posts: 36831
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| 36831 | Which form of transport has the smallest carbon footprint? | travel-carbon-footprint | post | publish | <!-- wp:html --> <div class="blog-info"> <p>Our World in Data presents the data and research to make progress against the world’s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href="https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions" target="_blank" rel="noopener noreferrer">CO<sub>2</sub> and Greenhouse Gas Emissions</a></strong> and <strong><a href="https://ourworldindata.org/energy" target="_blank" rel="noopener noreferrer">Energy</a></strong>.</p> <p> <p>Thank you to Shahid Ahmad for editorial feedback on this article.</p> </div> <!-- /wp:html --> <!-- wp-block-tombstone 45121 --> <!-- wp:paragraph --> <p>Transport accounts for around one-fifth of global carbon dioxide (CO<sub>2</sub>) emissions <em>[24% if we only consider CO<sub>2</sub> emissions from energy]</em>.{ref}The <em>World Resource Institute</em>’s Climate Data Explorer provides data from CAIT on the breakdown of emissions by sector. In 2016, global CO2 emissions (including land use) were 36.7 billion tonnes CO<sub>2</sub>; emissions from transport were 7.9 billion tonnes CO<sub>2</sub>. Transport therefore accounted for 7.9 / 36.7 = 21% of global emissions.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The IEA <a href="https://www.iea.org/data-and-statistics/?country=WORLD&fuel=CO2%20emissions&indicator=TotCO2">looks at CO<sub>2</sub> emissions</a> from energy production alone – in 2018 it reported 33.5 billion tonnes of energy-related CO<sub>2</sub> [hence, transport accounted for 8 billion / 33.5 billion = 24% of energy-related emissions.{/ref} In some countries – often richer countries with populations that travel often – transport can be one of the largest segments of an individual’s carbon footprint.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>If you need to travel – either locally or abroad – what is the lowest-carbon way to do so? </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>In the chart here we see the comparison of travel modes by their carbon footprint. These are measured by the amount of greenhouse gases emitted per person <em>to travel one kilometer</em>. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>This data is sourced from the UK Government’s <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf">methodology paper for greenhouse gas reporting</a>, widely used by companies to quantify and report their emissions. Greenhouse gases are measured in <a href="https://ourworldindata.org/greenhouse-gas-emissions#how-are-greenhouse-gases-measured">carbon dioxide equivalents</a> (CO<sub>2</sub>eq), meaning they also account for non-CO<sub>2</sub> greenhouse gases and the increased warming effects of aviation emissions at high altitudes.{ref}Aviation creates a number of complex atmospheric reactions at altitude – such as vapour contrails – which create an enhanced warming effect. In the UK’s <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf">Greenhouse gas methodology paper</a>, a ‘multiplier’ of 1.9 is applied to aviation emissions to account for this. This is reflected in the CO<sub>2</sub>eq factors provided in this analysis.<br><br>Researchers – David Lee et al. (2020) – estimate that aviation accounts for around 2.5% of global CO<sub>2</sub> emissions, but 3.5% of radiative forcing/warming due to these altitude effects. </p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Lee, D. S., Fahey, D. W., Skowron, A., Allen, M. R., Burkhardt, U., Chen, Q., ... & Gettelman, A. (2020). <a href="https://www.sciencedirect.com/science/article/pii/S1352231020305689">The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018</a>. <em>Atmospheric Environment</em>, 117834.{/ref}</p> <!-- /wp:paragraph --> <!-- wp:heading {"level":5} --> <h5><strong>Overall, the most efficient ways to travel are via walking, bicycle, or train.</strong> </h5> <!-- /wp:heading --> <!-- wp:paragraph --> <p>Using a bike instead of a car for short trips would reduce your travel emissions by ~75%. Taking a train instead of a car for medium-length distances would cut your emissions by ~80%. Using a train instead of a domestic flight would reduce your emissions by ~84%.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>However, there can be wide variation in emissions depending primarily on a) the length of your trip, b) the source of electricity in your local grid, c) the occupancy of public transport and d) in the case of driving -- your vehicle and number of passengers.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Over short to medium distances, walking or cycling are nearly always the lowest carbon way to travel. While not in the chart, the carbon footprint of cycling one kilometer is usually in the range of 16 to 50 grams CO<sub>2</sub>eq per km depending on how efficiently you cycle and what you eat.