Depth of information processing as a moderator to mental models of climate change

Master's Thesis, 2017

48 Pages, Grade: 1,5




1 Introduction

2 Theoretical background
2.1 The carbon cycle
2.2 The climate system
2.3 Climate change
2.4 Public beliefs about climate change
2.5 Stock-flow processes
2.6 Aim of this study and hypotheses

3 Method
3.1 Participants
3.2 Task description

4 Results
4.1 Preliminary analyses
4.2 Results regarding demographic variables
4.2.1 Ordinal data
4.2.2 Binary data
4.3 Results regarding the hypotheses
4.4 Qualitative analysis

5 Discussion

6 Conclusion

7 List of figures

8 References


In stock-flow relationships inflows and outflows of a stock accumulate over time. Previous studies have shown people’s poor understanding of accumulation (e. g. Sterman & Booth Sweeney, 2007). This study examines the relationship between performance in a stock- flow experiment and depth of information processing. Half of the participants read a text about the dangers of climate change to prompt deeper processing (and understanding) of the following stock-flow task. Then they were given one of two scenarios in which the atmospheric carbon dioxide level rose/fell from year 2000 and stabilized at a higher/lower level until the year 2100. They had to choose the correct carbon dioxide emissions and uptake trajectory in order to realize the development of the carbon dioxide level in their scenario. Performance was low. More than half of the participants chose emission trajecto­ries similar to the shape of the atmospheric carbon dioxide curve which is an indication for pattern matching. Giving participants information about the dangers of climate change did not increase their performance.

Keywords: climate change, accumulation, mental models, global warming, information processing, correlation heuristic

1 Introduction

Climate change or global warming refers to the rise of the Earth’s global mean temperature due to the increasing amount of carbon dioxide in the atmosphere (Gabler, Petersen & Tra- passo, 2007; IPCC, 2014). The IPCC “is now 95 percent certain that humans are the main cause of current global warming” (IPCC, 2014, p. V).

In international climate politics the United Nations Framework Convention on Climate Change (UNFCCC) was the first international treaty that called climate change a serious problem (UNFCCC, 1992). Entered into force 1994, its goal is to stabilize atmospheric carbon dioxide concentrations to prevent dangerous anthropogenic interference with the climate system. It called for a commitment of participating nations to restrict their carbon dioxide emissions and is the basis for further negotiations on international climate protec­tion. Currently it is ratified by 196 states and the EU (UNFCCC, 2017). The Kyoto Proto­col as next big climate agreement was entered into force in 2005 and controls emissions of the important greenhouse gases (carbon dioxide, methane, nitrous oxide, fluor gases) (Kyo­to Protocol, 1997). It obligates member states (only developed countries) to reduce their emissions by an average of 5.2 % compared to the levels in 1990. The latest Paris Agree­ment was entered into force in 2016 and set the maximum allowance for temperature rise to 2° C (better 1.5° C) compared to the preindustrial level (Paris Agreement, 2015). Reduc­ing carbon dioxide emissions sufficiently to reach that goal will prove difficult as the use of fossil fuels is still rising as of today as well as the level of atmospheric carbon dioxide (NASA/GISS, 2017b). The US as the second largest emitter of carbon dioxide (after Chi­na) withdrew from the Paris Agreement in 2017 (PBL, 2017; White House, 2017). And even if emissions are cut completely warming would continue, because of the carbon diox­ide already in the atmosphere (IPCC, 2014).

