Carbon Calculators

Olivia Macdonald and Dr Robin Russell-Jones


Introduction

The task of tackling climate change is one that is increasing both in urgency and importance, and requires everyone on the planet to play their part. To achieve this, individuals can adopt steps to reduce their carbon footprint by taking into consideration the carbon emissions that their everyday lifestyles produce. There is a natural level of carbon dioxide (CO2) and other greenhouse gases (GHGs) in the atmosphere that is necessary to sustain life on Earth, principally due to their ability to trap heat from the Sun. Without these naturally occurring greenhouse gases, the temperature of the Earth would be closer to minus 18°C compared with the present global average of plus 15°C (NASA). However, due to anthropogenic emissions, the level of GHGs are rapidly increasing, resulting in additional heating of the planet, or global warming.

In terms of the human contribution, carbon emissions can be broken down into two categories. The first is direct emissions. This primarily includes energy usage within the home, such as the amount of electricity and gas consumed annually, and transport which includes driving, and the number of flights taken each year. The second is known as “embedded carbon” which is the carbon footprint of a material and includes the carbon emitted during its extraction, manufacture and disposal. Recently, this has gained increased attention as it makes up a significant proportion of an individual’s carbon footprint both in terms of food, consumables and construction.

An individual’s carbon footprint can be defined as the amount of greenhouses gases, that are released into the atmosphere due to the activities of individuals, households, communities or organisations. This is commonly expressed as CO2e or carbon dioxide equivalent which allows for the global warming potential of any GHG compared with CO2. However, the carbon footprint of the average UK citizen varies depending upon the data that is fed into the calculation. In 2018, he total carbon emissions originating from within the UK (so-called territorial emissions) was 451.5 million tonnes carbon dioxide equivalent (National Statistics) If this is divided by the population of the UK (66 million people), then it would come to 6.8 tonnes CO2e per annum. Yet this figure has significant omissions. For example, the embedded carbon contained in goods imported from abroad are not included in this calculation but make up 46% of the UK carbon footprint (WWF). In addition it excludes international aviation. When these factors are taken into account, the actual carbon footprint of the average UK citizen is closer to 10 CO2e per annum. The question therefore, is which of these values truly represents of the impact the UK on global warming: its territorial emissions or its consumption-based emissions which takes into account both imports and exports.

That being said, each individual still can play a vital role in reducing this value. According to the Committee on Climate Change, 40% of UK emissions come from households, showing that reducing the carbon footprint within homes will be crucial in tackling climate change. Today, technological tools have been developed to quantify the impact a person’s lifestyle choices have on the environment, and these are known as carbon calculators. Not only have these proven to play an important role in educating people, but also in motivating lifestyle changes. These calculators typically contain a series of questions about your lifestyle to work out the amount of carbon that each sector produces before coming up with an overall value. However, it is important to note that these carbon calculators vary depending on the methodology, data and assumptions each organisation uses. Here 8 different calculators from various organisations will be compared both in terms of the values that they produce but also what information is included within them.

Results – comparing carbon calculators


Results – calculator breakdown

When given the option, the data was calculated for my household which consists of three people (and two dogs) and then either divided by three or adjusted so that my individual footprint could be reached. I inputted data from this past year, which for example included a trip to Bali which is significantly further than normally travelled. As a result, the calculated values are on the more generous side in terms of our household emissions compared to the average year.

WWF

This calculator is quick and simple to complete as well as being one of the more aesthetically pleasing ones. The questions are multiple choice and provide ‘did you know?’ facts alongside each one. Once completed, it displays your calculated footprint, the UK average and world average, and provides a more detail breakdown. This data suggests that my value is below the UK average. The categories covered have a good range of questions. That being said, it is somewhat oversimplified and does not offer exact figures to but inputted. This means that some assumptions have to be made and so makes it an approximation rather than an exact calculation. Overall, this is a good starting point before potentially completing a more detailed one.

Carbon Footprint

The Carbon Footprint calculator consisted of six categories, and unlike some other, all question required a numerical input rather than multiple choice. As a result, this took notably longer to complete and also required having to hand some very specific data. However, it does appear to be a much more accurate way of calculating the environmental impact due to the level of detail it requires. The results provide your footprint, the UK average and the world target. Whilst the WWF put the UK value at 10 tonnes CO2e per annum, this website suggests it is 6.5 which is an alarming difference. This is a thorough calculator which appears to calculate a relatively trustworthy value.


