Extreme heat effects on wheat senescence in India

Journal name:
Nature Climate Change
Year published:
Published online

An important source of uncertainty in anticipating the effects of climate change on agriculture is limited understanding of crop responses to extremely high temperatures1, 2. This uncertainty partly reflects the relative lack of observations of crop behaviour in farmers’ fields under extreme heat. We used nine years of satellite measurements of wheat growth in northern India to monitor rates of wheat senescence following exposure to temperatures greater than 34°C. We detect a statistically significant acceleration of senescence from extreme heat, above and beyond the effects of increased average temperatures. Simulations with two commonly used process-based crop models indicate that existing models underestimate the effects of heat on senescence. As the onset of senescence is an important limit to grain filling, and therefore grain yields, crop models probably underestimate yield losses for +2°C by as much as 50% for some sowing dates. These results imply that warming presents an even greater challenge to wheat than implied by previous modelling studies, and that the effectiveness of adaptations will depend on how well they reduce crop sensitivity to very hot days.

At a glance


  1. The study region of the IGP in northern India.
    Figure 1: The study region of the IGP in northern India.

    a, The location of the main study area (outlined) and names of three primary states. b, The green-up date (day of year) estimated by MODIS for harvest year 2001. c, The green-season length (days from green-up to senescence) estimated by MODIS for the same year. White areas indicate grid cells with less than 40% wheat, which were not included in this study. A total of 1,638,127 individual estimates of green-up and season length were used over the study period.

  2. The effects of GDD and EDD on GSL in the study area for 2000-2009.
    Figure 2: The effects of GDD and EDD on GSL in the study area for 2000–2009.

    a, Average GSL for grid cells with green-up on the week centred on 11 December, shown for different GDD and for the top (red) and bottom (blue) quartile of EDD at each GDD. High GDD shortens GSL (up to ~2,600°C per day), and high EDD results in further shortening. Shading indicates ±2σ. b, Estimated coefficients for GDD, EDD and growing season precipitation (PRE) in a regression to predict GSL for three common green-up dates using MODIS data. Error bars indicate 5–95% confidence interval, which accounts for heteroskedatic and spatially autocorrelated errors. Coefficients for GDD and EDD remained significantly negative (p<0.05) after including district-level fixed effects (Supplementary Table S1) or using an alternative satellite data set (Supplementary Fig. S3). Number of observations (n)=209,391, n=253,767 and n=165,257 for the three respective dates.

  3. Comparison of MODIS-based responses to crop models.
    Figure 3: Comparison of MODIS-based responses to crop models.

    a, Estimated response of season length to +2°C warming based on regression coefficients from MODIS analysis (shown in Fig. 2b) and two common crop models (CERES-Wheat and APSIM-Wheat). b, The same as in a but showing percentage estimated yield losses. As we did not estimate yields directly with MODIS, the yield losses for MODIS were based on the relationship between season-length shortening and yield loss as simulated by CERES. Error bars in both panels show 5–95% confidence interval based on 1,000 bootstrap samples for MODIS estimates and 5–95% interval for 27 simulations (three sites, nine years) for the crop models.


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Author information


  1. Department of Environmental Earth System Science and Program on Food Security and the Environment, Stanford University, Stanford, California 94305, USA

    • David B. Lobell &
    • Adam Sibley
  2. International Maize and Wheat Improvement Center (CIMMYT), Global Conservation Agriculture Program, Apdo. Postal 6-641, 06600 Mexico D.F., Mexico

    • J. Ivan Ortiz-Monasterio


D.B.L. conceived the study, D.B.L. and A.S. analysed data, A.S. carried out crop model simulations, and D.B.L., A.S. and J.I.O-M. interpreted results and wrote the paper.

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The authors declare no competing financial interests.

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