Re-examining tropical expansion

Abstract

Observations reveal a poleward expansion of the tropics in recent decades, implying a potential role of human activity. However, although theory and modelling suggest increasing GHG concentrations should widen the tropics, previous observational-based studies depict disparate rates of expansion, including many that are far higher than those simulated by climate models. Here, we review the rates and possible causes of observed and projected tropical widening. By accounting for methodological differences, the tropics are found to have widened about 0.5° of latitude per decade since 1979. However, it is too early to detect robust anthropogenically induced widening imprints due to large internal variability. Future work should target the seasonal and regional signatures of forced widening, as well as the associated dynamical mechanisms.

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Fig. 1: Schematics of the tropical/subtropical atmosphere.
Fig. 2: 1960–2100 modelled versus observed widening for three metrics.
Fig. 3: Factors and mechanisms for tropical expansion.
Fig. 4: Tropical expansion rates in previous studies.

Change history

  • 08 October 2018

    In the version of this Review originally published, the affiliations for author Sean M. Davis were incomplete. An additional affiliation, “Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, Colorado, USA”, has now been added.

References

  1. 1.

    Fu, Q., Johanson, C. M., Wallace, J. M. & Reichler, T. Enhanced mid-latitude tropospheric warming in satellite measurements. Science 312, 1179 (2006).

    CAS  Article  Google Scholar 

  2. 2.

    Seidel, D. J. & Randel, W. J. Recent widening of the tropical belt: evidence from tropopause observations. J. Geophys. Res. Atmos. 112, D20113 (2007).

    Article  Google Scholar 

  3. 3.

    Seidel, D. J., Fu, Q., Randel, W. J. & Reichler, T. J. Widening of the tropical belt in a changing climate. Nat. Geosci. 1, 21–24 (2008).

    Article  Google Scholar 

  4. 4.

    Hudson, R. D., Andrade, M. F., Follette, M. B. & Frolov, A. D. The total ozone field separated into meteorological regimes – Part II: Northern Hemisphere mid-latitude total ozone trends. Atmos. Chem. Phys. 6, 5183–5191 (2006).

    CAS  Article  Google Scholar 

  5. 5.

    Hu, Y. & Fu, Q. Observed poleward expansion of the Hadley circulation since 1979. Atmos. Chem. Phys. 7, 5229–5236 (2007).

    CAS  Article  Google Scholar 

  6. 6.

    Si, D., Ding, Y. & Liu, Y. Decadal northward shift of the Meiyu belt and the possible cause. Chinese Sci. Bull. 54, 4742–4748 (2009).

    Google Scholar 

  7. 7.

    Brönnimann, S. et al. Southward shift of the northern tropical belt from 1945 to 1980. Nat. Geosci. 8, 969–974 (2015).

    Article  CAS  Google Scholar 

  8. 8.

    Post, D. A. et al. Decrease in southeastern Australian water availability linked to ongoing Hadley cell expansion. Earth’s Future 2, 231–238 (2014).

    Article  Google Scholar 

  9. 9.

    Scheff, J. & Frierson, D. Twenty-first-century multimodel subtropical precipitation declines are mostly midlatitude shifts. J. Clim. 25, 4330–4347 (2012).

    Article  Google Scholar 

  10. 10.

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

    CAS  Article  Google Scholar 

  11. 11.

    Polovina, J. J., Howell, E. A. & Abecassis, M. Ocean’s least productive waters are expanding. Geophys. Res. Lett. 35, L03618 (2008).

    Article  Google Scholar 

  12. 12.

    Irwin, A. J. & Oliver, M. J. Are ocean deserts getting larger? Geophys. Res. Lett. 36, L18609 (2009).

    Article  Google Scholar 

  13. 13.

    Moore, J. K. et al. Sustained climate warming drives declining marine biological productivity. Science 359, 1139–1143 (2018).

    CAS  Article  Google Scholar 

  14. 14.

    Studholme, J. & Gulev, S. Concurrent changes to Hadley crculation and the meridional distribution of tropical cyclones. J. Clim. 31, 4367–4389 (2018).

    Article  Google Scholar 

  15. 15.

    Rankin, W. Population Histograms (Radical Cartography, 2008); http://www.radicalcartography.net/index.html?histpop

  16. 16.

