Analysis of News Coverage of Haze in China in the Context of Sustainable Development: The Case of China Daily

: This study examines the role of media in boosting environmental governance and monitoring sustainable development in China and explores the relationship between the Chinese government and media coverage, and helps audiences understand the positions of third world countries on climate governance. It also o ﬀ ers insights into strengthening international cooperation on the governance of air pollution. Drawing on the framing theory and issue-attention cycle literature, this study examines the frames, news sources, and media slants (negative, neutral, positive) that were used in haze coverage, between 2000 and 2018, by China Daily , the primary English-language newspaper in China. The results of a content analysis reveals that news coverage of haze in China Daily exhibits an issue-attention cycle. This study shows that the majority of haze coverage had a neutral slant, mainly adopted frames of deﬁne problems and suggest remedies , and cited sources from o ﬃ cials, agencies, specialists and scholars. Additionally, the usage of the science education frame signiﬁcantly correlated with the citing of specialists and scholars as news sources. The deﬁne problems frame signiﬁcantly correlated with the citing of o ﬃ cials and agencies as news sources.


Introduction
As with other international environmental issues, such as ozone depletion, the climate crisis, and acid rain, air pollution has been an environmental challenge to many countries [1]. According to a recent report from the World Health Organization (WHO) [2], air pollution should be regarded as the most significant environmental threat to human health. Since environmental issues are relevant to a growing number of countries and interest groups, their diversified standpoints are reflected in the media's coverage of it [3]. The media is considered to be "a public sphere" through which individuals perceive social reality, and it plays an active role in public agenda-setting [4]. Compared with online or social media, newspapers still play critical roles in shaping public opinion and in cultivating political consciousness. It can also affect policy-making, influence public attitudes, and strengthen global cooperation [5,6].
Within this context, this study seeks to examine the role of media in boosting environmental governance and monitoring sustainable development in China and explores the relationship between the Chinese government and media coverage. China has become one of the countries with the worst air pollution in the world [7]. In 2014, the International Agency for Cancer (IARC) listed air pollution as "the first type of carcinogen", for the first time [8]. The pollutants that affect the air in cities' environments are called "particulate matter", often abbreviated to PM, and they are seen as measures of air pollution. PM 2.5 is a particulate matter with an aerodynamic equivalent diameter of 2.5 microns or less. It is considered the major "culprit" of haze weather. Haze, a term used in China to describe the air pollution issue, directly impairs the everyday life and physical health of everyone, and therefore, it has become a major public concern, posing severe challenges for sustainable urban development. However, the emergence of air pollution is closely related to China's developmental stage of industrialization. In the latest annual SDG Index and Dashboards coverage, released by the Sustainable Development Solution and Network (SDSN), China ranked 54th out of 118 countries with a score of 70.1; higher than Brazil, Russia, and Turkey. Within the Sustainable Development Goals (SDGs), those related to air pollution (Goal 3, Good health and well-being; Goal 11, Sustainable cities and communities; and Goal 13, Climate action) are explicitly emphasized for China [9]. This means that China's specific performance needs to be improved with respect to these three goals.
It is necessary to deal with climate change in order to achieve sustainable development. In recent years, the relationship between sustainable development and the press has been very close. On one hand, sustainable development has been a basic argument in the government's communication policies, and the goal of sustainable development is mainly driven by political institutions. On the other hand, news coverage on topics concerning sustainable development and the environment depend mainly on political institutions and experts as news sources [4].
In addition, the development of information marketization has led to news coverage tending to be event-centered, profit-oriented, and less focused on long-term or sustainable social issues [10]. Downs' issue-attention cycle model provides one approach to examining the media's continued focus on the heated debate on climate crisis, and can be related to changes in the triggering events in each stage [11,12]. Additionally, frame analysis is commonly used in news content analysis [13], it also tries to understand complex information, to define the problems in news coverage, locate causes, moral judgements and to explain the reason [14].
Drawing on framing theory and the issue-attention cycle, this study conducted a content analysis of the news coverage of haze by China Daily, the leading English language newspaper, in the period 2000-2018. Our study examines the frames, news source, and the media slants (negative, neutral, and positive) used in the haze coverage in China. The purpose of this research is to extend and enrich framing theory and the issue-attention cycle, and lays a theoretical foundation for environmentally sustainable development news coverage. This study explores the media's role in facilitating air pollution governance and the course of sustainable development in China and provides insights for strengthening international cooperation in the global governance of climate, to understand the attitudes and positions of the Chinese media in tackling climate issues. At the same time, the findings of this study add to the framing literature and offer new explications focusing on Downs' issue-attention cycle model.

