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No projected global drylands expansion under greenhouse warming


Drylands, comprising land regions characterized by water-limited, sparse vegetation, have commonly been projected to expand globally under climate warming. Such projections, however, rely on an atmospheric proxy for drylands, the aridity index, which has recently been shown to yield qualitatively incorrect projections of various components of the terrestrial water cycle. Here, we use an alternative index of drylands, based directly on relevant ecohydrological variables, and compare projections of both indices in Coupled Model Intercomparison Project Phase 5 climate models as well as Dynamic Global Vegetation Models. The aridity index overestimates simulated ecohydrological index changes. This divergence reflects different index sensitivities to hydroclimate change and opposite responses to the physiological effect on vegetation of increasing atmospheric CO2. Atmospheric aridity is thus not an accurate proxy of the future extent of drylands. Despite greater uncertainties than in atmospheric projections, climate model ecohydrological projections indicate no global drylands expansion under greenhouse warming, contrary to previous claims based on atmospheric aridity.

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Fig. 1: Establishing an EI of drylands in CMIP5 models.
Fig. 2: Divergent AI and EI projections under climate change in CMIP5 models.
Fig. 3: Different sensitivities of the EI and the AI to hydroclimatic changes.
Fig. 4: Plant physiology decouples AI and EI projections.
Fig. 5: Changes in drylands area in CMIP5 models under the AI and EI definitions.
Fig. 6: Changes in drylands in ISIMIP.

Data availability

All climate model simulations used in the Article are from CMIP5 and are publicly available—for instance, at All ISIMIP simulations are freely available as well—for example, at All calculated data generated from these sources are available from the corresponding author upon request.

Code availability

The custom R code written to read and analyse the data and generate the figures is available on GitHub at (ref. 51).


  1. 1.

    D’Odorico, P. & Porporato, A. Dryland Ecohydrology (Springer, 2019).

  2. 2.

    Smith, W. K. et al. Remote sensing of dryland ecosystem structure and function: progress, challenges, and opportunities. Remote Sens. Environ. 233, 111401 (2019).

    Google Scholar 

  3. 3.

    Reynolds, J. F. et al. Global desertification: building a science for dryland development. Science 316, 847–851 (2007).

    CAS  Google Scholar 

  4. 4.

    Ahlström, A. et al. The dominant role of semi-arid ecosystems in the trend and variability of the land CO2 sink. Science 348, 895–899 (2015).

    Google Scholar 

  5. 5.

    Middleton, N. & Thomas, D. S. G. World Atlas of Desertification 2nd edn (Wiley, 1997).

  6. 6.

    Budyko, M. I. & Miller, D. H. International Geophysics Series: Climate and Life Vol. 18 (Academic Press, 1974).

  7. 7.

    Feng, S. & Fu, Q. Expansion of global drylands under a warming climate. Atmos. Chem. Phys. 13, 10081–10094 (2013).

    CAS  Google Scholar 

  8. 8.

    Fu, Q. & Feng, S. Responses of terrestrial aridity to global warming. J. Geophys. Res. Atmos. 119, 7863–7875 (2014).

    Google Scholar 

  9. 9.

    Scheff, J. & Frierson, D. M. W. Terrestrial aridity and its response to greenhouse warming across CMIP5 climate models. J. Clim. 28, 5583–5600 (2015).

    Google Scholar 

  10. 10.

    Huang, J., Yu, H., Guan, X., Wang, G. & Guo, R. Accelerated dryland expansion under climate change. Nat. Clim. Change 6, 166–171 (2016).

    Google Scholar 

  11. 11.

    Huang, J., Yu, H., Dai, A., Wei, Y. & Kang, L. Drylands face potential threat under 2 °C global warming target. Nat. Clim. Change 7, 417–422 (2017).

    Google Scholar 

  12. 12.

    Park, C.-E. et al. Keeping global warming within 1.5 °C constrains emergence of aridification. Nat. Clim. Change 8, 70–74 (2018).

    Google Scholar 

  13. 13.

    Koutroulis, A. G. Dryland changes under different levels of global warming. Sci. Total Environ. 655, 482–511 (2019).

    CAS  Google Scholar 

  14. 14.

    Park, C. E. et al. Inequal responses of drylands to radiative forcing geoengineering methods. Geophys. Res. Lett. 46, 14011–14020 (2019).

    Google Scholar 

  15. 15.

    Wei, Y. et al. Drylands climate response to transient and stabilized 2 °C and 1.5 °C global warming targets. Clim. Dyn. 53, 2375–2389 (2019).