    Birner, T., Davis, S. M. & Seidel, D. J. The changing width of Earth’s tropical belt. Phys. Today 67, 38–44 (2014).

    Article  Google Scholar 

  17. 17.

    Lu, J., Vecchi, G. A. & Reichler, T. Expansion of the Hadley cell under global warming. Geophys. Res. Lett. 34, L06805 (2007).

    Google Scholar 

  18. 18.

    Lu, J., Deser, C. & Reichler, T. Cause of the widening of the tropical belt since 1958. Geophys. Res. Lett. 36, L03803 (2009).

    Article  Google Scholar 

  19. 19.

    Staten, P. W., Rutz, J. J., Reichler, T. & Lu, J. Breaking down the tropospheric circulation response by forcing. Clim. Dynam. 39, 2361–2375 (2012).

    Article  Google Scholar 

  20. 20.

    Min, S.-K. & Son, S.-W. Multimodel attribution of the Southern Hemisphere Hadley cell widening: major role of ozone depletion. J. Geophys. Res. Atmos. 118, 3007–3015 (2013).

    CAS  Article  Google Scholar 

  21. 21.

    Waugh, D. W., Garfinkel, C. I. & Polvani, L. M. Drivers of the recent tropical expansion in the Southern Hemisphere: changing SSTs or ozone depletion? J. Clim. 28, 6581–6586 (2015).

    Article  Google Scholar 

  22. 22.

    Kim, Y.-H., Min, S.-K., Son, S.-W. & Choi, J. Attribution of the local Hadley cell widening in the Southern Hemisphere. Geophys. Res. Lett. 1015–1024 (2017).

    Article  Google Scholar 

  23. 23.

    Davis, N. & Birner, T. On the discrepancies in tropical belt expansion between reanalyses and climate models and among tropical belt width metrics. J. Clim. 30, 1211–1231 (2016).

    Article  Google Scholar 

  24. 24.

    Homeyer, C. R. & Bowman, K. P. Rossby wave breaking and transport between the tropics and extratropics above the subtropical jet. J. Atmos. Sci. 70, 607–626 (2012).

    Article  Google Scholar 

  25. 25.

    Waugh, D. W. et al. Revisiting the relationship among metrics of tropical expansion. J. Clim. 31, 7565–7581 (2018).

    Article  Google Scholar 

  26. 26.

    Birner, T. Recent widening of the tropical belt from global tropopause statistics: sensitivities. J. Geophys. Res. Atmos. 115, D23109 (2010).

    Article  Google Scholar 

  27. 27.

    Davis, S. M. & Rosenlof, K. H. A multidiagnostic intercomparison of tropical-width time series using reanalyses and satellite observations. J. Clim. 25, 1061–1078 (2011).

    Article  Google Scholar 

  28. 28.

    Davis, N. A., Davis, S. M. & Waugh, D. W. New insights into tropical belt metrics. Variations 16, 1–7 (2018).

    Google Scholar 

  29. 29.

    Solomon, A., Polvani, L. M., Waugh, D. W. & Davis, S. M. Contrasting upper and lower atmospheric metrics of tropical expansion in the Southern Hemisphere. Geophys. Res. Lett. 43, 10496–10503 (2016).

    Article  Google Scholar 

  30. 30.

    Fu, Q. & Lin, P. Poleward shift of subtropical jets inferred from satellite-observed lower-stratospheric temperatures. J. Clim. 24, 5597–5603 (2011).

    Article  Google Scholar 

  31. 31.

    Manney, G. L. & Hegglin, M. I. Seasonal and regional variations of long-term changes in upper-tropospheric jets from reanalyses. J. Clim. 31, 423–448 (2017).

    Article  Google Scholar 

  32. 32.

    Zurita-Gotor, P. & Álvarez-Zapatero, P. Coupled interannual variability of the Hadley and Ferrel cells. J. Clim. 31, 4757–4773 (2018).

    Article  Google Scholar 

  33. 33.

    Amaya, D. J., Siler, N., Xie, S.-P., & Miller, A. J. The interplay of internal and forced modes of Hadley Cell expansion: lessons from the global warming hiatus. Clim. Dynam. 305–319 (2017)..

    Article  Google Scholar 

  34. 34.

    Allen, R. J., Sherwood, S. C., Norris, J. R. & Zender, C. S. Recent Northern Hemisphere tropical expansion primarily driven by black carbon and tropospheric ozone. Nature 485, 350–354 (2012).