When looking at international climate treaties one could argue that global warming is pri­marily a topic for science and politics. Therefore policies regarding climate change should only be based on scientific expertise and the public need not concern themselves. Why then do people need to understand climate change? It is a valid question. While true, that scientific concepts are necessary to understand climate change and policies for complex natural systems should definitely be based on scientific knowledge the public does have a major role to fulfil. At least in democratic governments the beliefs of the public decisively shape future goals and policies through election and political participation. Successful pol­icies need to be understood and accepted by citizens. But making an informed decision requires accurate knowledge. In some cases this is simple - for the majority of today’s is­sues it is not (e. g. the conflict between the US and North Korea, gender equality, war ref­ugees, the “Brexit”). One other difficult issue is climate change. Surveys show generally poor knowledge and understanding of causes and effects of climate change and scientific principles (Bostrom, Morgan, Fischhoff & Read, 1994; Lorenzoni & Pidgeon, 2006; Read, Bostrom, Morgan, Fischhoff & Smuts, 1994; Weber & Stern, 2011). This poses a problem due to the influence of the public on government policies. If people’s understanding of issues is faulty they could favour policies with different outcomes than they intended with their support. Bord, O’Connor and Fisher (2000) showed that both accurate and inaccurate beliefs about the causes of global warming lead to believing it is happening. But false be­liefs can lead to uncertainty about the right policies. So with inaccurate knowledge people may not be able to distinguish between effective and ineffective strategies to deal with cli­mate change (Bostrom et al., 1994). In recent years many people adopted a “wait and see strategy”, which means not doing anything until climate change is really seen to be a prob­lem (Sterman & Booth Sweeney, 2007). As it is seen as a gradual process they believe it can be dealt with gradually. Especially since there is still uncertainty about the causes and consequences of climate change, they think that costly action should be suspended until the dynamics of global warming are better understood (Sterman & Booth Sweeney, 2007). The majority of everyday lives consist of simple systems where cause and effect are closely related and time delays are short (Sterman, 2008). For most things it is enough to wait for a system to reach a certain state and then take corrective action. Wait and see strategies are valuable heuristics for most common tasks with short time delays, plenty of time for cor­rective action, timely outcome feedback and low costs of error (Sterman, 2008). Waiting and seeing is useful in simple systems, but not in a complex issue like climate change. This strategy imposes linearity and simplicity on a non-linear and complex system with long delays between causes and effects (Scheffer, Carpenter, Foley, Folkes, Walker, 2001). With short delays consequences can be reasonably safely attributed to a cause and knowledge about the cause enables one to employ effectively countermeasures. But the climate system has long response delays (Thomas et al., 2004; Houghton et al., 2001). Some delays arise from the need to first develop a scientific consensus about what is hap­pening and how this can be countered. Then time is required to build up public support to pass legislation and international agreements. But major response delays reside within the climate systems itself. To understand this accurate knowledge of stock and flow relation­ships between key features of the system and the carbon cycle is required. In stock and flow relationships the flows in and out of a stock accumulate over time.

The following will provide theoretical background for this study. I will give a short over­view of the carbon cycle and the climate system with all the necessary basic information for the main part. I will outline causes and effects of climate change and summarize the public’s opinion of global warming. Then I will explain stock-flow processes and examine a few studies that have researched understanding of accumulation and stock-flow reason­ing.

2 Theoretical background

Why is the climate system so difficult to understand? It is described as a complex system and as such its properties make really understanding it a challenge (Amelung & Funke, 2013; Frensch & Funke, 1995; Gabler et al., 2007). Complex systems are comprised of a great number of interconnected and interacting elements that can form not-foreseeable large overall patterns. They have an inherent dynamic which means that systems continu­ously change their state even without outside (anthropogenic) input. This is realised through multiple positive and negative feedback loops within the system itself. Negative feedback processes within the system counteract one another which helps the system main­tain its equilibrium. Positive feedback processes reinforce each other and the system can behave non-linearly and exponentially which can account for rapid change. Foreseeing such changes is impossible as the underlying structure and dynamics of a system are usual­ly largely unknown. The state of the system depends on previous states and so cannot be described (and interpreted correctly) without taking its history into account.

Natural systems are usually stable (Holling, 1973). This means that they go back to their original state after a disturbance (resilience). However if a disturbance is great enough a system’s balance may be critically affected so that the system will evolve to another stable state with different descriptive qualities (Scheffer, Carpenter, Foley, Folke & Wagner, 2001). Sometimes this change is permanent and catastrophic. There are certain tipping points in the climate system that when broken will have abrupt, catastrophic and irreversi­ble consequences with severe long-lasting shifts of the climate (Lenton et al., 2008). Ex­amples are the collapse of tropical rain forests or the thawing of the Arctic, Antarctic and Greenland. In certain regions of the Earth these changes can severely overstrain people’s potential for adaptation.

