Communicating Climate Change: A Comparison Between Tweets and Speeches by G erman Members of Parliament (2023)

Abstract: Twitter and parliamentary speeches are very different communication channels, but many members of parliament (MPs) make use of both. Focusing on the topic of climate change, we undertake a comparative analysis of speeches and tweets uttered by MPs in Germany in a recent six-year period. By keyword/hashtag analyses and topic modeling, we find substantial differences along party lines, with left-leaning parties discussing climate change through a crisis frame, while liberal and conservative parties try to address climate change through the lens of climate-friendly technology and practices. Only the AfD denies the need to adopt climate change mitigating measures, demeaning those concerned about a deteriorating climate as climate cult or fanatics. Our analysis reveals that climate change communication does not differ substantially between Twitter and parliamentary speeches, but across the political spectrum.

## introduction anthropogenic climate change (cc) is one of the major issues that societies are facing today. this is reflected in the vast amount of cc-related discourse that is distributed via different forms of media including, for instance, traditional newspapers and various social media. by their nature, platforms like twitter are available to professional users and to the general public alike. in our work, we focus on members of the german parliament (mps) as one specific group of actors that engages in cc discourse. more precisely, we are interested in their communication on twitter on the one hand, and their parliamentary speeches on the other. while twitter is a more recent development, parliamentary speeches are a traditional means for politicians to convey their ideas and positions. obviously, these domains imply different audiences: tweets are aimed at the general public (and thus to potential voters), while speeches are first of all directed at other mps, and only indirectly meant to -sometimes -reach a broader audience. this situation prompts us to compare the communications of mps in the two arenas: is cc equally prominent as a topic? are the same aspects of cc discussed? how does this differ between parties? -we take the german bundestag, and especially a six-year period starting in 2016, as the basis for our study. the paper is structured as follows: after discussing related work, we explain our data collection and present corpus statistics in section 3. then, in section 4 we provide analyses of term and hashtag use, while section 5 conducts a topic modeling experiment. the findings are discussed in section 6, and we conclude the paper in section 7. among various currently popular social platforms, twitter has become a major player in political communication @xcite . in germany, the 2009 bundestag elections became the first instance in which mps used twitter on a large-scale @xcite . since then, twitter has established itself as a crucial communication channel for many mps. yet, social media creates a distinct communication environment, in which salient topics do not necessarily resemble those discussed among a mass audience @xcite . as stier et al. point out, however, when discussing policies, politicians and their followers on twitter tend to share similar priorities, pointing to a communication approach that is targeted at a like-minded audience @xcite . recently, this aspect has been investigated from the perspective of news-sharing behavior by mps in the u.s., the uk, and in germany @xcite . with this growing relevance of twitter for political communication, the platform has also become a tool for science communication, in particular in respect to cc. in 2013, the united nations intergovernmental panel on climate change (ipcc) released its fifth assessment report (ar5), which was the first report that utilized twitter as a communication tool @xcite . newman found that events such as the ipcc report provide an opportunity to draw attention to cc-related issues on twitter, allowing actors to strategically communicate with their audience, e.g., by adjusting their language in the interaction with different audiences @xcite . given that cc becomes an increasingly pressing issue @xcite , cc-related communication of political elites also deserves further attention. recent evidence shows that politicians promoting environmental messages on twitter are also more likely to vote pro-environmentally @xcite . besides such approaches in the social sciences, the nlp community has recently also given more attention to cc communication @xcite . for example, @xcite detect subtopics as well as stances toward cc on a twitter dataset. an interesting combination of methods was proposed by @xcite , who use lda to generate topics containing keywords that represent sentiment targets, and employ sentiwordnet to annotate that part of text with a sentiment value. in this way, they try to distinguish different media for reporting with specific attitudes toward cc topics. @xcite uses nlp to identify several ten thousand people and philanthropic organizations in the u.s. engaged in disseminating cc misinformation. parliamentary speech on cc has recently been tackled with manual analyses of framing, for the european parliament @xcite and in comparison to the u.s. @xcite . automatic approaches, on the other hand, to our ## data in this work, we gather mp communications from two sources: tweets and parliament speeches. we use a subset of a tweet set collected by @xcite who compared the distribution of lowquality news sources on twitter by political elites in the u.s., the uk and germany from january 1st 2016 until march 15th 2022. we apply the same timeframe to our present study that addresses only germany. during this time, six parties were represented in parliament foot_0 -see ## analyses for determining the relevance of the cc issue, and the stances toward it, we first analyse our data statistically, looking at speech and tweet volumes, frequencies of hashtags, and use of subjective "cli-matex" noun compounds (e.g., klimapolitik, klimaschutz, klimakrise). we are interested in differences between parties, and between tweets and speeches. we present absolute counts and proportions, where proportions in section 4.1 are calculated with respect to corpus sizes, while in the other two sections, proportions for hashtags and compounds are calculated with respect to total hashtag/compound counts by party. ## topic modeling for topic modeling we use bertopic (grootendorst, 2022), a technique based on transformers @xcite , clustering and a class-based