CAS  Google Scholar 

  8. Lelieveld, J., Evans, J. S., Fnais, M., Giannadaki, D. & Pozzer, A. The contribution of outdoor air pollution sources to premature mortality on a global scale. Nature 525, 367–371 (2015).

    Article  CAS  Google Scholar 

  9. Vecchi, G. A. & Soden, B. J. Global warming and the weakening of the tropical circulation. J. Clim. 20, 4316–4340 (2007).

    Article  Google Scholar 

  10. Held, I. M. & Soden, B. J. Robust responses of the hydrological cycle to global warming. J. Clim. 19, 5686–5699 (2006).

    Article  Google Scholar 

  11. Pye, H. et al. Effect of changes in climate and emissions on future sulfate‐nitrate‐ammonium aerosol levels in the United States.J. Geophys. Res. Atmos. 114, D01205 (2009).

    Article  Google Scholar 

  12. Racherla, P. N. & Adams, P. J. Sensitivity of global tropospheric ozone and fine particulate matter concentrations to climate change.J. Geophys. Res. Atmos. 111, D24103 (2006).

    Article  Google Scholar 

  13. Fang, Y. et al. The impacts of changing transport and precipitation on pollutant distributions in a future climate.J. Geophys. Res. Lett. 116, D18303 (2011).

    Article  Google Scholar 

  14. Lamarque, J.-F. et al. The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP): overview and description of models, simulations and climate diagnostics. Geosci. Model Dev. 6, 179–206 (2013).

    Article  CAS  Google Scholar 

  15. Silva, R. A. et al. Future global mortality from changes in air pollution attributable to climate change. Nat. Clim. Change 7, 647–651 (2017).

    Article  Google Scholar 

  16. Textor, C. et al. Analysis and quantification of the diversities of aerosol life cycles within AeroCom. Atmos. Chem. Phys. 6, 1777–1813 (2006).

  17. Allen, R. J. & Landuyt, W. The vertical distribution of black carbon in CMIP5 models: comparison to observations and the importance of convective transport. J. Geophys. Res. Atmos. 119, 4808–4835 (2014).

    Article  CAS  Google Scholar 

  18. Byrne, M. P. & O’Gorman, P. A. Land–ocean warming contrast over a wide range of climates: convective quasi-equilibrium theory and idealized simulations. J. Clim. 26, 4000–4016 (2013).

    Article  Google Scholar 

  19. Byrne, M. P. & O’Gorman, P. A. Link between land–ocean warming contrast and surface relative humidities in simulations with coupled climate models. Geophys. Res. Lett. 40, 5223–5227 (2013).

    Article  Google Scholar 

  20. Joshi, M. & Gregory, J. Dependence of the land‐sea contrast in surface climate response on the nature of the forcing.Geophys. Res. Lett. 35, L24802 (2008).

    Article  Google Scholar 

  21. Fasullo, J. T. Robust land–ocean contrasts in energy and water cycle feedbacks. J. Clim. 23, 4677–4693 (2010).

    Article  Google Scholar 

  22. Clark, R. T., Murphy, J. M. & Brown, S. J. Do global warming targets limit heatwave risk?. Geophys. Res. Lett. 37, L17703 (2010).

    Article  Google Scholar 

  23. Neale, R. B. et al. Description of the NCAR Community Atmosphere Model (CAM 5.0) (NCAR, 2012).

  24. Atlas, E. & Giam, C. Ambient concentration and precipitation scavenging of atmospheric organic pollutants. Water Air Soil Pollut. 38, 19–36 (1988).

    CAS  Google Scholar 

  25. Rowell, D. P. & Jones, R. G. Causes and uncertainty of future summer drying over Europe. Clim. Dynam. 27, 281–299 (2006).

    Article  Google Scholar 

  26. Simmons, A., Willett, K., Jones, P. & Dee, D. Low‐frequency variations in surface atmospheric humidity, temperature, and precipitation: inferences from reanalyses and monthly gridded observational data sets.J. Geophys. Res. Atmos. 115, D01110 (2010).

    Google Scholar 

  27. Byrne, M. P. & O’Gorman, P. A. Understanding decreases in land relative humidity with global warming: conceptual model and GCM simulations. J. Clim. 29, 9045–9061 (2016).

    Article  Google Scholar 

  28. Joshi, M., Lambert, F. & Webb, M. An explanation for the difference between twentieth and twenty-first century land–sea warming ratio in climate models. Clim. Dynam. 41, 1853–1869 (2013).

    Article  Google Scholar 

  29. Allen, R. & Zender, C. The role of eastern Siberian snow and soil moisture anomalies in quasi‐biennial persistence of the Arctic and North Atlantic Oscillations.J. Geophys. Res. 116, D16125 (2011).

    Article  Google Scholar 

  30. Sejas, S. A., Albert, O. S., Cai, M. & Deng, Y. Feedback attribution of the land–sea warming contrast in a global warming simulation of the NCAR CCSM4. Environ. Res. Lett. 9, 124005 (2014).

    Article  Google Scholar 

  31. Chang, E. K., Guo, Y., Xia, X. & Zheng, M. Storm-track activity in IPCC AR4/CMIP3 model simulations. J. Clim. 26, 246–260 (2013).

    Article  Google Scholar 

  32. Chang, E. K., Guo, Y. & Xia, X. CMIP5 multimodel ensemble projection of storm track change under global warming.J. Geophys. Res. Atmos. 117, D23118 (2012).

    Google Scholar 

  33. Liu, X. et al. Toward a minimal representation of aerosols in climate models: description and evaluation in the Community Atmosphere Model CAM5. Geosci. Model Dev. 5, 709–739 (2012).

    Article  Google Scholar 

  34. Rasch, P. et al. A comparison of scavenging and deposition processes in global models: results from the WCRP Cambridge Workshop of 1995. Tellus B 52, 1025–1056 (2000).

    Article  Google Scholar 

  35. Hou, P., Wu, S., McCarty, J. L. & Gao, Y. Sensitivity of atmospheric aerosol scavenging to precipitation intensity and frequency in the context of global climate change. Atmos. Chem. Phys. 18, 8173–8182 (2018).

  36. Emmons, L. K. et al. Description and evaluation of the Model for Ozone and Related chemical Tracers, version 4 (MOZART-4). Geosci. Model Dev. 3, 43–67 (2010).

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T.H. is supported in part by the Fellowships and Internships in Extremely Large Data Sets programme, which is funded by the NASA MUREP Institutional Research Opportunity and developed by the University of California, Riverside and NASA’s Jet Propulsion Laboratory. R.J.A., T.H. and C.A.R. also acknowledge support from the ExxonMobil Research and Engineering Company. H.S. is supported by the NASA ACMAP programme, and conducted the work at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.

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Authors and Affiliations



R.J.A. conceived the project, designed the study and performed the CAM5 simulations. R.J.A. and T.H. led the writing of the paper. T.H. carried out the data analysis and figure construction. C.A.R. and H.S. advised on interpretation of the results. All authors discussed the results and commented on the manuscript.

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Correspondence to Robert J. Allen.

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Supplementary Discussion, Supplementary Table 1, Supplementary Figures 1–11

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Allen, R.J., Hassan, T., Randles, C.A. et al. Enhanced land–sea warming contrast elevates aerosol pollution in a warmer world. Nat. Clim. Chang. 9, 300–305 (2019).

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