Satellites reveal contrasting responses of regional climate to the widespread greening of Earth

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Science  16 Jun 2017:
Vol. 356, Issue 6343, pp. 1180-1184
DOI: 10.1126/science.aal1727
  • Fig. 1 Relative interannual variations of LAI and the components of the surface energy balance across climatological gradients.

    (A to H) Global relative variations in annual longwave outgoing (ΔLWout), absorbed radiation (ΔRα), latent heat flux (ΔLE), and sensible heat flux (ΔH) are illustrated against the interannual relative variations in leaf area index (ΔLAI, y axis) and the climatological median of air temperature [Ta, x axis, in (A), (C), (E), (G), respectively] and precipitation [P, x axis, in (B), (D), (F), (H), respectively] (supplementary text S2, materials and methods).

  • Fig. 2 Climate anomalies and relationship between surface energy balance terms and LAI.

    (A to D) Ratios of interannual variations in energy fluxes [(A) ΔLWout, (B) ΔRα, (C) ΔLE, and (D) ΔH] to ΔLAI expressed as a function of the empirical cumulative probabilities of the anomalies in precipitation [FP), x axis] and air temperature [FTa), y axis]. F close to zero indicates extremes with low values of the climate variables, equivalent to cold-dry anomalies, and F close to one indicates extremes with high values, equivalent to warm-wet anomalies.

  • Fig. 3 Long-term trends in LAI and associated changes in surface temperature.

    (A) Spatial map of the satellite-based LAI trends (δLAI; 1982–2011). Areas labeled with black dots indicate trends that are statistically significant (Mann-Kendall test; P < 0.05) (supplemenatry text S5, materials and methods). (B) Zonal median of LAI trends at 5° latitudinal resolution and corresponding interquartile range shown as a black line and gray shaded band, respectively. (C) Trends in LAI binned as a function of climatological medians of precipitation (P, x axis) and air temperature (Ta, y axis). (D to F) Same as (A) to (C), but for the sensitivity of mean daily surface temperature to LAI (Embedded Image). Latitudinal profiles of daily, nighttime, and daytime surface temperatures are shown in (E) in black, blue, and red, respectively. (G to I) Same as (D) to (F), but for the trends in daily surface temperature (Embedded Image) related to variations in LAI, as computed with Eq. 2.

  • Fig. 4 Biophysical effects of the global greening on recent temperature trends.

    (A) Variation in LAI, LAI-related surface temperature (Embedded Image), overall land surface temperature (TS), and air temperature (Ta) expressed with respect to the first observational year (1982) and spatially aggregated over cold-wet regions (annual Ta < 280 K and P > 800 mm). Regression lines are overlaid for each variable, and corresponding coefficients of determination are reported in the label (supplementary text S7, materials and methods). (B) As (A), but for warm regions (annual Ta > 290 K). (C) Relations between the long-term trend in air temperature (δTa, on the x axis) and the LAI-related trend in surface temperature (Embedded Image, on the y axis) spatially aggregated for different biomes. Upward- and downward-pointing triangles indicate positive and negative sensitivity of TS to LAI (Embedded Image), respectively. The size of the triangle refers to absolute value of sensitivity. Spatial domains of biomes are shown in fig. S6.

Supplementary Materials

  • Satellites reveal contrasting responses of regional climate to the widespread greening of Earth

    Giovanni Forzieri, Ramdane Alkama, Diego G. Miralles, Alessandro Cescatti

    Materials/Methods, Supplementary Text, Tables, Figures, and/or References

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    • Materials and Methods
    • Figs. S1 to S11
    • Table S1 and S2
    • References

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