Rise in UK car CO2 emissions largely a result of increasing SUV sales, not declining diesel

The increase in UK new car CO2 emissions by 0.8% in 2017 reported by the UK industry arises mainly from a shift to larger SUV and dual-purpose vehicles rather than from declining diesel sales that the UK car industry association (SMMT) claims.

UK new car average CO2 emissions rose from 120.1 grammes per km in 2016 to 121g/km in 2017. But although the share of diesel cars declined (from 47.7% to 42%) the share of much lower carbon alternatively fuelled vehicles (AFVs, mainly plug-in and hybrid cars) grew strongly. AFVs on average emit 66.8g/km of CO2, which is around half that of a diesel (120.1g/km). The average gasoline car emits 123.7g/km, only marginally more than a diesel which tends to be far more powerful. (Figures for average emissions by fuel type are for 2016 as 2017 data are not yet available.) T&E calculations show that the overall changes in market shares would have been expected to lower emissions by around 0.5g/km, but instead emissions rose!

The primary reason for the increase is buried in a footnote to the SMMT statement on 2017 vehicles sales. It shows that there has been a sharp increase in SUV (dual purpose) vehicles sales while the rest of the market declined. SUVs now represent 18.1% of all new car sales. The average new SUV had emissions of 141.4g/km compared to 119g/km for an upper medium segment car (Passat, for example) or 114.8g/km for a lower medium segment car – Golf, for example. (Figures for vehicle segments are for 2016 as 2017 data are not yet available.) This shift to larger, heavier and less aerodynamic cars has been ongoing for more than a decade and the increase in 2017 entirely predictable.

The other contributory factor to the rise in new car emissions is that the gap between the old NEDC test (on which the emissions continue to be based) and real-world performance has stabilised. The gap has grown year on year from 9% in 2001 to 42% in 2016. The widening gap, caused largely by carmakers manipulating laboratory tests, has exaggerated the claimed reduction in CO2 emissions in previous years. Now the gap is not growing (probably because of the shift to the new test cycle and because most of the useable flexibilities in the test procedures have been exploited) it is harder for carmakers to claim big improvements in emissions since these must be delivered through technology, not cheating the test. In reality, on the road, new cars CO2 emissions have changed little in five years.

Overall, the industry claims that declining diesel sales are worsening CO2 emissions is largely a smokescreen for their own failure to fit sufficient technology to improve the efficiency of the cars they sell. Instead they have focused on promoting larger, higher performance diesel cars that are more profitable. Carmakers are also anxious to rebuild consumer trust in diesel following the Dieselgate scandal. They are desperate to promote diesel as lower carbon whereas in practice these are much higher emitting than hybrid, plug-in hybrid and electric cars for which there is little supply in the market.

A 2017 T&E report highlighted that, on a life-cycle basis EU wide, diesel cars are higher emitting than equivalent gasoline cars. This was because: diesels have higher embedded emissions; diesels use high-carbon biodiesel; refining the fuel requires more energy; and diesels are driven more as fuel is cheaper. Electric cars are significantly lower carbon, even taking into account the higher emissions in manufacturing and emissions from electricity generation.

The Dieselgate scandal has seriously and probably irreparably damaged the appeal of diesel cars after it exposed these as much less clean than previously claimed. A new diesel car still typically emits six times more toxic nitrogen oxides than an equivalent petrol car. It is a scandal entirely of the car industry's own making and their cheating and deceit is the primary cause for the loss of consumer trust along with the long overdue action of cities and Governments to clean up the air.

It is time for the industry to stop claiming declining diesel sales are the cause of their increasing inability to tackle CO2 emissions. Instead they should fit more efficient technology to new cars that would radically lower their fuel costs for buyers. By taking advantage of falling battery prices and providing more choice in plug-in vehicles (just 20 battery models are presently available) and marketing these cars more aggressively sales will rise – just 3.7% of marketing spend is on plug-in vehicles. It is time to end the misinformation that is endemic in the industry and which the SMMT announcement is a further example of. Instead carmakers should start providing and marketing the plug-in cars that are needed to tackle our toxic air and climate crisis and are fit for the 21st century.


Luke 's picture


The Outlandish PHIB is a 2 tonne SUV that gets 28mpg on Fossil petrol not the claimed 148 mpg NEDC. The vast majority of "low co2" petrols have to be driven very very gently with minimal torque to achieve low consumption. 50% of ALL urban NOx in the UK is from PETROL euro 1-3 cars DEFRA 2014 roadside tests reported. This demonstrates that petrols increase emissions much more rapidly than diesels with age, mileage and wear. After 50,000 miles a petrol emits more NOx than equivalent diesel.

The answer lies in reducing #vehicleobesity and refuelling existing diesels with non fossil waste based #hvo ( see Helsinki buses). Electricity and battery based vehicles have their own footprint in a world where electricity is far from mostly renewable.

Ekranoplan's picture


The vast majority of that 3.7% plugin spend is on heavy, large mostly petrol powered SUVs like the Mitsubishi Outlandish. Giving £4.5k to rich people to effectively scrap reliable smaller vehicles is hardly ethical or environmentally friendly I agree we need to cull the sale of obese fossil powered cars but let's not replace them with energy guzzling part or full electric SUVs. 2/3rds or roadside PMs comes from road contact - the bigger the car the heavier it is and hence larger wheels and tyres. Plastic waste is a real issue as are ultra fine particulates. Wear down a large tyre (say 235r19 to 1.6mm and its much worse than an older car with 145r14 tyres.

The grid is not that green, we import coal from South America and wood from USA s well as natural gas from Qatar. The Govt wants to frack under our feet which pollutes the ground water and releases methane ( more potent than CO2 in global warming terms. Time to #addlightness see #scrappingiswasteful #pluginretrofit older cars with electric pre heaters and run diesels on non fossil alternatives. EVs have a part to play but we need to address the dirty secrets just like the oil industry ones - why are batteries cheaper? Ask a Congolese child mining cobalt!

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About the author

Greg Archer's picture

Director, UK