Sustainable Development and News Media
The 2030 Agenda for Sustainable Development, which was passed by the United Nations (UN) General Assembly on September 2015, has replaced the previous Millennium Development Goals and covers seventeen SDGs and 169 sub-goals. It is a programmatic document for international development cooperation and, at the same time, sets new requirements for global development [15].
The concept of sustainable development in China can be understood as "sustainability" and "sustainable development". Both concepts are in line with China's construction of an ecological civilization. The core of this is a harmonious development between man and nature, and its fundamental purpose is to be people-oriented and to improve their well-being [16]. China raised the goal of sustainable development to a national-level strategy as early as 1996. The Chinese government's announcement of sustainable development encouraged a harmonious cooperation in economic, environmental, and social sustainability sectors. The Chinese government also integrated the 2030 Agenda for Sustainable Development into China's 13th Five-Year Plan in 2015 [17]. The advent of the media's producing and circulating environmental discourse has helped environmental issues enter into public discussion, and there has been a growing call for the formation of public opinion and the generation of a "green public sphere" [17].
Over the past two decades, an increasing number of media outlets have included coverage on sustainable development-related topics, and discussed media affects audiences' perceptions on environmental issues, and also contributed to the action, undertaken during periods of crisis [18][19][20]. At the same time, public awareness of environmental sustainability is also growing, which in turn will affect the relevant policy-making and adjustment [21]. Extant studies into environmentally sustainable development mainly focus on a "sustainable broad semantic field". This refers to environmental issues, including climate change (air pollution, climate warming) [22][23][24], and EU environmental policy [25]. In addition to that, in other studies into the press, which were identified as being associated with sustainable development topics, news sources play a role in the news coverage in the process of economic sustainable [4].

China Daily and Environmental Coverage
There are several reasons why China Daily is appropriate for this study. Currently, and despite the rise of digital and social media, newspapers are still recognized as playing a critical role in setting the agenda for other types of media and can influence the opinions of policymakers [26]. More importantly, due to their large circulation and broad audience, newspaper articles are often archived as the historical data of social organizations, making it easier to access [27]. China Daily is the most important and widely circulated national, English-language newspaper in China. At the same time, China Daily is a Chinese newspaper that has been effective in reaching overseas readers. It has been distributed to more than 150 countries and regions around the world (as of 2019); its global circulation runs to 900,000 copies (600,000 distributed overseas). Its readers mainly include domestic and overseas high-end persons, as well as foreign people working, visiting, studying and traveling in China. The mission of China Daily is to "let the world know about China, let China go to the world" [28]. China Daily transmits the voice of the third world to audiences in English-speaking countries, helping them to understand third world countries' position on climate governance. As such, it is an important platform to know China. Duan and Takahashi (2017) compared the China Daily and New York Times newspaper coverage of environmental issues, on the basis that China Daily was leading national newspapers with international news-gathering abilities [29]. In conclusion, when compared with the domestic press, China Daily shows a greater participation in global issues and influences international cooperation in global climate governance.
The amount of environmental coverage in Chinese newspapers has been growing [17], evidenced by the most frequently mentioned sub-topics; air and water pollution. Earlier research has emphasized the media's role in endorsing environmental actions [24]. For example, Xu (2012) focused on the coverage of air quality in Beijing and highlighted the increasing impact that media coverage in China has on environmental issues [30]. Previous research has also investigated the dissemination of haze-related news via digital and mobile platforms [19,31,32].
In addition, news coverage related to air pollution carries different weights for audiences across countries, depending on the political system, cultural context, and media regimes of those countries. Duan and Takahashi (2017) suggested that news coverage reflected the differences in ideology and media systems between China and America [29]. Brossard (2004) conducted a cross-cultural comparison between French and American media coverage of climate change, illustrated how different news regimes affected public opinion [33]. In short, the media's environmental coverage reflects the relationship between its government and the public.