2.1 The carbon cycle

The carbon cycle is one of the main biogeochemical cycles of the Earth (see figure one) (Gabler et al., 2007; Wigley & Schimel, 2000). Carbon is stored in large reservoirs in the Earth’s crust, oceans, terrestrial ecosystems (vegetation, soils) and the Earth’s atmosphere. Carbon cycle refers to fast and slow carbon flows between the reservoirs. In the fast carbon cycle atmospheric carbon dioxide is assimilated by primary producers (plants) which con­vert it into oxygen and organic compounds (lipids, sugars for plant biomass) through pho­tosynthesis. The oxygen is partly used by the plants themselves for respiration (energy production) and partly released into the atmosphere. Secondary consumers (animals and humans) use oxygen for respiration and release the resulting carbon dioxide back into the atmosphere. In the slow cycle carbon from dead organic material is incorporated into soils by tertiary consumers (e. g. fungi, bacteria) where it remains for decades/centuries before it is broken down by soil microbes and released back into atmosphere.

Abbildung in dieser Leseprobe nicht enthalten

Figure 1. The carbon cycle (U.S. Department of Energy, 2008)

In oceans at a depth of up to 75 m carbon dioxide diffusion processes occur in both ways - atmospheric carbon dioxide gas dissolves in and ventilates out of the ocean (Gabler et al., 2007; Salby, 2012; Wigley & Schimel, 2000). Phytoplankton assimilates dissolved carbon dioxide in the water for photosynthesis. Marine life uses plankton as a food source and releases carbon dioxide through respiration and organic waste. Organic waste is broken down and stored in oceanic sediments in the deep ocean. It takes even longer for organic matter buried in deep sediments to be slowly turned into deposits of coal, oil, gas (fossil fuels). Humans influence the carbon cycle mainly through the burning of fossil fuels (oil, gas, coal) which releases carbon dioxide into the atmosphere.

2.2 The climate system

It is important to differentiate between weather and climate (Gabler et al., 2007; Salby, 2012). Weather is the state of the atmosphere at a certain time in a certain area. It is de­scribed with physical parameters like temperature, air pressure, humidity and precipitation. Climate is the average state of the atmosphere over a longer time period (usually decades) in a certain area and describes the characteristic weather patterns for this area. The climate in a region is mainly influenced by its energy balance (Gabler et al., 2007; Salby, 2012). Incoming solar energy is absorbed by the Earth, but the intensity varies for different lati­tudes. It is strongest in the equatorial region and gets weaker with further distance from the equator. This imbalance in the intensity of solar radiation causes a heat transport from higher to lower latitudes and is essentially the reason for atmospheric circulation (winds) and ocean currents.

The Earth’s climate system is an open circuit system with a continuous input of solar ener­gy (see figure two on the next page) (Gabler et al., 2007; Trenberth et al., 2009). During the day 341 Watt/m'2 of solar energy reaches the Earth. 30 % is reflected back into space by clouds and the Earth’s surface. The remaining 70 % is absorbed by the atmosphere and to a higher degree by the surface. During night time heat released from the surface is partly emitted into space and partly reflected back by natural greenhouse gases. This “traps” heat in the Earth’s atmosphere (radiative forcing). This process is called the natural greenhouse effect and causes the Earth to be warm enough to make it habitable for life. Certain aero­sols and volcanic ash particles in the Earth’s atmosphere cause an increase of the reflection

Abbildung in dieser Leseprobe nicht enthalten

Figure 2. The climate system (Trenberth, Fasullo & Kiehl, 2009)

The most important natural greenhouse gas is water vapour (Gabler et al., 2007). The at­mosphere can only absorb a certain amount of water vapour before it is saturated. The higher the air temperature the more water vapour can be absorbed which increases the greenhouse effect and the Earth’s temperature. Other greenhouse gases are carbon dioxide, methane, fluor gases and nitrous oxide (see below).