{ref}Finding a figure for the carbon footprint of cycling seems like it should be straightforward, but it can vary quite a lot. It depends on a number of factors: what size you are (bigger people tend to burn more energy cycling); how fit you are (fitter people are more efficient); the type of bike you’re pedalling; and what you eat (if you eat a primarily plant-based diet, the emissions are likely to be lower than if you get most of your calories from cheeseburgers and milk). People often also raise the question of whether you actually eat more if you cycle to work rather than driving i.e. whether those calories are actually ‘additional’ to your normal diet.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>Estimates on the footprint of cycling therefore vary. Some estimates <a href="https://ecf.com/news-and-events/news/how-much-co2-does-cycling-really-save">put this figure</a> at around 16 grams CO<sub>2</sub>e per kilometer based on the average European diet. In his book ‘<a href="https://www.goodreads.com/book/show/7230015-how-bad-are-bananas">How bad are bananas: the carbon footprint of everything</a>’, Mike Berners-Lee estimates the footprint based on specific food types. He estimates 25 grams CO<sub>2</sub>e when powered by bananas; 43 grams CO<sub>2</sub>e from cereal and cow’s milk; 190 grams CO<sub>2</sub>e from bacon; or as high as 310 grams CO<sub>2</sub>e if powered exclusively by cheeseburgers.{/ref}</p> <!-- /wp:paragraph --> <!-- wp:heading {"level":5} --> <h5>What if you can’t walk or cycle, or you need to travel longer distances and can’t take a train?</h5> <!-- /wp:heading --> <!-- wp:paragraph --> <p>Taking a flight or driving alone are the most carbon-intensive options. Between the two, which is better depends on the distance travelled. If you’re travelling moderate distances (<1000 kilometers or a domestic flight within the UK), then flying has a higher carbon footprint than a medium-sized car. If the distance is longer (>1000 kilometers or an international flight), then flying would actually have a slightly lower carbon footprint per kilometer than driving alone over the same distance.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>The carbon intensity of your local electrical grid matters too. If your electricity is supplied by nuclear or renewable energy instead of coal, electric vehicles and electric rail are even more efficient. For example, France has a very ‘green’ electricity mix: more than 90% of its electricity <a href="https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France&region=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Low-carbon&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total">comes from low-carbon sources</a> – ~70% <a href="https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France&region=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Nuclear&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total">from nuclear</a>. If you took the Eurostar in France instead of a short-haul flight, you’d cut your journey’s footprint by around 96%.{ref}Taking the Eurostar emits around 6 grams of CO<sub>2</sub> per passenger kilometer, compared to 156 grams from a short-haul flight. So the footprint of Eurostar is around 4% of a flight: [ 6 / 156 *100 = 4%].{/ref}</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>When driving, your emissions will depend mainly on which vehicle you use and the number of passengers. Driving a small Mini car emits 111 g CO<sub>2</sub>eq per km while a large 4×4 car emits ~200 gCO<sub>2</sub>eq per km. Adding one additional passenger travelling to the same location would halve emissions per passenger-kilometer.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>To tie it together, let’s say you were to drive from Edinburgh to London (~500km). You’d emit close to 100 kilograms CO<sub>2</sub>eq. If you were to fly, this would increase by almost one-third (128 kg CO<sub>2</sub>eq).{ref}Taking a domestic flight emits 255 grams CO<sub>2</sub>e per km * 500 km = 127.5 kg CO<sub>2</sub>e.{/ref} Taking the train would be 80% lower (21 kg CO<sub>2</sub>eq).{ref}Traveling by train emits around 41 g per km * 500 km = 20.5 kg CO<sub>2</sub>e.{/ref}</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>There are some nuances that you might want to explore for yourself: for example, what if I drive a small or a large petrol car; what if I fly business or first class rather than economy; what if I share my car trip with 3 other passengers? For this reason we’ve included the data for a number of additional options which you can explore in the interactive chart using the blue “Add travel mode” button.</p> <!-- /wp:paragraph --> <!-- wp:heading {"level":5} --> <h5>Some general takeaways on how you can reduce the carbon footprint of travel:</h5> <!