Issue-Attention Cycle
The issue-attention cycle model was first postulated by Downs, during an analysis of environmental coverage in America. Downs (1972) argued that the public's attention to environmental issues typically had five stages. In the first pre-problem stage, only a few experts are concerned about an issue, and widespread public attention has not yet been raised. In the second alarmed discovery stage, the public enthusiastically seeks solutions to problems. In the third realizing the cost stage, the public is aware that the cost of solving the problem is very high. In the fourth gradual decline of interest stage, the public's attention and interest declines as another issue rises. In the fifth post-problem stage, this specific issue enters a prolonged state of limbo [11,34].
Much of the current literature contains new discoveries that are based on Downs' views [23,35,36]. Firstly, most issue-attention cycles have been focused on environmental coverage in single or multiple countries [35,36], but were not used in the context of media coverage in China. Secondly, the more strongly the issue-attention cycle influenced public attitudes and the broader the coverage of topics, the longer the public attention remained on them [35,36]. Additionally, the focus of each stage was different. McComas and Shanahan (1999) postulated that media attention to global climate change issues had three stages: rising, maintaining, and weakening, and they stated that the focus of each stage was different [34]. Thirdly, the peak of news coverage concerning environmental problems was closely related to specific triggering events. Some scholars regard triggering events as hot topics and, depending on the extent to which the media pays attention to an issue, believe the public's perception of it will also change [37,38]. Once triggering events have occurred (such as an economic crisis), attention to climate change declines and shifts to the new topic, which confirms Downs' fourth stage [37].
Based on the literature review, this study assumes that haze coverage in China Daily will exhibit an issue-attention cycle and experience five stages. However, after triggering events occur, public attention will increase or decline. The following research hypothesis and question are postulated:

Hypothesis 1 (H1). If China Daily's haze coverage exhibits an issue-attention cycle, then this is in accordance with Downs' five stages.
RQ1: What are the triggering events that affect issue-attention cycle changes in China Daily's haze coverage?

Framing Theory, News Source and Media Slant
Thus, far, previous studies have linked issue-attention cycle, used in news coverage, with framing theory [12]. The news frame changes as an issue evolves [39]. Trumbo (1996) showed that news coverage on climate change was closely related to frame and the source changes. In the past decades of studies, studies only exhibited three of the five stages of Downs' issue-attention cycle; also, there should be a politicization of the problem, an increase in its level of controversy, and a shift to judgments and solutions [12].
Initially, frame theory became an important method for analyzing content [13]. Framing can be used in the media and thus, it gives meaning to events and issues and helps the public understand the outside world. Framing has gradually affected the discourse of news, as well as becoming a paradigm of media research, and framing theory is used as a tool to study media content [40]. Entman (1993) argues that framing involves mainly selection and salience, whereas framing theory is used to analyze the motivations behind environmental news coverage [40]. Entman (1993) also points out that frames have four functions. They: Define problems, determining what costs and benefits the causal subjects have, defining a problem by explaining it; Diagnose causes, determining the causes by producing the problem; Make moral judgment, assessing causality and its effects; Suggest remedies, providing and justifying treatments for the problem and predict any possible impact [40]. However, Kim et al. (2011) investigated the news coverage of illegal immigration in newspaper and television, but did not adopt the make moral judgment frame from Entman, on account of its concerning a specific event [41].
Across different contexts, frames are usually conceptualized at the generic and issue-specific levels [42]. In other words, the framing literature is full of framing studies that focus on a particular issue. For instance, Iyengar (1991) demonstrated that, in the media and policy landscape, episodic vs. thematic frames influence the public perceptions about the causes of a policy problem. Episodic frames were more likely to attribute responsibility to the individual (e.g., family and enterprise), offering a case study, or an "event-oriented report"; but, in a more broader context, thematic frames were more likely to attribute responsibility to systematic causes (e.g., government and society) [43]. We suggest that the haze problem by news coverage is a specific issue, and both Entman's frames and Iyengar's frames are included. Using Entman's diagnose causes frame may explain the responsibility attribution cause of news coverage. In other words, the intention of the diagnose causes frame can be explained by episodic vs. thematic frames. Therefore, the second research question is: RQ2: Which frames does China Daily's haze coverage use?
Part of the framing process is that news sources influence the selection of news and content. This affects the credibility of news stories, also plays a decisive role in the construction of issues [44,45]. Kuban (2007) found that media coverage of climate change depended on whether the news sources were governmental or political persons [46]. Liu (2008) showed that news coverage most frequently cited scientists as sources, to reduce problems of uncertainty. Some scholars believe that media frame significantly influences the source they use [3]. Takahashi (2011) found that government sources were often cited in Peruvian media coverage on environmental news, when the solutions to climate change frame was used [47]. Thus, journalists mainly tended to cite government sources and experts, inferring they were neutral and therefore credible [48][49][50]. However, news source diversity rarely appeared in environmental news. This paper aims to understand whether the media frame is also relevant to its news sources. Therefore, the third research questions are: RQ3a: Which news sources used in China Daily's haze coverage? RQ3b: Does the frame of haze coverage correlate with the use of news sources?
Finally, Kiousis (2004) found that the positive, neutral, and negative tones of political news coverage during the 2000 US presidential elections were an essential part of the media slant [50]. Entman (2007Entman ( , 2010 also argues that there is a media slant in the news coverage on political conflicts. News slant appears when coverage of news emphasizes one side's preferred frame and ignores or devalues the other side [51,52]. Lu et al. (2018) suggested that the US local media adopts a media slant strategy to degrade the image of China. Other researchers have also found that negative coverage of China affected the US elections [53]. Further research suggests that China's mainstream media outlet, the Xinhua News Agency, tends to frame the Chinese government more positively [54]. Therefore, this article focuses on the emotional slant of the media (positive, neutral, and negative) and the second research hypothesis is:

Hypothesis 2 (H2). If China
Daily's haze coverage shows a media slant, then the media slant can be positive, neutral, or negative.

Sampling Procedure
This study conducted a content analysis of China Daily's haze coverage between 1 January 2000 and 31 December 2018. We used the Factiva database to collect China Daily news stories, using key search words such as "haze" or "PM 2.5 ", to select relevant coverage, of which we found 1105 news stories. The news story was the unit of analysis. After determining the connotation of each coding variable in detail, and removing any irrelevant coverage and deleted duplicates, a final list of 494 articles was found on coverage.

Coding Scheme
News framing often differs from one country to the other, depending on issue-specific frame (specific topics or event-centered information) and generic frame (structural and inherent to the conventions of journalism) in different cultural contexts [42,43]. The haze issue belongs to both issue-specific frame and generic frame. A reading of article content in the China Daily revealed three categories (define problems, diagnose causes, and suggest remedies) that agreed well with Entman's purposes of frames. The make moral judgment frame was not adopted in this study, because the diagnose causes frame already generalized the attribution of responsibility (see Appendix A Table A1). Sharman (2014) argues that the scientific frame can provide an interpretation of the scientific elements of climate knowledge, in blogs, and may shape a public sphere of expertise [55]. Olausson (2009) considers that the collective action frame reflects the policy agenda of climate crisis and emphasizes transnational concerns about how society should react to climate change [56]. In the literature reviews, considering the unique context of the content, two issue-specific frames were developed from the content and the themes in news articles, and then rename to two news frames of categories: science education (haze related to scientific knowledge) and action initiatives (although suggest remedies is similar to action initiatives, the former focuses on elite, and the latter on non-elite sources). Each article may have more than one frame (see Appendix A Tables A1 and A2).
This study aims at analyzing the overall style or tone of news coverage, and to explores whether media slant is neutral, positive or negative. We drew upon Roseman's structural model of discrete emotions-positive emotions and negative emotions [57]. However, since the analysis is not about the audience's attitude towards haze coverage, and also based on Barnes and Hevron's (2018) study into ways to devise a coding schema [58], we judged slant according to the theme, tone and keywords of the article (see Appendix A Table A3), and we attached some examples of positive and negative coverage in the article (see Appendix B).