2.3 Climate change

Since the industrial revolution increas­ing amounts of carbon dioxide have been released into the atmosphere due to burning of fossil fuels (coal, gas, oil)

(Gabler et al., 2007; IPCC, 2014) (see figure three). The higher level of car­bon dioxide in the atmosphere caused more heat to be “trapped” due to stronger radiative forcing (anthropo­genic greenhouse effect). The energy balance was disrupted in favour of in­coming energy. This means that there was more sun energy entering the at- Figure 3- Carbon dioxide concentration during the last millennium (Malhi, Meir & Brown, mosphere than leaving it which in- 2002) creased the Earth’s global mean temperature (see figure four). As carbon dioxide continues to be released into the atmosphere, the temperature is still rising. For the year 2016 NASA reported an average temperature of 0.99° C relative to 1951-1980 average temperatures which makes it the warmest year on record (NASA/GISS, 2017a).

The Kyoto Protocol names four important anthropogenic greenhouse gases[1]: Carbon diox­ide (76 %), methane (16 %), fluor gases (CFCs, 2 %) and nitrogen oxides (6 %) (IPCC, 2014; Kyoto Protocol, 1997). Apart from fossil fuels carbon dioxide is also released by land cover changes (deforestation, urbanization) and cement production (Wigley & Schimel, 2000). Through deforestation plants are removed that would otherwise remove carbon dioxide from the atmosphere and so precious carbon sinks (= storage reservoirs) are lost. Methane is primarily generated by rice cultivation and cattle breeding, but also by the thawing of permafrost (Montzka, Dlugokencky & Butler, 2011). It has few natural sinks and is 20 times more effective as a greenhouse gas than carbon dioxide (Gabler et al., 2007). Nitrogen oxides are generated from fertilizers (Montzka et al., 2011). Fluor gases are used in liquid coolants and solvents in industrial processes. Both fluor gases and nitro­gen oxides stay in the atmosphere for centuries due to weak reactivity with other substanc­es (Malhi et al., 2002). The atmospheric concentrations of all greenhouse gases still con­tinue to rise (IPCC, 2014).

Climate change has several impacts on ecosystems and human systems (IPCC, 2014). As global ice reserves (Arctic, Antarctic, Greenland, glaciers) melt and due to the expansion of warmer water the sea level has risen and continues to rise (Salby, 2012). This increased the likelihood and severity of storms and flooding which threatens coastal regions. Because the carbon dioxide uptake of oceans increases the water continues to become more acidic which stresses pH-sensitive marine life (IPCC, 2014). The likelihood of extreme weather events has increased which includes heavy rainfalls, heat waves and storms (IPCC, 2014). Due to more hot days and fewer cold days heat-related mortality has increased. The higher global temperature has changed the geographical range of infectious diseases spread by insects (e. g. dengue fever, lyme disease, malaria, yellow fever, leishmaniasis) (Patz, Campbell-Lendrum, Holloway & Foley, 2005; Patz, Olson, Uejio & Gibbs, 2008). Droughts, floods and wildfires have a negative impact on crop yields which can lead to increased malnutrition (Patz et al., 2005; Patz et al., 2008). Changes in migration patterns and geographical distribution of animals have been observed and some species show risk of extinction (Parmesan & Yohe, 2003; Thomas et al., 2004).

With greenhouse gas emissions still rising further warming is expected which will result in long-lasting and likely irreversible changes of the climate system according to the Fifth Assessment Report of the IPCC (2014). They outline several scenarios for future climate changes which I cannot discuss here in detail. To summarize: Even if we cut emissions completely right now warming would still continue, because of the inherent time lags of the climate and the already accumulated carbon dioxide in the atmosphere. The atmospher­ic carbon dioxide level would peak and stabilize in a few centuries. It will take even longer for the global mean temperature (several centuries) and sea level (centuries to millennia) to reach equilibrium. 90 % of the energy accumulated between 1972 and 2010 is stored in oceans which act as great heat reservoirs (Salby, 2012). This makes warming much more gradual and it will likely continue for at least another century. Eventual future climate ca­tastrophes cannot be predicted, because of the complexity of the climate system and in­complete data. Climate change is not a single hazard, but a process which changes the like­lihood of hazards (Weber & Stern, 2011).

2.4 Public beliefs about climate change

Most people consider climate change a serious problem and think that it has already begun (Bostrom et al., 1994; Lorenzoni & Pidgeon, 2006; Read et al., 1994; Weber & Stern, 2011). But laypeople’s mental models of global warming have several basic misconcep­tions.

