"Previous studies have shown that it is difficult for the public to imagine a given quantity of carbon-dioxide emission and its potential environmental impact," says Rui Zhao from the University of Hull, UK. "Thus, we believe that the current carbon-labelling scheme does not communicate a sufficiently meaningful message to the consumer, especially if the label only conveys the emissions value."

With colleagues Pauline Deutz, Gareth Neighbour and Michael McGuire, Zhao has proposed a new carbon-labelling scheme that better conveys a product's life-cycle carbon emissions. Published by Environmental Research Letters, the study has put forward a novel indicator, the Carbon Emissions Intensity Ratio (CEIR). This is derived from the ratio of the Carbon Emissions Intensity (CEI) for the product to the annual national greenhouse-gas emissions per unit of gross domestic product.

"In order to help compare values of different products, the developed indicator is dimensionless," explains Zhao. "The value of the CEIR can be applied to assess a product on a simple scale with values from extremely low, low, and medium to high and extremely high, by using a straightforward diagram with colour gradients. In this way a consumer can easily and rapidly glean the performance of a given product by looking at the indicator printed on its packaging."

Spurred on by this preliminary work, the researchers now plan to analyse feedback from consumers regarding the new label. "We will set up questionnaires, focus groups and interviews to investigate whether our label can be easily understood," said Zhao. "We hope our study will lead to an improvement in the clarity of current carbon-labelling schemes and encourage consumers to select low-carbon products, and become more 'green'".