-- /wp:heading --> <!-- wp:list --> <ul><li>Walk, cycle or run when possible – this comes with many other benefits such as lower local <a href="https://ourworldindata.org/air-pollution">air pollution</a> and better health;</li><li>Trains are nearly always the winning option over moderate-to-long distances;</li><li>If travelling internationally, going by train or boat is lower-carbon than flying;</li><li>If travelling domestically, driving – even if it’s alone – is usually better than flying;</li><li>If it’s a choice between driving or flying internationally, flying economy class is often better;</li><li>Car-sharing will massively reduce your footprint – it also helps to reduce local <a href="https://ourworldindata.org/air-pollution">air pollution</a> and congestion;</li><li>Electric vehicles are nearly always lower-carbon than petrol or diesel cars, especially in a country that produces much of its electricity by renewables or nuclear.</li></ul> <!-- /wp:list --> <!-- wp:html --> <iframe src="https://ourworldindata.org/grapher/carbon-footprint-travel-mode?tab=chart&stackMode=absolute&region=World" loading="lazy" style="width: 100%; height: 600px; border: 0px none;"></iframe> <!-- /wp:html --> <!-- wp:owid/additional-information {"defaultOpen":true} --> <!-- wp:heading {"level":3} --> <h3><strong>Why is the carbon footprint per kilometer higher for domestic flight than long-haul flights?</strong></h3> <!-- /wp:heading --> <!-- wp:columns {"className":"is-style-sticky-right"} --> <div class="wp-block-columns is-style-sticky-right"><!-- wp:column --> <div class="wp-block-column"><!-- wp:paragraph --> <p>You will notice that the CO<sub>2</sub> emissions per passenger-kilometer are higher for domestic flights than short-haul international flights; and long-haul flights are slightly lower still. Why is this the case?</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>In its report on the <a href="https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf">CO<sub>2</sub> Emissions from Commercial Aviation</a>, the International Council on Clean Transportation provides a nice breakdown of how the carbon intensity (grams CO<sub>2</sub> emitted per passenger kilometer) varies depending on flight distance.{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). <a href="https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf">CO2 emissions from commercial aviation, 2018</a>. International Council on Clean Transportation.{/ref} This chart is shown here – with carbon intensity given as the red line. It shows that at very short flight distances (less than 1,000 km), the carbon intensity is very high; it falls with distance until around 1,500 to 2,000 km; then levels out and changes very little with increasing distance.</p> <!-- /wp:paragraph --> <!-- wp:paragraph --> <p>This is because take-off requires much more energy input than the ‘cruise’ phase of a flight. So, for very short flights, this extra fuel needed for take-off is large compared to the more efficient cruise phase of the journey. The ICCT also notes that often less fuel-efficient planes are used for the shortest flights.</p> <!-- /wp:paragraph --></div> <!-- /wp:column --> <!-- wp:column --> <div class="wp-block-column"><!-- wp:heading {"level":6} --> <h6>Carbon intensity (gCO<sub>2</sub> per passenger-kilometer) by flight distance{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). <a href="https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf">CO2 emissions from commercial aviation, 2018</a>. International Council on Clean Transportation.{/ref}</h6> <!-- /wp:heading --> <!-- wp:image {"id":36922,"sizeSlug":"large"} --> <figure class="wp-block-image size-large"><img src="https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance-678x550.png" alt="" class="wp-image-36922"/></figure> <!-- /wp:image --></div> <!-- /wp:column --></div> <!-- /wp:columns --> <!-- /wp:owid/additional-information --> | {
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"text": "eq per km depending on how efficiently you cycle and what you eat.{ref}Finding a figure for the carbon footprint of cycling seems like it should be straightforward, but it can vary quite a lot. It depends on a number of factors: what size you are (bigger people tend to burn more energy cycling); how fit you are (fitter people are more efficient); the type of bike you\u2019re pedalling; and what you eat (if you eat a primarily plant-based diet, the emissions are likely to be lower than if you get most of your calories from cheeseburgers and milk). People often also raise the question of whether you actually eat more if you cycle to work rather than driving i.e. whether those calories are actually \u2018additional\u2019 to your normal diet.",