Inter-Coder Reliability
Two coders were trained and coded samples independently. They randomly selected fifty articles (representing around 10% of the total number of sampled articles) to measure intercoder reliability, and this was calculated using Krippendorff's alpha, which ranged from 0.70 to 1.0 [59]. Finally, the overall reliability of the coefficients was 0.86, which can be considered an acceptable level. The reliability for the frames ranged from 0.82 to 0.95; the reliability for news sources ranged from 0.92 to 0.96; and the reliability for media slant ranged from 0.85 to 0.93.

Issue-Attention Cycle
Hypothesis 1 (H1) posits that, "If China Daily's haze coverage exhibits an issue-attention cycle, then this is in accordance with Downs' five stages" and RQ1 asked which triggering events affected issue-attention cycle changes in China Daily's haze coverage. Figure 1 shows the line chart graph and curve fitting we used to reflect China Daily's coverage of haze. The statistics show that it did present an issue-attention cycle and that it followed the cycle of rise-peak-decline, which was reflected in the changes in the number of news stories. The frequency of news articles is calculated piece by piece.
The statistics in Figure 1 show that there are only four stages in terms of Downs' opinion, and Hypothesis 1 (H1) is not supported. Specifically, during the first stage (2001 to 2008), the first relevant coverage appeared in 2001 (1 news story), the Beijing Olympic Games meant that national and foreign press paid more attention to how the haze in Beijing affected the public's health and events. In the second stage (2009-2010), the overall amount of coverage declined slightly, remaining at around six to ten articles, which gradually stimulated the public's awareness and interest, the public suddenly became curious, and enthusiasm for the issue emerged.
In the third stage (2011 to 2013), the numbers began significant growth. This is where the public were gradually becoming aware of the severity of the haze issue and were beginning to seek solutions. In 2011, after the triggering event of "US Embassy PM 2.5 ", China Daily responded to the US Embassy's questions. In 2013, the amount of haze coverage reached its peak (130 news stories), in accord with coverage about China enduring the worst haze in history: haze spread to twenty-five provinces, including to more than 100 large-and medium-sized cities. The average number of haze days per month, in those cities, reached 29.9, which was a record high at that time [60]; in terms of Downs' opinion, the public gradually came to understand the needed high cost of solving the problem [11], and even the sacrifice of some of their own interests, such as Beijing's traffic restrictions, which were based on the last digit of license plate numbers. problem [11], and even the sacrifice of some of their own interests, such as Beijing's traffic restrictions, which were based on the last digit of license plate numbers. The fourth stage was 2014-2018, where the amount of coverage began to decline rapidly. Examples were "APEC Blue" in 2014, as Chinese netizens described the excellent air quality of Beijing during the week of the APEC meeting that was held in the city, and which prompted a gradual increase in the amount of positive coverage on haze. The "military parade blue" and the 2030 Sustainability Agenda proposed by the UN in 2015 also significantly reduced adverse coverage.

Frequency of Frames
RQ2 asked about which frames China Daily used for haze coverage. As shown in Table 1, the frames that China Daily used the most for its coverage were Suggest remedies (49.8%, 246 news stories), Define Problems (47.8%, 236 news stories); Science Education (33.2%, 164 news stories). The rest were Diagnose Causes (25.5%, 126 news stories), Action Initiative (15%, 74 news stories).
Above all else, China Daily mainly adopted the frame of suggested remedies. Action was taken to implement specific activities, such as using natural gas to replace coal, strictly controlling the regular discharge of large-scale factory pollution sources and reducing the content of fine particles. Such actions were followed by the formulation of relevant policies, such as the "Air Pollution Prevention Action Plan", issued in 2013; the revised "Atmospheric Pollution Prevention Law", issued in 2014; and the "Environmental Protection Law", which came into effect in 2015.  The fourth stage was 2014-2018, where the amount of coverage began to decline rapidly. Examples were "APEC Blue" in 2014, as Chinese netizens described the excellent air quality of Beijing during the week of the APEC meeting that was held in the city, and which prompted a gradual increase in the amount of positive coverage on haze. The "military parade blue" and the 2030 Sustainability Agenda proposed by the UN in 2015 also significantly reduced adverse coverage.

