Four Choices to Rapidly Reduce UK CO2 Emissions: Which One to Choose?

UK road transport is the largest single CO2 emitting sector – a tonne for every UK resident – but has no emission reduction momentum so far – that has to change dramatically. It has the ability to suddenly alter the emissions landscape, as well as transform local jobs, health and global climate progress.

Here is an interesting exam question from the UK 2020 Energy Transition syllabus (1,2), along with a worked answer.

Section 2 – Question 1

Note: links refer to syllabus information and data which have been covered in the standard texts and are expected to be known. 

This is the profile of the UK CO2 emissions from 2000 to 2018 – of a total of 350MT of CO2 emitted, four sectors contributed over 75% of the total as shown in the chart.

The UK government has also set a net Zero 2050 Greenhouse Gas target that aims to reduce CO2 emissions by 15MT pa (ca 3% pa), and wants to be a world leader in green technologies where it has an advantage through renewable investments.

The government also highlights its major progress in removing coal from the power sector to be replaced by renewables – mainly wind and solar – as a great achievement in this long-term vision.

Brexit means that it will also look for technology leading opportunities to attract trade inflow and talent, and create sustainable jobs.

The Covid-19 issue has now highlighted the links between urban air quality and local emissions and their impact on health.

Therefore: which ONE of the following options should the UK government focus on over this current parliament (2020-24) to reduce emissions rapidly, and maintain progress on the wider 2050 aims?

A. Focus strongly on the power sector, maintain declining momentum of its emissions
B. Invest heavily in new technology options such as green hydrogen to reduce residential and industrial emissions
C. Concentrate on reducing road passenger car / light commercial (LCV) emissions
D. All of the above

Estimated time 15 minutes. 20 marks.

NOTE: All governments have options and choices to make – but they have to focus if they are to make significant progress in short periods of time – thus although all answers may have merit, only ONE answer is acceptable, and accounts for 40% of marks (8 marks)

Additional marks will be given for showing working, irrespective of the choice made (12 marks).

Worked answer and exam marking notes

Choice (8 marks)

The accepted answer is C.  Concentrate on reducing passenger car emissions

See options section.

Any student choosing this answer alone without working notes should be awarded 8 marks.

Any other choice without working notes will score 0 marks.

Working Notes (12 Marks)

Chart / Context

Visual inspection of the analysis shows that of the four key sectors, power generation has disproportionately contributed to the emissions reductions.

The data shows that over 75% of the emissions reductions are due to progress in electricity generation – this is largely due to the noted phase out of coal in the UK from 2010 – 2018. Over the period, emissions dropped by almost 60%, or 11MT pa.

The other three sectors have shown more limited progress: residential and industrial power and heat sectors reduced by only about 20% per year or about 2MT pa each.

The car / van transport sector – now the largest emitter as of 2016 – showed flat progress over the period, in fact increasing slightly by 0.2MT pa on average.

Taken together these four sectors combine to create the 15MT pa reduction over the period that the government needs to sustain to meet the 2050 GHG goals.

However it should be clear that the power sector has dominated emissions decline, whilst the next three largest sectors have reduced emissions slowly or not at all.

This context should inform the selection of the answer provided.

The Options (Approved Answer C)

A. Focus strongly on the power sector, maintain declining momentum of its emissions 

The power sector is a conundrum: it is historically the driver of emissions reductions: but its success means it will be unable to shoulder the majority of future improvements.

Much of the progress has been on the back of an almost complete exit from coal – an event that can’t be reproduced.

Even with accelerated progress in the penetration of more solar / wind and hydro / nuclear a singular focus on this sector will lead to declining progress overall.

For example, even if reductions could deepen a further 50% by 2030 – well ahead of the average 30% decline 2010-18 – that would only contribute -4MT pa CO2 emissions – or a quarter of the reduction required.

Support for the sector’s progress is of course required: but a singular focus will likely result in the wider target missed and run into target gaps very quickly.

B. Invest heavily in new technology options such as green hydrogen to reduce residential and industrial emissions

The data shows that these two sectors of residential and industrial emissions have contributed steady but limited emissions progress – about 3-4MT pa reductions combined.

Introduction of new technologies such as green hydrogen will have a potentially major impact on CO2 emissions, but in the short term (2020-2024 as requested), the impact will be limited.

This is due to two factors: new technologies at commercial scale take time to become viable, and green hydrogen is still emergent.

Added to this is the “dependency problem” (which students are familiar with from the syllabus section Dependency vs Growth: The Strange Long-Term View of Fossil Fuel Dominance given its Short-Term Emergence) – the widespread UK fossil gas grid retrofit may take several more years than the current parliament.

In the near-term energy efficiency via smart-metering and other efficiency improvements should all be reinforced – but at best this is likely to result in a continued decade-long moderate decline in emissions, and not a step change.

C. Concentrate on reducing road passenger car / LCV emissions 

Light transport (passenger cars and light commercial vehicles) now contribute the largest amount of emissions of all UK sectors: 69 MT pa or 1 MT pa for every UK resident (covered in syllabus Demography and UK in the World sections)

Over the period, despite vehicle efficiency improvements and other initiatives, transport emissions have remained high and contributed negligible amounts to emissions reduction.

In addition, of all emissions sources, transport emissions are the most invasive in the UK and elsewhere – along with other pollutants such as fine particulates and nitrogen dioxide, car / van emissions permeate every aspect of UK life (see syllabus section Urban Pollution via the Mobile Power Plant Fleet (aka Cars))

Even with the growth of EVs in recent years to 5% market share of new cars, almost every mile driven in the UK in 2020 is still fossil-fueled (> 99%).

However, if by 2030 50% of all vehicle miles driven (ie the fleet) were emission-free electric miles, emissions from the passenger car / LCV sector would fall to 35MT pa, or almost 4MT pa.

It may also facilitate the UK’s wider aims of leadership in global technologies and job creation such as EV charging and associated services. (See syllabus Section: Vehicles as Devices not Machines, employment growth ecosystem versus factory-led job decline).

Finally, of all emissions sources fossil-fuel cars and vans are the largest contributor to urban air quality issues – each vehicle a constantly-emitting power plant that snakes along each urban road and street.

D. All of the above

It is difficult to avoid this answer – but it is wrong.

Indeed – added together the four key sectors above can get to 15MT pa reduction

This table summarises the analysis above

Whilst all sectors contribute to the emissions reduction, transport clearly has to shoulder the emissions reduction effort over the next decade.

The other sectors at best will offer 60% of the requirement: power is on a declining impact path, and residential and industrial have limited room to improve rapidly.

Transport is the clear outlier and has the greatest opportunity to improve – and hence needs to be targeted.

It is feasible that 50% of the passenger fleet in 2030 can be electric – feasible, but very difficult. It therefore needs single-minded attention.

Hence “all of the above” will not get the emissions target achieved. It will divert effort and funding into too many incremental areas that are already well supported.


Only Option C will make a quantum shift in emissions reduction, and needs a primary focus.

All other options can be supported and encouraged – they are in motion and have strong momentum. But their ability to shift emissions outcomes are heavily constrained.

UK road transport is the largest single emitting CO2 sector  – a tonne for every UK resident – but has no emission reduction momentum so far – that has to change dramatically. It has the ability to suddenly alter the emissions landscape, as well as transform local jobs, health and global climate progress.

Hence that is the focus.

12 Marks. 

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(1) – This is a fictional post structure, but the data as far as is known correct

(2) – Is there such a thing ? There ought to be.