By Jorn Madslien
Business reporter, BBC News, Geneva motor show
Better engines are crucial to reach the goals
The motor industry has been urged to halve CO2 emissions from cars by 2050 by four leading international agencies.
The "50 by 50" initiative is seeking ways to reconcile aspirations for mobility with reduced emissions and a global economic recovery.
The number of cars in the world is set to triple by 2050, so the sector is being urged to play its part to reduce its contribution to global warming.
Industry executives at the Geneva motor show have responded positively.
The call for the cut in emissions came from the UN Environment Programme (UNEP), the International Energy Agency (IEA), the International Transport Forum (ITF) and the FIA Foundation.
"The world's car fleet is expected to triple by 2050 with 80% of this in developing economies," predicted Achim Steiner, United Nations Under-Secretary General and executive director of UNEP.
"We would urge the world's car and component makers to get on board to prove that they too are part of the solution."
Broadly speaking, automotive industry executives say such emission cuts are perfectly feasible, though they would come at a cost.
"This industry has a capacity of being very innovative when it needs to be," said Ian Robertson, BMW Group board member in charge of marketing and chairman of Rolls-Royce Motor Cars.
"I think we can do an awful lot," he says, pointing out how the V8 engine in BMW's 7-series executive model is 10% more efficient than the previous V8, yet it delivers the same performance as the previous V12.
"There are more than enough chances for the industry to aspire to the challenge and we as a company are intent on doing that," Mr Robertson told the BBC, insisting that engine development by high-end firms such as BMW soon trickle down to mainstream carmakers and thus improve fuel efficiency across the board.
Toyota Motor Europe executive Graham Smith, until recently president the Society of Motor Manufacturers and Traders (SMMT) in the UK, agrees that the target sounds achievable.
The Toyota fleet's average carbon dioxide emissions are currently 140 grams per kilometre, already well below the industry average and set to drop to 95 grams by 2020.
"By the time we've gone to 95, we've gone quite a long way towards the '50 by 50' target," he told the BBC.
Electric cars will need a broader look at where emissions are coming from
The "50 by 50" initiative, albeit broadly supported by the industry, should nevertheless be treated with caution, according to Dieter Zetsche, chief executive of Daimler, owner of car marques Mercedes, Smart and Maybach.
"Fifty per cent in 100 years is certainly achievable," he says, picking a hypothetical time-scale.
"It's always a question of how fast you can develop. Ultimately, the goal must be emission-free driving."
But the internal combustion engine, powered by petrol or diesel, is likely to remain the power source of choice for the mainstream for a long time to come, and there are limits to how much more efficient conventional engines can be, Mr Zetsche said.
Toyota's Mr Smith pointed out that for many drivers, particularly in wealthy countries, by 2050 a wide range of energy sources will be available, ranging from alternative fuels via plug-in hybrids combining fuel with electricity, to better electric vehicles than the ones available today, or even hydrogen fuel cells.
Mr Smith also added another complication to the equation.
As the industry increasingly switches to electric power, or even hydrogen, the focus with regards to emissions needs to be directed at the power companies delivering the energy that goes into the cars batteries or is used to create the hydrogen.
"Just as we will have a range of powertrain solutions, the power companies will have a range of power generation capabilities," he says.
Power generators "see road transport as a tremendous possibility for them," Mr Smith points out, though in order to make meaningful comparisons in terms of emissions it is crucial to identify how electricity used to power electric cars is being produced.
Aston Martin chief Ulrich Bez was more blunt in his call for a broader look at emissions, which are emitted by power generators delivering electricity to households and factories, as well as by cars and airlines.
"England blows £800m per year by not insulating houses," he told the BBC. "That represents more CO2 emissions than the running of 20,000 Aston Martins for 100 years."