    CAS  Article  Google Scholar 

  35. 35.

    Allen, R. J., Norris, J. R. & Kovilakam, M. Influence of anthropogenic aerosols and the Pacific decadal oscillation on tropical belt width. Nat. Geosci. 7, 270–274 (2014).

    CAS  Article  Google Scholar 

  36. 36.

    Hu, Y., Zhou, C. & Liu, J. Observational evidence for poleward expansion of the Hadley circulation. Adv. Atmos. Sci. 28, 33–44 (2011).

    CAS  Article  Google Scholar 

  37. 37.

    Hu, Y., Tao, L. & Liu, J. Poleward expansion of the Hadley circulation in CMIP5 simulations. Adv. Atmos. Sci. 30, 790–795 (2013).

    Article  Google Scholar 

  38. 38.

    Grise, K. M., Davis, S. M. & Staten, P. W. Regional and seasonal characteristics of the recent expansion of the tropics. J. Clim. https://doi.org/10.1175/JCLI-D-18-0060.1 (2018).

    Article  Google Scholar 

  39. 39.

    McGraw, M. C. & Barnes, E. A. Seasonal sensitivity of the eddy-driven jet to tropospheric heating in an idealized AGCM. J. Clim. 29, 5223–5240 (2016).

    Article  Google Scholar 

  40. 40.

    Johanson, C. M. & Fu, Q. Hadley cell widening: model simulations versus observations. J. Clim. 22, 2713–2725 (2009).

    Article  Google Scholar 

  41. 41.

    Tao, L., Hu, Y. & Liu, J. Anthropogenic forcing on the Hadley circulation in CMIP5 simulations. Clim. Dynam. 46, 3337–3350 (2016).

    Article  Google Scholar 

  42. 42.

    Allen, R. J. & Kovilakam, M. The role of natural climate variability in recent tropical expansion. J. Clim. 30, 6329–6350 (2017).

    Article  Google Scholar 

  43. 43.

    Mantsis, D. F., Sherwood, S., Allen, R. & Shi, L. Natural variations of tropical width and recent trends. Geophys. Res. Lett. 44, 3825–3832 (2017).

    Article  Google Scholar 

  44. 44.

    Perlwitz, J. Tug of war on the jet stream. Nat. Clim. Change 1, 29–31 (2011).

    Article  Google Scholar 

  45. 45.

    Held, I. M., Salmon, R., Fields, J. & Thiffeault, J.-L. in The General Circulation of the Atmosphere: 2000 Program in Geophysical Fluid Dynamics Technical Report No. WHOI-2001-03 1–54 (Woods Hole Oceanographic Institute, 2000); http://hdl.handle.net/1912/15

  46. 46.

    Korty, R. L. & Schneider, T. Extent of Hadley circulations in dry atmospheres. Geophys. Res. Lett. 35, L23803 (2008).

    Article  Google Scholar 

  47. 47.

    Son, S.-W., Tandon, N. F., Polvani, L. M. & Waugh, D. W. Ozone hole and Southern Hemisphere climate change. Geophys. Res. Lett. 36, L15705 (2009).

    Article  Google Scholar 

  48. 48.

    Polvani, L. M., Waugh, D. W., Correa, G. J. P. & Son, S.-W. Stratospheric ozone depletion: the main driver of twentieth-century atmospheric circulation changes in the Southern Hemisphere. J. Clim. 24, 795–812 (2010).

    Article  Google Scholar 

  49. 49.

    Son, S.-W. et al. Impact of stratospheric ozone on Southern Hemisphere circulation change: A multimodel assessment. J. Geophys. Res. Atmos. 115, D00M07 (2010).

    Article  Google Scholar 

  50. 50.

    Lucas, C., Nguyen, H. & Timbal, B. An observational analysis of Southern Hemisphere tropical expansion. J. Geophys. Res. Atmos. 117, D17112 (2012).

    Article  Google Scholar 

  51. 51.

    Robock, A., Adams, T., Moore, M., Oman, L. & Stenchikov, G. Southern Hemisphere atmospheric circulation effects of the 1991 Mount Pinatubo eruption. Geophys. Res. Lett. 34, L23710 (2007).

