One of the many consequences of the Paris Climate Accord is that it has made the diesel engine, the underlying diesel technology, politically controversial again. As we’ll see below, that was the case at least once before, in the post-war U.S. when diesel was shaking up the railroad industry.

A one paragraph history? It’s worth a shot. The diesel engine was invented by Rudolf Diesel in the 1890s. In a test in February 1897, he demonstrated 26.2% efficiency: a big deal, since the steam engines of the day were getting by at an efficiency level of 10%. Over the decades that follow, diesel prevailed over steam as a way of pulling heavy loads, on rails or eventually on the road. But diesel proved inferior to spark-ignition technology, and thus diesel fuel proved inferior to gasoline, when it came to smaller loads, that is, when it came to the beloved family car.

Like gasoline, diesel fuel is carbon-based (a “fossil fuel”) and so its emissions contribute to the greenhouse effect. A naïve question at this point might be, “is diesel technology preferable to spark-ignition technology from the point of view of climate change?” But there is no straightforward answer to that, largely because the chemistry of the fuels and the technology of the engines both evolve over time.

If you believe (as many do) that environmental realities will force the world to learn to live without the gasoline-burning family car, then the question naturally arises: will large-haul commerce and industry have to learn to live without diesel technology, too?

Left Wing View

Very broadly speaking, the ‘environmentalist’ view is that the industrial world must transition away from the burning of carbon as a way of moving people or freight around. From that high level of abstraction, the distinction between gasoline and diesel is a small one – both ought to be on the way out.

Jennifer Macedonia, writing for the Center for American Progress early this year, put it this way: “policymakers should combine carbon pricing with policies that push technology development in order to cut carbon pollution from the transportation sector.”

Policymakers can most readily impact “pricing” through the tax system, but of course taxing “carbon,” whether in diesel or in gasoline, is a chancy political proposition.

In almost any imaginable scenario, transitional decisions have to be made. Some contend that not all fossil fuels are created equal, and that the transition to worry about just now is not the eventual one away from carbon altogether, but one toward relatively cleaner carbon burning systems.  Clean diesel has a place in that vision.

Right Wing View

Of course, many on the political right in the United States don’t reach the question of the role of diesel in a world adapting itself to issues of sustainability, because they don’t believe for example, that climate is responsive to human decisions in any predictable way.

More than that, though: there is a cultural connection between diesel and conservatives. Two words: monster trucks. Is a monster truck show with Tesla engines in the near future?

Three years ago Business Insider ran a piece about how conservatives “are purposely making their cars spew black smoke,” because they associate cleaner engines with their political foes.

When conservatives propose to “make America great again,” the great days for which they yearn were full of unapologetic diesel engines.

Diesel, by the way, was once a very disruptive technology. As the diesel engines took over the railroad industry in the late 1940s, they made the role of the “foremen” on trains redundant, and this upset existing labor-management relationships. Although the added efficiencies of diesel were too great to be overcome by such concerns: managements often did agree under pressure to find other jobs for the firemen, but the transition continued.

One generation’s disruptor is the next generation’s normalcy and, a couple of generations after that, it’s a nostalgia-tinged symbol for bygone days of greatness.