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For individuals, transport can be the largest part of their carbon footprint. If you need to travel, what is the lowest-carbon way to do so? | 2020-10-05 18:22:04 | 2021-09-24 12:38:37 | https://ourworldindata.org/wp-content/uploads/2020/10/carbon-footprint-travel-mode-3.png | {} |
Our World in Data presents the data and research to make progress against the world’s largest problems. This blog post draws on data and research discussed in our entries on **[CO2 and Greenhouse Gas Emissions](https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions)** and **[Energy](https://ourworldindata.org/energy)**. Thank you to Shahid Ahmad for editorial feedback on this article. Transport accounts for around one-fifth of global carbon dioxide (CO2) emissions _[24% if we only consider CO2 emissions from energy]_.{ref}The _World Resource Institute_’s Climate Data Explorer provides data from CAIT on the breakdown of emissions by sector. In 2016, global CO2 emissions (including land use) were 36.7 billion tonnes CO2; emissions from transport were 7.9 billion tonnes CO2. Transport therefore accounted for 7.9 / 36.7 = 21% of global emissions. The IEA [looks at CO2 emissions](https://www.iea.org/data-and-statistics/?country=WORLD&fuel=CO2%20emissions&indicator=TotCO2) from energy production alone – in 2018 it reported 33.5 billion tonnes of energy-related CO2 [hence, transport accounted for 8 billion / 33.5 billion = 24% of energy-related emissions.{/ref} In some countries – often richer countries with populations that travel often – transport can be one of the largest segments of an individual’s carbon footprint. If you need to travel – either locally or abroad – what is the lowest-carbon way to do so? In the chart here we see the comparison of travel modes by their carbon footprint. These are measured by the amount of greenhouse gases emitted per person _to travel one kilometer_. This data is sourced from the UK Government’s [methodology paper for greenhouse gas reporting](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf), widely used by companies to quantify and report their emissions. Greenhouse gases are measured in [carbon dioxide equivalents](https://ourworldindata.org/greenhouse-gas-emissions#how-are-greenhouse-gases-measured) (CO2eq), meaning they also account for non-CO2 greenhouse gases and the increased warming effects of aviation emissions at high altitudes.{ref}Aviation creates a number of complex atmospheric reactions at altitude – such as vapour contrails – which create an enhanced warming effect. In the UK’s [Greenhouse gas methodology paper](https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf), a ‘multiplier’ of 1.9 is applied to aviation emissions to account for this. This is reflected in the CO2eq factors provided in this analysis. Researchers – David Lee et al. (2020) – estimate that aviation accounts for around 2.5% of global CO2 emissions, but 3.5% of radiative forcing/warming due to these altitude effects. Lee, D. S., Fahey, D. W., Skowron, A., Allen, M. R., Burkhardt, U., Chen, Q., ... & Gettelman, A. (2020). [The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018](https://www.sciencedirect.com/science/article/pii/S1352231020305689). _Atmospheric Environment_, 117834.{/ref} ## **Overall, the most efficient ways to travel are via walking, bicycle, or train.** Using a bike instead of a car for short trips would reduce your travel emissions by ~75%. Taking a train instead of a car for medium-length distances would cut your emissions by ~80%. Using a train instead of a domestic flight would reduce your emissions by ~84%. However, there can be wide variation in emissions depending primarily on a) the length of your trip, b) the source of electricity in your local grid, c) the occupancy of public transport and d) in the case of driving -- your vehicle and number of passengers. Over short to medium distances, walking or cycling are nearly always the lowest carbon way to travel. While not in the chart, the carbon footprint of cycling one kilometer is usually in the range of 16 to 50 grams CO2eq per km depending on how efficiently you cycle and what you eat.{ref}Finding a figure for the carbon footprint of cycling seems like it should be straightforward, but it can vary quite a lot. It depends on a number of factors: what size you are (bigger people tend to burn more energy cycling); how fit you are (fitter people are more efficient); the type of bike you’re pedalling; and what you eat (if you eat a primarily plant-based diet, the emissions are likely to be lower than if you get most of your calories from cheeseburgers and milk). People often also raise the question of whether you actually eat more if you cycle to work rather than driving i.e. whether those calories are actually ‘additional’ to your normal diet. Estimates on the footprint of cycling therefore vary. Some estimates [put this figure](https://ecf.com/news-and-events/news/how-much-co2-does-cycling-really-save) at around 16 grams CO2e per kilometer based on the average European diet. In his book ‘[How bad are bananas: the carbon footprint of everything](https://www.goodreads.com/book/show/7230015-how-bad-are-bananas)’, Mike Berners-Lee estimates the footprint based on specific food types. He estimates 25 grams CO2e when powered by bananas; 43 grams CO2e from cereal and cow’s milk; 190 grams CO2e from bacon; or as high as 310 grams CO2e if powered exclusively by cheeseburgers.