The ‘Envimpact’ rating weighs the most environmentally-sensitive phase in the life cycle of the products or services delivered by 140 corporate sectors, according to Centre Info, a Swiss company that specialises in social and environmental rating tools for investors.

Envimpact also focuses on the quantity of carbon dioxide emissions, which are regarded by many scientists as the main cause of global warming.

Centre Info devised the system along with Swiss private bank Pictet.

‘The idea came during a discussion with Pictet and the Ethos investment foundation, we had the feeling the classical methods missed the key point,’ said Yvan Maillard, an analyst at Centre Info.

‘We decided to develop a method that focuses on a few key indicators that analyse the real impact of companies, not their statements of intent, but really their current performance,’  Maillard told AFP.

The rating assesses the climate change footprint of the world’s 1,800 largest companies in terms of capitalisation in sectors that include the motor industry, oil, electronics, retail, banking and insurance industries.

‘It’s a very intuitive way of judging companies,’ said Christoph Butz, a sustainability expert at Pictet.

The bank adopted the evaluation alongside the existing brace of about 150 mainly qualitative environmental indicators available for its sustainable or ethical investment funds.

That helps investors make an informed choice and lends greater credibility to the evaluation by being more scientific, Butz argued.

‘I felt that the many criteria that have accumulated over time in some way dilute the true figures,’ he explained.

French carmakers Renault and Peugeot, followed by Italy’s Fiat, achieved the best ratings in the auto industry under the system.