variation of tf-idf, i.e. c-tf-idf. the bertopic algorithm works as follows: in a first step, documents are embedded in order to create vector space representations that can be used for semantic clustering. here, we use sentence-bert (sbert) @xcite . second, the dimensionality of embeddings is reduced using umap @xcite , after which documents are clustered using hdb-scan @xcite , a hierarchical version of the original dbscan algorithm. this allows for soft clustering as unrelated documents are treated as noise. third, topic representations are created using c-tf-idf. we use the same hyperparameters for both the tweet and speech datasets. we remove frequent words 1) by applying bm-25 weigthing and 2) by taking the square root of the term frequency after normalizing the frequency matrix instead of taking the default term frequency in the c-tf-idf algorithm. both options can be set in bertopic. we use the sbert model all-mpnet-base-v2. the minimum cluster size of hdbscan is set to 15. finally, we apply the maximal marginal relevance algorithm @xcite to diversify the topic representation, using a mild score of 0.2 (with 0=no diversity, 1=complete diversity). we train topic models on the full tweet and speech corpora and on individual party subsets, resulting in 14 topic models. in the following, we will describe the topics provided by the trained models. due to space limitations we will concentrate on the topics that were associated with most documents and were interpretable from a climate (policy) perspective. the topic labels, which were manually derived from the models, can be found in ## discussion although political communication can be domain dependent @xcite , our findings indicate a strong overlap between compounds, hashtags, and topics prevalent on social media and in parliamentary debates. politically left-leaning parties (such as the left, the greens, and the spd) tend to discuss cc in terms of its negative and heterogeneous impact (as indicated by the use of the compound climate crisis (klimakrise) and climate justice (klimagerechtigkeit) in both speeches and tweets. especially the greens make use of this terminology, thereby connecting to various activist groups (e.g., fridays for future, extinction rebellion, last generation) that use climate crisis as a frame to highlight the severe and urgent need to counteract the negative consequences of cc. the left uses climate justice more consistently on twitter and in parliament, compared to both greens and spd. while also using climate crisis, the spd most frequently uses climate-friendly (klimafreundlich), which might be indicative for an approach that tries to balance the urgency of cc with measures that are seen as not too invasive for citizens and the economy. this balanced approach is also reflected in the topics, including cities, transport; climate protection, elites (twitter); and climate protection, costs; technology, industry; and money, investment (speeches). in contrast, traditionally more business-friendly parties, such as the fdp and cdu/csu, use climate-friendly to a greater extent, which might indicate a stronger orientation towards economic transformation and technological advancements. this interpretation is supported by the topics for both parties, which include innovation and technology, energy sources and transition, as well as e-mobility and fuels in case of the cdu/csu. whereas these five parties acknowledge the need to address cc, although using different framings, the afd uses terminology that frames cc and corresponding protective measures as hysterical (klimahysterie), fanatical (klimawahn, klimareligion), or cult-like (klimakult). a similar pattern is found in the afd topics, which include climate hysteria and socialism on twitter and climate religion as well as climate dogma in parliament speeches. this general pattern is reflected by the hashtags #transporttransition (#verkehrswende) and #energytransition (#energiewende). while the greens, the spd, the fdp and the cdu/csu frequently use the latter, only the left and the greens explicitly mention the transition of transport. this difference also emerges in the topics, where those related to transport infrastructure or railroads are associated with left-leaning parties, while topics related to energy transition and emissions reduction are more broadly distributed. this may be due to transport being framed as a social topic by the left and the greens, e.g., with a potential for many people to benefit from lower train ticket prices and improved railroad infrastructure. the fdp and cdu/csu, however, may interpret transport transition as having negative consequences for the automobile industry, a traditionally strong industry sector in germany, which is why the cdu/csu discusses emobility and alternative fuels in parliament and uses #hydrogen (#wasserstoff ). in contrast, the energy transition is seen as having a strong potential for economy and technological innovation, while being at the same time crucial for emissions reduction. this makes it a more suitable topic to be adopted by parties of different orientations. in sum, compounds, hashtags, and topics reflect the respective parties' political orientation and their stance towards cc and climate protection, with comparatively small differences between parliamentary speeches and communication on twitter. ## conclusion we studied the communication of german mps on twitter and in parliamentary speeches, concentrating on the topic of cc, for which we created corpora that cover the same 6-year period. by topic modeling, hashtag analysis and comparing the use of stance-marked noun compounds, we looked for differences between parties on the one hand, and between the communication in the two channels, on the other hand. our analysis reveals, that differences in climate communication primarily emerge across the political spectrum, with left-leaning parties focusing more heavily on the negative impacts of cc and economics-oriented parties concentrating more on economic transformation and technological advancements. the afd is the only party denying the need to adopt cc mitigating measures and demeaning those concerned about a deteriorating climate as climate cult or fanatics. differences between tweets and speeches are less salient. in a follow-up study, we plan to investigate the climate communicative behavior of individual mps with respect to their roles in climate-related committees, as well as conduct a time-sensitive analysis using dynamic topic modeling. frank wendler. 2022. framing climate change in the eu and us after the paris agreement. palgrave macmillan, cham/switzerland.