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.