A scenario that meets the “net-zero by 2050” goal would be the “cheapest” option for the UK, according to modelling by the National Energy System Operator (NESO).
In a new report, the organisation that manages the UK’s energy infrastructure says its “holistic transition” scenario would have the lowest cost over the next 25 years, saving £36bn a year – some 1% of GDP – compared to an alternative scenario that slows climate action.
These savings are from lower fuel costs and reduced climate damages, relative to a scenario where the UK fails to meet its climate goals, known as “falling behind”.
The UK will need to make significant investments to reach net-zero, NESO says, but this would cut fossil-fuel imports, support jobs and boost health, as well as contributing to a safer climate.
Slowing down these efforts would reduce the scale of investments needed, but overall costs would be higher unless the damages from worsening climate change are “ignored”, the report says.
In an illusory world where climate damages do not exist, slowing the UK’s efforts to cut emissions would generate “savings” of £14bn per year on average – some 0.4% of GDP.
NESO says that much of this £14bn could be avoided by reaching net-zero more cheaply and that it includes costs unrelated to climate action, such as a faster rollout of data centres.
Notably, the report appears to include efforts to avoid the widespread misreporting of a previous edition, including in the election manifesto of the hard-right, climate-sceptic Reform UK party.
Overall, NESO warns that, as well as ignoring climate damages, the £14bn figure “does not represent the cost of achieving net-zero” and cannot be compared with comprehensive estimates of this, such as the 0.2% of GDP total from the UK’s Climate Change Committee (CCC).
Net-zero is the ‘cheapest option’
Every year, NESO publishes its “future energy scenarios”, a set of four pathways designed to explore how the nation’s energy system might change over the coming decades.
(Technically the scenarios apply to the island of Great Britain, rather than the whole UK, as Northern Ireland’s electricity system is part of a separate network covering the island of Ireland.)
Published in July, the scenarios test a series of questions, such as what it would mean for the UK to meet its climate goals, whether it is possible to do so while relying heavily on hydrogen and what would happen if the nation was to slow down its efforts to cut emissions.
The scenarios have a broad focus and do not only consider the UK’s climate goals. In addition, they also explore the implications of a rapid growth in electricity demand from data centres, the potential for autonomous driving and many other issues.
With so many questions to explore, the scenarios are not designed to keep costs to a minimum. In fact, NESO does not publish related cost estimates in most years.
This year, however, NESO has published an “economics annex” to the future energy scenarios. It last published a similar exercise in 2020, with the results being widely misreported.
In the new annex, NESO says that the UK currently spends around 10% of GDP on its energy system. This includes investments in new infrastructure and equipment – such as cars, boilers or power plants – as well as fuel, running and maintenance costs.
This figure is expected to decline to around 5% of GDP by 2050 under all four scenarios, NESO says, whether they meet the UK’s net-zero target or not.
For each scenario, the annex adds up the total of all investments and ongoing costs in every year out to 2050. It then adds an estimate of the economic damages from the greenhouse gas emissions that primarily come from burning fossil fuels, using the Treasury’s “green book”.
When all of these costs are taken into account, NESO says that the “cheapest” option is a pathway that meets the UK’s climate goals, including all of the targets on the way to net-zero by 2050.
It says this pathway, known as “holistic transition”, would bring average savings of £36bn per year out to 2050, relative to a pathway where the UK slows its efforts on climate change.
The overall savings, illustrated by the dashed line in the figure below, stem primarily from lower fuel costs (orange bars) and reduced climate damages (white bars).
Note that the carbon pricing that is already applied to power plants and other heavy industry under the UK’s emissions trading system (ETS) is excluded from running costs in the annex, appearing instead within the wider “carbon costs” category.
This makes the running costs of fossil-fuel energy sources seem cheaper than they really are, when including the ETS price.
Net-zero requires significant investment
While NESO says that its net-zero compliant “holistic transition” pathway is the cheapest option for the UK, it does require significant upfront investments.
The scale of the additional investments needed to stay on track for the UK’s climate goals, beyond a pathway where those targets are not met, is illustrated in the figure below.
This shows that the largest extra investments would need to be made in the power sector, such as by building new windfarms (shown by the dark yellow bars). This is followed by investment needs for homes, such as to install electric heat pumps instead of gas boilers (dark red bars).
These additional investments would amount to around £30bn per year out to 2050, but with a peak of as much as £60bn over the next decade.
