Later this month, the latest advice on how the UK can cut its greenhouse gas emissions will be published by the Climate Change Committee (CCC) – the independent body that advises parliament – with aviation and shipping set to be included for the first time.

The recommendations of the committee to government will shape the UK’s next carbon budget, which sets binding targets for reducing emissions to help the UK move towards net zero.

So what is a carbon budget, and what does it mean for travel?

Under the 2008 Climate Change Act, the UK is legally required to reduce greenhouse gas emissions by at least 100% compared with 1990 levels by 2050.

To keep the UK on course, the government sets legally binding five-year caps on emissions – known as carbon budgets – 12 years in advance.

To date, there have been six carbon budgets, covering the period from 2008 to 2037. The next will cover the period from 2038 to 2042.

The next carbon budget, covering 2038 to 2042, will be set on 26 February. For the first time, emissions from international aviation and shipping will be included in the calculations.

CCC spokesperson Tom Dooks said its lobbying had led to the inclusion, putting their past omission down to “the complexities of decarbonising aviation and shipping”.

How big is the problem?

The UK’s net emissions in 2022, including aviation and shipping, were calculated at 441 million tonnes – a huge amount, but 47% less than in 1990. In this context, aviation is a small percentage, and shipping smaller still.

In 2022, aviation contributed 28.5 million tonnes of emissions, the vast majority of which is CO2, with methane and nitrous oxide a tiny fraction of this figure.

The government calculates emissions from flying and shipping by the amount of fuel used at UK airports and ports, whether by UK or non-UK operators. Shipping accounted for 6.3 million tonnes.

The CCC, made up largely of academics from the energy and sustainability sectors, advises government on what it should demand from industries needing to decarbonise.

For travel, the message is worrying; the CCC said a fall in total emissions in 2022 was “driven by reductions in buildings and industry”.

However, this was “offset by increases in aviation demand and, to a lesser extent, surface transport”, so airlines have some work to do.

Why is flying so maligned?

Pressure group Transport & Environment characterises aviation as the “most climate-intensive form of transport” with the fastest emissions growth – pollution levels having more than doubled since 1990.

It also highlights the warming effects of contrails (formed by condensation of jet engine exhausts into ice in cold, humid air), soot and nitrous oxide, adding: “Accounting for non-CO2 emissions, aviation’s climate footprint is three times bigger.”

What’s the latest picture?

The CCC estimates 2023 emissions, including aviation and shipping, will have fallen by around 4% compared with 2022 to 423.3 million tonnes, which would bring the total below the 2020 pandemic low.

The bad news is aviation emissions increased by 15.5% to 35 million tonnes last year as demand returned, although this figure is only a third of surface transport’s output.

What has previous CCC advice said?

In its last report, the committee recommended halting all airport expansion unless there is “a UK-wide capacity-management framework”.

However, the CCC said it was “too late” to affect the decision on bringing Gatwick’s second runway into permanent use, which is due to be made by the end of this month.

The future may be different. “There are a number of airports looking to expand,” said Dooks. “If they all do, you will exceed emissions levels and you have to make sure there are reductions in other sectors.”

Energy suppliers, he said, had already made strides, adding other sectors – including aviation and shipping – would have to do their bit next.

What does the airline industry say?

Airlines know they have to be seen to be doing something. Rob Griggs, Airlines UK’s policy and public affairs director, described its relationship with the CCC as “constructive”, saying it had spelled out its pathway to net zero “even as we continue to grow to meet demand”.

“We’ll achieve this through scaling up sustainable fuels, modernising our airspace and introducing zero-emission flight technologies,” he said.

What about cruise?

Jon Hood, Transport & Environment UK’s sustainable shipping manager, said UK shipping produced “almost one-fifth” of UK transport greenhouse gases. “We need regulations to limit emissions and drive uptake of renewable, hydrogen-based fuels.

“For shipping, we also need to see large-scale deployment of shore power at UK ports, with a requirement for ships to plug in and shut down their polluting engines. This is particularly important for cruise ships, which spend lots of time in ports.”

He added: “Charging UK shipping fairly for its pollution could generate £1 billion a year, which could be used to support the sector’s decarbonisation. This opportunity must not be wasted.”

Any big ideas?