Our statistical study is, to our knowledge, the broadest coverage of news sources in the US to date.
Expanding coverage leads to some findings that are robust when compared with elite news outlets. Both heartland and elite sources show upward trends. This is consistent with results already widely reported (e.g., AAAS Commission, etc): the public is paying more attention to climate change, and so are the media. Heartland coverage more than doubled (increase in 144%) from 2011 and 2022. The five elite sources rose three-fold (299%) over that same period, when measured as the fraction of all news sources that addressed climate change. Using just a narrower search on the term “climate change” yielded a 227% growth for the heartland sources and a 449% growth for the elite sources.
While the daily data are volatile, even semi-yearly averages show some volatility. There are six periods for the elite dataset and seven periods for the heartland dataset when semi-yearly coverage declined (Figure SI-6). Those include:
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early 2013 when coverage appears to shift to the early days of the second term of the Obama administration, a period with little attention to climate change.
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early 2016 as the US national election began to heat up;
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early 2018 as the high average coverage of 2017—driven by President Trump’s withdrawal from the Paris Agreement—abated;
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throughout the first half of 2020 when news coverage shifted, for a while, to the COVID-19 pandemic.
Of these declines, the largest for the heartland sources occurred in the latter half of 2013, where the six-month average dropped 39% from the previous six-month average. For the elite sources, the largest drop occurred in the first half of 2020 as Covid-19 began to spread in the United States. The shift in attention to the pandemic resulted in the six-month average in elite sources dropping 41% from their previous six-month average. The covid crash was not long lived, and the upward trend resumed within a year.
The single most striking finding in this study is the divergence between the two datasets over time. In the first four years of the study (2011–2015) on any given day there was a 20% probability that the fraction of total daily stories addressing climate in heartland news sources would exceed the fraction in elite sources. Elite news outlets have always given more attention to climate change than heartland outlets. But in the early 2010s those differences were small enough that one day in five climate change would play a more prominent role in the average American’s news feed than it did for the elite. In the last four years of our study the differences were much more extreme: only 5% of days saw more coverage in heartland sources than the elite sources.
When looking at the events that drive extreme peaks in coverage of climate change there is a lot of similarity across heartland and elite news sources. The top two spikes in both datasets were increases in coverage by a factor of 4 to five due to President Trump’s withdrawal from Paris in 2017 and the convening of the UN Climate Summit in September 2014, which set the final stage for the Paris conference a few months later (Tables 3 & 4). Both types of new outlets give extensive coverage to the Paris conference (2021) and the climate conference four years earlier, in Durban, that framed the diplomatic road that ended in Paris. (The Durban conference in 2011, known as COP17, was the first major reset after the disastrous COP15 in Copenhagen that ended in disarray with no agreement on the road ahead. By Durban the road was coming into focus.).
There are notable differences in the spikes in coverage. In the heartland dataset there is extensive coverage of a series of billboards erected by the heartland Institute (no relation) in 2012 opposing action on climate change. Heartland news sources also gave a lot of attention to two clusters of comments on climate change by Pope Francis in 2015 in the runup to the negotiation of the UN Climate summit and the issuance that year of the Pope’s encyclical Laudato Si. In the elite dataset there is heavy coverage of the US-China climate summit in 2014, which many analysts see as the key political agreement that made it possible to conclude, a year later in Paris, a similar agreement with nonbinding emission pledges that included all countries. The elite dataset also saw a spike in coverage when the Bulletin of the Atomic Scientists changed its Doomsday Clock to a mere one minute before midnight. Diplomatic agreements with China and the machinations of atomic scientists don’t attract as much attention in the heartland.
Our findings parallel other divergences in American attitudes about climate change—between left and right, and between Washington and the rest of the country. While we focus on the incidence of coverage of climate change, not the content of the articles, there is a strong divergence over the period of study.
Finally, this study points to several areas for fruitful additional research. Here we focus on three.
First, if MediaCloud is to be a richer source of data for research on climate change then more research is needed to understand underlying shifts in coverage and coding within the dataset. There are significant changes in total coverage in the dataset that could affect trends and other empirical patterns—even when those trends are computed (as we do) in percentage of total coverage. Among the empirical patterns that need more explanation—and accounting for in statistical assessments—are bursts of new coverage notably in 2013 and 2018 (see Fig. 1). In addition, there are brief unexplained drops in the number of articles available for query in the database. In particular, there was a three-week period in January of 2022 where the number of U.S. articles available for query dropped to just 5% of the number of articles available in the months preceding and proceeding the drop (figure SI-1).
Despite the normalization of our data to the percentage of articles addressing climate change as the unit of our analysis we still find an underlying correlation between the total number of articles queried, per day, and the percentage of articles on that day related to climate change. Simple linear models using total articles per day as the independent variable and the percentage of articles related to climate change as the dependent variable, show that the number of article queried per day explains 20% of the variance in the dataset. The relationship between the two variables has a slight positive correlation. This relationship is only relevant for the heartland dataset, as the elite dataset had a roughly consistent number of articles queried per year (Table SI-1). Despite this growth in non-elite sources we still find that the elite and heartland data sets diverge over time. Nonetheless, this temporal trend in the heartland data set needs explanation.
There are clear structural questions that remain with the MediaCloud dataset. A lot of spadework is needed, and with such a huge dataset the spades will be hefty. Related, our search method—like nearly all other media pattern studies—is a dragnet approach with possibly lots of data bycatch. We are assuming that the errors are normally distributed and unbiased, but more work—with finer attention to search terms and their catch—is needed.
Second is the matter of explanation. We looked at fifteen spikes in coverage in each of the two datasets and then used brute force to identify the story that was driving the cycle. But spike analysis is quite limited in what it can say, especially in the early years of the data set where a small number of articles over a three-day period can exceed the threshold that qualifies as a “spike” in our formulation. With automated text analysis it should be possible to do more granular analysis of spikes in news coverage and also, perhaps, begin to explain larger patterns in the stories that catch the attention of editors and readers. (Empirical research on letters to the editor, where those exist, could also help round out the picture by showing what motivated readers do in response). Multivariate analysis of the entire data set—not just spikes—can add to explanation but will require particularly careful attention to the construction of dependent variables given the large changes in coverage included in the MediaCloud data set. Explanation should also look at geographical focus of non-elite news outlets, political leanings, and other factors that plausibly could explain patterns. Better explanation will require looking more closely at the content of coverage, not merely incidence.
Third is the need to disaggregate original stories from those that are simply reprinted. Wire services (like the Associated Press), in particular, generate a lot of reprinting through which the lines between elite and heartland might be blurred because news articles in multiple places have common origin. Reprinting should affect measures of incidence and may also be a fruitful way to explore where and how connections between elite and heartland news sources remain more durable. Such a reprinting effect would produce a tendency toward convergence between the elite and heartland datasets—suggesting that the divergence results we present here are robust.
The United States is early in a long process of developing and implementing a national policy strategy on climate change (American Academy of Arts and Sciences 2023). What it does at home will affect how it is seen abroad and its ability to get other nations to take a collective approach to climate change. The political viability of the American national policy depends, in large part, on what American think about climate change. For too long the efforts to understand what question have focused on elites and not the whole country.