The words global warming would probably have made cantankerous old Inspector Morse choke on his pint.

But his trusted sidekick Lewis, now promoted to Inspector and with a series of his own, is taking the matter very seriously.

Programme maker ITV said it was so concerned about the future of the planet, that it had calculated the carbon footprint of the new drama series.

Following the first of four new Lewis episodes last week, viewers saw the following flash up on their screens after the credits: "The verified carbon footprint of Lewis is 830 tonnes."

In a bid to reduce greenhouses gases, those taking part in the shoot shared vehicles and read scripts on recycled paper.

It's the first occasion that ITV has calculated the carbon footprint of a drama series and the 830-tonne total is for the whole series.

Lisa Vanoli, a spokesman for ITV, said: "ITV Productions were interested to understand what the carbon footprint of their productions were and Lewis was one of a number of shows that volunteered for this exercise."

Oxford author Colin Dexter, who wrote the Morse novels and appeared in the first of the new Lewis episodes wearing a Panama hat, said: "I took the bus to the shoot because I can never find a parking space in Oxford.

"I'm delighted programme makers are paying attention to global warming."

Paul Allen, whose book Endeavouring to Crack the Morse Code focuses on the locations of Morse and Lewis films, said it was the first time he had seen a TV drama calculate a carbon footprint.

He added: "It's fascinating because in the old days Morse and Lewis spent a lot of time in the Jaguar, or driving to pubs, and that was where they did most of their thinking in terms of solving the mystery.

"But in the latest episode of Lewis, you hardly see Kevin Whately and Laurence Fox in their cars at all.

"A lot of scenes are shot on location in Oxford, but there are quite a few scenes in the office looking at computers - which reflects how policing has changed over the years.

"In tomorrow night's episode, Laurence Fox flies to Berlin and there are scenes filmed in Berlin, so I would expect the carbon footprint to go up a bit."

Dr Antony Richards, a spokesman for the Inspector Morse Society, said: "I think Lewis was driving a Vauxhall in the first series which probably runs on lower emissions than the old Jag, which only did about 14 miles to the gallon."

Green city councillor Craig Simmons said: "It's good to hear that programme makers are thinking about how to reduce emissions."

Lewis is on again tomorrow on ITV1 at 9pm.

The carbon footprint of Lewis was measured using the World Business Council for Sustainable Development's Greenhouse Gas Protocol methodology which covers Scope 1, 2 and 3 emissions (direct energy use, indirect energy use and travel/supply chain). Lewis, in consultation with ITV, established the scope of the footprint as measuring the following: Scope 1 emissions (use of diesel generators on location) Scope 2 emissions (electricity use in production offices) Scope 3 emissions (transport to and from production office to location, transport use for other purposes (couriers, taxis, flights).