The term carbon footprint crops up a lot these days. What exactly does it actually mean?
Carbon footprint is a horribly abused phrase, so it’s worth spelling out exactly what it means.
When talking about climate change, footprint is a metaphor for the total impact that something has. And carbon is a shorthand for all the different greenhouse gases that contribue to global warming.
The term carbon footprint, therefore, is a shorthand to describe the best estimate that we can get of the full climate change impact of something. That something could be anything – an activity, an item, a lifestyle, a company, a country or even the whole world.
The carbon footprint, as I have defined it, is the climate change metric that we need to be looking at. The dilemma is that it is also impossible to pin down accurately. We don’t stand a hope of being able to understand how the impact of our bananas compares with the impact of all the other things we might buy instead unless we have some way of taking into account the farming, the transport, the storage and the processes that feed into those stages. So how should we deal with a situation in which the thing we need to understand is impossibly complex?
One common response is to give up and measure something easier, even if that means losing most of what you are interested in off the radar. The illusionist Derren Brown refers to one of his core techniques as the misdirection of attention: by focusing his audience on something irrelevant he can make them miss the bit that matters. Examples include an airport waxing lyrical about the energy efficiency of its buildings without mentioning the flights themselves.
The same thing can happen by accident. If you settle for a toe-print, there is a very good chance it will misdirect your attention away from the big deals. An alternative response to the dilemma, and the approach that this book is all about, is to do the best job you can, despite the difficulties, of understanding the whole picture. My work is about making the most realistic estimates that are possible and practical, and being honest about the uncertainty.
Man-made climate change, or global warming, is caused by the release of certain types of gas into the atmosphere. The dominant man-made greenhouse gas is carbon dioxide (CO2), which is emitted whenever we burn fossil fuels in homes, factories or power stations. But other greenhouse gases are also important. Methane (CH4), for example, which is emitted mainly by agriculture and landfill sites, is 25 times more potent per kilogram than CO2. Even more potent but emitted in smaller quantities are nitrous oxide (N2O), which is about 300 times more potent than carbon dioxide and released mainly from industrial processes and farming, and refrigerant gases, which are typically several thousand times more potent than CO2.
In the UK, the total impact on the climate breaks down like this: carbon dioxide (86%), methane (7%), nitrous oxide (6%) and refrigerant gases (1%). Given that a single item or activity can cause multiple different greenhouse gases to be emitted, each in different quantities, a carbon footprint if written out in full could get pretty confusing. To avoid this, the convention is to express a carbon footprint in terms of carbon dioxide equivalent or CO2e. This means the total climate change impact of all the greenhouse gases caused by an item or activity rolled into one and expressed in terms of the amount of carbon dioxide that would have the same impact.
The most common abuse of the phrase carbon footprint is to miss out some or even most of the emissions caused, whatever activity or item is being discussed. For example, many online carbon calculator websites will tell you that your carbon footprint is a certain size based purely on your home energy and personal travel habits, while ignoring all of the goods and services you purchase.
Similarly, a magazine publisher might claim to have measured its carbon footprint but in doing so looked only at its office and cars while ignoring the much greater emissions caused by the printing house that produces the magazines themselves. These kinds of carbon footprint are actually more like carbon ‘toe-prints’ – they don’t give the full picture.
Much of the confusion around footprints comes down to the distinction between ‘direct’ and ‘indirect’ emissions. The true carbon footprint of a plastic toy, for example, includes not only direct emissions resulting from the manufacturing process and the transportation of the toy to the shop: it also includes a whole host of indirect emissions, such as those caused by the extraction and processing of the oil used to make the plastic in the first place. These are just a few of the processes involved. If you think about it, tracing back all the things that have to happen to make that toy leads to an infinite number of pathways, most of which are infinitesimally small. To make the point clearly, let’s try following just one of those pathways. The staff in the offices of the plastic factory used paper clips made of steel. Within the footprint of that steel is a small allocation to take account of the maintenance of a digger in the iron mine that the steel originally came from … and so on for ever. The carbon footprint of the plastic toy includes the lot, so working it out accurately is no easy task.
To give another example, the true carbon footprint of driving a car includes not only the emissions that come out of the exhaust pipe, but also all the emissions that take place when oil is extracted, shipped, refined into fuel and transported to the petrol station, not to mention the substantial emissions caused by producing and maintaining the car.
One of the most effective ways to begin thinking about how to reduce your carbon footprint is to reconsider how much, and how often, you travel.
In November 2017 carbon dioxide emissions from transportation surpassed emissions from electricity generation as the top source of greenhouse gases. Why? Electricity generation is shifting away from the use of coal to more renewable sources and natural gas.
Going carless for a year could save about 2.6 tons of carbon dioxide, according to 2017 study from researchers at Lund University and the University of British Columbia — that’s a little more than a roundtrip transatlantic flight. How can you stop using a car? Try taking a train, bus or better yet, ride a bike.
But let’s be realistic. You will likely need to use a car this year. So, when you do, here are some tips to make your trip more climate-friendly:
Shopping for a new car is a great opportunity to consider how you can reduce your personal carbon footprint. When choosing between gasoline, hybrid and electric, there are a number of factors to take into account, which will determine how “clean” your purchase is. The following can help:
Fly often? Taking one fewer long round-trip flight could shrink your personal carbon footprint significantly. Think about it this way: If you use public transportation often, and fly home to visit family just occasionally, your carbon footprint might still be relatively sustainable, but if you drive and fly a lot, your emissions will be higher.
