The Committee on Climate Change (CCC) said it had concerns over how the Department for Transport (DfT) had presented its case. It warned the business plan for Heathrow projects a 15 per cent increase in aviation emissions by 2050.
The committee members added that if the increase is allowed, ministers will have be prepared to cut emissions from other sectors of Britain’s economy.
Heathrow expansion, which led to the resignation of Zac Goldsmith as a Conservative MP and an on-going by-election, was announced by Theresa May’s administration last month following a review by the Airports Commission.
In a letter to Business Secretary Greg Clark, the chairman of the CCC, Lord Debden, said: "The Committee has concerns about how it (DfT) presented the implications for greenhouse gas emissions from aviation in that business case."
He added: "The committee is now concerned that there is scope for misunderstanding of the DfT's position based on the business case for a third runway at Heathrow," Lord Debden wrote.
"Using the Government's publications, it is not possible to assess whether the investment makes sense when emissions conform to the planning assumption."
Lord Debden warned that plans to expand Heathrow while keeping current targets meant "all sectors would have to prepare for correspondingly higher emission reductions by 2050". "My committee has limited confidence about the options for other sectors to go beyond these levels by 2050," he added.
But the Department for Business, Energy and Industrial Strategy told said the Government agreed with the Airports Commission's assessment that a new runway at Heathrow will not breach emissions targets.
In pictures: 70 years of Heathrow
In pictures: 70 years of Heathrow
1/22 Inside one of the terminal tents in 1946
The year the airport opened. Comfortable armchairs and flowers try to distract from the conditions
Graham Bridges collection
2/22 An aerial view of the airport in 1949
Construction of the runway layout and Central Area are under way
3/22 A Pan Am crew checks out the Boeing Stratocruiser N1029V Clipper Golden Eagle in 1954
During the early 1950s, Pan Am and American Overseas Airlines operated Statocruisers into London Airport in direct competition on the North Atlantic route operated by BOAC
4/22 One of the first official London Airport guidebooks
C.1953, priced 1s
5/22 In 1950 a permanent concrete terminal building was built
This replaced the tents previously used at London Airport North and is seen still in use for charter and cargo flights in this 1959 view
via Graham Bridges
6/22 BOAC check-in desk in 1954
Inside the new London Airport North terminal building, just before the move to the Central Area
Graham Bridges collection
7/22 Air traffic control tower in the 1960s
Inside the visual control room
CAA Archives via Pete Bish
8/22 Rear cover of the 1956 guidebook
Showing a plan of the airport at the time, with entrance prices to the spectators’ viewing terraces and for airport coach tours
9/22 Spectators in 1958
How close can you get? As soon as the Central Area was open, spectators were afforded unprecedented views of the airliners
10/22 Terminal 3 was opened as the Oceanic Terminal on 13 November 1961
It was built to handle flight departures for long-haul routes. Renamed Terminal 3 in 1968, it was expanded in 1970 with the addition of an arrivals building
11/22 Inside Terminal 3 in 1969
Check-in desks for BOAC and QANTAS airlines
12/22 Plane spotting on Heathrow’s viewing terraces in the 1960s
Wrap up warm, take your spotting logbooks, pen and binoculars and get your mum to pack your sandwiches
13/22 No 1 Passenger Building
Also called the Europa Building. In this photo, taken on 22 June 1963, flags of the many airlines it serves are flown
14/22 Luggage-trailer-towing Routemaster buses
When BEA and BOAC merged to form BA on 1 April 1974, both fleets had to be repainted in the new livery, but so did all the ground support equipment
15/22 The entrance to the traffic tunnel in 1974
A Lufthansa Boeing 737 is seen on the runway
16/22 A 40 per cent scale model of Concorde
In September 1990 it was erected on the roundabout at the entrance to the tunnel that passes under the northern runway at Heathrow Airport. It was built in four main parts, with an 80ft-long central fuselage section, to which the wings and tail fin were attached. The completed model was placed on the roundabout in September 1990 and was monitored by CCTV and surrounded by an infrared perimeter alarm that was connected to the local Heathrow police station to ensure it was not vandalised
17/22 Heathrow Airport's 50th anniversary
On 2 June 1996, Heathrow marked its anniversary with a flypast of representative airliner types that have served the airport over the years. This culminated in a formation flypast by Concorde with Hawks of the RAF Red Arrows aerobatic team
18/22 The roof of Terminal 3’s car park
One of the last bastions for plane spotters and spectators was here. This is the unfriendly notice that greets anyone who attempts this today
19/22 On 24 October 2003 BA withdrew its Concordes from service
The final scheduled commercial flight was BA002 from JFK operated by G-BOAG. Here we see three of the Concordes parked together outside the BA hangar on 8 November 2003 following withdrawal
20/22 The new control tower
Costing £50 million to construct, it gives controllers an excellent 360-degree panoramic view
21/22 The new Terminal 2
The Queen’s Terminal
Looking due west down Runway 27L
A spokesman said: "We are considering how we will continue to reduce our emissions across the economy through the 2020s and will set this out in our emissions reduction plan, which will send an important signal to the markets, businesses and investors.
"Our commitment to meeting our Climate Change Act target of an at least 80 per cent emissions reduction below 1990 levels by 2050 is as strong as ever."
Responding to the warning, the Green party co-leader Jonathan Bartley said: “The Committee on Climate Change has confirmed what we already knew – expanding Heathrow will put a wrecking ball through any hope of meeting climate change targets.
“The Government must stop giving air travel special treatment. The reality is that endless growth in our aviation capacity is incompatible with the UK's climate change commitments. The Government must open its eyes to the only sensible option: no new runways.
“The Government must urgently look into the proposed frequent flier levy as a fair way of reducing the demand for flights from those who fly the most, whilst benefiting the majority of people and protecting us all from the threat of climate change.”Reuse content