As the budget approaches, and a potential restructuring of government departments, the question arises: what to do about climate change – or, more specifically, the Department of Climate Change that was absorbed by the Department for Business, Energy and Industrial Strategy, along with the ‘Energy’ half of the Department for Energy and Climate Change (Decc) in the previous restructuring.

I detect a bit of nostalgia for Decc around; sometimes even a wish to have things back as they were. That’s missing an opportunity.

The battle to slow and stop climate change in energy has not been won, but the argument is over. Low carbon is the othodoxy and, crucially, low carbon is where the investment is going.

Moving climate to BEIS was seen as a downgrade by some and maybe that was true. But I think it helped concentrate minds and, if nothing else, it has been ideally placed in the last year as the notion of climate change as business risk has risen up the agenda.

What now?

For the Committee on Climate Change, agriculture and the environment is a major focus this year, and it is a key challenge and opportunity for reform as we leave the EU and the Common Agricultural Policy. That’s a tough nut to crack, so maybe any restructuring should see those two functions brought together in a department for agriculture, climate and environment (climate’s previous stint in Defra notwithstanding).

But not for ever.

Once the framework for our natural environment is fully climate-aware, we should think about transport. Electric vehicles, CNG and hydrogen vehicles, low-carbon trains, flight and shipping emissions and much more will have to be grappled with in this decade. It will be necessary to concentrate that around a low carbon agenda: it might be time for a Department for Transport and Climate Change.

But not for ever.

You might see where I am going with this. Would a Department for Climate, Communities and Local Government help regions and districts as they address their ‘climate emergencies’?  Would it –  at last – be able to improve the energy and carbon perfomance of our homes? That’s a useful home foe the climate department for a while.

But not for ever.

What’s next on the list? Everyone will have their priority, but I would not rule out the Ministry of Defence. It will be time for some innovation, and the MInistry has a particular interest in, for example, off-grid power supplies. It concentrates the mind when all your diesel has to be transported across hostile territory. And if we are truly likely to see conflict over climate-change induced issues like flooding and sea level rise, a Department for Defence and Climate might be a necessity.

But not for ever.

Should our wandering Climate Change Department ever come to rest? Yes of course.

In the end, carbon emissions could be the lens through which all our activities will be viewed, and the ability to emit will be tradeable. The Treasury is the place to consider carbon costs alongside monetary ones. In the long term it should be the natural home for the minstry of climate change.