Governments get plenty of media air time to spout their policies at us. Often, it seems, they are simply chasing the voter, even after an election is over, always with an eye on the next democratic opportunity. They are endlessly advised of the best opinion to offer and use their "random policy generator" to come up with a scheme, a plan, you might say, that will appease advocates of a particular viewpoint and attract those to their side of the political spectrum based on often rather spurious notions. This is often at its most frustrating, irritating and downright annoying when the spokesperson throws in the phrase "supported by the scientific evidence" into their argument (for media interviews with governments are always confrontational the world over). More often than not, the scientific evidence is mixed on a given issue, and science can never be definitive either way.

Take the debate on diesel vehicles versus electric vehicles (EVs), for instance, currently in the news as the UK government announces a ban on the sale of new cars with internal combustion engines for the year 2040. There is certainly a case for using EVs in towns and cities, they make less noise, of course, but also the pollution their use generates is displaced to the source of generation. If that is a solar power farm or an oceanic field of wind turbines, perhaps even a tidal or wave power station, or a hydroelectric dam, then that is a positive thing. The city dwellers and workers are then not confronted with a lungful of sooty diesel particulates. This could indeed be a change for the better. After all, inhaling diesel particulates has been linked to poorer health, particularly poorer lung function, but also cardiovascular problems and even cognitive health problems.

But, my hackles rise every time I hear a government representative posit the "scientific evidence" in this debate. They tell us diesel is evil (despite having told us for many years that it was better than petrol/gasoline) and that we should now switch to electric as soon as possible. Unfortunately, it is as if they imagine this could be an almost instantaneous zero-cost transition. Let's forget the personal financial cost to drivers and vehicle fleet owners for now. What is generally always ignored is the cost - in terms of energy, resources, materials, and workforce - involved in scrapping all of those diesel vehicles. Even if some of the components might be recycled, or even repurposed, there are millions of diesel vehicles with vast amounts of energy and materials locked up in them that will simply be wasted when they're scrapped.

Moreover, the EVs that replace them will have to be built, again using huge amounts of energy, resources, workforce, materials (including rare metallic elements for circuitry, computers and batteries), and infrastructure such as factories and the factory refits. There is also the new infrastructure that will be required to switch on those EVs and disable the diesel vehicles and thence the petrol vehicles. This, I suspect is all likely to come with its own massive global pollution cost that will not in any way be offset. Other than the cleaner city air (which is important!), the energy and pollution balance sheet will be well into the red for many years to come.

There is another factor to consider. How long do an EV motor and battery last compared to a diesel engine? With current technology, rechargeable batteries have a rather limited lifespan unfortunately. Each charge-discharge cycle is not 100%, it cannot be so, and the battery wears out. Unfortunately, renewable biomass powered fuel cell vehicles are not likely to hit the roads any time soon, if ever. And, I suspect an electric motor at the tolerances and price required of a personal vehicle, as opposed to a bus or train, will have a road distance of a few tens of thousands of miles compared to the couple of hundred thousand miles a diesel driver might expect from their engine. It all adds up to more energy, materials, and resources being used and ultimately wasted with a short vehicle lifespan.

It may well be that EVs are the future, although I think better public transport systems rather than personal transport, specifically in towns and cities should be the way forward. Regardless, there needs to be a more natural transition from the infernal combustion engine to EVs that allows for natural wastage. Given the longevity of diesel engines, that could be a very long transition. In the meantime, EV technology could advance rapidly and we would find early adopters abandoning the primitive EVs of today very quickly in a similar spiral of technological redundancy we have seen with personal computers over the last couple of decades.

Materials scientists, engineers and others must accelerate us out of the 19th century technology of batteries and motors and give us a better, much more efficient, longer-lasting solution faster. If they are successful then the energy offset might be possible and the diesel engine becomes a museum piece sooner, rather than later. But, I don't see the requisite new physics on the horizon that would displace magnets and electrodes any time soon, unfortunately.

Bigger picture? Cradle to grave? Holistic perspective? Governments rarely see those in their frenetic attempts to latch on to the latest vote-winning strategy and will enlist, if not wholly "pseudo"-science, then science from which the data has been cherry-picked to fit their world model. I suspect we will continue to be irritated and frustrated by their representatives given air time on this topic for many years to come.

David Bradley blogs at Sciencebase Science Blog and tweets @sciencebase, he is author of the popular science book "Deceived Wisdom".