KEY POINTS:
Ships in sea lanes off the southern California coast each year dump more exhaust emissions on Los Angeles than the city's seven million vehicles, according to a BBC World Service report on global warming.
New Zealand contributes only 0.2 per cent of CO2 emissions, yet China remains unchecked and is planning and building a new Huntly-sized coal power station every week until 2030, says Mazda New Zealand managing director Andrew Clearwater.
Porsche has reduced fuel consumption and exhaust emissions over the past 15 years by 1.7 per cent annually, says Porsche chief executive Dr Wendelin Wiedeking, adding: "Porsche drivers shouldn't feel they need to wear a hair shirt."
Carbon dioxide (CO2) is not a pollutant, it is a climate gas. The German carmaker says man-made CO2 emissions account for 3.5 per cent of annual worldwide output. CO2 generation from natural sources - decomposing organic matter, for example - provides 96.5 per cent.
Of that man-made 3.5 per cent, it says, power stations contribute 25 per cent, households 23 per cent, industry 26 per cent and transport - planes, boats, vehicles, trains - 26 per cent.
Burning fossil fuels like oil or coal sends man-made emissions into the atmosphere. They form a thin blanket around the Earth, which prevents heat aborbed from the sun's rays during the day from escaping at night.
This leads to global warming and makes CO2 partly responsible for the greenhouse effect.
The car industry has been working on improving fuel efficiency and emissions for years. It spends 55 billion ($110 billion) a year on research in Europe alone.
Some are doing it better than others. Makers of small cars with smaller motors have a head-start over big-car makers with big motors. Peugeot and Fiat are leading the way here. Diesel carmakers have an advantage over those making mostly petrol engines. Diesel produces roughly 20 per cent fewer CO2 emissions from the tailpipe than petrol.
BMW pulled down average emissions across its British fleet by 48 per cent to head the car industry in 2007 and win a green gong from consumer magazine What Car? Porsche says it will reduce CO2 emissions by another 20 per cent by 2012.
Mercedes-Benz, Volkswagen, Audi, Honda, Toyota, Nissan, Mazda, Mitsubishi, Suzuki ... they are all working to improve fuel consumpion and reduce emissions. Mazda cut the weight of its small Mazda2 by an unheard-of 100kg to help the environment. One of the reasons why the car won the recent World Car award.
Carmakers say they are easy targets for governments rushing in climate change legislation and fuel economy standards. Exhaust fumes are visible, household emissions are not.
Says Mazda New Zealand managing director Andrew Clearwater: "Whether you subscribe to global warminig and climate change or not, the Government is rolling out a raft of legislation specifically targeting our industry.
"While New Zealand ratified the Kyoto Protocol in 2002 (the United Nations framework for climate change) there has been no policy in the past five years to constrain emissions, and now the government is set to roll out a plethora of policies which haven't necessarily been well thought out, but which will have a significant cost on business compliance and fuel inflation.
"Apart from the emission trading scheme, which will progressively impact on all businesses, the Government is also making some bold statements about the widespread deployment of electric cars in this country, despite the fact this technology has a way to go before commercially viable product is available.
"But perhaps the biggest challenge facing the industry is the Government's intention of introducing a fuel economy standard to become mandatory with an overall industry target of 170gms of CO2 per km in 2015.
"As an industry, our argument is if New Zealand is to introduce an all-encompassing emission trading scheme, treating all greenhouse gas emissions equally, why is it necessary to impose additional penalties on vehicles entering the fleet - it seems to be a case of double taxation/penalty."
Only a handful of new vehicles - nearly all of them small models - on New Zealand roads at the moment meet 170g/km.
The Motor Industry Association wants the Government instead to accept an industry-led scheme it calls "burden sharing", where each carmaker has to improve its CO2 exhaust emissions.
The NZ Government's discussion paper has a CO2 penalty as one of the options. Carmakers that don't meet the 2015 limit would be forced to pass on to buyers a penalty of $200 for every gram of CO2 above the 170g/km ceiling.
The MIA says this would force up by thousands of dollars the price of big cars like the Holden Commodore or Ford Falcon.
The proposed 2015 emissions legislation for New Zealand is as complex as fuel-economy laws unveiled by the Bush Administration for the US. The US didn't sign the Kyoto Protocol.
The new rules want a 40 per cent improvement in car and truck fuel economy by 2020 to an industry average of 8litres/100km, or 35mpg. The regulations also want a 25 per cent improvement in the 2011-15 model years.
But under the proposal, Mercedes-Benz' cars would have to achieve better average fuel economy than Toyota's. BMW's sports utility vehicles like the X5 would have to be more fuel efficient than those built by General Motors.
Under the rules, the relative increase is highest for the smallest vehicles. Vehicles are measured by their footprint, roughly the area bounded by the wheels.
The effects would vary dramatically among carmakers. The winners in the US are companies such as GM, Toyota and Chrysler, mass-market companies with broad product portfolios. The losers are independent luxury brands such as Porsche, BMW and Mercedes-Benz.
Regulators based the new standards on their projections of the number of cars and trucks of different sizes that the industry will produce by 2015.
The US National Highway Traffic Safety Administration developed the rules. The agency's plan creates two sliding scales of fuel economy targets for cars and trucks of different sizes.
Each carmaker is assigned its own separate fuel-economy standards for cars and trucks, based on the number of vehicles of each footprint size that it sells.
The sliding scales aim to achieve better fuel economy in vehicles of all sizes. Under the rules, carmakers that build large vehicles might find it advantageous to keep doing so.
If they downsize, their standards would go up. At the same time, US industry and government officials argue that if fuel prices remain high, consumers will demand smaller, fuel-efficient vehicles.
The proposed system creates anomalies. The most extreme example is Porsche. The company's powerful sports cars have short wheelbases and consequently small footprints, thus higher fuel economy targets.
If the industry builds the mix of vehicle sizes that NHTSA projects, Porsche cars in 2015 would have to average 6.8 litres/100km, or 41.3mpg, about 7mpg better than Toyota, Lexus and Scion cars collectively.
Carmakers with smaller, less diverse product offerings - such as Volkswagen, Mitsubishi, Subaru and Suzuki - also face much higher standards under the proposal.
Variations among the six largest carmakers are less striking because of their broader product line-ups. But they are still significant.
For cars, Chrysler's 2015 fuel economy standard would be the lowest, at 8.4litres/100km, or 33.6mpg. Honda's would be highest, at 7.7 litres/100km, 36.4mpg.
The requirements that Porsche faces in 2015 help explain why the company lobbied Congress hard to give it an exemption in the energy bill. Lawmakers refused.
Some industry executives predict Porsche and several other carmakers will pay hefty fines rather than change their line-ups.
Carmakers generally support the new fuel standards, despite the anomalies. They say a tough national US standard is preferable to greenhouse gas regulations, which they claim would create market chaos.
