In the previous post we have presented one part of our topic modelling exercise in which we have investigated which of the 100 identified topics were represented in the journal of Global Environmental Change (GEC) more than any other journal. These topics represent the distinctive aspects of the journal and analysing their distribution over the years will allows us to investigate whether and how the journal has changed over the years. By correlating the results of our labelling exercise and multi-dimensional analysis we can observe in what manner, or which type of papers and contexts, these topics are usually discussed. More importantly, as these topics are computationally calculated groups of words, identifying the contexts in which these topics occur in will allow us to interpret the topics themselves.

Previously we have described our first topic, Topic 7, as ‘International Development’ based on both the words included in the topic as well as the use of the topic mainly in ‘Policy Discussion’ and ‘Research Agenda’ papers, since the field of International Development is strongly associated to global and international policy and agenda discussions. What is interesting about this topic is that it was strongly represented in the early years of the journal and gradually reduced as the years went by. When this is correlated with the lower number of empirical papers in the early years of the journal and their subsequent rapid increase, we can assume that research field represented in the journal moved on from the agenda setting and discussion to empirical investigation.

 Topic 50 is the second topic strongly associated with GEC and includes the following word stems: will, can, may, need, requir, must, target, howev, limit, possibl, current, future, like, make, becom, potenti, necessari, provid, exist and example. The topic is usually used in ‘Policy Discussion’ type of papers and has also been prominent in the early years of the journal and been on the decrease ever since. We have interpreted the topic as dealing with prediction of future outcomes of policies or expressing the requirements for the desired outcomes to be achieved. For example, what needs to be done for the level of carbon emissions to be reduced by a certain degree.

Topic 58 is a topic which is consistently used throughout 20 years of the journal, usually in ‘Research Agenda and Research Framework’ type of papers. The topic includes the following word stems: research, paper, section, discuss, focus, approach, work, develop, analysi, issu, understand, framework, scienc, literatur, process, address, knowledg, review, studi, provid. Based on the use of these words in the context of agenda and framework discussion, we have interpreted the topic as ‘Research Framework Discussion’ since the topic represents a narrative reviewing previous and proposing new approaches to research. At the moment, it is unclear why such general research topic is particularly related to GEC, but we speculate it may be more prominent in newer, less-formulated research fields.

Topic 60 includes the following word stems: govern, policies, develop, public, state, nation, local, institut, plan, issu, project, intern, agenc, polit, implement, communiti, environment, program, fund, particip.  As we can see, Topic 60 is quite similar to our first topic, Topic 7 – International Development, in some of the words included in the topic, as well as the types of papers it occurs in. However, there are some important differences. Firstly, Topic 60 is mainly associated with policy discussion type of papers and is consistently used over the 20 years of the journal. Also, by observing the papers, we can see that the topic indeed represents a discussion of policy implementation at the local, state and national level, and also relating to different governmental and international programs, funds and agencies. Thus, we decided to label this topic ‘Policy Implementations’, which also allows us to differentiate it from ‘Policy Discussion’ type of paper used in the labelling exercise.

Topic 81 includes the following word stems: chang, climat, scenario, adapt, impact, vulner, futur, global, assess, capac, project, polici, uncertainti, respons, will, current, region, rise, warm, ipcc (Intergovernmental Panel on Climate Change). The topic mainly occurs in ‘Research Agenda and Research Frameworks’ type of papers and has been increasingly used over the year in GEC. The topic represents the key climate and environmental agenda discussed in the journal; hence we have labelled it ‘Environmental Change’.

Topic 86 is all about carbon emissions and includes words stems: emiss, carbon, reduct, gas, reduc, estim, greenhous, atmospher, sourc, contribut, year, sequestr, total, inventori, potenti, gase, methan, ghg (greenhouse gases), result, emit. As the topic represents discussions about carbon and greenhouse emissions, it is not surprising that the topic is mainly represented in ‘Policy Discussion’ type of papers. Although papers from GEC scored the strongest in the topic, the topic is also prominent in the journal of Transportation Research Part D: Transport and Environment (TRTE), which is not surprising as the topic relates both to the issues of transport and environment. The use of the topic in GEC has also decreased over the years. We have labelled the topic ‘Carbon Footprint’ as it discusses the sources and potential reductions of carbon emissions, as well as the impacts on environment.

Topic 96 is a recurring topic in GEC, meaning that it was very prominent in the early years of the journal but decreased over the years up to a point where it started to become more prominent again and its use has been on the increase ever since. The topic includes the following word stems: environment, risk, natur, resourc, manag, environ, human, ecolog, sustain, ecosystem, health, protect, conserv, impact, concern, develop, biodivers, potenti, need, include. We have interpreted the topic as ‘Sustainability’ since it discusses the issues of resource management, risks to environment and ecosystems, preservation of biodiversity etc.  The topic correlates with ‘Research Agenda and Research Framework’ type of papers, but not so much with ‘Policy Discussion’ type of papers, which implies that the topic is more related to pointing out issues of concern in GEC rather than sustainability policies.

To conclude, it is not surprising to see these topics highly represented in GEC. However, it is very reassuring to see that a computational method can effectively discriminate topics, which are interpretable and make sense to researchers, but can also be attributed to particular journals. Additionally, it is very interesting to observe that certain topics tend to occur in particular types of papers, which means that there is a particular way we talk about certain issues. In the next post we will present how this correlates with the results of our multi-dimensional analysis, i.e. whether topics correlate with particular linguistic features. In the meantime, leave us a comment below o on what you think about our topics, their interpretation or their use in GEC.