as these two hashtags exactly correspond to climate change and global warming, respectively, the two
competing deﬁnitions of climate issues. We did not follow [ 79] to include #AGW (anthropogenic
global warming) as query hashtags in our research because we think that this refers to global
warming in a deﬁned category so cannot be regarded in parallel with the two considered hashtags.
We limited the scope of the search to English-language tweets generated between 1 January 2009
and 31 December 2018. We only collected tweets containing either of the two hashtags in the body
of the tweets rather than those containing these hashtags in the retweeted or quoted text, as we
think that retweeted text or quoted texts cannot directly represent the tweeter’s usage pattern of the
two terminologies.
To collect these tweets, we used a Python-based crawler to send requests to the Twitter server to
select hashtags, language, start date, and end date as inputs. Once the ﬁrst request was completed,
the server responded with a ﬁle in json format and the ﬁrst 20 qualiﬁed tweets in a time-descending
order. By parsing the json ﬁle, we obtained a string for the crawler to build the next request and obtain
the next 20 tweets. Thus, a loop was written to keep the crawler sending requests and the crawler was
automatically terminated when all the qualiﬁed tweets publicly available were collected. Our crawler
respected Twitter’s robot.txt and we did not collect, analyze or display any user information in
our study.
Given our goal of exploring the difference between the two discourses, the 615,816 tweets
containing both hashtags simultaneously were excluded to differentiate between the two datasets
following [ 67,80]. A total of 6,662,478 tweets were retained, of which 5,774,747 contained
#climatechange, and 887,731 contained “#globalwarming”. The number of qualiﬁed tweets containing
#climatechange and #globalwarming in each year is displayed in Figure 1a.
(a)
 (b)
Figure 1. The number of tweets containing #climatechange or #globalwarming, and their ratio from
2009 to 2018 ( a). The number of hashtags contained in the “climate change” or “global warming”
datasets, and their ratio from 2009 to 2018 (b).
Figure 1. The number of tweets containing #climatechange or #globalwarming, and their ratio from
2009 to 2018 ( a). The number of hashtags contained in the “climate change” or “global warming”
datasets, and their ratio from 2009 to 2018 (b).