{/ref} ## What if you can’t walk or cycle, or you need to travel longer distances and can’t take a train? Taking a flight or driving alone are the most carbon-intensive options. Between the two, which is better depends on the distance travelled. If you’re travelling moderate distances (<1000 kilometers or a domestic flight within the UK), then flying has a higher carbon footprint than a medium-sized car. If the distance is longer (>1000 kilometers or an international flight), then flying would actually have a slightly lower carbon footprint per kilometer than driving alone over the same distance. The carbon intensity of your local electrical grid matters too. If your electricity is supplied by nuclear or renewable energy instead of coal, electric vehicles and electric rail are even more efficient. For example, France has a very ‘green’ electricity mix: more than 90% of its electricity [comes from low-carbon sources](https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France®ion=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Low-carbon&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total) – ~70% [from nuclear](https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France®ion=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Nuclear&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total). If you took the Eurostar in France instead of a short-haul flight, you’d cut your journey’s footprint by around 96%.{ref}Taking the Eurostar emits around 6 grams of CO2 per passenger kilometer, compared to 156 grams from a short-haul flight. So the footprint of Eurostar is around 4% of a flight: [ 6 / 156 *100 = 4%].{/ref} When driving, your emissions will depend mainly on which vehicle you use and the number of passengers. Driving a small Mini car emits 111 g CO2eq per km while a large 4×4 car emits ~200 gCO2eq per km. Adding one additional passenger travelling to the same location would halve emissions per passenger-kilometer. To tie it together, let’s say you were to drive from Edinburgh to London (~500km). You’d emit close to 100 kilograms CO2eq. If you were to fly, this would increase by almost one-third (128 kg CO2eq).{ref}Taking a domestic flight emits 255 grams CO2e per km * 500 km = 127.5 kg CO2e.{/ref} Taking the train would be 80% lower (21 kg CO2eq).{ref}Traveling by train emits around 41 g per km * 500 km = 20.5 kg CO2e.{/ref} There are some nuances that you might want to explore for yourself: for example, what if I drive a small or a large petrol car; what if I fly business or first class rather than economy; what if I share my car trip with 3 other passengers? For this reason we’ve included the data for a number of additional options which you can explore in the interactive chart using the blue “Add travel mode” button. ## Some general takeaways on how you can reduce the carbon footprint of travel: * Walk, cycle or run when possible – this comes with many other benefits such as lower local [air pollution](https://ourworldindata.org/air-pollution) and better health; * Trains are nearly always the winning option over moderate-to-long distances; * If travelling internationally, going by train or boat is lower-carbon than flying; * If travelling domestically, driving – even if it’s alone – is usually better than flying; * If it’s a choice between driving or flying internationally, flying economy class is often better; * Car-sharing will massively reduce your footprint – it also helps to reduce local [air pollution](https://ourworldindata.org/air-pollution) and congestion; * Electric vehicles are nearly always lower-carbon than petrol or diesel cars, especially in a country that produces much of its electricity by renewables or nuclear. <Chart url="https://ourworldindata.org/grapher/carbon-footprint-travel-mode?tab=chart&stackMode=absolute®ion=World"/> ## Additional information You will notice that the CO2 emissions per passenger-kilometer are higher for domestic flights than short-haul international flights; and long-haul flights are slightly lower still. Why is this the case? In its report on the [CO2 Emissions from Commercial Aviation](https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf), the International Council on Clean Transportation provides a nice breakdown of how the carbon intensity (grams CO2 emitted per passenger kilometer) varies depending on flight distance.