Key phrase trends in climate change research and communication

Figure showing database search results using CC as the key phrase. The annual counts for research articles and New York Times articles are displayed on the primary axis while annual counts for NSF grants are displayed on the secondary axis. The vertical lines denote years with notable climate change-related events.

Figure 1. Database search results using CC as the key phrase. The annual counts for research articles and New York Times articles are displayed on the primary axis while annual counts for NSF grants are displayed on the secondary axis. The vertical lines denote years with notable climate change-related events.


Since the late 1980s, research to understand the scientific basis of anthropogenic climate change has gained momentum. Communicating this body of knowledge has proved challenging but is essential for decision-making, public understanding and adaptation and mitigation [1]. The public relies on media dissemination of climate change information, however, complex science and portrayal of uncertainty can cause confusion [2, 3, 4, 5, 6]. Terminology has been suggested to play a role in public perception. Early on, the issue was referred to as the greenhouse effect, or a direct reference to the heat-trapping process. Today, commonly used terms are global warming (GW) or climate change (CC). According to the U.S. Environmental Protection Agency (EPA), GW is the “recent and ongoing rise in global average temperature near Earth’s surface… caused mostly by increasing concentrations of greenhouse gases,” while CC “refers to any significant change in the measures of climate lasting for an extended period of time” [7].

According to a study from the University of Michigan, partisan affiliation is the most important factor of an individual’s views on climate change. Those who accept that climate change is occurring generally believe it is a serious issue. However, the level of belief declined from 2008 to 2010, and still remains below the levels observed in 2008 [8]. While addressing climate change, White House Science Advisor John Holdren said that GW is a misnomer because it implies a uniform trend that primarily involves temperature [9]. Holdren suggests using the term ‘global climate disruption’ instead. Climate scientists have advocated for using the more technically correct phrase of ‘climate change,’[10] which encompasses the additional processes of the warming climate including ice melt and hydrological extremes. Although often used interchangeably, polling data revealed that GW

Figure showing the same as in Fig. 1, but using Global warming as the key phrase.

Figure 2. As in Fig. 1, but using GW as the key phrase.

is seen as a more threatening term than CC [11]. In a famous memo, political strategist Frank Luntz urged Republicans to challenge climate science and emphasize uncertainty [12]. He advised using CC instead of GW because it sounds more controllable [10]. “Framing is an unavoidable reality of the communication process….”[12] Communication research has found that framing climate change in terms of public health elicits hopeful emotions and support of mitigation and adaptation [13].

In this study, the trends in GW and CC discourse in the U.S. and relative usage of each key phrase in the media and scientific research are explored. The objectives are to identify key phrase trends among high-circulation newspapers, research articles, and grant proposals from 1985 to 2012, and compute correlation coefficients between all pairs of datasets to better understand climate science communication.

Data and Methodology

Three high-circulation newspapers with digital archives are used to represent media coverage of climate change: The New York Times, the Chicago Tribune, and The Washington Post. Although television, websites, podcasts and other alternative media are also comprehensive sources of information, newspaper archives provide the most consistent data over multiple decades. National Science Foundation awarded research grants are used to represent discourse within the science community. Lastly, the University of Georgia (UGA) Libraries GALILEO catalog serves as a source for peer-reviewed research articles which represent climate science communication. GALILEO multi-search spans more than 90 databases including Academic Search Complete, Elsevier ScienceDirect, JSTOR and Web of Science.

Table showing key phrase totals over the study period for each dataset with the dominant key phrase in bold. A usage ratio is computed by dividing GWtotal by CCtotal. A higher ratio equates to higher GW key phrase usage.

Table 1. Key phrase totals over the study period for each dataset with the dominant key phrase in bold. A usage ratio is computed by dividing GWtotal by CCtotal. A higher ratio equates to higher GW key phrase usage.

The exact key phrase “climate change” is searched within each database to compile annual counts of CC-related grants, research publications and newspaper articles from 1985 to 2012. The method is repeated for the key phrase ‘global warming.’ Although search results are not filtered by removing paleoclimate-related topics, it is assumed that any increase in discourse after1988 is primarily related to current climate change. Time series of annual counts provide a visual analysis of trends and reveal years of peak climate discourse. The similarities of temporal trends across databases are assessed with Pearson’s Correlation Coefficient where r ≥ 0.70 is a very strong positive correlation.