Frequency of Frames
RQ2 asked about which frames China Daily used for haze coverage. As shown in Table 1, the frames that China Daily used the most for its coverage were Suggest remedies (49.8%, 246 news stories), Define Problems (47.8%, 236 news stories); Science Education (33.2%, 164 news stories). The rest were Diagnose Causes (25.5%, 126 news stories), Action Initiative (15%, 74 news stories). Above all else, China Daily mainly adopted the frame of suggested remedies. Action was taken to implement specific activities, such as using natural gas to replace coal, strictly controlling the regular discharge of large-scale factory pollution sources and reducing the content of fine particles. Such actions were followed by the formulation of relevant policies, such as the "Air Pollution Prevention Action Plan", issued in 2013; the revised "Atmospheric Pollution Prevention Law", issued in 2014; and the "Environmental Protection Law", which came into effect in 2015.

News Sources
RQ3a asked the news sources used in China Daily's haze coverage. Table 2 provides an overview of news sources. Mainly cited were officials and associations (67.4%, 333 news stories); specialists and scholars (38.5%, 190 news stories); and lay public (19.8%, 98 news stories); with the rest citing business and enterprise, NGOs and media. Compared with the elite sources, the lay public and other interest groups, such as NGOs, had relatively fewer opinions, and their perspectives were more at the edge of the subject. The frequency of news articles is calculated piece by piece. China Daily mostly cited various authorities (officials and associations, specialists and scholars) as news sources. On the one hand, while the official parties control the release of information concerning professional issues such as haze, these same specialists and scholars are also under the administration of the Chinese government. On the other hand, the government is itself an essential participant in the haze problem.

Media Slant
Hypothesis 2 (H2) focused on "If China Daily's haze coverage shows a media slant, then the media slant can be positive, neutral, of negative". Table 3 shows that the proportion of neutral coverage was 47.8%, followed by a negative coverage of 30%, and a positive coverage of 22.3%. The results supported Hypothesis 2 (H2). China Daily, which caters to a large foreign readership in China, strove to adhere to the "objective and fair" positioning of journalism, with a neutral media slant in their haze coverage. At the same time, its coverage position took into account the perspectives of the public and the government, as well as those of humanistic care in the process of structuring the haze problem. Thus, it consistently centered its coverage on people's livelihood and living conditions.

Correlation Analysis
To solve RQ3b, does the frame of haze coverage correlate with the use of news sources, this study used a bivariate correlation analysis. Table 4 shows the results we obtained: (1) The frame of science education was positively correlated with news sources from specialists and scholars, and haze coverage mainly cited experts and scholars as news sources. (2) The frame of define problems was positively correlated with news sources from officials and associations, and haze coverage mostly cited officials and associations as news sources. (3) The frame of suggestion remedies was positively correlated with news sources from officials and associations, and negatively correlated with news sources from the lay public. Haze coverage mostly cited officials and associations as news sources and cited fewer members of the lay public as news sources. (4) The frame of action initiative was positively correlated with news sources from businesses and enterprises, NGOs, and the lay public, and negatively correlated with news sources from officials and associations. Haze coverage mostly cited businesses and enterprises, NGOs, and lay public as news sources, and cited fewer officials and associations as the same. Table 4. Correlation analysis of the frames and news sources.

Correlation Analysis
To solve RQ3b, does the frame of haze coverage correlate with the use of news sources, this study used a bivariate correlation analysis. Table 4 shows the results we obtained: (1) The frame of science education was positively correlated with news sources from specialists and scholars, and haze coverage mainly cited experts and scholars as news sources. (2) The frame of define problems was positively correlated with news sources from officials and associations, and haze coverage mostly cited officials and associations as news sources. (3) The frame of suggestion remedies was positively correlated with news sources from officials and associations, and negatively correlated with news sources from the lay public. Haze coverage mostly cited officials and associations as news sources and cited fewer members of the lay public as news sources. (4) The frame of action initiative was positively correlated with news sources from businesses and enterprises, NGOs, and the lay public, and negatively correlated with news sources from officials and associations. Haze coverage mostly cited businesses and enterprises, NGOs, and lay public as news sources, and cited fewer officials and associations as the same. Table 4. Correlation analysis of the frames and news sources.