{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). [CO2 emissions from commercial aviation, 2018](https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf). International Council on Clean Transportation.{/ref} This chart is shown here – with carbon intensity given as the red line. It shows that at very short flight distances (less than 1,000 km), the carbon intensity is very high; it falls with distance until around 1,500 to 2,000 km; then levels out and changes very little with increasing distance. This is because take-off requires much more energy input than the ‘cruise’ phase of a flight. So, for very short flights, this extra fuel needed for take-off is large compared to the more efficient cruise phase of the journey. The ICCT also notes that often less fuel-efficient planes are used for the shortest flights. ###### Carbon intensity (gCO2 per passenger-kilometer) by flight distance{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). [CO2 emissions from commercial aviation, 2018](https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf). International Council on Clean Transportation.{/ref} <Image filename="co2-intensity-flight-distance.png" alt=""/> | {
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"rendered": "\n<div class=\"blog-info\">\n<p>Our World in Data presents the data and research to make progress against the world\u2019s largest problems.<br>This blog post draws on data and research discussed in our entries on <strong><a href=\"https://ourworldindata.org/co2-and-other-greenhouse-gas-emissions\" target=\"_blank\" rel=\"noopener noreferrer\">CO<sub>2</sub> and Greenhouse Gas Emissions</a></strong> and <strong><a href=\"https://ourworldindata.org/energy\" target=\"_blank\" rel=\"noopener noreferrer\">Energy</a></strong>.</p>\n<p>\n<p>Thank you to Shahid Ahmad for editorial feedback on this article.</p>\n</div>\n\n\n\n<p>Transport accounts for around one-fifth of global carbon dioxide (CO<sub>2</sub>) emissions <em>[24% if we only consider CO<sub>2</sub> emissions from energy]</em>.{ref}The <em>World Resource Institute</em>\u2019s Climate Data Explorer provides data from CAIT on the breakdown of emissions by sector. In 2016, global CO2 emissions (including land use) were 36.7 billion tonnes CO<sub>2</sub>; emissions from transport were 7.9 billion tonnes CO<sub>2</sub>. Transport therefore accounted for 7.9 / 36.7 = 21% of global emissions.</p>\n\n\n\n<p>The IEA <a href=\"https://www.iea.org/data-and-statistics/?country=WORLD&fuel=CO2%20emissions&indicator=TotCO2\">looks at CO<sub>2</sub> emissions</a> from energy production alone \u2013 in 2018 it reported 33.5 billion tonnes of energy-related CO<sub>2</sub> [hence, transport accounted for 8 billion / 33.5 billion = 24% of energy-related emissions.{/ref} In some countries \u2013 often richer countries with populations that travel often \u2013 transport can be one of the largest segments of an individual\u2019s carbon footprint.</p>\n\n\n\n<p>If you need to travel \u2013 either locally or abroad \u2013 what is the lowest-carbon way to do so? </p>\n\n\n\n<p>In the chart here we see the comparison of travel modes by their carbon footprint. These are measured by the amount of greenhouse gases emitted per person <em>to travel one kilometer</em>. </p>\n\n\n\n<p>This data is sourced from the UK Government\u2019s <a href=\"https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf\">methodology paper for greenhouse gas reporting</a>, widely used by companies to quantify and report their emissions. Greenhouse gases are measured in <a href=\"https://ourworldindata.org/greenhouse-gas-emissions#how-are-greenhouse-gases-measured\">carbon dioxide equivalents</a> (CO<sub>2</sub>eq), meaning they also account for non-CO<sub>2</sub> greenhouse gases and the increased warming effects of aviation emissions at high altitudes.{ref}Aviation creates a number of complex atmospheric reactions at altitude \u2013 such as vapour contrails \u2013 which create an enhanced warming effect. In the UK\u2019s <a href=\"https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/901692/conversion-factors-2020-methodology.pdf\">Greenhouse gas methodology paper</a>, a \u2018multiplier\u2019 of 1.9 is applied to aviation emissions to account for this. This is reflected in the CO<sub>2</sub>eq factors provided in this analysis.<br><br>Researchers \u2013 David Lee et al. (2020) \u2013 estimate that aviation accounts for around 2.5% of global CO<sub>2</sub> emissions, but 3.5% of radiative forcing/warming due to these altitude effects. </p>\n\n\n\n<p>Lee, D. S., Fahey, D. W., Skowron, A., Allen, M. R., Burkhardt, U., Chen, Q., … & Gettelman, A. (2020). <a href=\"https://www.sciencedirect.com/science/article/pii/S1352231020305689\">The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018</a>. <em>Atmospheric Environment</em>, 117834.