The CC key phrase search revealed that climate change discourse became most evident in the late 1980s (Figure 1). Several events in 1988 called attention to anthropogenic warming including testimony by NASA scientist Dr. James Hansen, a speech by British Prime Minister Margaret Thatcher, and a major drought in North America [15]. The number of research grants peaked in 2009 with research articles following a similar exponential increase in the early to mid 2000s. New York Times article counts oscillate with two major peaks in 2001 and 2008. The Intergovernmental Panel on Climate Change (IPCC) and National Academy of Sciences (NAS) released global warming reports in 2001. The film “An Inconvenient Truth” was released in January 2006 and Al Gore and the IPCC won the Nobel Peace Prize for drawing attention to climate change in October 2007. These events increased discourse and debate over anthropogenic warming and may have led to the increase in media attention during those years. The GW key phrase search presents a similar exponential increase in grants and research, although not as continuous as CC results from year to year (Figure 2). As with CC, GW topics in the New York Times peaked in 2001 and 2008. Clearly, media-worthy events must have occurred in those two years. Both graphs show a downward trend in climate change research beginning around 2009.

Figure showing a time series of annual CC and GW key phrase totals for research articles (primary axis) and NSF grants (secondary axis) 1985-2012.

Figure 3. Time series of annual CC and GW key phrase totals for research articles (primary axis) and NSF grants (secondary axis) 1985-2012.

A comparison of research articles and grants between CC and GW key phrases reveals CC is used about four times more for both datasets (Figure 3). This is expected as CC is a broader term and is used more frequently in scientific communication. The New York Times, Washington Post, and Chicago Tribune exhibit similar trends with peaks in discourse around 2007 (Figure 4). For most of the period, the newspapers use GW more than CC. An interesting finding, however, is that this trend reverses for all three newspapers around 2008 (highlighted). Presidential debates followed by President Obama’s climate change goals may have increased the term’s usage. A 2008 climate change report by the National Academies stated “The phrase ‘climate change’ is growing in preferred use to ‘global warming’…” [16]. The New York Times has an additional reversal between 2000 and 2004. The totals for the entire time period verify that in newspapers, GW is used to nearly the same extent as CC (New York Times) or more often (Post and Tribune) (Table 1). However, in grants and research articles, CC is used significantly more often. A usage ratio is computed by GWtotal divided by CCtotal 1985 to 2012. A higher ratio signifies greater usage of the GW key phrase. The datasets ranked from highest to lowest usage are the Post, Tribune, Times, research articles, and grants. This illustrates that the media preferred the term “global warming” over the study period, despite the fact that research was using “climate change”.

Pearson’s correlation coefficients between all pairs of datasets are shown in Table 2. Research articles correlate very well with grants (r=0.80 to 0.98) as predicted with the time series graph. Research article trends do not correlate as well with newspaper articles, but still indicate a strong positive relationship. The key phrases CC and GW within a particular database have consistently strong correlations (highlighted values). The lowest correlation is between research grant CC and newspaper GW trends.


The media plays an important role in communicating climate change science to the public. Due to various agendas or misinterpretation, the media does not always report research as intended by the scientific source. It has been suggested that terminology itself influences perceptions of climate issues. In this study, newspapers, peer-reviewed research articles and National Science Foundation (NSF) grants were analyzed for trends in the key phrases ‘climate change’ (CC) and ‘global warming’ (GW). CC is arguably the more meaningful term because it facilitates communication between scientists, the media, and the general public and it conveys that the range of risks associated with a warming climate are not limited to temperature alone. Results indicate that the media preferentially uses the term GW while research tends to use CC. Three high-circulation newspapers exhibit similar trends in usage over time and have recently increased usage of CC. All data sources indicate climate change discourse peaked around 2008 to 2011, however, this trend may be a result of the discussion turning from general climate change to specific risks. Additional key phrase searches such as ‘glacier melt’ and ‘sea level rise’ may yield different results.

Theresa Andersen is a doctoral student at the University of Georgia Geography Department. She is a member of the American Meteorological Society and Southeastern Division of the Association of American Geographers. Her research interests include climate change, the hydrological cycle, and land surface-atmospheric feedbacks.


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