text: In the global warming network, politics was the second-largest discourse cluster (20% of the 
  network), where “tcot”, short for “Top Conservatives on Twitter”, was the node ranked highest, 
  and “p2”, short for “Progressives 2.0”, is also included. Several political ﬁgures, such as Obama and Al 
  Gore, are frequently mentioned. Action toward the global climate issue was the third-largest cluster 
  (16%), including both domestic eﬀorts, such as “us”, “trump”, “climatechangeisreal”, “climateaction”, 
  and “epa”, and two international items, like “china” and “india”. The fourth cluster (in blue) referred 
  to emissions, including hashtags like “co2”, “green”, and “carbon”. The smallest cluster (8%) was 
  composed of “snow”, “winter”, “heatwave”, and “summer”, referring to the temperature abnormalities 
  on the earth. 
  
  4.3. Temporal Analysis of the Associations in the Two Discourses 
  
  The online presentations of the climate change and global warming discourses are dynamic. 
  As shown in Table 2, for the global warming discourse, 11 key concepts remained in the top 50 central 
  hashtags each year for all 10 years, with 16 for the climate change”discourse. By comparing the 11 
  nodes of the global warming discourse and the 16 nodes of the climate change discourse, we found that 
  the two lists shared nine concepts. We found “pollution” and “earth” were unique to the keyword list 
  of the global warming discourse, and “economy”, “water”, “china”, “coal”, “solar”, “sustainability”, 
  and “food” only occurred on the critical list for the climate change discourse. 