The PM is not a magician - how can he weaken net zero policies but still hit his targets?

At the Conservative Party Conference last week, the one thing that seemed to cheer the party's MPs up was Rishi Sunak's net zero policy. There was a feeling that the watering down of targets had landed well with voters. And if it did, that would make sense. After all, polls suggest people do tend to support the ambition to reach net zero by 2050, but are also apprehensive of measures that will inflict direct costs upon them along the way. So who could disagree with Mr Sunak's headline claim that it is possible to soften the policies designed to get us to net zero - but still arrive there, unimpeded, on time?

The problem is that Mr Sunak is not a magician. So how on earth is he going to achieve the seemingly impossible feat that he is promising? After all, the whole point of policies like banning new sales of petrol and diesel cars by 2030 and getting people to switch from gas boilers to heat pumps is to reduce enough carbon from the atmosphere and bring us closer to our net zero goal. That goal is not just what happens in 2050 but in five-year blocks along the way. The Climate Change Committee has developed so-called carbon budgets that set limits, which are themselves legally binding.

The sixth carbon budget covers 2033-2037 and Mr Sunak insists it will be met. But how?

In analysis carried out by Simon Evans for Carbon Brief - which we used on ITV1's Peston - the evidence is not optimistic. It shows clearly that the policies will shift the trajectory of our carbon reduction, lifting us clearly above the levels legally required in the 2030s. The CCC is not convinced, saying: "We need to go away and do the calculations but [the net zero] announcement is likely to take the UK further away from being able to meet it's legal commitments." Even the Conservative chair of Parliament's Environmental Audit Committee is sceptical. Philip Dunne has written to the PM to point out there is no public explanation as to how the targets can remain. He points to specific problems with the policy, like offering more financial support to swap out each person's boiler (the subsidy has risen from £5,000 to £7,500) without increasing the overall budget for the scheme. "Without a corresponding increase in scheme funding, the scheme will in fact deliver fewer upgrades to properties," writes Mr Dunne. He calls on the PM to bring forward an amended Carbon Budget Delivery Plan to explain how this works.

The deadline for a response has been extended from the 12th October (Friday) to the 25th, but sources in government tell me it's more imminent than that.

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So what might they say? Sources I speak to have suggested how Mr Sunak's logic might be made to add up. They say the PM is "very confident" the targets will be met. "CCC and others have consistently said we wouldn't hit previous carbon budgets, yet we overexceeded massively," they said - pointing to 14% over-delivery for the second carbon budget (2013 to 2017) and 15% for the third (2018-2022). They say that was in part because technology expands "beyond expectations" and because people's behaviour changes in "unpredictable ways". One example, they say, was that offshore wind was 70% cheaper than had been predicted. They also say the law only requires "loose confidence" they will hit the targets - allowing wriggle room - and they suggest they could allow emissions to be rolled over from one carbon budget to the next. But is any of that feasible? I suspect a lot of it will be met with pretty stark scepticism.

On overachieving past targets, senior folk in the climate sector point out to me that the reasons for that are usually linked to unexpected shocks - like the financial crisis, or for the third budget, the pandemic. Is it reasonable for the government to claim that reduced emissions during lockdowns mean we can loosen future ambitions? And if we do make the next step slightly easier, that arguably just makes the ones after that steeper and less achievable, given the final aim of zero is not going to be shifted. Moreover, alongside the carbon budgets is our NDC (national determined contribution) plan submitted at Cop26, which pledges to cut emissions by 68% between 1990 and 2030. That is an absolute target that doesn't allow for similar flexibility. One source claimed to me the argument was "ridiculous". As for the outperformance of technology, it is true that some things have been different to expectations, including the pricing of offshore wind. But predictive models do tend to include assumptions of technological advances, and can sometimes work in the opposite direction when inventions are not as transformative as was hoped. So, will the government's official advisors - the Climate Change Committee - accept such arguments if they are the response to Mr Dunne's letter? I suspect not - but we shall soon see. And beyond these arguments are a couple of other things that ministers might lean on. One is Mr Sunak's suggestion that parliament should spend longer debating the carbon budget targets (something that both the CCC and environmental audit committee would encourage). Why does the PM want that? Some believe he thinks the targets are too ambitious and that parliament as a whole should accept that and weaken them. That is a fear in the climate sector, which is already very nervous about what the PM has changed so far.

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