Discussion
This study drew on an analysis of the content concerning haze coverage in China Daily, and sought to shed light on framing theory and the issue-attention cycle as applied to environmental communication with a Chinese context. It explored the media on news coverage facilitation function in terms of air pollution governance and the course of sustainable development in China, as well as in raising public perception of seriousness of air pollution and sustainable development issues. China Daily facilitates overseas audiences in understanding the positions and actions of the Chinese government on climate governance, and offers insights into how cooperation on global environmental and climate governance could be strengthened. The main contributions of this research are elaborated as follows.
First, the adaptability of the theory is explored and lays a theoretical foundation for environmentally sustainable development news coverage. The issue-attention cycle model, as proposed by Downs, is based on the rule of commercial media in the United States, whereas this study explores how the (Chinese) government can effectively control the applicability of media, and combined with the triggering events of each stage, we showed that China Daily's new interpretation of the fourth stage (the public gradual decline of interest). This occurred not merely because their attention shifted to other hot issues that were emerging, but also because the Chinese government adopted effective solutions and robust governance, over a short period of time, which reduced the public controversy over haze. Additionally, Downs' fifth stage, "post-problem", was not apparent in this study [11], because there was no explicit boundary between the fourth stage and the fifth stage, which is also inconsistent with the results of previous studies [11].
Second, we extended and enriched framing theory, as applied in the issue-attention cycle, and based on the framing theory proposed by Entman. The issue-specific frames reflected the specificity of haze coverage, which can be seen as an urgent and solvable issue. The diagnose cause frame reflected the public's perception and comprehension of the haze policy, depending on the responsibility attributes of news coverage, and this reflected the media's communication strategy. Furthermore, it also demonstrated that, from the perspective of Iyengar's episodic vs. thematic frames [40,43], if the haze coverage is attributed to the behavior of enterprises or individuals, it will not be able to solve the haze problem as a whole. However, because the emergence of haze is a structural contradiction between China's economic development and environment protection at this stage, it can be solved through reform of the economic system and adjusting energy structures. Under the science education frame, and from a scientific angle, new light was shed on the notions of how haze occurs, consistent with previous literature [55]. In addition, the communicators explained the different actions on the path to climate change. In contrast to the frame of suggesting remedies, the frame of action initiative prompted contemporary non-elite groups to advocate for climate action and, understanding the citizens' concerns and fears, the voices of diverse actors evidenced the necessity and urgency of public action on climate governance, which differ from former study [56].
In the next stage, in terms of contribution to practice, China Daily's haze coverage relied mostly on authorities as a news source, i.e., officials and associations, and specialists and scholars, a fact that has been discussed in earlier literature. Governmental and elite sources (scientists, etc.) remained the main sources for journalists, thus increasing the degree of credible information passed to their audience, and also proving that sustainable development is driven by the government [4,48,49]. However, ultimately, the decrease in the diversity of news sources reflected the public's distancing of themselves from climate change-related issues and prevented their taking climate action. Additionally, most of the haze coverage had a neutral slant, and higher credibility-which is consistent with China Daily's mission. There was also a correlation between the variables.
Finally, the air pollution that is caused by the climate crisis is a multivariate environment. The main body is in the global public sphere, but it has also become a global political issue, affecting one community with a common destiny. The more severe the haze that China experiences, the higher the potential pollution risks that its neighboring countries also face [61]. Haze is not only an air pollution problem for a single country, but also affects the global healthy living environment and sustainable urban development. As such, it greatly hinders the achievement of the UN's SDGs and impacts on China's economy and society. For these reasons, the Chinese government has promised to promote coordinated and sustainable economic and ecological development in the future.

Limitations
This study has some limitations. Because we conducted our content analysis on haze coverage in the China Daily only, our findings were limited to one newspaper in China. Although we analyzed media coverage of haze by the China Daily over almost two decades, we did not look into other Chinese media coverage during the same period of time. Because Chinese newspapers that target domestic readers may have different agendas from that of China Daily, future research should consider examining other Chinese newspapers. As air pollution can be caused by natural and human factors, accordingly, their evaluation standards are different. Haze is a kind of air pollution air pollution is measured by the "air quality index (AQI)", and PM 2.5 is also one of the pollutants monitored by AQI. To allow a more in-depth examination, we chose "haze" and "PM 2.5 " as keywords instead of "air pollution". Nonetheless, we acknowledge that this may limit the generalizability of the findings. Lastly, due to the nature of our findings, no causal relationships can be drawn. Future research should consider conducting experiments to ascertain whether any causal relationships exist between the studied constructs.
Author Contributions: Y.H. equally contributed to writing the original draft, conceptualization, data collection, formal analysis, and methodology. G.Z. and L.C. contributed to the theorization, review, and revision of the paper. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.