United Nations Carbon Offset Platform

This calculator was much briefer and therefore makes me question the reliability of the results as very few questions were asked. It consisted of 3 categories and a total of 16 questions with a combination of numerical inputs or drop-down options. As this was calculated for my household, I divided this by 3 putting my individual footprint at 10.4 tonnes CO2e per annum which was identical to the Carbon Footprint website figure. I would therefore treat this as providing a rough idea of what a person’s individual footprint could be rather than a highly accurate measure.


Global Footprint Network

This calculator consisted of sliding dial options or multiple choice however, within this, does have some questions that require specific percentages or numerical statistics. That being said, some assumptions are required for example it asks how far you travel by car each week which obviously will vary. One question it does include which it less commonly used is about the level of trash generated which is an important aspect to consider. It is fairly quick, easy and interactive and provides a good breakdown of the results at the end.


Go Zero

Go Zero is an American website which consists of just 3 categories with limited questions and excludes food or lifestyle. As a result, it required some values to be converted to equivalent units. I do not believe this to be an accurate value as it simply does not have enough data to generate a truly reflective reading. This calculated my value to be 14.3 tonnes which was the highest value and above the UK average. However, it does state that the average American consumption is 20 tonnes.


Cool Climate Network

Again, this is an American website consisting of 4 categories and has a simple and advanced option. The advanced allows for a greater range of data to be inputted. As this is American, the units were different for example, pounds to dollars so required some conversion. One category included with is lacking in many other calculators was water usage. It calculated the household footprint to be 23 tonnes which divided by 3 brings my individual footprint to 7.7 tonnes which is the lowest of the values. It also states this value is 3% better than average compared to households with the same size and income in the UK. So, whilst being a generally good one, I would not consider this to be the best.

Carbon Independent

The Carbon Independent calculator is a fairly detailed but quick one to complete which covered a good range of categories. It is broken down into 2 main sections with subsections within. It consisted predominantly of multiple choice meaning these questions were more of an approximation, with some numerical data required. One particularly detailed category was food which included information such as food packaging and processing, composting and how much of this food is thrown away, which no other one specifically had. Whilst my result was higher than others at 14.0 tonnes it was close to what they say is the UK average of 14.1 tonnes.

My Climate

The final calculator consisted of only 7 questions, all with 3 options. More so than any other this really relied on generalisation, assumptions and approximation. It did however include water usage unlike many others. Due to the limited data input and lack of precise data I am not confident with the reliability of this website.


Why the disparity?

Clearly there are large differences between the carbon footprint of the same individual using different carbon calculators. Four of the eight produced similar results between 9.1-10.4 tonnes CO2e/annum (WWF Carbon Footprint, UN Carbon offset platform, and Global Footprint Network) which is reassuring as this corresponds with the expected carbon footprint of the average UK citizen. The other four gave much more variable results ranging from 7.7-14.3 tonnes CO2e/annum (Go zero, Cool Climate, Carbon Independent, and My Climate). Go zero and Cool Climate are both American calculators and gave the biggest disparity. Whilst some calculators, such as Carbon Footprint, use specific numerical data, others, such as WWF, rely more on approximations. However it was not possible to identify the specific reasons for the disparities between the calculators except in general terms. Thus they vary in terms of their scope, the methodology used, the assumptions made, and the data inputted, and the range of values highlights the need for better standardisation. An example is the energy conversion factor used to calculate the number of kilograms of CO2 produced per kilowatt of electricity. Many use 0.43 which is the conversion figure provided by DEFRA but the exact figure will vary depending on mix of fuels, and the specific supplier. The conversion factor will be lower as renewables form a greater part of the mix. Similarly, the amount of CO2 produced by burning natural gas will depend on the amount of biogas in the mixture.


Every single calculator includes the categories of home energy and transport but with varying degrees of detail. Some include recycling and waste but fewer than one might expect. Only 2 of the 8 include any mention of water usage, which is surprising as water requires energy during its extraction, storage , and disposal. In addition most calculators failed to ask about renewable energy generated within the home. Some calculators were unclear as to whether they are calculating for the individual or the household which will obviously produce very different results. On a more positive note, many of these calculators did include options to either take action or suggested ways to reduce an individual’s footprint. It is

Conclusion

Carbon calculators are more of a convenient tool than a strict science. It is a useful way to assess the global warming impact of an individual, but tackling climate change requires action at both a community, national and international level.

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