The term 'Carbon footprint' means

Correct — D, (d) The amount of greenhouse gases produced by our day-to-day activities.

A carbon footprint, also called a greenhouse gas footprint, is a calculated measure of the total quantity of greenhouse gases that an activity, a product, a person, a company or a country adds to the atmosphere. It is normally reported in tonnes of carbon dioxide equivalent, so that gases of different warming strengths can be added together, and it is expressed per unit of comparison — per year, per kilometre travelled, per kilogram of food, per garment.

The keyed option gives that idea in plain words: the amount of greenhouse gases produced by our day-to-day activities. The two features that make it right are that it measures emissions, and that it attributes them to activity. Every journey, meal, purchase and unit of electricity has emissions attached to it somewhere along the chain, and the footprint is the way of totalling them.

Two refinements are worth having, because questions often turn on them. First, the accounting is over the whole life cycle: a product’s footprint includes the emissions of producing its materials, manufacturing it, moving it, using it and disposing of it, not merely those released at the moment of use. Second, an organisation’s footprint includes indirect as well as direct emissions — the greenhouse gas accounting standards separate direct emissions from the organisation’s own sources, those from the electricity it buys, and those arising elsewhere in its supply chain.

So the concept is deliberately wide. It is a way of assigning responsibility for emissions to the activity that occasions them, wherever in the world the gas actually leaves a chimney or an exhaust pipe.

Why the others are wrong

• (a)A region which is rich in coal mines — ‘A region which is rich in coal mines’ reads the word ‘carbon’ as though it named the element in the ground, and ‘footprint’ as though it meant a place. Both halves are wrong. The footprint metaphor is about the mark an activity leaves, not about where it is carried on; and although coal is largely carbon and burning it is the single largest source of the emissions being measured, a coalfield is not a footprint any more than a forest is one. The option is worth noticing because it shows how a technical term can be dismantled into two ordinary words and reassembled into something with no meaning. Terms of this kind — carbon footprint, carbon sink, carbon credit, carbon neutrality — should be learned whole, since each of them uses ‘carbon’ in the same figurative way to stand for greenhouse gases generally.
• (b)The amount of reduction in the emission of CO2 by a country — ‘The amount of reduction in the emission of CO2 by a country’ turns the measure upside down. A footprint counts emissions made, not emissions avoided; a reduction is measured against a footprint rather than being one. The confusion is with a different family of ideas that grew up alongside it — emission reduction commitments, carbon credits earned by projects that emit less than a baseline, and the offsetting of one activity’s emissions against another’s reductions. Those are all defined by reference to a quantity avoided, and they are as important in climate policy as the footprint itself, which is why the option is a fair trap. Note also that the option confines the measure to a country and to carbon dioxide alone, where a footprint may be calculated for anything from a single meal to a multinational company and covers greenhouse gases generally, expressed as carbon dioxide equivalent.
• (c)The use of Carbon in manufacturing industries — ‘The use of Carbon in manufacturing industries’ treats carbon as a raw material and the footprint as a record of how much of it industry consumes. Industry certainly does use carbon in that literal sense — as coke in steelmaking, as feedstock in chemicals — but that is not what the term measures. The footprint counts what is released to the atmosphere as greenhouse gas, whether from burning fuel, from an industrial process, from farming, or from the electricity purchased from a distant power station. The option also narrows the concept to industry, whereas the whole point of the term in popular use is that individuals and households have footprints too, which is what the keyed option’s phrase ‘our day-to-day activities’ conveys.

The footprint metaphor came into environmental discussion with the ecological footprint, which measures the area of land and water a population needs to supply what it consumes and absorb its wastes. The carbon footprint applies the same idea to greenhouse gases: instead of an area, it reports a mass of emissions attributable to a defined activity or entity.

The accounting conventions are what make the number usable. Different gases warm the atmosphere by different amounts, so each is converted into the mass of carbon dioxide that would have the same effect, and the total is expressed in tonnes of carbon dioxide equivalent. The boundary of the calculation must then be declared. For a product, the usual boundary is the life cycle, from raw materials to disposal. For an organisation, the standard divides emissions into three scopes: those from sources it owns or controls, those from the energy it buys, and those that occur elsewhere in its value chain.

The caution attached to the measure is worth knowing, because examiners like it. A single indicator cannot capture everything: reducing a carbon footprint can conflict with other environmental aims such as protecting biodiversity or avoiding toxic pollution, and consumers often read the footprint as though it were a complete measure of environmental impact, which it is not.

Related terms in the same family are carbon sink, a reservoir that absorbs more carbon than it releases; carbon credit, a tradable unit representing a reduction; carbon neutrality, a state in which emissions are balanced by removals; and carbon sequestration, the capture and storage of carbon dioxide.

Key facts

• A carbon footprint, or greenhouse gas footprint, is a calculated value for the total greenhouse gases that an activity, product, company or country adds to the atmosphere.
• It is normally reported in tonnes of carbon dioxide equivalent, so that gases of different warming strengths can be summed, and expressed per unit of comparison such as a year or a kilometre.
• A product’s footprint covers its entire life cycle — production along the supply chain, use and disposal — not only the emissions at the point of use.
• An organisation’s footprint includes both direct and indirect emissions, which greenhouse gas accounting divides into three scopes: own sources, purchased energy, and the rest of the value chain.
• The measure has limits: it says nothing about biodiversity loss, ecotoxicity or habitat destruction, and consumers often mistake it for a complete measure of environmental impact.
• Related terms are carbon sink, carbon credit, carbon neutrality and carbon sequestration, in all of which ‘carbon’ stands for greenhouse gases generally.

Common traps

• Reading ‘carbon’ as the element and looking for an option about coal or about industrial raw materials.
• Confusing the footprint with the quantity of emissions avoided, which is what a carbon credit or a reduction commitment measures.
• Restricting the term to countries or to industry; individuals, households and single products all have footprints.
• Assuming the footprint measures environmental damage in general rather than greenhouse gas emissions alone.

• practice — not a real PYQ

  A carbon footprint is normally expressed in

  • (a)hectares of land required
  • (b)tonnes of carbon dioxide equivalent
  • (c)kilowatt-hours of energy consumed
  • (d)parts per million in the atmosphere

  Answer(b) tonnes of carbon dioxide equivalent — the conversion allows gases of different warming strengths to be added together. Hectares are the unit of the ecological footprint, kilowatt-hours measure energy rather than emissions, and parts per million describe the concentration of a gas in the atmosphere rather than any actor’s contribution to it.

• practice — not a real PYQ

  Which of the following best describes a carbon sink ?

  • (a)A reservoir that absorbs more carbon than it releases, such as a forest or the ocean
  • (b)A tradable permit representing one tonne of emissions avoided
  • (c)An industrial process that captures carbon dioxide from flue gases
  • (d)The total emissions attributable to a household in a year

  Answer(a) A reservoir that absorbs more carbon than it releases, such as a forest or the ocean — that is what a sink is. Option (b) describes a carbon credit, option (c) describes capture technology, and option (d) describes a carbon footprint.