{/ref}</p>\n\n\n\n<h5><strong>Overall, the most efficient ways to travel are via walking, bicycle, or train.</strong> </h5>\n\n\n\n<p>Using a bike instead of a car for short trips would reduce your travel emissions by ~75%. Taking a train instead of a car for medium-length distances would cut your emissions by ~80%. Using a train instead of a domestic flight would reduce your emissions by ~84%.</p>\n\n\n\n<p>However, there can be wide variation in emissions depending primarily on a) the length of your trip, b) the source of electricity in your local grid, c) the occupancy of public transport and d) in the case of driving — your vehicle and number of passengers.</p>\n\n\n\n<p>Over short to medium distances, walking or cycling are nearly always the lowest carbon way to travel. While not in the chart, the carbon footprint of cycling one kilometer is usually in the range of 16 to 50 grams CO<sub>2</sub>eq per km depending on how efficiently you cycle and what you eat.{ref}Finding a figure for the carbon footprint of cycling seems like it should be straightforward, but it can vary quite a lot. It depends on a number of factors: what size you are (bigger people tend to burn more energy cycling); how fit you are (fitter people are more efficient); the type of bike you\u2019re pedalling; and what you eat (if you eat a primarily plant-based diet, the emissions are likely to be lower than if you get most of your calories from cheeseburgers and milk). People often also raise the question of whether you actually eat more if you cycle to work rather than driving i.e. whether those calories are actually \u2018additional\u2019 to your normal diet.</p>\n\n\n\n<p>Estimates on the footprint of cycling therefore vary. Some estimates <a href=\"https://ecf.com/news-and-events/news/how-much-co2-does-cycling-really-save\">put this figure</a> at around 16 grams CO<sub>2</sub>e per kilometer based on the average European diet. In his book \u2018<a href=\"https://www.goodreads.com/book/show/7230015-how-bad-are-bananas\">How bad are bananas: the carbon footprint of everything</a>\u2019, Mike Berners-Lee estimates the footprint based on specific food types. He estimates 25 grams CO<sub>2</sub>e when powered by bananas; 43 grams CO<sub>2</sub>e from cereal and cow\u2019s milk; 190 grams CO<sub>2</sub>e from bacon; or as high as 310 grams CO<sub>2</sub>e if powered exclusively by cheeseburgers.{/ref}</p>\n\n\n\n<h5>What if you can\u2019t walk or cycle, or you need to travel longer distances and can\u2019t take a train?</h5>\n\n\n\n<p>Taking a flight or driving alone are the most carbon-intensive options. Between the two, which is better depends on the distance travelled. If you\u2019re travelling moderate distances (<1000 kilometers or a domestic flight within the UK), then flying has a higher carbon footprint than a medium-sized car. If the distance is longer (>1000 kilometers or an international flight), then flying would actually have a slightly lower carbon footprint per kilometer than driving alone over the same distance.</p>\n\n\n\n<p>The carbon intensity of your local electrical grid matters too. If your electricity is supplied by nuclear or renewable energy instead of coal, electric vehicles and electric rail are even more efficient. For example, France has a very \u2018green\u2019 electricity mix: more than 90% of its electricity <a href=\"https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France&region=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Low-carbon&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total\">comes from low-carbon sources</a> \u2013 ~70% <a href=\"https://ourworldindata.org/explorers/energy?tab=chart&xScale=linear&yScale=linear&stackMode=absolute&endpointsOnly=0&time=earliest..latest&country=~France&region=World&Total%20or%20Breakdown=Select%20a%20source&Select%20a%20source%20=Nuclear&Energy%20or%20Electricity=Electricity%20only&Metric%20=%%20of%20total\">from nuclear</a>. If you took the Eurostar in France instead of a short-haul flight, you\u2019d cut your journey\u2019s footprint by around 96%.{ref}Taking the Eurostar emits around 6 grams of CO<sub>2</sub> per passenger kilometer, compared to 156 grams from a short-haul flight. So the footprint of Eurostar is around 4% of a flight: [ 6 / 156 *100 = 4%].{/ref}</p>\n\n\n\n<p>When driving, your emissions will depend mainly on which vehicle you use and the number of passengers. Driving a small Mini car emits 111 g CO<sub>2</sub>eq per km while a large 4\u00d74 car emits ~200 gCO<sub>2</sub>eq per km. Adding one additional passenger travelling to the same location would halve emissions per passenger-kilometer.</p>\n\n\n\n<p>To tie it together, let\u2019s say you were to drive from Edinburgh to London (~500km). You\u2019d emit close to 100 kilograms CO<sub>2</sub>eq. If you were to fly, this would increase by almost one-third (128 kg CO<sub>2</sub>eq).