The true cost of ignoring climate change: a UK perspective for a global climate
Simon Judd has over 35 years’ post-doctorate experience in all aspects of water and wastewater treatment technology, both in academic and industrial R&D. He has (co-)authored six book titles and over 200 peer-reviewed publications in water and wastewater treatment.
1. The Net Zero debate
Depending on your point of view, the UK's commitment to reaching Net Zero greenhouse-gas emissions by 2050 represents either an essential response to climate change or an expensive and unnecessary exercise in environmental policy.
The debate too often focuses on the cost of getting there, rather than on that of doing nothing. Add into the mix the political and emotional dimensions, and the argument reaches boiling point. And all the while, the clock is ticking.
On a purely financial level, the question is not really whether Net Zero will cost £650 billion, as is forecast. It is whether investing heavily now to change the UK's energy, transport, industrial and building infrastructure is a better bet than retaining the existing system and accepting the consequences (with fingers firmly crossed).
The latest assessment from the UK Climate Change Committee (CCC), in its Seventh Carbon Budget, estimates that its Balanced Pathway to Net Zero will require additional capital investment averaging around £26,000 million (£26 billion) per year between 2025 and 2050, equivalent to about 0.9% of GDP. Investment is front-loaded, peaking at around £46,000 million in 2029 before declining as technologies mature and deployment slows [1]. Hence, a back-of-envelope calculation (£26 billion x 25 years) yields the indicative cumulative capital requirement of ~£650 billion for the UK alone.
This £650 billion price tag will not all fall on the heavy shoulders of the UK taxpayer. The CCC expects much of the investment to come from the private sector. In addition, capital expenditure on, for example, electric vehicles, renewable power, heat pumps and other infrastructure replaces expenditure which would otherwise have been required on conventional assets.
More importantly, investment is only half of the balance sheet. The CCC estimates that the additional capital expenditure will be offset by operating-cost savings averaging around £22 billion per year, principally through reduced energy consumption and the greater efficiency of electrification. The actual net economic cost of the transition is consequently estimated at around £4,000 million per year, or approximately 0.2% of GDP. Across 2025–2050, the estimated cumulative net cost is around £110,000 million. By about 2041, the annual balance actually becomes positive, with the CCC projecting a net saving of around £35,000 million in 2050 [1].
So the UK faces the choice of investing for change or taking a chance that it’ll all work out fine. Either way, the numbers are not small. And who trusts scientists anyway?
2. Money saved?
So what happens if we shut tight our wallets and don’t bother with any of this?
The environmental consequences of continued global greenhouse-gas emissions are reasonably well understood, even if their precise magnitude is not. For the UK, we can expect hotter and drier summers with more severe heatwaves and droughts. These themselves come with a financial penalty; the 2026 heatwave alone cost the UK around £4.4b between May and end of July 2026, according to the recently published report from the think tank Verdant [2]. Along with this will be the economic consequences of increased river and surface-water flooding and continuing sea-level rise, as well as warmer and wetter winters [3].
For the UK water industry, some of this has a familiar ring. The CCC's 2026 assessment suggests that – by mid-century – water-supply shortfalls in England could exceed five billion litres per day. Peak river flows could increase by up to 45%, increasing the severity and frequency of flooding [4]. These are not abstract environmental effects. They imply additional storage, treatment and transfer capacity, greater resilience requirements, flood protection and, almost certainly, increased energy and significant infrastructure costs.
There is an important qualification here. The UK accounts for only 0.7–0.8% of global greenhouse-gas emissions, compared with the big polluters like the USA (12%) and China (33%) [5]. The UK achieving Net Zero cannot, by itself, prevent these impacts. Climate outcomes in the UK – as well as in every country on Earth – will depend on what happens to global
emissions, demanding a global response.
In view of this, it’s perhaps more meaningful to compare the costs for the UK of tackling climate change against the costs for the UK where the world fails to take sufficient global mitigation measures.
3. The UK’s bill for a world that fails to act
Putting a monetary value on future climate damage is considerably more difficult than costing up a wind turbine or heat pump, but the UK’s Office for Budget Responsibility (OBR) has at least attempted to quantify the financial implications for the UK in a world where climate change is not effectively remediated.
Its 2025 Fiscal Risks and Sustainability analysis considered a world approaching 3°C of warming. In this scenario, climate-related damage is estimated to reduce the level of UK GDP by around 8% by the early 2070s. The associated deterioration in the public finances could add around 56% of GDP to government debt, principally because a smaller economy generates lower tax receipts while climate-related expenditure increases [6].
The OBR stresses that such estimates are highly uncertain – making it easier for the headbangers to pooh-pooh these figures. The figures include the consequences of flooding, coastal damage and heatwaves, together with the considerably larger indirect effect of reduced economic productivity. Previous OBR analyses estimated direct annual fiscal costs from river and surface flooding alone at £260–370 million, coastal flooding at £170–260 million, and heatwaves at £420–560 million under its modelled climate scenarios [7] – all excluding much of the wider economic loss.
The CCC has subsequently approached the comparison from the other direction. Its 2026 cost–benefit analysis estimates that the climate damage avoided by pursuing its Net-Zero pathway could be worth £40,000–130,000 million in 2050 alone. Overall, it calculates that every £1 of cost associated with its Balanced Pathway produces benefits worth approximately £2.20–£4.10 [8] – a reasonably healthy return for attempting to save the planet.
4. Cost or investment?
None of this means that every measure proposed under the banner of Net Zero is economically sensible. Technologies still have to work, infrastructure has to be appropriately designed, and expenditure needs to produce a demonstrable benefit. Engineers would hardly argue otherwise.
But comparing the cost of Net Zero with a zero-cost alternative is misleading, because there is no zero-cost alternative.
On the CCC's current numbers – as discussed earlier – reaching Net Zero in the UK requires something approaching £650 billion of additional capital investment over 25 years. But much of that investment generates subsequent operating savings and leaves an estimated net transition cost of only around £110 billion. Against this must be set climate damages potentially running into tens of billions of pounds annually, together with effects that become increasingly difficult and expensive to mitigate as temperatures rise.
As is so often the case with environmental engineering, the real question is not whether we can afford to intervene.
It is what we are prepared to pay if we don't.