Conflicts of Interest:
The authors declare no conflict of interest.
Appendix A Table A1. The frames among news coverage theme of haze.

Frames
Coding Scheme

Science Education
Scientific knowledge about haze; methods of detecting haze, e.g., introducing the concept of PM 2.5 and its harm to health.

Define Problems
The definition of and disputes over the haze, e.g., the US Embassy in Beijing questioned using PM 2.5 as an air quality index and other health data standards.

Diagnose Causes
The influence and causes of haze. Responsibility attribution to individual behaviors or enterprise behaviors; responsibility attribution to the government and society.

Suggest Remedies
Including policies change, promoting a green economy, improving technology to control haze, and strengthening international cooperation.

Action Initiative
The environmental actions advocated by individuals and NGOs, e.g., encouraging citizens to advocate air pollution law, promoting a green lifestyle among the community.

Appendix B Some Examples of Positive or Negative Coverage in the Article
Negative coverage: Beijing residents responded with their views on the air quality through Weibo, a micro-blogging website operated by Sina Corp. Some posted photos of buildings blurred by the thick haze, and some said they feel choked by the smoky air. "It's like walking in a huge chimney, or having countless people keep puffing secondhand smoke at you-All the time," Yanhanyh wrote on Weibo. "I do not believe the air is only 'slightly polluted' today. I started to cough after 10 min' walk in the open air, and I do not even dare to let my kid go out," said another Weibo user, Dapeng. A public trust crisis is spreading over the official readings of Beijing's air quality, especially when some residents find alternatives that are more in line with their own senses.
("Weather debate shrouded in fog", Li Jing, Duan Yan and Cui Jia, 2 November 2011, China Daily). Shanghai braced for a second day of severe pollution on Monday after the city's Air Quality Index hit record hazardous levels. The city's environmental authority issued its first orange alert-he second-highest in its four-level warning system-after the index reached 317. The concentration of PM 2.5 -particulate matter smaller than 2.5 microns in diameter that can penetrate the lungs-stood at an average of 266 micrograms per cubic meter in the previous 24 h, running from noon to noon. It was the third day of severe pollution within a month, and the Shanghai Environmental Monitoring Center predicted the Air Quality Index would remain between 285 and 305 on Tuesday. The index is an integrated assessment of six main air pollutants: sulfur dioxide, nitrogen dioxide, carbon monoxide, ozone, PM 10 and PM 2.5 . China's meteorological departments issue an orange warning for haze when visibility is less than 2000 m and pollution is sustained. Some commuters wore face masks, and some reported having sore throats and eyes.
Positive coverage: NGOs distribute protective gear as people urged to stay indoors Though Beijing has been shrouded in smog containing dangerously high levels of pollutants for several days, prompting authorities to urge the public to stay indoors, some people are hitting the streets to help those in need.
As the stench of coal and automobile exhaust hangs in the air, NGOs are preparing to hand out masks to people who work outside, including street cleaners, traffic wardens and doormen, in cities including Beijing and Tianjin and in Hunan province. "People working outdoors are vulnerable when they are exposed to pollution, which has soared past dangerous level, with no protective measures," said Feng Yongfeng, an organizer of Green Beagle, an environmental protection NGO in the capital. "It's urgent that people who work in the heavy smog are well protected, because the air quality has been worsening since Friday." Environmental protection NGO Greenpeace has about 300 masks and is recruiting volunteers to help deliver them to people exposed to pollution.
China is stepping up its efforts in strengthening anti-pollution laws. The Environmental Protection Law, which took effect on Jan 1, has increased the responsibility of local governments in dealing with environmental problems and made polluters liable to pay unlimited daily fines for violations. In December, the country's top legislature reviewed the first amendment to the Law on Air Pollution Prevention and Control since 2000. The draft is reported to have details on dealing with various pollution sources, including the required use of advanced equipment and technology in production.