    Article  Google Scholar 

  52. 52.

    Barnes, E. A., Solomon, S. & Polvani, L. M. Robust wind and precipitation responses to the Mount Pinatubo eruption, as simulated in the CMIP5 models. J. Clim. 29, 4763–4778 (2016).

    Article  Google Scholar 

  53. 53.

    Kovilakam, M. & Mahajan, S. Confronting the “Indian summer monsoon response to black carbon aerosol” with the uncertainty in its radiative forcing and beyond. J. Geophys. Res. Atmos. 121, 7833–7852 (2016).

    CAS  Article  Google Scholar 

  54. 54.

    Allen, R. J. & Ajoku, O. Future aerosol reductions and widening of the northern tropical belt. J. Geophys. Res. Atmos. 121, 6765–6786 (2016).

    Article  Google Scholar 

  55. 55.

    Bonfils, C. & Santer, B. D. Investigating the possibility of a human component in various Pacific decadal oscillation indices. Clim. Dynam. 37, 1457–1468 (2011).

    Article  Google Scholar 

  56. 56.

    Newman, M. et al. The Pacific decadal oscillation, revisited. J. Clim. 29, 4399–4427 (2016).

    Article  Google Scholar 

  57. 57.

    Xu, Y. & Hu, A. How would the twenty-first-century warming influence Pacific decadal variability and its connection to North American rainfall: assessment based on a revised procedure for the IPO/PDO. J. Clim. 31, 1547–1563 (2017).

    Article  Google Scholar 

  58. 58.

    Wills, R. C., Schneider, T., Wallace, J. M., Battisti, D. S. & Hartmann, D. L. Disentangling global warming, multidecadal variability, and El Niño in Pacific temperatures. Geophys. Res. Lett. 45, 2487–2496 (2018).

    Article  Google Scholar 

  59. 59.

    Simpson, I. R. Natural variability in the width of the tropics. Variations 16, 14–20 (2018).

    Google Scholar 

  60. 60.

    Lu, J., Chen, G. & Frierson, D. M. W. Response of the zonal mean atmospheric circulation to El Niño versus global warming. J. Clim. 21, 5835–5851 (2008).

    Article  Google Scholar 

  61. 61.

    Chen, G., Lu, J. & Frierson, D. M. W. Phase speed spectra and the latitude of surface westerlies: interannual variability and global warming trend. J. Clim. 21, 5942–5959 (2008).

    Article  Google Scholar 

  62. 62.

    Lau, N.-C. & Nath, M. J. A model study of heat waves over North America: meteorological aspects and projections for the twenty-first century. J. Clim. 25, 4761–4784 (2012).

    Article  Google Scholar 

  63. 63.

    Nguyen, H., Lucas, C., Evans, A., Timbal, B. & Hanson, L. Expansion of the Southern Hemisphere Hadley cell in response to greenhouse gas forcing. J. Clim. 28, 8067–8077 (2015).

    Article  Google Scholar 

  64. 64.

    Seager, R., Harnik, N., Kushnir, Y., Robinson, W. & Miller, J. Mechanisms of hemispherically symmetric climate variability. J. Clim. 16, 2960–2978 (2016).

    Article  Google Scholar 

  65. 65.

    Garfinkel, C. I., Waugh, D. W. & Polvani, L. M. Recent Hadley cell expansion: the role of internal atmospheric variability in reconciling modeled and observed trends. Geophys. Res. Lett. 42, 10824–10831 (2015).

    Article  Google Scholar 

  66. 66.

    Eyring, V. et al. Multimodel projections of stratospheric ozone in the 21st century. J. Geophys. Res. Atmos. 112, D16303 (2007).

    Article  CAS  Google Scholar 

  67. 67.

    McLandress, C. et al. Separating the dynamical effects of climate change and ozone depletion. Part II: Southern Hemisphere troposphere. J. Clim. 24, 1850–1868 (2010).

    Article  Google Scholar 

  68. 68.

    Simpson, I. R., Shaw, T. A. & Seager, R. A diagnosis of the seasonally and longitudinally varying midlatitude circulation response to global warming. J. Atmos. Sci. 71, 2489–2515 (2014).

    Article  Google Scholar 

  69. 69.

    Quan, X.-W., Hoerling, M. P., Perlwitz, J., Diaz, H. F. & Xu, T. How fast are the tropics expanding? J. Clim. 27, 1999–2013 (2013).

