Key facts about Heathrow 3rd runway: total EXTRA CO2 emissions would be about 183 MtCO2 between 2022 – 2050 (above staying with 2 runways)

Heathrow is attempting to make out that the carbon emissions to be caused by its 3rd runway would be insignificant. They would either not be counted in UK totals; or they would all be offset by airlines and so “vanish”. They also ignore all non-CO2 impacts. Or they would in some other miraculous ways be offset by various untested, unproven technologies.  These are the key facts people need to realise:  Heathrow’s own figures show a total of 173 MtCO2 MORE carbon emitted, over 2022-2050, with the 3rd runway than without building it. The emissions could reach 25MtCO2 per year from flights alone. The increased CO2 would be as much as 9MtCO2 per year more, in the peak year (2035) than with 2 runways. The total extra CO2 from more surface access transport would be 7MtCO2 over that time period. The extra CO2 from all the construction work would be 3.7MtCO2, to build it all. The total of all that would be 183MtCO2 MORE carbon produced in total (flights, surface access + construction) than if the runway was not built. The estimates may be on the low side, as Heathrow has factored in future carbon efficiencies. Heathrow has taken no account of the fact that we now have a net zero target for 2050. The CCC has now said the total cap for UK aviation CO2 should be no more than 31MtCO2. Not the earlier 37.5MtCO2 it had recommended earlier.




There are 2 documents in which you will find the information:

1. Chapter 9 itself at

2. The Appendices for Chapter 9 at

Then there is the main consultation summary document at
which gives no numbers at all.


Below are the key facts about the carbon figures for the Heathrow 3rd runway proposal:

Flights themselves:

Basic problem is that the carbon emissions with the new runway will be about 8 – 9 million tonnes of CO2 more, with the 3rd runway, than without it.

The main facts are in the The Appendices for Chapter 9 at   


This shows how they expect carbon emissions from flights to reduce slightly over time, with just two runways. And how they would increase – theoretically to a peak in 2035. That would be about 25 Million tonnes of CO2 per year.

Compared to about 19 million tonnes now.

And about 16 million tonnes by 2035, with just two runways, if their expected carbon efficiencies are working then.  ie. there is 25 cf. 16. (their numbers – see in the attached document – are 16.17 and 25.09 MtCO2). Which is almost 9 million tonnes CO2 (8.92 is their number) more with a 3rd runway, than sticking with two, in 2035.

Their figures suggest the difference, by 2050, between having the 3rd runway and not having it, would be 7.53 MtCO2 per year.   (ie. 19.9 MtCO2 with the 3rd runway, compared to 12.37 Mt CO2 by 2050 if they stuck with two runways.)

The key graphic to use is this.   Graphic 9.3.2  in the Appendix 3.   Document does not have page numbers ….

Heathrow admits the cumulative emissions of Heathrow flights would be, over the period 2022 to 2050,  456 MtCO2 (Table 9.3.9)  if they stuck with two runways – and 629 MtCO2 (see Table 9.3.11 of this )  with the 3rd runway.

That would mean a difference of  173 MtCO2 over the 29 years – so a total of 173 MtCO2  MORE with the 3rd runway.

That spread over the 29 years (2022 to 2050) is on average 6.18 MtCO2 more CO2 per year.  More in peak years, less in others.  (They give some rather unconvincing explanations are given for the assumed carbon reductions.)

While we need serious carbon cuts starting now. Heathrow plans to be increasing its carbon emissions – rather than lowering them – from about 2025 to 2035.


Surface access

The carbon emissions from surface transport would be about 0.95 MtCO2 in 2022 to 0.9 MrCO2 by 2050 with 2 runways.

Up to about ? 1.24 MtCO2 by 2050 with a 3rd runway.  (There is just a chart, not actual numbers given).

  1. a difference of something of the order of 0.25MtCO2 per year.

Heathrow says ( Graphic 9.4.2.) the cumulative carbon emissions from surface access would be, by 2050, about 27 MtCO2, and it would be about 34 MtCO2 with the 3rd runway  (and even with their “mitigation” it would be 30MtCO2).

ie. about 7 Mt CO2 more over the 29 years, with a 3rd runway.

