A.Roca, R.Pestana, J.Nosas, N.Mertens, G.Martínez, H.Cano, M.Fernández, M.Constantí


Currently, the impacts generated by climate change are already noticeable in our environment. Sea level rise and intensification of extreme weather events, such as storms and hurricanes, are some examples of these manifestations that are already noticeable. Climate change is a reality that is causing serious consequences and unless we take action to prevent and/or mitigate its impacts, it will only intensify.

The purpose of this study is to evaluate the main causes and consequences of climate change, focusing on the identification of prevention and mitigation barriers that could/should be applied by the society  (i.e. citizens, businesses and governments) to avoid and/or mitigate the consequences of climate change.

In order to carry out this analysis the BowTie methodology has been applied. This methodology allows the thorough discussion and identification of risks in the form of a diagram, from their causes to their consequences, resulting in a very powerful tool for risks’ communication and management. With it, it is possible to consider all types of risks at all its levels (more generic at the corporate level or more specific at the operational, departmental level…). Furthermore, it allows the analysis of any vector, e.g. safety and health, environmental, financial, strategy and planning, operational and infrastructure or reputation.


2.1. What is BowTie analysis?

The BowTie analysis is a simple way to describe the risks from their causes to their consequences and to represent it in the form of a diagram.

It can be viewed as a combination of two risk analysis methodologies centered on a main event: the Fault Trees (cause identification) and the Event Trees (consequence identification). The BowTie methodology combines both studies through a main event (Top Event), whose function is to “connect” the mentioned studies, resulting in a bowtie-shaped diagram; hence its name «BowTie». Additionally, this methodology considers the barriers that can be applied for the prevention of the causes as well as for the mitigation of the consequences. This process can lead to actions to be implemented, moreover it allows risk quantification.

The first BowTie diagrams appeared in the 70s and 80s as a result of distinct catastrophes in the oil and transportation industries, which evidenced the necessity to develop a systematic analysis methodology to assess the protection degree of such facilities. It soon became popular as tool that allows a straightforward identification and risk management on a larger scale, when compared to the traditional methodologies and, therefore, it ended up being a complementary method to previous ones. Currently, the application of the BowTie Methodology has expanded to a multitude of fields, from the oil, chemistry, mining, aviation and maritime transport (ports included) industries, as well as to different areas, i.e. health and emergency response, or financial and government sectors.

2.2. Analysis’ process

Typically, BowTie diagrams are generated directly in brainstorming sessions with the different agents involved in the main event to be evaluated. The study team must have experts in different disciplines work with and under advisement of a coordinator with experience in the BowTie methodology´s application.

The sessions should be conducted in positive thinking environment, allowing the discussion to flow in a natural way, exposing the necessary arguments and objections that help clarify the points of view and ideas of the team members.

In order to conduct the Climate Change’s BowTie study, experts of TEMA Group developed discussion sessions counting with 8 participants.

The process for Risk Analysis includes the following stages:

  1. Hazard identification or process’ risk. A hazard is a source or a potentially harm situation in terms of injuries or negative effects on people’s health, assets, the environment or a combination of them. Hazards should not be considered as something negative, but an aspect part of the normal activity.
  2. Definition of the Top Event that corresponds to the moment when the hazard is uncontrolled. This constitutes the event to avoid in order to prevent the consequences, and it takes place when the control or the effectiveness of prevention barriers are lost.
  3. Identification of causes that may lead to the development of the Top Event, i.e., the unwanted events that release the hazard and produce the main event. They are listed on the diagram’s left side and must be directly related to develop the Top Event.
  4. Identification of consequences or unwanted events caused by the Top Event’s unfavorable development. There may be more than one consequence for the same Top Event and they can affect different areas such as health and safety, environmental, financial, strategy and planning, operational and infrastructure or reputation. These consequences can lead the potential losses and damages generated by the unfavorable development of the danger and are the effects that should be avoided. They are represented on the right side of the diagram.
  5. Identification of prevention and mitigation barriers. It consists in the subsequent stage and probably is the most important phase in a BowTie study, since the Risk Management relies in the identification and availability of these barriers. Depending on whether the effect of such barrier occurs before or after the development of the main event, it will be defined as a prevention barrier (located on the left side of the diagram, between the cause and the Top Event), or a mitigation barrier (located on the right part of the diagram, between the Top Event and the consequence). Prevention barriers reduce the main event’s frequency of occurrence and mitigation measures reduce the consequence’s severity and possible subsequent negative effects.
  6. Escalation factors. These factors will measure the effectiveness and the failure rate of either prevention or mitigation barriers. The identification of the escalation factors and their respective barriers is necessary to evaluate the failure rate of barriers that could potentially cause the occurrence of the main event and / or its consequences (these are the causes associated with a prevention barrier failure and / or mitigation barrier failure that have not been included a cause).
  7. Moreover, there are two transversal stages in the development of the BowTie analysis that can also be examined: the Actions and / or Recommendations Identification and the Consequences’ Evaluation.