    Article  Google Scholar 

  70. 70.

    Barnes, E. A. Revisiting the evidence linking Arctic amplification to extreme weather in midlatitudes. Geophys. Res. Lett. 40, 4734–4739 (2013).

    Article  Google Scholar 

  71. 71.

    Grise, K. M. & Polvani, L. M. Is climate sensitivity related to dynamical sensitivity? J. Geophys. Res. Atmos. 121, 5159–5176 (2016).

    Article  Google Scholar 

  72. 72.

    Schmidt, D. F. & Grise, K. M. The response of local precipitation and sea level pressure to Hadley cell expansion. Geophys. Res. Lett. 44, 10,510–573,582 (2017).

    Article  Google Scholar 

  73. 73.

    Huang, R., Chen, S., Chen, W. & Hu, P. Interannual variability of regional Hadley circulation intensity over Western Pacific during boreal winter and its climatic impact over Asia‐Australia region. J. Geophys. Res. Atmos. 123, 344–366 (2017).

    Article  Google Scholar 

  74. 74.

    Zhang, H. & Delworth, T. L. Detectability of decadal anthropogenic hydroclimate changes over North America. J. Clim. 31, 2579–2597 (2018).

    Article  Google Scholar 

  75. 75.

    Hartmann, D.L. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) Ch. 2 (IPCC, Cambridge Univ. Press, 2013).

  76. 76.

    Choi, J., Son, S.-W., Lu, J. & Min, S.-K. Further observational evidence of Hadley cell widening in the Southern Hemisphere. Geophys. Res. Lett. 41, 2590–2597 (2014).

    Google Scholar 

  77. 77.

    Lucas, C. & Nguyen, H. Regional characteristics of tropical expansion and the role of climate variability. J. Geophys. Res. Atmos. 120, 6809–6824 (2015).

    Article  Google Scholar 

  78. 78.

    Lamarque, J.-F. & Solomon, S. Impact of changes in climate and halocarbons on recent lower stratosphere ozone and temperature trends. J. Clim. 23, 2599–2611 (2010).

    Article  Google Scholar 

  79. 79.

    Archer, C. L. & Caldeira, K. Historical trends in the jet streams. Geophys. Res. Lett. 35, L08803 (2008).

    Google Scholar 

  80. 80.

    Zhou, Y. P., Xu, K.-M., Sud, Y. C. & Betts, A. K. Recent trends of the tropical hydrological cycle inferred from Global Precipitation Climatology Project and International Satellite Cloud Climatology Project data. J. Geophys. Res. Atmos. 116, D09101 (2011).

    Google Scholar 

  81. 81.

    Schneider, E. K. & Lindzen, R. S. Axially symmetric steady-state models of the basic state for instability and climate studies. Part I. Linearized calculations. J. Atmos. Sci. 34, 263–279 (1977).

    Article  Google Scholar 

  82. 82.

    Held, I. M. & Hou, A. Y. Nonlinear axially symmetric circulations in a nearly inviscid atmosphere. J. Atmos. Sci. 37, 515–533 (1980).

    Article  Google Scholar 

  83. 83.

    Lindzen, R. S. & Hou, A. V. Hadley circulations for zonally averaged heating centered off the Equator. J. Atmos. Sci. 45, 2416–2427 (1988).

    Article  Google Scholar 

  84. 84.

    Robinson, W. A. On the midlatitude thermal response to tropical warmth. Geophys. Res. Lett. 29, 31–34 (2002).

    Article  Google Scholar 

  85. 85.

    Walker, C. C. & Schneider, T. Eddy influences on Hadley circulations: simulations with an idealized GCM. J. Atmos. Sci. 63, 3333–3350 (2006).

    Article  Google Scholar 

  86. 86.

    Rodrigo, C. Role of eddies in the interannual variability of Hadley cell strength. Geophys. Res. Lett. 34, L22705 (2007).

    Article  Google Scholar 

  87. 87.

    Palmén, E. & Newton, C. W. Atmospheric circulation systems: their structural and physical interpretation. Science 167, 972 (1970).

    Google Scholar 

  88. 88.

    Schneider, T., O’Gorman, P. A. & Levine, X. J. Water vapor and the dynamics of climate changes. Rev. Geophys. 48, RG3001 (2010).

