In his Nature Correspondence “Time to give due weight to the ‘carbon footprint’ issue”, Geoffrey Hammond writes: “The media are increasingly using the term ‘carbon footprint’ in articles about the need to mitigate climate change by reducing our carbon dioxide emissions. Footprints are spatial indicators, measured in hectares or square metres. The property that is often referred to as a carbon footprint is actually a ‘carbon weight’ of kilograms or tonnes per person or activity.

To improve public understanding of the issues surrounding climate change, it is necessary to be precise. Other ‘footprints’, such as the ecological or environmental footprint, convert resource consumption and waste production into spatial units. The term ‘ecological footprint’ was coined by William E. Rees, a planner at the University of British Columbia — who had previously used the term ‘appropriated carrying capacity’ — after a computer delivery man told him that the new machine, which took up less space than his old model, had a ‘smaller footprint’.

As well as the media, many government agencies and environmental groups now use the expression ‘carbon footprint’. Those who favour precision in such matters should perhaps campaign for it to be called ‘carbon weight’, or some similar term. That would avoid lasting confusion. Losing weight might even take on a whole new meaning.”

Nature 445, 256 (18 January 2007) | doi:10.1038/445256b; Published online 17 January 2007.

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