An insignificant amount compared to the planes (which would add, on Heathrow’s calculation, 173 Mt CO2 more).

Though they are assuming (Webtag apparently) 25% use of electric vehicles by 2050, their graph of carbon emissions (the “unmitigated”scenario) shows a rise in carbon emissions from transport.  While they say there will be no more vehicles on the roads. The carbon does include carbon from trips made by bus and rail.



The construction cumulative GHG emissions for the modelled scenario from 2022 to 2050 result in 3.70 MtCO2e over the 29 years.   (See Table 9.2.4).

ie. 3.7 Mt CO2 more with a 3rd runway.


Total carbon

So adding – for the 29 years, 2022 to 2050 – the extra 173 Mt CO2 from flights, the 3.7 MtCO2 from construction, and the 7Mt CO2 from surface access, that comes to about 183 MtCO2 more if the 3rd runway is built.   That is using Heathrow’s own figures, which make various assumptions about aircraft and vehicle fuel efficiency.


General stuff

When Heathrow claims its carbon will not be a problem, they say themselves . “The carbon emissions from an expanded Heathrow are calculated to be equivalent to 1.2% of the UK 2050 carbon target set by the Climate Change Act 2008. This comparison excludes Greenhouse Gas emissions from international aviation”

Heathrow would like to pretend all the carbon will be offset by the airlines, and so it is not of concern to the airport.

Heathrow uses 3 scenarios.    No 3rd runway.  Runway with mitigation.  Runway without mitigation.

A key problem is that  though “The CCC has also recommended that UK aviation CO2 emissions, from both international and domestic flights, should total no more than 37.5MtCO2 in 2050.” this is from the time when the UK carbon target  was an 80% cut on 1990; not the net-zero -ie. 100% cut – there is now as the policy.

A crucial lie in the Heathrow documents is : “Any increase in carbon emissions alone is not a reason to refuse development consent, unless the increase in carbon emissions resulting from the project is so significant that it would have a material impact on the ability of Government to meet its carbon reduction targets, including carbon budgets.”  And they then try to claim there is hardly any impact.

The key point Heathrow tries to get away with is that “The CCC Net Zero report provides recommendations to the Government and is therefore not adopted UK policy.”

Heathrow is hoping that the UK government is going to allow international offsets:  The report advises that the aim should be to meet the target through UK domestic effort, without relying on international carbon units, though the CCC do not completely rule out international carbon units as a useful contingency. ”

Heathrow hopes it can kick the can down the road, in putting key issues off until the Environment Statement.  “The assumptions and uncertainties regarding future improvements scenarios should be clearly set out in the ES [Environmental Statement]”.

Heathrow is NOT taking into account any non-CO2 impacts.

Heathrow hopes to con the gullible into believing their CO2 is not a problem:  “Heathrow’s carbon neutral growth aspiration means that growth in CO2 emissions from additional flights after expansion would be offset through carbon credits, resulting in no net growth in emissions.”


See also the post from Teddington Action Group (TAG) with a lot more information at 

TAG says: 

The target of CO2 limitation has been for only an 80% reduction of 1990 levels and not 100%. The Committee on Climate Change agreed that the target 80% reduction overall requires aviation CO2 emissions to be 37.5 MtCO2 by 2050 (which is 100% of the 2005 total).

We do know from the report of the Department for Transport entitled “Beyond the Horizon” of June 2018 that predicted CO2 is likely to be 40.8 MtCO2 in 2050 having peaked at 43.4 MtCO2 in 2030. Thus, aviation, with Heathrow expansion, will fail even on an 80% reduction over 1990 values – never mind a 100% reduction. Any reduction from 40.8 MtCO2 in 2050 is highly speculative and the Government should not be gambling with climate change in this way. 

The likely required reduction of aviation emissions as a result of net zero is considered by the CCC to be down to no more than 31MtCO2 by 2050 (CCC Net Zero report May 2019 at page 148).