    Article  Google Scholar 

  89. 89.

    Lu, J., Chen, G. & Frierson, D. M. W. The position of the midlatitude storm track and eddy-driven westerlies in aquaplanet AGCMs. J. Atmos. Sci. 67, 3984–4000 (2010).

    Article  Google Scholar 

  90. 90.

    Yin, J. H. A consistent poleward shift of the storm tracks in simulations of 21st century climate. Geophys. Res. Lett. 32, L18701 (2005).

    Article  CAS  Google Scholar 

  91. 91.

    Brayshaw, D. J., Hoskins, B. & Blackburn, M. The storm-track response to idealized SST perturbations in an aquaplanet GCM. J. Atmos. Sci. 65, 2842–2860 (2008).

    Article  Google Scholar 

  92. 92.

    Sampe, T., Nakamura, H., Goto, A. & Ohfuchi, W. Significance of a midlatitude SST frontal zone in the formation of a storm track and an eddy-driven westerly jet. J. Clim. 23, 1793–1814 (2009).

    Article  Google Scholar 

  93. 93.

    Rivière, G. A dynamical interpretation of the poleward shift of the jet streams in global warming scenarios. J. Atmos. Sci. 68, 1253–1272 (2011).

    Article  Google Scholar 

  94. 94.

    Tandon, N. F., Gerber, E. P., Sobel, A. H. & Polvani, L. M. Understanding Hadley cell expansion versus contraction: insights from simplified models and implications for recent observations. J. Clim. 26, 4304–4321 (2012).

    Article  Google Scholar 

  95. 95.

    Chen, G. & Held, I. M. Phase speed spectra and the recent poleward shift of Southern Hemisphere surface westerlies. Geophys. Res. Lett. 34, L21805 (2007).

    Article  Google Scholar 

  96. 96.

    Williams, G. P. Circulation sensitivity to tropopause height. J. Atmos. Sci. 63, 1954–1961 (2006).

    Article  Google Scholar 

  97. 97.

    Lorenz, D. J. Understanding midlatitude jet variability and change using Rossby wave chromatography: poleward-shifted jets in response to external forcing. J. Atmos. Sci. 71, 2370–2389 (2014).

    Article  Google Scholar 

  98. 98.

    Wittman, M. A. H., Charlton, A. J. & Polvani, L. M. the effect of lower stratospheric shear on baroclinic instability. J. Atmos. Sci. 64, 479–496 (2007).

    Article  Google Scholar 

  99. 99.

    Kidston, J. & Vallis, G. K. The relationship between the speed and the latitude of an eddy-driven jet in a stirred barotropic model. J. Atmos. Sci. 69, 3251–3263 (2012).

    Article  Google Scholar 

  100. 100.

    Lu, J., Sun, L., Wu, Y. & Chen, G. The role of subtropical irreversible PV mixing in the zonal mean circulation response to global warming-like thermal forcing. J. Clim. 27, 2297–2316 (2013).

    Article  Google Scholar 

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Acknowledgements

P.W.S., K.M.G., T.B. and S.M.D. are members of working groups related to the topic of this review—the International Space Science Institute (ISSI) Tropical Width Diagnostics Intercomparison Project and the US Climate Variability and Predictability Program (US CLIVAR) Changing Width of the Tropical Belt Working Group. We thank the the ISSI and US CLIVAR offices, and sponsoring agencies (the ESA, Swiss Confederation, Swiss Academy of Sciences, University of Bern, NASA, NOAA, NSF and DOE) for supporting these groups and activities. J.L. is supported by the US Department of Energy Office of Science Biological and Environmental Research (BER) as part of the Regional and Global Climate Modeling Program. We acknowledge F. Liu for his assistance in drawing Fig. 4.

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P.W.S. wrote and revised the majority of the paper. J.L. contributed to the writing, produced the summary figure and produced the schematic figures with help from a graphic designer at PNNL. K.M.G. contributed to the writing, and created the time series plot. S.M.D. and T.B. both contributed to the writing and revision of the paper.

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Correspondence to Jian Lu.

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Staten, P.W., Lu, J., Grise, K.M. et al. Re-examining tropical expansion. Nature Clim Change 8, 768–775 (2018). https://doi.org/10.1038/s41558-018-0246-2

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