How can Tesco increase its carbon dioxide emissions by almost 400,000 tonnes, as it did in 2007, and still claim to be "setting an example" on climate change? Easy. By coming up with a bizarre test to demonstrate its carbon virtue.
The latest corporate responsibility report from Britain's biggest retailer admits to an 8.6% increase in its emissions in a single year, but says that it increased its "floor space" by 14%, so actually its carbon intensity "per square foot of net sales area" was down by 4.7%.
How does it get away with such a formulation? This is not, you will notice, carbon emissions per tonne of groceries sold, or even emissions per pound of our money handed over at the till. Just floor space. Why not "per Bangladeshi sweatshop worker" or "per migrant vegetable-picker working in Lincolnshire fields"? It would make about as much sense.
We can be fairly sure the "floor space" measure shows Tesco in a good light – and until the government lays down some proper rules about how to measure and declare corporate carbon emissions, they can do what they like.
Carbon intensity is the new gambit for companies trying to spruce up their green images. They're all doing it. And, sadly, last year the Advertising Standards Authority gave them a green light to carry on.
Most companies don't go for the outlandish "per-square-foot" measurement of Tesco. They largely measure the carbon intensity of their operations as tonnes of CO2 against product produced or cash turnover.
But this is scarcely better. It means you can keep churning out more stuff, or flying people to more places or burning more coal in power stations, while claiming all is well because you are doing it with greater carbon efficiency. And many companies do.
The problem is that the atmosphere doesn't recognise this increased efficiency. All it does is respond to the extra carbon dioxide in the air by raising temperatures.
Christian Aid, which asked me to look into this, has recently been checking company carbon-emissions targets, and found that most go for carbon intensity and ignore actual emissions.
British Airways and Virgin Atlantic, for instance, both promise big improvements in the fuel efficiency of their airline fleets, measured as (hold your breath) "emissions per revenue tonne kilometre". They will achieve their targets largely by buying new planes that need less fuel. The Boeing 787 uses 30% less fuel than the 767. Good. But, for all Virgin's publicity-grabbing trials with biofuels, neither company makes any promises about cutting actual emissions.
George W Bush started this. Unable to cope with the Kyoto protocol's calls for modest but real reductions in actual emissions, he announced in 2002 that the US would cut the "carbon intensity" of its economy by 18% by 2012. The US will probably achieve this target. But its emissions continue on up.
China recently promised to improve its carbon intensity by 40% by 2020 – far greater than most western corporate promises. But its actual emissions will continue on up.
The trouble is that none of this is much more than business as usual. Virtually all industrial economies are reducing their carbon intensity virtually all the time. Every new generation of technology is more energy-efficient than the last – hence greater carbon efficiency. Any company that did not do this would soon be bankrupt.
But it is not enough. Economies and corporate output have been growing too quickly. We don't need reduced carbon intensity, we need real cuts in emissions. Globally, nationally and corporately. Nothing else will do.
But meanwhile companies are using the carbon-intensity mantra to bamboozle us about what they are doing and what they promise.
Last summer, the UK Advertising Standards Authority, an industry-run watchdog, rejected complaints that electricity company EDF was misleading the public with TV adverts boasting of its plants to reduce the carbon intensity of its operations by 60% by 2020. Complainants said viewers might think it was planning to cut actual emissions by that amount. The ASA said viewers were unlikely to be misled, and said other advertisers would be allowed to make similar claims about carbon intensity.
Not misled? I doubt if many viewers realised that EDF's carbon emissions reached a new record in 2007. Nor that the carbon intensity of its British power stations, far from improving, was the worst for at least six years. I can't help thinking the ASA got this one wrong.
Copyright Speakers Corner 2016