Int. J. Environ. Res. Public Health 2020, 17, 1062 8 of 22
Table 1. Cont.
No. #Climatechange #Globalwarming
Hashtag Centrality Hashtag Centrality
23 co2 0.174 snow 0.161
24 weather 0.169 world 0.157
25 solar 0.165 gop * 0.156
26 economy 0.164 arctic 0.150
27 auspol 0.163 * winter 0.145
28 education 0.155 p2 * 0.144
29 news 0.152 drought 0.142
30 drought 0.150 epa * 0.141
31 coal 0.147 global 0.137
32 sustainable 0.147 eco 0.137
33 cdnpoli 0.144 * actonclimate 0.136
34 sdgs 0.143 * health 0.134
35 china 0.143 un * 0.133
36 gop 0.143 * solar 0.132
37 food 0.141 economy 0.131
38 un 0.141 * hoax 0.131
39 cop24 * 0.140 california 0.130
40 agriculture 0.138 politics 0.129
41 environmental 0.136 india 0.128
42 fossilfuels 0.134 china 0.127
43 arctic 0.134 planet 0.127
44 epa * 0.133 parisagreement * 0.126
45 biodiversity 0.132 heatwave 0.125
46 future 0.131 summer 0.121
47 canada 0.128 nyc * 0.118
48 emissions 0.128 nasa 0.118
49 obama 0.127 future 0.118
50 politics 0.125 oil 0.117
4.2. Association Network Analysis
The association networks of #climatechange and #globalwarming are shown in Figure 2. Nodes
are labelled with the hashtags and the undirected edges are weighted to reﬂect the frequency of
co-occurrence. The modularity analysis identiﬁed four clusters in the #climatechange network and
ﬁve in the #globalwarming network, where clusters are diﬀerentiated by color (resolution is 0.75 for
climate change and 0.85 for global warming). The theme, top hashtags, and the proportion of each
cluster are also summarized and represented in the network depicted in Figure 2.
The largest cluster (green nodes) of both #climatechange and #globalwarming network refer
to general facts about global climate issues, sharing words about the causes or e ﬀects concerning
sustainability. The diﬀerence is that the largest cluster of #globalwarming (46% of the network) includes
more slogan words, such as “world”, “planet”, “global”, and “climatechangeisreal”, whereas the
largest cluster of #climatechange (40% of the network) tends to discuss some speciﬁc problems, such as
agriculture, biodiversity, education, and politics.
For the climate change discourse, the second-largest cluster (34%) is indicated in red and focuses
on the responsibility to tackle climate change, where several global action hashtags are included, such
as “un”, “parisagreement”, “cop21”, and “cop24”. The theme of the third largest cluster (20%) in
the climate change discourse was energy (in blue). The smallest cluster (6%) in yellow sits in the
central part of the network with a mixed theme composed of three highly ranked hashtags, including
“environment” (No. 2), “climateaction” (No. 3), and “energy” (No. 6).