By Roger Harrabin
BBC Environment Correspondent
The UK government publishes its new climate strategy next week. Labour's stated aim is to cut carbon dioxide (CO2) by 20% from 1990 levels in the next four years, and by 60% by 2050. Our correspondent Roger Harrabin considers how transport fits into the climate policy mix.
Emissions from vehicles in the UK are supposed to be going down from the base year of 1990 - but instead they are going up. Growth in traffic is swamping gains from engine efficiency.
The Department for Transport is extremely nervous of being portrayed in the press as anti-motorist and has been unwilling to impose restrictions that would lead to big CO2 cuts.
Ministers are pinning their greatest hopes for CO2 emission reductions on their biofuels obligation. But independent experts warn that the department's calculations of these savings may be over-estimated by 100%.
The biofuels obligation requires that by 2010, 5% of all UK road fuel should be derived from plant-based sources.
The Transport Secretary Alistair Darling says this would save a million tonnes of carbon emissions a year. The Low Carbon Vehicles Partnership expect biofuels to save only half that amount.
It says the government has taken a very optimistic view of the carbon efficiency of biofuels. On average, plant fuels save only about a third of the CO2 of oil-based fuels because it still takes energy to grow, refine and transport the crops.
What is more, the Partnership says, any gains from biofuels will be outstripped by the growth in annual vehicle mileage.
The fuel tax escalator did dampen traffic growth until it was scrapped after the truckers' industrial protest in 2000; but the Chancellor has ruled out extra tax while oil prices are high.
Climate campaigners were pleased to see the recent budget put higher rates of road tax (Vehicle Excise Duty) on so-called gas guzzlers. The cleanest cars will be subject to zero duty and the most polluting will pay £210 annually, up from £175 now. But campaigners say the top rate is still far too low; and some are pushing for £1,800 a year.
The Governor of California, Arnold Schwarzenegger, has ordered that new cars in California should cut CO2 by 30%. The EU could do the same - but the car manufacturers are a much more powerful lobby in Europe than in California.
Transport Secretary Alistair Darling likes the idea of road pricing. Although it is clearly a congestion policy, it has important climate implications, too. Mainstream motoring groups say they may support charging drivers for using the busiest roads, but only if the policy is revenue-neutral (it does not increase the total tax taken from motorists by government).
So, if the government wants to count on support from motorists, it will need to compensate for road charging by reducing other road taxes.
The left-leaning think-tank the Institute for Public Policy Research warns that if government agrees to this revenue-neutral policy, it will need to compensate drivers by lowering fuel duty. This in turn will encourage more driving in rural areas, which will increase overall CO2, not lower it.
ENFORCING SPEED LIMITS
Petrol cars are much more polluting the faster they go above cruising speeds. The AA Trust estimates that the government could save 800,000 tonnes of carbon a year by stopping people driving above 80mph, but ministers have so far rejected this option.
These are not considered in the government's stated 2010 target of a 20% reduction in CO2 - and yet they are the fastest growing source of emissions. Professor David Lee, from the Centre of Air Transport and the Environment, says all the engine improvements could not compensate for the growth in passenger numbers. What is more, major improvements in design to the larger part of the aeroplane fleet may not happen for decades - way beyond the time scientists say we need to have cut CO2.
Does this mean aviation has to get a special deal - to be allowed to increase CO2 while every other sector is supposed to be reducing CO2?
The government's answer is to put aviation in the EU emissions trading scheme (EU ETS). Experts say if airlines have to buy pollution permits it will put a tiny amount on ticket prices and will not affect passenger growth at all. It is a fig leaf, they say.
However, some analysts such as Professor Michael Grubb, of the Carbon Trust, warn that if the airlines snap up all the carbon permits on the EU market, it could put some industrial giants out of business.
One former aviation minister, Chris Mullin, said: "The demands of the aviation industry are insatiable and successive governments have usually given way to them." 2006 is the year of an aviation review. Will it do anything about CO2?
The UK is currently on track to meet its Kyoto commitment to reduce emissions of six different greenhouse gases by an average of 12.5% compared with 1990 levels over the years 2008 to 2012
The fall in emissions through the 1990s and early part of the 2000s was achieved at a time of strong growth in the UK economy
Carbon dioxide emissions have risen recently, largely due to increased burning of coal in power stations. This was prompted by a rise in the price of gas (gas is 'cleaner' than coal)
The Labour administration has stated in three election manifestos that it would like to see a 20% cut in CO2 emissions by 2010