text: Large amounts of user-generated data on social media, which have been valued in computer science, 
  communication, and environmental studies [5,9,15–18], have enabled the acquistion of the social media 
  representation of the two discourses in a decade. In this study, by analyzing hashtag co-occurrence 
  patterns in 6,662,478 tweets containing “climate change” and “global warming” between 1 January 2009 
  and 31 December 2018, two semantic networks of public climate discourse were constructed to identify 
  the critical concepts and links surrounding the two terminologies. We conducted temporal analysis to 
  observe the evolution of the two discourses and to measure whether the discrepancy between the two 
  has widened or narrowed within the 10-year period. 
  
  To be speciﬁc, we formulated three research questions (RQs) to be explored in this study: 
  
  RQ1: What is the diﬀerence in how the two the discourses are associated with important climate 
  concepts in people’s minds? 
  RQ2: How did the two competing climate discourses evolve from 2009 to 2018? 
  RQ3: Did the two competing discourses converge or diverge in this decade? 