Car exhaust emissions in the U.S. account for 5% of worldwide carbon emissions.

FORBES: Magazine Article

With its new catalyst, Honda said enhanced performance of lower-cost palladium in purification of exhaust emissions enabled it to replace a portion of rhodium use.

FORBES: Honda's Reduced Use Of Rhodium Part Of Effort To Shift Away From More-Expensive Metals

Diesel exhaust emissions from lorries, which contain concentrations of particulates, are responsible for many of the 9, 000 deaths a year attributed to particulate emissions by the government's expert advisory body.

ECONOMIST: Vehicle taxes

The Jetta TDI has a 2.0-liter four-cylinder turbodiesel engine that operates efficiently enough not to require the new urea-injection technology that many larger, heavier diesels do in order to comply with exhaust emissions standards.

FORBES: 2012 Volkswagen Jetta TDI

Recording equipment will measure exhaust pipe emissions of vehicles travelling through the sites.

BBC: Traffic pollution tested across Sheffield

But it did say that the engine is 10 percent lighter than a 2.2-liter diesel engine currently sold in markets outside the U.S. and that it runs clean enough not to require complicated exhaust treatments to meet emissions regulations.

FORBES: Mazda Bets Big On Diesel With The All-New 2014 Mazda 6

Corning thinks those filters, which strip particulate emissions out of the exhaust of diesel engines, will soon be its next big hit.

FORBES: Magazine Article

Burns touts the cars' zero emissions instead of exhaust, they emit water vapor and their reliance on hydrogen made primarily from natural gas, but also from water.

NPR: On the Road with GM's Newest Hydrogen Car

But improved (yet still expensive) exhaust treatments have at least made it possible to reduce emissions to acceptable levels.

FORBES: How To Burn Trash For Power

Michael Cross, who heads up emissions solutions at diesel engine maker Cummins, says they will need help from an exhaust treatment system.

FORBES: Clearing the Air

Siemens and Shell, for example, have just announced a new fuel-cell technology for oil rigs that will capture emissions of carbon dioxide and methane, generate power from them cleanly, and sequester the exhaust.

ECONOMIST: Emissions

Wednesday's Supreme Court argument about whether to regulate carbon dioxide from auto emissions might have made you wonder why we don't just remove the greenhouse gas from auto exhaust the way we do a lot of other pollutants.

NPR: Has the Move to Make Cars Greener Stalled?

It also said emissions could be reduced by making wider use of low carbon fossil fuels like natural gas, and decarbonising exhaust gases from power plants.

BBC: Impact of global warming may be severe and wide-ranging