Could Rishi Sunak's green review threaten UK net zero?

The prime minister has said he wants to be honest about the "costs and trade-offs" of tackling climate change.

In a statement on Tuesday, Rishi Sunak said he was proud that "Britain is leading the world on climate change", and will stick by the agreements the UK has made internationally.

But he then overhauled measures designed to meet these targets.

So, is the UK really a world leader on emissions cuts, and how will the changes the PM announced affect its efforts?

Mr Sunak said the government was still "completely committed" to the 2050 net zero target which his predecessor, Theresa May, made law back in 2019.

Net zero means a country does not add any additional greenhouse gases like carbon dioxide to the atmosphere.

"This country is proud to be a world leader in reaching net zero by 2050. But we simply won't achieve it unless we change. We'll now have a more pragmatic, proportionate, and realistic approach that eases the burdens on families," he said.

It is true the UK has been successful in cutting emissions compared to other countries.

Since 1990, emissions within the UK have fallen by 48.7% up to the end of 2022 - excluding international aviation and shipping - according to government data.

These cuts are greater than other countries in the G7 (Group of Seven), an organisation of the world's seven largest so-called "advanced" economies - although Germany has reduced its emissions at a faster rate compared with the UK since 2016.

But the cuts the UK has made so far are - arguably - the easiest ones.

One of the main ways they have been achieved is by switching away from fossil fuels - coal, oil and gas - to generate electricity.

Emissions from electricity generation have fallen by around three-quarters since 1990, while the proportion of electricity generated by renewables - like wind and solar - has soared.

The government has bold plans to continue this "decarbonisation" process.

But achieving net zero means cutting emissions across all sectors of the economy.

That is why there are targets for phasing out petrol and diesel vehicles and switching from gas boilers to heat pumps or other low-carbon alternatives to heat our homes.

And, despite the UK's achievements on climate so far, there have been a number of warnings that progress is beginning to falter. These came even before today's announcement.

Earlier this year, the Climate Change Committee (CCC) - the government's independent advisers on cutting carbon emissions - warned that the UK's efforts to meet its net zero commitments were already "worryingly slow".

It also said it was "markedly less confident" than a year earlier that it would meet its 2030 and 2035 emissions reduction targets.

Similar warnings on electricity have come from the National Audit Office and a cross-party group of MPs.

But contrary to these findings, Mr Sunak claimed in his announcement that the UK was "on track" to meet its commitments.

He also announced a substantial increase in the subsidies available to people who want to install heat pumps to heat their home, with the grant increased by 50% to £7,500.

The CCC says it was not consulted ahead of the announcement, and needed to do the full calculations before determining the carbon cost.

But the changes certainly seem to make the current targets much harder to achieve - as any extra carbon costs would have to be balanced by extra savings in other areas. And how much carbon the UK can use in coming years has already been set down in carbon budgets.

"Today's announcement is likely to take the UK further away from being able to meet its legal commitments," said Piers Forster, the CCC's chair.

"This, coupled with the recent unsuccessful offshore wind auction, gives us concern," and "more action is needed," he added.

"What's depressing about all the changes [the PM] has told us about is they all go in the same direction," Prof Miles Allen of the University of Oxford told the BBC.

"If we do everything slower, we're just going to make it more difficult to reach that target," he said.

One of the most eye-catching changes is delaying the 2030 ban on sales of new, fully petrol and diesel cars, announced by Mr Sunak's predecessor Boris Johnson.

Despite what's often assumed, electric car sales are actually surging. In 2022, nearly 17% of new car sales were battery electric - ahead of the CCC's schedule and up from less than 2% in 2019.

Some in the car industry have warned that delaying the ban on new petrol and diesel cars could hit investment and therefore electric vehicle sales.

Achieving the 2030 phase-out of new fully petrol and diesel car and van sales is "vital to meeting the UK's decarbonisation pathway", the CCC warned in June.

But Mr Sunak says it should be the consumer who decides whether or not to buy an electric car and not "government forcing you to do it". He also says the new plan is in line with countries including Germany, France, Spain and Canada.

Mr Sunak says his review of the government's green pledges is all about putting the "long-term interests of our country before the short-term political needs of the moment."

He said "some of the things that were being proposed would have cost typical families upwards of five, ten, fifteen thousand pounds".

But the Energy and Climate Intelligence Unit (ECIU) - an independent climate change think tank - points out that nobody is being forced to take up these measures right now.

For example, the planned ban on the sale of new gas boilers was due to start in 2035 for all households. It is only relevant when your boiler breaks or you choose to switch.

It is a similar story with cars. Four out of five of us buy second-hand cars - for which there is no phase-out date - and older cars can continue to be driven after 2030.

The 20% of people who can afford to buy a new car already had six years until they would have had to choose between fully electric vehicles and hybrids - which can be filled up with petrol. Now they have 11 years.

The changes to net zero policy "will add to the cost of living for those struggling, not make things easier", argues Peter Chalkley, a director of the ECIU.

And an analysis by the ECIU suggests the PM's announcements could cost British households almost £8bn in higher bills over the next decade - and more if gas prices spike again - due to cancelling new energy efficiency regulations for the private rental sector.

The CCC has estimated that meeting the legally binding 2050 goal will require an extra £50bn of investment every year by 2030.

It said that once the savings from reduced use of fossil fuels are factored in, the overall resource cost of the transition to net zero is less than 1% of GDP over the next 30 years. By 2044 it should become cost-saving, the CCC said, as newer cleaner technologies are more efficient than those they are replacing.

Many scientists have pointed out to the BBC that delaying investment simply increases the ultimate cost.

And of course, the global costs of climate inaction would be much higher, as the world would be hit by increasingly damaging climate impacts.