If you can’t avoid flying, one way of making up for the emissions caused is to offset them by donating money to sustainable projects, such as supplying efficient stoves to rural homes, or projects which help farmers in India sell crop waste as biomass. Sometimes airlines will give you this option themselves, or you can use a third-party like Atmosfair or Terrapass. (You can calculate the emissions per flight here.)
Globally, emissions are linked to what we put on our plates.
While food systems are complicated, and research is still evolving on what the most environmentally-friendly diet is, experts mostly agree that cutting down on meat, and red meat in particular, is a better choice for the environment. This is because the production of red meat uses a lot of feed, water and land. Cows themselves also give off methane emissions (a harmful greenhouse gas).
For that reason, eating a vegan diet is likely to be best for the environment, say experts. According to a study published in 2017 in the journal Environmental Research Letters, red meat can have up to 100 times the environmental impact of plant based food. (According to some estimates, beef gives off more than six pounds of carbon dioxide per serving; the amount created per serving by rice, legumes carrots, apples or potatoes is less than half a pound.)
Eating a vegetarian or pescetarian diet are also likely to be better for the environment than a diet which includes a lot of meat. Each of these, however, depend on exactly what you are eating, and how much of it. If you replace that meat with dairy, for example, your emissions could rise again. “Deep net fishing can emit as much as beef,” said Marco Springmann, a senior researcher on environmental sustainability and public health at the University of Oxford. Following national health guidelines, with further reductions in meat, fish and dairy (this is similar to a Mediterranean diet) is a good option too, Dr. Springmann said. These diets can also have health benefits.
Overall, eating low down the food chain as often as you can is a probably a good way to reduce your carbon footprint and stay healthy, say experts. That means filling your plate with vegetables, fruits, grains and beans. For meat-lovers, even swapping carbon-intensive meats like beef and lamb with chicken can make a difference. Better still, swap a few meals per-week to vegan or vegetarian. This protein card can help you make climate (and wallet) friendly choices at the grocery store.
When it comes to food, most greenhouse gas emissions happen during production, rather than transportation: What you eat is more important than where it comes from. But eating local can still make a difference.
Fewer food-miles can mean fewer emissions. The complicating factor in eating locally happens when you start to consider how the food got to you, not just from how far away it came. “This ‘eat local’ argument, I would take it with a pinch of salt,” Dr. Springmann said. Tomatoes brought a short distance to a farmers market by truck, or shipped further to the grocery store by a train, could release similar emissions. (The transportation you take to get your tomatoes, and bring them home, also matters.)
What about local meat versus imported vegetables? Eating only locally grown food for one year would save the greenhouse gas equivalent of driving 1,000 miles, but eating just one vegetarian meal a week for a year saves 160 miles more than that, according to one study from researchers at Carnegie Mellon.
How about organic? You might choose organic if you prefer to eat produce grown with fewer chemical pesticides, but when it comes to reducing your carbon footprint, you’re better off shifting to low-impact, plant-based foods, according to a recent study published in the journal Environmental Research Letters. The study found that organic systems use less energy than conventional ones, but they often require more land and, therefore, emit similar greenhouse gas emissions.
This is a big one: on average, Americans waste around 40 percent of the food they buy.
Luckily, there are simple solutions to lower your food waste (and these tips will save you money, too.):
What to Eat On. Skip the disposable dishes and wash your dinnerware instead. Washing dishes, whether it is by hand or in a dishwasher, is likely to be more environmentally friendly than using disposable ones (assuming your dishwasher is energy efficient). If you do need to use disposable plates, bowls and cutlery, there are climate-friendly options (look for compostable or biodegradable options). If you order takeout, wash and reuse the plastic containers that food often comes in.
There are simple changes you can make at home that will save you energy, and money.
In the average American home, 25 percent of energy is used to heat spaces, 13 percent is used to heat water, 11 percent is used for cooling and the remainder is spent on appliances, according to estimates from the Natural Resources Defense Council. Making even small changes to these can make a big difference, said Noah Horowitz, a senior scientist and director of the N.R.D.C.’s Center for Energy Efficiency. “There’s a lot you can do without having to pick up a hammer or write a check,” he said. (This calculator can help you work out your energy usage before and after you make these changes.)
Americans generate about roughly 258 million tons of trash a year, 169 million tons of which ends up in landfills and incinerators, according to a 2014 report from the E.P.A. That year, American’s recycled and composted 89 million tons of municipal solid waste — this saved the same amount of energy as generated by 25 million homes. But much of the waste that can be recycled still ends up in landfills.
Here are some tips to make sure your waste ends up in the right place:
Small changes to the insulation and design of your home — from do-it-yourself hacks to building changes — can help you reduce your carbon footprint at home. Before starting, you can also do an energy audit, or have a professional come in to rate and score your home’s energy efficiency.
Buying less is the first step. Beyond that, there are simple ways to reduce the impact from your purchases.
According to the World Resources Institute, 20 items of clothing are manufactured per person, per year. This is because of “fast fashion”: clothes that are produced quickly, cheaply and unsustainably. As the price of our clothes drops, the environmental (and human) costs increase.
Here are some tips to minimize your impact when you purchase clothing:
You shop for more than just clothes, so whatever you’re shopping for — groceries, home goods, toys and whatever else — there are ways to take the climate into account.
Here are some tips:
In addition to changing your day-to-day habits, exercising your rights as a citizen is one of the most significant things you can do to help the planet.
Taking climate change into consideration when you vote is a good start. Here are some other tips:
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