2.3. Barriers’ classification

For the present “Climate Change” BowTie study, preventive and mitigation barriers were categorized according to their implementation’s “responsible entities”. For the implementation of each barrier, one or a group of responsible entities belonging to the categories of citizens, businesses and government were selected. The possible groups are shown in the following table:


3.1. Climate Change’s BowTie Diagram

In this BowTie analysis, the study team selected 7 Causes and 5 Consequences for the “Climate Change” central event:


  • CO2 emission
  • NOx emission
  • CH4 emission
  • Emission of O3 precursors (NOx, VOCs and CO)
  • CFC and HCFCs emission
  • SOx emission
  • Deforestation


  • Famines, diseases, migrations, wars: decline of world population.
  • Animals and plants mass extinction.
  • Changes in costal line due to sea level rise.
  • Ocean’s warming and acidification.
  • Extreme events intensification/ rain cycle alteration / desertification.

Furthermore, prevention and mitigation barriers were identified for each responsible entities selected:

Responsible and Prevention barriers:

  • Citizens:
    • Prioritization of public / collective transport
    • Responsible consumption (Km 0).
    • Reduction of meat consumption.
    • Replacement of household equipment that use CFCs and HFCs.
    • Replacement of wood as fuel by other alternative sources.
    • Ethical consumerism (reduce meat, palm oil, or soy consumption, etc.)
  • Citizens and businesses:
    • Usage of more efficient (less contaminant) vehicles.
    • Organic farming prioritization.
  • All (citizens, businesses and governments):
    • Replacement of fossil fuels with alternative energy.
    • Education, training and awareness.
    • Reduce consumption and promote reuse and recycling.
    • Circular economy
  • Business:
    • Industrial processes’ technological change.
    • Improvement of oil and gas extraction and transportation processes.
    • Reduction of products’ usage with organic solvents.
    • Green industry promotion.
    • Replacement of CFC and HFC gases in industry.
    • Substitution of fossil fuels with sulfur used in industrial processes by alternative fuels.
  • Business and governments:
    • Solvent recycling promotion.
  • Governments:
    • Green tax policy.
    • Active strategies to prevent climate change.
    • Territory planning and protection.

Mitigation barriers:

  • Citizens and governments:
    • Assistance to the proper third world development.
  • Business and governments:
    • Usage of carbon captures technologies.
    • Application of geoengineering techniques to reduce the solar radiation incidence on the planet.
    • Research aimed at reducing climate changes’ effects.
  • Governments:
    • International cooperation.
    • World seed bank.
    • International cooperation for biodiversity protection.
    • Replanning of cities in coastal lines.
    • Evacuation plans.

The BowTie diagram developed is presented below:

3.2. Other functionalities of the BowTie diagram

In addition to the parameters that can be visualized in the previous diagram, BowTie diagrams allow the incorporation and visualization of many other important parameters, establishing a great communication and risk management tool.

These additional parameters are presented below:

3.2.1. Escalation factors and escalation factors’ barriers:

One of the steps of the BowTie analysis methodology is to identify the escalation factors, which will measure the effectiveness and the failure rate of the barriers and, consequently, the escalation factors’ barriers.

