text: then the associations suddenly strengthened in 2012 when numerous hashtags about phenomena were 
  included in the discourse. Notably, the red node in the top right-hand corner named “2012” refers 
  to the Maya prediction that the year 2012 would be the end of the world and that the world would 
  be destroyed by extreme natural events, and was linked to other climate hashtags for the ﬁrst time 
  in the graph exactly in 2012. The blue nodes included the political hashtags, such as “maga”, “ows”, 
  “p2”, “tcot”, and “obama”. The involvement of political hashtags in the global warming discourse was 
  signiﬁcantly higher than that in the climate change discourse according to the comparison between 
  Figure 5a,b. From 2009 to 2018, the number of associations with political hashtags (blue nodes) faded, 
  as shown in Figure 4, and its importance in the semantic network gradually decreased, as shown in 
  Figure 5, except for variation in 2014. The yellow nodes describe the hesitation about climate facts 
  and actions, where words describing global eﬀorts, such as “ipcc”, “cop15”, and “un”, and words 
  questioning global warming, such as “hoax” and “fraud”, were both included. The associations 
  between the yellow nodes were most salient in 2010 and 2011 but were less dominant in the following 
  years. The green nodes occupied 50.7% of all the nodes representing talk about the scientiﬁc hashtags of 
  climate issue, including words such as “ecology”, “ocean”, and “cleanenergy”. Associations between 
  scientiﬁc hashtags (green nodes) exploded and the centrality sum of this cluster also showed an obvious 
  rising trend in dominating the theme of the global warming discourse, according to Figure 5. 