With automotive emissions regulations again coming under political pressure, we thought we'd re run this Earth Day question from 2014 in an attempt to answer the question: Why all the fuss? Why do we still focus on green cars some 40 years after the EPA imposed the most significant emissions limits on cars? We hope it will provoke thought engender constructive discussion tor today's political environment:

Economists call them "externalities."

They're the costs of people's actions on other people or communities—though the people taking those actions don't have to pay for those costs, even as they harm others.

The emissions from combusting fossil fuels to propel vehicles are clearly a prime example.

DON'T MISS: A Brief History Of Smog, Which Led To Electric Cars

While complaints about air quality in the Los Angeles Basin date back centuries, research established more than 50 years ago that vehicle emissions were the primary cause of photochemical smog.

That led the state of California to begin efforts to regulate tailpipe emissions—well before the U.S. Environmental Protection Agency even existed—which led in turn to the first catalytic converters in U.S. vehicles in 1975.

Catalysts spread throughout most of the automaking world over the next 20 years, hugely reducing emissions of carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx), all toxic in various ways.

Los Angeles Smog

Los Angeles Smog

An entirely new problem is added by the recognition and scientific acceptance of climate change due to rapid, unparalleled human emissions of carbon dioxide (CO2) since the dawn of the Industrial Revolution around 1750.

Against the combined efforts of automakers and the Bush White House, in 2007 the U.S. Supreme Court ruled that CO2 is a vehicle emission that the EPA not only can but must regulate.

That led to rules that steadily reduce carbon emission levels (and parallel rules to increase corporate average fuel economy) from 2012 through 2025. Those rules are joined by even stiffer reductions from legislation in the European Union, China, and elsewhere.

CHECK OUT: Poll: When will it be unacceptable to drive a car with a tailpipe?

It is well established that electric cars have the lowest wells-to-wheels CO2 footprint of any near- or medium-term alternative, varying from the equivalent of about 39 miles per gallon on the dirtiest U.S. grids to more than 100 mpg on the cleanest grids.

And the carbon footprint per mile of driving an electric car declines every time the grid gets cleaner, whether from adding renewable energy sources or replacing a coal-fired generation plant with one using natural gas.

Image courtesy of Friends of the Earth

Image courtesy of Friends of the Earth

Obviously that non-renewable electricity generation has its own carbon footprint, but it's easier to control hundreds of power plants than hundreds of millions of vehicles.

The graphic above came from Friends of the Earth.

And it got us thinking about the following question.

ALSO WATCH: Honda Film: Controlling Air Pollution A 'Never-Ending Race'

With increasing availability of zero-emission cars over the coming years, when will citizens at large start to question the idea that every vehicle has an "exhaust pipe" that just belches harmful substances into our shared air?

And when will driving a car that emits carbon dioxide every time it moves become morally unacceptable?

[hat tip: John C. Briggs]

Smog in Hong Kong [Image by Flickr user inkelv1122]

Smog in Hong Kong [Image by Flickr user inkelv1122]

EDITOR'S NOTE: We originally published this article in November 2015, and it continues to provoke discussion.

We were prompted to re-run it for Earth Day by a friend in public-health advocacy who drew a parallel between smoking and tailpipes. Smoking is banned in public venues not because of the harm it does to smokers, who are free to make their own bad decisions, but due to the harm it imposes on others through the effects of second-hand smoke.

Our friend asked when the same rule would be applied to the carbon dioxide emitted by vehicles. That harms everyone on earth through its contribution to climate change.

We had no answer to the question.

Green Car Reports respectfully reminds its readers that the scientific validity of climate change is not a topic for debate in our comments. We ask that any comments by climate-change denialists be flagged for moderation. Thank you in advance for helping us keep our comments on topic, civil, respectful, and fact-based.


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