{ref}Taking a domestic flight emits 255 grams CO<sub>2</sub>e per km * 500 km = 127.5 kg CO<sub>2</sub>e.{/ref} Taking the train would be 80% lower (21 kg CO<sub>2</sub>eq).{ref}Traveling by train emits around 41 g per km * 500 km = 20.5 kg CO<sub>2</sub>e.{/ref}</p>\n\n\n\n<p>There are some nuances that you might want to explore for yourself: for example, what if I drive a small or a large petrol car; what if I fly business or first class rather than economy; what if I share my car trip with 3 other passengers? For this reason we\u2019ve included the data for a number of additional options which you can explore in the interactive chart using the blue \u201cAdd travel mode\u201d button.</p>\n\n\n\n<h5>Some general takeaways on how you can reduce the carbon footprint of travel:</h5>\n\n\n\n<ul><li>Walk, cycle or run when possible \u2013 this comes with many other benefits such as lower local <a href=\"https://ourworldindata.org/air-pollution\">air pollution</a> and better health;</li><li>Trains are nearly always the winning option over moderate-to-long distances;</li><li>If travelling internationally, going by train or boat is lower-carbon than flying;</li><li>If travelling domestically, driving \u2013 even if it\u2019s alone \u2013 is usually better than flying;</li><li>If it\u2019s a choice between driving or flying internationally, flying economy class is often better;</li><li>Car-sharing will massively reduce your footprint \u2013 it also helps to reduce local <a href=\"https://ourworldindata.org/air-pollution\">air pollution</a> and congestion;</li><li>Electric vehicles are nearly always lower-carbon than petrol or diesel cars, especially in a country that produces much of its electricity by renewables or nuclear.</li></ul>\n\n\n\n<iframe src=\"https://ourworldindata.org/grapher/carbon-footprint-travel-mode?tab=chart&stackMode=absolute&region=World\" loading=\"lazy\" style=\"width: 100%; height: 600px; border: 0px none;\"></iframe>\n\n\n\t<block type=\"additional-information\" default-open=\"true\">\n\t\t<content>\n\n<h3><strong>Why is the carbon footprint per kilometer higher for domestic flight than long-haul flights?</strong></h3>\n\n\n\n<div class=\"wp-block-columns is-style-sticky-right\">\n<div class=\"wp-block-column\">\n<p>You will notice that the CO<sub>2</sub> emissions per passenger-kilometer are higher for domestic flights than short-haul international flights; and long-haul flights are slightly lower still. Why is this the case?</p>\n\n\n\n<p>In its report on the <a href=\"https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf\">CO<sub>2</sub> Emissions from Commercial Aviation</a>, the International Council on Clean Transportation provides a nice breakdown of how the carbon intensity (grams CO<sub>2</sub> emitted per passenger kilometer) varies depending on flight distance.{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). <a href=\"https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf\">CO2 emissions from commercial aviation, 2018</a>. International Council on Clean Transportation.{/ref} This chart is shown here \u2013 with carbon intensity given as the red line. It shows that at very short flight distances (less than 1,000 km), the carbon intensity is very high; it falls with distance until around 1,500 to 2,000 km; then levels out and changes very little with increasing distance.</p>\n\n\n\n<p>This is because take-off requires much more energy input than the \u2018cruise\u2019 phase of a flight. So, for very short flights, this extra fuel needed for take-off is large compared to the more efficient cruise phase of the journey. The ICCT also notes that often less fuel-efficient planes are used for the shortest flights.</p>\n</div>\n\n\n\n<div class=\"wp-block-column\">\n<h6>Carbon intensity (gCO<sub>2</sub> per passenger-kilometer) by flight distance{ref}Graver, B., Zhang, K. & Rutherford, D. (2018). <a href=\"https://theicct.org/sites/default/files/publications/ICCT_CO2-commercl-aviation-2018_20190918.pdf\">CO2 emissions from commercial aviation, 2018</a>. International Council on Clean Transportation.{/ref}</h6>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" width=\"678\" height=\"550\" src=\"https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance-678x550.png\" alt=\"\" class=\"wp-image-36922\" srcset=\"https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance-678x550.png 678w, https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance-400x325.png 400w, https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance-150x122.png 150w, https://owid.cloud/app/uploads/2020/10/co2-intensity-flight-distance.png 706w\" sizes=\"(max-width: 678px) 100vw, 678px\" /></figure>\n</div>\n</div>\n\n</content>\n\t</block>",
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