    Google Scholar 

  16. 16.

    Yao, J. et al. Accelerated dryland expansion regulates future variability in dryland gross primary production. Nat. Commun. 11, 1665 (2020).

    CAS  Google Scholar 

  17. 17.

    Berdugo, M. et al. Global ecosystem thresholds driven by aridity. Science 367, 787–790 (2020).

    CAS  Google Scholar 

  18. 18.

    Rajaud, A. & de Noblet-Ducoudré, N. Tropical semi-arid regions expanding over temperate latitudes under climate change. Climatic Change 144, 703–719 (2017).

    Google Scholar 

  19. 19.

    Yang, Y. et al. Disconnection between trends of atmospheric drying and continental runoff. Water Resour. Res. 54, 4700–4713 (2018).

    Google Scholar 

  20. 20.

    Greve, P., Roderick, M. L., Ukkola, A. M. & Wada, Y. The aridity index under global warming. Environ. Res. Lett. 14, 124006 (2019).

    CAS  Google Scholar 

  21. 21.

    Milly, P. C. D. & Dunne, K. A. Potential evapotranspiration and continental drying. Nat. Clim. Change 6, 946–949 (2016).

    Google Scholar 

  22. 22.

    Yang, Y., Roderick, M. L., Zhang, S., McVicar, T. R. & Donohue, R. J. Hydrologic implications of vegetation response to elevated CO2 in climate projections. Nat. Clim. Change 9, 44–48 (2019).

    Google Scholar 

  23. 23.

    Norby, R. J. & Zak, D. R. Ecological lessons from free-air CO2 enrichment (FACE) experiments. Annu. Rev. Ecol. Evol. Syst. 42, 181–203 (2011).

    Google Scholar 

  24. 24.

    Berg, A. & Sheffield, J. Soil moisture–evapotranspiration coupling in CMIP5 models: relationship with simulated climate and projections. J. Clim. 31, 4865–4878 (2018).

    Google Scholar 

  25. 25.

    Mahowald, N. et al. Projections of leaf area index in Earth system models. Earth Syst. Dyn. 7, 211–229 (2016).

    Google Scholar 

  26. 26.

    Sherwood, S. & Fu, Q. A drier future? Science 343, 737–739 (2014).

    CAS  Google Scholar 

  27. 27.

    Berg, A. et al. Land–atmosphere feedbacks amplify aridity increase over land under global warming. Nat. Clim. Change 6, 869–874 (2016).

    Google Scholar 

  28. 28.

    Berg, A. & Sheffield, J. Climate change and drought: the soil moisture perspective. Curr. Clim. Change Rep. 4, 180–191 (2018).

    Google Scholar 

  29. 29.

    Lavergne, A. et al. Observed and modelled historical trends in the water‐use efficiency of plants and ecosystems. Glob. Change Biol. 25, 2242–2257 (2019).

    Google Scholar 

  30. 30.

    Friedlingstein, P. Carbon cycle feedbacks and future climate change. Phil. Trans. R. Soc. A 373, 20140421 (2015).

    Google Scholar 

  31. 31.

    Swann, A. L., Hoffman, F. M., Koven, C. D. & Randerson, J. T. Plant responses to increasing CO2 reduce estimates of climate impacts on drought severity. Proc. Natl Acad. Sci. USA 113, 10019–10024 (2016).

    CAS  Google Scholar 

  32. 32.

    Lemordant, L., Gentine, P., Swann, A. S., Cook, B. I. & Scheff, J. Critical impact of vegetation physiology on the continental hydrologic cycle in response to increasing CO2. Proc. Natl Acad. Sci. USA 115, 4093–4098 (2018).

    CAS  Google Scholar 

  33. 33.

    Berg, A. & Sheffield, J. Evapotranspiration partitioning in CMIP5 models: uncertainties and future projections. J. Clim. 32, 2653–2671 (2019).

    Google Scholar 

  34. 34.

    Cao, L., Bala, G., Caldeira, K., Nemani, R. & Ban-Weiss, G. Importance of carbon dioxide physiological forcing to future climate change. Proc. Natl Acad. Sci. USA 107, 9513–9518 (2010).

    CAS  Google Scholar 

  35. 35.

    Skinner, C. B., Poulsen, C. J. & Mankin, J. S. Amplification of heat extremes by plant CO2 physiological forcing. Nat. Commun. 9, 1094 (2018).

    Google Scholar 

  36. 36.

