Against these targets, our policy can look rather cautious. 2045 seems like a long way away; doesn’t that mean that government will do nothing until a few years beforehand and then rush to hit it? I’m sure Lib Dem Voice readers know what’s wrong with that argument – although this was the approach that a Conservative minister genuinely suggested to Ed Davey when we were in government.

Arguing over the net zero target date in isolation is simplistic and misleading. In reality, reaching net zero will require enormous effort, stretching over decades and affecting all sectors of the economy; it’s not something you can leave to the last moment. The real debate we need to have is over how we plan to meet the target; what’s the policy programme that cuts emissions fast where we know how to, and lays the foundations for progress where we don’t yet know the right solutions? And when you start to think about what’s needed for electricity, heating, transport, aviation, industry, farming and land use – and how you persuade people to change the way they live their lives, because it isn’t only about government action – you start to understand why near-term targets like 2025 or 2030 are an unrealisable fantasy.

Liberal Democrats set out, in our policy paper and in the manifesto, how we can make rapid progress in cutting emissions from power generation, through accelerating the uptake of renewables, and in heat in buildings, through a massive energy efficiency programme. Between them we think we can cut UK emissions by more than half over ten years.

When you look at other sources of emissions it gets more difficult. We will have to replace gas in space heating, but we don’t yet know the most cost-effective alternative. If it’s electric it will require roughly a six-fold increase in total electricity generation capacity, and every household will have to rip out its boiler and radiators. If it’s hydrogen (the other main option) we will have to develop an entirely new country-wide industry for manufacturing hydrogen that does not now exist.

To get to zero emissions from transport, we have to replace 36 million petrol and diesel cars and light vans with electric vehicles; while demand for EVs is growing fast, in 2018 just 60,000 were sold, compared to over 2 million fossil fuel vehicles. We can try to persuade a significant number of drivers to give up their cars and switch to public transport – but building new electric buses and coaches, and electrifying the whole of the rail network, can’t be done overnight. And when we come to aviation – the fastest growing source of emissions in the UK – there is currently no cost-effective means of reducing emissions other than by flying less.

Not all greenhouse gas emissions stem from energy use: waste disposal, industrial processes like iron, steel and cement production, and almost every type of farming – especially, but not only, meat and dairy – are all sources. 

To cut emissions to zero from all of these different sectors will be a titanic effort, mobilising industry, retooling factories, inventing entirely new processes, training and retraining hundreds of thousands of workers, and persuading millions of individuals to do things differently. However much money you can throw at it – and under our plans we’re throwing a lot – this all takes time. 

And since we can never eliminate emissions completely, we also need to develop means of removing carbon dioxide from the atmosphere and storing it safely. The best and cheapest means is growing trees, which is why we’re proposing planting at least an additional 40,000 hectares (or 60 million trees) a year, adding extra woodland of about two-thirds the size of the New Forest every year. But young trees, although they grow fast, don’t absorb much carbon because they’re small, so the amount they remove from the atmosphere in the first ten or even twenty years is important, but not enough. And forests are vulnerable to disease and wildfires, which are themselves getting worse because of climate change. In the long run we will have to rely on new technological solutions to remove carbon dioxide from the atmosphere – and while there are several ideas being discussed, most of them aren’t even at pilot stage. 

Underpinning all this we will have to reform the country’s regulation and frameworks for finance and investment, skills, innovation and industrial support, and reshape the institutions of British government, central and local. I hope you can begin to see why this will take time. There is no possible way to do all this in five or ten or probably even twenty years. This is what underpins our target of net zero by 2045 – but why there is so much more to our proposals than just the date by which the last few megatonnes are phased out. 

Labour doesn’t have a comprehensive net zero emissions target at all. Their manifesto aims to ‘put the UK on track for a net-zero-carbon energy system within the 2030s’ – but by ‘energy’ they only mean power and heat in buildings (including industrial use but not industrial processes). They therefore ignore about half UK emissions. They have no targets for any other sector, including transport, industry, and agriculture and land use. And on top of that their obsession with nationalisation and centralised control would waste billions and use up valuable time.

There is much to admire in the Green Party’s proposals, but they don’t match their 2030 net zero target. We argue for an end to sales of new fossil fuel vehicles by 2030 (and then for them to be taken off the road by 2045 – 15 years is a typical lifespan for a car). The Green manifesto has exactly the same 2030 target, which means there will be still be millions of petrol and diesel cars on the road in ten years’ time. Their policies for aviation are almost exactly the same as ours – which should curb demand, but won’t eliminate emissions by 2030. And there are gaps in their policies on heating and agriculture. They propose a slightly faster rate of tree planting than we do, but for the reasons I explain above, that won’t be enough to offset remaining emissions in ten years’ time. 

Of course we haven’t got it perfect. There are some good ideas in the Green and even in the Labour manifestos that we should consider. But neither of them are being honest with the country about the huge challenges that reaching net zero will bring and about the measures we need to take now to start on that path. That’s the debate that we should all be having. 

I and other members of the group that drafted Tackling the Climate Emergency have produced an analysis of Labour and Green Party climate policies compared to Liberal Democrat proposals, available here. 

* Duncan Brack is the Editor of the Journal of Liberal History and Vice Chair of the Federal Policy Committee.