For instance, two possible escalation factors for the prevention barrier  “Usage of more efficient (less contaminant) vehicles » are shown in the following image (the escalation factors  aremarked in red) with their respective barriers (marked in green):

3.2.2. Barriers’ associated activities

For each of the prevention and mitigation barriers, the Activities associated with such Barrier can be added in the diagram. Identifying all the Activities associated with a Barrier allows an overview of its control and monitoring, which facilitates the identification of which Activities are associated with the Barrier’s effectiveness and their responsible.

As an example, some of the activities associated with the prevention barrier “Active strategies to prevent climate change” are presented:

3.2.3. Actions and/or recommendations

One of the transversal steps in the development of BowTie analysis is the identification of Actions/Recommendations. These Actions/Recommendations are represented in the BowTie diagram through post-it’s, and can be incorporated in a specific Barrier and/or on the Causes, Consequences, Escalation factors…

The main advantage of including these Actions/Recommendations is that they allow the incorporation of improvements in the existing Barriers and/or to include new Barriers in the Causes, Consequences… Additionally, it is possible to designate the responsible for such Actions/Recommendations execution, the period to do so and the priority of each action.

As an example, an Action/Recommendation (marked in red) associated with the mitigation barrier “Reforestation” is presented in the following image:

To follow-up the Actions/Recommendations identified during the BowTie analysis, it is possible to present it in a table detailing the description of such Actions/Recommendations, along with the identification of the person responsible its execution, the execution period and their priority, such as the one presented next:

3.2.4. Consequence Evaluation

Another step developed transversally is the Evaluation of the Consequences, which is carried out based on a risk assessment matrix in which the areas of evaluation are identified (injury to people, environment, property or reputation damage …) as well as and the risk values. Those are defined according to the consequences’ severity and probability for each of evaluation area.

In the next image it shown the graphic representation of a hypothetical “Consequence 1”, assessed with a risk matrix defined with four evaluation areas and 20 risk levels:

  • Low risk (green): from 0 to 5.
  • Moderate risk (yellow): from 6 to 10.
  • High risk (orange): from 11 to 15.
  • Critical risk (red): from 16 to 20:


Climate change is a reality that is causing serious consequences and unless we take action to prevent and/or mitigate its impacts, it will only intensify.

In order to analyze the Causes and Consequences of climate change, and to thoroughly evaluate what we can do (as citizens, business and governments) to avoid or reduce its consequences, the BowTie analysis methodology has been used.

After the event’s BowTie analysis, it is evident that it is our responsibility to act to prevent the causes of climate change and to mitigate its consequences. With this in mind, the Citizens can / should act mainly on the causes, delaying climate change. Since, once the climate change has begun, we can hardly act individually to mitigate its consequences.

  • Some of the main prevention barriers that citizens should consider would be:
    • Prioritization of public / collective transport.
    • Responsible consumption (Km 0).
    • Reduction of meat consumption.
    • Use of more efficient (less polluting) vehicles
    • Reduction of consumption, reuse and recycling of paper and cardboard.
  • Business can / should act both to prevent the causes of climate change, and to mitigate its consequences. Some of the main prevention barriers:
    • Replacing fossil fuels with alternative energy.
    • Industrial processes’ technological change.
    • Improvement of gas extraction and transport processes.
    • Reduction of usage of products containing organic solvents.
    • Green industry promotion.
    • Circular Economy

Some of the main prevention barriers:

  • Carbon capture technologies.
  • Research aimed at reducing the effects of climate change.
  • Finally, governments can / should act both to prevent and to mitigate climate change. Some of the main prevention barriers that governments should apply would be:
    • Active strategies to prevent climate change.
    • Planning and protection of the territory.
    • Education, training and awareness.
    • Circular Economy.

And the main mitigation barriers would be:

  • International cooperation.
  • Replanning of cities in coastal lines.

This study highlights the work done so far in raising awareness of all entities responsible for actions to prevent the causes of climate change and mitigate its consequences. The BowTie analysis is a tool that helps to identify and implement the mentioned barriers. It also brings up the necessity to implement research projects focusing on mitigation of possible consequences.

It should not be forgotten that zero risk does not exist, even if all barriers and/or actions/recommendations identified in the study are implemented. However, the application of the barriers and/or actions/recommendations identified in this analysis would bring us closer to this objective.