    Kooperman, G. J. et al. Forest response to rising CO2 drives zonally asymmetric rainfall change over tropical land. Nat. Clim. Change 8, 434–440 (2018).

    Google Scholar 

  37. 37.

    Frieler, K. et al. Assessing the impacts of 1.5 °C global warming—simulation protocol of the Inter-sectoral Impact Model Intercomparison Project (ISIMIP2b). Geosci. Model Dev. 10, 4321–4345 (2017).

    Google Scholar 

  38. 38.

    Zhu, Z. et al. Greening of the Earth and its drivers. Nat. Clim. Change 6, 791–795 (2016).

    CAS  Google Scholar 

  39. 39.

    He, B., Wang, S., Guo, L. & Wu, X. Aridity change and its correlation with greening over drylands. Agric. For. Meteorol. 278, 107663 (2019).

    Google Scholar 

  40. 40.

    Brandt, M. et al. Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa. Nat. Ecol. Evol. 1, 0081 (2017).

    Google Scholar 

  41. 41.

    Burrell, A. L., Evans, J. P. & De Kauwe, M. G. Anthropogenic climate change has driven over 5 million km2 of drylands towards desertification. Nat. Commun. 11, 3853 (2020).

    CAS  Google Scholar 

  42. 42.

    Berg, A., Sheffield, J. & Milly, P. C. D. Divergent surface and total soil moisture projections under global warming. Geophys. Res. Lett. 44, 236–244 (2017).

    Google Scholar 

  43. 43.

    Mankin, J. S., Seager, R., Smerdon, J. E., Cook, B. I. & Williams, A. P. Mid-latitude freshwater availability reduced by projected vegetation responses to climate change. Nat. Geosci. 12, 983–988 (2019).

    CAS  Google Scholar 

  44. 44.

    Liu, Y. et al. Field-experiment constraints on the enhancement of the terrestrial carbon sink by CO2 fertilization. Nat. Geosci. 12, 809–814 (2019).

    CAS  Google Scholar 

  45. 45.

    Zeng, Z. et al. Responses of land evapotranspiration to Earth’s greening in CMIP5 Earth System Models. Environ. Res. Lett. 11, 104006 (2016).

    Google Scholar 

  46. 46.

    Peñuelas, J. et al. Shifting from a fertilization-dominated to a warming-dominated period. Nat. Ecol. Evol. 1, 1438–1445 (2017).

    Google Scholar 

  47. 47.

    Brodribb, T. J., Powers, J., Cochard, H. & Choat, B. Hanging by a thread? Forests and drought. Science 368, 261–266 (2020).

    CAS  Google Scholar 

  48. 48.

    Scheff, J., Seager, R., Liu, H. & Coats, S. Are glacials dry? Consequences for paleoclimatology and for greenhouse warming. J. Clim. 30, 6593–6609 (2017).

    Google Scholar 

  49. 49.

    Ault, T. R. On the essentials of drought in a changing climate. Science 368, 256–260 (2020).

    CAS  Google Scholar 

  50. 50.

    Berg, A. & Sheffield, J. Historic and projected changes in coupling between soil moisture and evapotranspiration (ET) confounded by the role of different ET components. J. Geophys. Res. Atmos. 124, 5791–5806 (2019).

    Google Scholar 

  51. 51.

    Berg, A. & McColl, K. R code for ‘No global drylands expansion under greenhouse warming’. Zenodo (2021).

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We thank the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups (listed in Supplementary Table 1 of this paper) for producing and making available their model output. For CMIP, the US Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led the development of software infrastructure in partnership with the Global Organization for Earth System Science Portals. For their roles in producing, coordinating and making available the ISIMIP input data and impact model output, we thank the modelling groups, the ISIMIP sector coordinators and the ISIMIP cross-sectoral science team for the Biomes sectors. K.A.M. acknowledges funding from a Winokur Seed Grant in Environmental Sciences from the Harvard University Center for the Environment.

Author information




A.B. and K.A.M. designed the study. A.B. conducted the analysis and wrote the manuscript. K.A.M. advised on the interpretation of the results and contributed to the manuscript preparation.

Corresponding author

Correspondence to Alexis Berg.

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The authors declare no competing interests.

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Peer review information Nature Climate Change thanks Peter Greve, Congbin Fu and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Table 1, Discussions 1–3 and Figs. 1–14.

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Berg, A., McColl, K.A. No projected global drylands expansion under greenhouse warming. Nat. Clim. Chang. 11, 331–337 (2021).

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