Mental models are internal representations of people’s assumptions and beliefs about the world (Kearney & Kaplan, 1997). They are cognitive knowledge structures that influence how we see the world and react to it. Through formulating actions and behaviour they are the basis for the individual approach to and solving of problems. They are the framework for interpreting new information. Therefore mental models are vulnerable to the confirma­tion bias (Lewicka, 1998). This means that people usually process new information in a way that it is supportive to their pre-existing beliefs by selectively choosing information. But they can also contain major flaws especially for complex issues like climate change.

Bostrom et al. (1994) conducted mental model interviews with well-educated laypeople about causes and effects of climate change. This means asking general non-directive ques­tions to invite people to tell their own beliefs. Few could explain the process of global warming correctly. Many people confused the greenhouse effect with stratospheric ozone depletion or general air pollution. Weather and climate were often used interchangeably. Perceived primary causes of global warming included deforestation, automobile use, indus­trial processes, aerosol spray cans and pollution in general. The role of carbon dioxide and fossil fuel combustion was seldom realized. As effects of global warming interviewees mentioned increase in temperature, increased risk of skin cancer and sunburn, changes in precipitation patterns, melting of polar ice caps, sea level rise, agricultural and ecosystem impacts, increase in floods and droughts and changes in living standards and economic conditions.

Other studies have similar results (Lorenzoni & Pidgeon, 2006; Read et al., 1994; Weber & Stern, 2011). Most people believed that humans contribute to global warming and thought that something should be done about it. But compared to other threats (e. g. terrorism, do­mestic issues, personal problems) climate change ranked lower as a priority (Bord et al., 2000; Helgeson, van der Linden & Chabay, 2012; Lorenzoni & Pidgeon, 2006). This may be, because people think climate change will not affect them personally and so dealing with it is not that urgent. Public concern about climate change fluctuates with media cover­age and adverse weather events (Bord et al., 2000; Weber & Stern, 2011). It is not a salient risk, because it usually has only little impact on people’s everyday lives (Lorenzoni & Pidgeon, 2006). Climate change is viewed as something impersonal and distant (O’Neill & Nicholson-Cole, 2009). Some people display unrealistic optimism with seeing the risk for society from climate change, but downplaying the risk for themselves (Bord et al., 2000; Helgeson et al., 2012; Lorenzoni & Pidgeon, 2006). This may be, because the risks of cli­mate change are not directly observable (Helgeson et al., 2012; Weber & Stern, 2011). Climate change is a slow, on-going and often invisible process with few cues for percep­tion. As most problems in people’s environment are observable and therefore relatively easy to deal with, we are not used to a complex problem like climate change which can lead to underestimation.

2 In short: The ozone layer in the atmosphere acts as a shield against UV light. Industrial compounds (e. g. formerly in aerosol spray cans) can destroy the ozone layer. People believed that warming occurs, because of the increase in UV light due to the hole in the ozone layer (Bostrom et al., 1994).

2.5 Stock-flow processes

Several studies show that people do not have any intuitive feeling of stocks and flows - the process of accumulation (Cronin, Gonzalez & Sterman, 2009; Dutt & Gonzalez, 2009; Dutt & Gonzalez, 2013; Moxnes & Saysel, 2009; Newell, Kary, Moore & Gonzalez, 2015; Sterman, 2008; Sterman & Booth Sweeny, 2007). Even highly educated laypeople have difficulties solving stock flow tasks correctly. In stock flow relationships there is one stock, one inflow to the stock and one outflow from the stock. So the level of the stock at a certain point of time is the previous level plus the difference between inflow and outflow. The stock falls when the inflow is less than the outflow and rises when the inflow is ex­ceeding the outflow. It remains stable when inflow and outflow are equal. Instead of taking this relationship into account people often rely on a pattern matching heuristic where out­puts are correlated with inputs (Cronin et al., 2009; Dutt & Gonzalez, 2009; Dutt & Gonza­lez, 2013; Moxnes & Saysel, 2009; Newell et al., 2015; Sterman, 2008; Sterman & Booth Sweeny, 2007). They assume that the accumulating variable (the stock) should “look” like the inflow while disregarding the outflow (pattern matching). This allows for quick prob­lem solving in simple linear systems, but fails at more complex ones. With stock flow structures the stock can continue to rise even if the inflow falls as long as the inflow ex­ceeds the outflow. Pattern matching would falsely suggest that the stock must fall, because the inflow is falling. Chen (2011) explains the robust nature of pattern matching with static mental models that ignore change over time. Stock-flow relationships are dynamic in that the difference between inflow and outflow defines not the level of the stock but its change at a particular point of time.

