The impact of indicator selection on assessment of global greening

Figures & data

Figure 1. The methodology framework

Notes: The red dots in vegetation indicators time series represented the annual maximum, which revealed the annual peak growth. Greening (G), Browning (B), No trend (N) in the 3*3 grid-denoted greening, browning, or no trend when estimated by one indicator. Consistent Greening (CG), Consistent Browning (CB), and Consistent No trend (CN) indicated that vegetation trends from both indicators exhibited greening, browning, or no trends, respectively. Inconsistent results represented that vegetation trends from both indicators did not agree with each other. Unanimous Greening (UG), Unanimous Browning (UB), unanimous no trend (UN) denoted that vegetation trends from six indicators all showed greening, browning, or no trends, respectively. Discrepant result (DR) represented that vegetation trends from six indicators was discrepant.

Figure 2. Maps of trends in six vegetation indicators (a-f), and the corresponding greening, browning, and net greening (g-i)

Notes: ENF, EBF, DNF, DBF, MF, and OWV represented the evergreen needle-leaf forest, evergreen broad-leaf forest, deciduous needle-leaf forest, deciduous broad-leaf forest, mixed forest, and other woody vegetation, respectively. MOD and PML denoted the MOD-GPP and PML-GPP, respectively.

Figure 3. (a) Maps of proportions of unanimous greening, (b) and browning at country level, (c) probability distribution of change magnitudes; (d) and their associations with proportion of unanimous results; (e) net changes at country level; (f) major discrepancy

Notes: “MOD-GPP↑” denoted an increasing trend from MOD-GPP versus no trends from other vegetation indicators. “PML-GPP↓” represented a decreasing trend in peak vegetation growth from PML-GPP versus no trends from other vegetation indicators, etc.

Figure 4. (a) Concordance ratios between different indicators at the global scale; (b) and under changes in climate; (c) boxplots of greening and browning under changes in climate (warming or cooling conditions, wetting or drying)

Notes: In Figure 4(a), ENF, EBF, DNF, DBF, MF, and OWV represented the evergreen needle-leaf forest, evergreen broad-leaf forest, deciduous needle-leaf forest, deciduous broad-leaf forest, mixed forest, and other woody vegetation, respectively. MOD and PML denoted the MOD-GPP and PML-GPP, respectively. In Figure 4(b), the global average values in each pair of indicators were shaded in gray. In Figure 4(c), the white line parallel to the x-axis represented the medium level of changes in climatic variables.

Figure 5. Inter-annual variations of six vegetation indicators and climatic variables globally (a) and across different latitudes (c-f)

Notes: In order to facilitate the comparability between different indicators, the original annual time series of six vegetation indicators were normalized through subtracting the mean divided by its corresponding standard derivations. The gray area indicates the mean values of six indicators. Some abnormal years with climatic extremes were highlighted in pink.