Trends of low-cloud fraction

Our results reveal that the ΔCF on global landmasses ranges between -104.2 ×10-4and 68.7 ×10-4 CF year-1(Fig. 1 ), with a mean that decays (i.e., becomes negative) over time at the rate of -7.4 ×10-4 CF year-1. On tropical landmasses between the Tropic of Cancer and Capricorn, ΔCF ranges between -104.2 ×10-4and 61.2 ×10-4 CF year-1, with a mean rate of -13.9 ×10-4 CF year-1(Fig. 2 ). The ΔCF distribution of these tropical landmasses appeared to have negative skewness (skewness: -1.75). Thus, the peak value of their density distribution (-2.3 ×10-4 CF year-1) is likely to be a better descriptor of the overall trends that prevail in the region. At the TMCFs, specifically, ΔCF ranges between -64.7 ×10-4 and 51.4 ×10-4 CF year-1 with a peak density distribution value 235% lower (-7.8 ×10-4 CF year-1) than that of the tropical landmasses. The mean estimate of ΔCF in these ecosystems indicated a rate of change of -6.49 ×10-4CF year-1 (CI: -7.69 ×10-4 – -5.31 ×10-4 CF year-1) with a high probability (0.99) of being lower than zero (Table S2). Our trends also revealed that 70% of the evaluated sites showed negative ΔCF; however, this percentage appears to differ among biogeographic realms. For instance, 79.1% of the Neotropic TMCF present negative ΔCF, while at the Indomalayan, Palearctic, and Australasia realms, the percentages are lower (70.6%, 60.0%, and 47.4%, respectively). A comparison of the peak values of the distributions (Fig. 2 ), Neotropic and Indomalayan TMCFs show ΔCF that are 346% (-10.4 ×10-4CF year-1) and 266% (-8.55 ×10-4 CF year-1) lower than that of tropical landmasses. Mean estimates of ΔCF at these realms indicate rates of -11.33 ×10-4 CF year-1 (CI: -13.23 ×10-4 – -9.45 ×10-4 CF year-1) and -4.90 ×10-4 CF year-1 (CI: -7.11 ×10-4 – -2.75 ×10-4 CF year-1), respectively with a high probability (0.99) of being lower than zero (Table S3 ). Less contrasting, Australasia and Palearctic TMCFs present peak values of distribution that are 128% (-5.25 ×10-4 CF year-1) and 78% (-4.16 ×10-4 CF year-1) lower than that of tropical landmasses. Despite this, mean estimates of ΔCF at Australasia’s TMCFs are more likely to be higher than zero (0.87) with rates of changes of 2.60 ×10-4 CF year-1 (CI: -2.07 ×10-4 – 7.19 ×10-4 CF year-1). Although many Palearctic’s TMCFs show positive and negative trends of ΔCF, there is a high probability (0.95) that the mean estimate at this macro-ecological region is lower than zero (μ: -1.51 ×10-4 CF year-1; CI: -3.30 ×10-4 – 0.36 ×10-4 CF year-1). The only TMCF present in Oceania has a trend of 5.9 ×10-4 CF year-1.