Regarding atmospheric carbon dioxide there is one stock (the atmospheric carbon dioxide), one inflow (carbon dioxide emissions) and one outflow (carbon dioxide uptake by plants and oceans). The atmospheric carbon dioxide level accumulates emissions minus the natu­ral uptake rate. Radiative forcing is affected by the level of carbon dioxide in the atmos­phere and the global mean temperature rises with net radiative forcing. So even if emis­sions are reduced the atmospheric concentration of carbon dioxide would continue to rise until the rate of emissions and removal is the same. Therefore warming would also contin­ue. The carbon dioxide concentration can only begin to fall when emissions are less than the removal rate. Pattern matching would incorrectly suggest that atmospheric carbon diox­ide level and global mean temperature would immediately fall following a decrease in
emissions. Relying on pattern matching vastly underestimates the long time lags in the climate system and how much emissions really need to be cut to stabilize the climate in the long term. Anthropogenic carbon dioxide emissions are now roughly double the removal rate, so the carbon dioxide level would continue to rise even if emissions fall (Houghton et al., 2001). The carbon dioxide level can only stabilize if emissions and removal rate are equal. It can only fall if emissions are less than the removal rate.

Abbildung in dieser Leseprobe nicht enthalten

Experiments have been conducted to test for pattern matching in stock flow problems:

from year 2000 and held at +/-8 % in the year 2100. The task was now to sketch the emis­sions and removal rate needed in order to realize the development of the carbon dioxide level in the given scenario (climate stabilization task; see figure five). Subjects also es­
timated how Earth’s temperature would develop in their scenario by selecting one of seven given tra­jectories (multiple choice). In sce­nario one the emission rate should fall and then remain equal to the removal rate as atmospheric car­bon dioxide first rises and then remains unchanging. In scenario two the emission rate should be less than the removal rate and then remain equal to it as atmospheric carbon dioxide is declining and then remains unchanging. In both scenarios 75 % of the participants sketched emission rates that were above the removal rate. Figure six shows a typical response for scenario one. They believed that the carbon dioxide level can be stabilized (or fall) even if emissions exceed removal rates. The shapes of the sketched curves closely followed the atmospheric carbon dioxide curve for both scenarios which is evidence for pattern matching. Participants saw a non-existing direct correlation between emissions and carbon dioxide level, so that stopping the growth of emissions would stop the growth of the carbon dioxide concentration. The removal rate was often overestimated probably due to lacking knowledge about the carbon cycle. It is likely to fall as terrestrial and oceanic carbon sinks fill and because of deforestation (Bostrom et al., 1994; Mackey et al., 2013). Many participants even believed that carbon dioxide uptake would rise. Their sketched removal curves closely matched the shape of their emissions curve. This is anoth­er example of pattern matching. Temperature responses also show pattern matching. In scenario one where carbon dioxide rises participants could reasonably conclude that the temperature would continue to rise as pattern matching would suggest as well. In scenario two where carbon dioxide falls participants should assume that the temperature would con­tinue to rise at a diminished rate, because radiative forcing would likely fall, but still be above preindustrial levels (where anthropogenic radiative forcing was roughly zero). Here pattern matching leads to wrong conclusions. Nearly half the participants answered that the temperature would immediately fall following the decline of atmospheric carbon dioxide.

One could argue that the graphical display of carbon dioxide levels from the preindustrial period up to the year 2000 could predispose subjects to use pattern matching. In this time period both atmospheric carbon dioxide level and emissions rise in a similar shape.


[1] In the brackets are the shares in greenhouse gas emissions for each greenhouse gas.

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Depth of information processing as a moderator to mental models of climate change
University of Kassel  (Center for Environmenal Systems Research)
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Marie-Rose Degg (Author), 2017, Depth of information processing as a moderator to mental models of climate change, Munich, GRIN Verlag,


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