The operation of passenger cars and pickups in the United States contributes about 12 percent of global carbon dioxide emissions and about 19 percent of U.S. CO2 emissions, said Tim Wallington, a scientist with Ford's Research and Advanced Engineering department in Dearborn, Mich.

Vehicles are a significant source of greenhouse gases, Wallington told UPI's Climate, but not the dominant source. We can have a high degree of confidence that there have been significant changes in greenhouse gas concentrations and climate since the industrial revolution.

Ford helps to fund a group at the Massachusetts Institute of Technology, he said. That group concluded there is a 90 percent probability that at least 60 percent of the current warming is attributable to man-made forcings.

For 2003 and 2004, Wallington said, preliminary estimates are the years will be the third or fourth warmest on record.

To reduce the vehicle contribution is going to be difficult and complicated, he said. Everybody projects that the demand for mobility around the world is going to increase tremendously ... over the next 50 years. (Vehicle numbers) are going to approximately double.

Wallington said when he talks to his colleagues at Ford about climate change, their eyes glaze over. It is very difficult for them to care.

He said one reason for this is the major impacts of climate change will manifest themselves beyond the planning horizon of most companies. Nevertheless, there seems to be more interest in the subject in the business community, for two reasons:

First, some impacts are beginning to be felt, particularly in the Arctic regions.

Second, he said, there is a confluence of the scientific and business timescales. The business timescale is about 20 years. That's now the same time frame in which the effects of climate change are going to be seriously felt. There is big money to be made and lost, depending upon what choices you make.

Wallington said Ford has assessed the contribution to atmospheric CO2 of a Ford Taurus, a mid-sized automobile. Over its manufacture and operating lifetime, the vehicle emits 61.9 tons. Of that total, the vast majority - 55.1 tons - is gasoline burned over about 120,000 miles. Other emissions come from manufacture (3.5 tons), assembly (2.5 tons), shipping (0.1 ton) and maintenance and repair (0.7 tons).

Along with CO2 emissions, the vehicle contributes other greenhouse over its lifetime, notably the use and leakage of air conditioner refrigerant -- though these contributions are very small compared to CO2.

The only emissions over which Ford has direct control are those due to manufacturing and assembly, Wallington said, and the company has done a fairly good job of reducing those. The manufacturer can exert only indirect influence over operating emissions, primarily through fuel economy.

CO2 is a large and long-term issue, Wallington said, adding there are only a few strategies available to address the essential problem of fuel use:

- Build smaller conventional vehicles;

- use use diesel instead of gasoline (pending implementation of improved diesel technology);

- convert to gas-electric hybrids;

- use biofuels and, in the distant future,

- move to hydrogen and hydrogen fuel-cell technology.

To improve efficiency, you can reduce the friction in the engine, Wallington said. They are pretty damned efficient at the moment. They might get 10 percent more efficient, but not much more. Lots of very intelligent engineers have been working on these engines for many years.

Small cars emit less, but Americans are not showing much inclination at the moment to drive them. Improved diesel technology also holds some promise. A German study has shown diesel vehicles emit 30 percent less CO2 per mile.

Widespread use of hybrid engine technology also would add incremental savings, particularly in city driving. Using a diesel hybrid engine would gain still more, but diesel is more costly and the technology is still under development.

Hydrogen fuel cells are a lot further into the future, Wallington said. There has been a lot of press on fuel cells - that these are the vehicles of the future, but there are a lot of technical hurdles that have to be overcome.

He listed six such hurdles. First is operating temperature - the cells do not function well at temperatures lower than 32 degrees Fahrenheit (0 degrees Celsius), which would make them problematic in colder regions.

Second, fuel cells are expensive. Wallington declined to give Ford's cost estimates for its hydrogen prototype vehicle, but noted that it costs $10,000 a month to rent a Toyota fuel-cell-powered Camry in California. This is prohibitive compared to renting, say, a Ford Focus at $120 a month.

Other problems include hydrogen-fuel production, distribution, storage and liability.

Hydrogen problems aside, solutions are available in the meantime. For instance, a recent study by the Pew Center on Global Climate Change compared passenger vehicles and emissions standards around the world and found the United States could achieve some strides in reducing CO2 from vehicles.

The fuel-economy and greenhouse-gas-emission performance of U.S. cars and light trucks - both historically and projected based on current policies - lags behind most other nations, said the report, which was written by Feng An and Amanda Sauer.

The United States and Canada have the lowest standards in terms of fleet-average fuel economy rating, and they have the highest greenhouse gas emission rates based on the EU testing procedure, the report continued. "The new Chinese standards are more stringent than those in Australia, Canada, California and the United States, but they are less stringent than those in the European Union and Japan.

The Pew report also said when California's new greenhouse-gas standards go into effect in 2009, they will narrow the gap between U.S. and EU standards, but the California standards would still be less stringent than the EU standards.

That would be a tangible bit of progress. The Pew report estimates the California standards would reduce greenhouse-gas emissions from passenger vehicles by about 25 percent, and Californians buy about 10 percent of the passenger vehicles sold in the United States.

Climate is a weekly series examining the potential human impact on global climate change, by veteran environmental reporter Dan Whipple. E-mail: [email protected]

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