These investments would be offset by lower fuel bills, including reduced gas use in homes (pale red) and lower oil use in transport (mid green).
Notably, NESO says it expects EVs to be cheaper to buy than petrol cars from 2027, meaning there are also significant savings in transport capital expenditure (“CapEx”, dark green).
Again, the biggest savings in “holistic transition” relative to “falling behind” would come from avoided climate damages – described by NESO as “carbon costs”.
Net-zero cuts fossil-fuel imports
In addition to avoided climate damages, NESO says that reaching the UK’s net-zero target would bring wider benefits to the economy, including lower fuel imports.
Specifically, it says that climate efforts would “materially reduce” the UK’s dependency on overseas gas, with imports falling to 78% below current levels by 2050 in “holistic transition”. Under the “falling behind” scenario, imports rise by 35%”, despite higher domestic production.
This finding, shown in the figure below, is the opposite of what has been argued by many of those that oppose the UK’s net-zero target.
NESO goes on to argue that the shift to net-zero would have wider economic benefits. These include a shift from buying imported fossil fuels to investing money domestically instead, which “could bring local economic benefits and support future employment”.
The operator says that there is the “potential for more jobs to be created than lost in the transition to net-zero” and that there would be risks to UK trade if it fails to cut emissions, given exports to the EU – the UK’s main trading partner – would be subject to the bloc’s new carbon border tax.
Beyond the economy, NESO points to studies finding that the transition to net-zero would have other benefits, including for human health and the environment.
It does not attempt to quantify these benefits, but points to analysis from the CCC finding that health benefits alone could be worth £2.4-8.2bn per year by 2050.
Investment is higher for net-zero than for ‘not-zero’
It is clear from the NESO annex that its net-zero compliant “holistic transition” pathway would entail significantly more upfront investment than if climate action is slowed under “falling behind”.
This idea, in effect, is the launchpad for politicians arguing that the UK should walk away from its climate commitments and stop building new low-carbon infrastructure.
As already noted, the NESO analysis shows that this would increase costs to the UK overall.
Still, NESO’s new report adds that “falling behind” would “save” £14bn a year – relative to meeting the UK’s net-zero target – as long as carbon costs are “ignored”.
Specifically, it says that ignoring carbon costs, “holistic transition” would cost an average of £14bn a year more out to 2050 than “falling behind”, which misses the net-zero target. This is equivalent to 0.4% of the UK’s GDP and is illustrated by the solid pink line in the figure below.
Some politicians are indeed now willing to ignore the problem of climate change and the damages caused by ongoing greenhouse gas emissions. These politicians may therefore be tempted to argue that the UK could “save” £14bn a year by scrapping net-zero.
However, NESO’s report cautions against this, stating explicitly that the “costs discussed here do not represent the cost of achieving net-zero emissions”. It says:
“Our pathways cannot provide firm conclusions over the relative costs attached to the choices between pathways…We reiterate that the costs discussed here do not represent the cost of achieving net-zero emissions.”
It says that the scenarios have not been designed to minimise costs and that it would be possible to reach net-zero more cheaply, for example by focusing more heavily on EVs and renewables instead of hydrogen and nuclear.
Moreover, it says that some of the difference in costs between “holistic transitions” and “falling behind” is unrelated to climate action. Specifically, it says that electricity demand from data centres is around twice as high in “holistic transitions”, adding some £5bn a year in costs in 2050.
In addition, NESO says that most of the “saving” in “falling behind” would be wiped out if fossil fuel prices are higher than expected – falling from £14bn per year to just £5bn a year – even before considering climate damages and wider benefits, such as for health.
Finally, NESO says that failing to make the transition to net-zero would leave the UK more exposed to fossil-fuel price shocks, such as the global energy crisis that added 1.8% to the nation’s energy costs in 2022. It says a similar shock would only cost 0.3% of GDP in 2050 if the country has reached net-zero – as in “holistic transition” – whereas costs would remain high in “falling behind”.
The post Net-zero scenario is ‘cheapest option’ for UK, says energy system operator appeared first on Carbon Brief.
Net-zero scenario is ‘cheapest option’ for UK, says energy system operator
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The planet is heating up more quickly than ever before.
For decades, greenhouse gas emissions caused by human activity have been building up in the atmosphere and trapping ever-higher levels of heat.
The resulting asymmetry between incoming solar energy and energy radiated back out into space – known as “Earth’s energy imbalance” – provides a direct measure of the extent to which humans are disrupting the Earth’s climate system.
This imbalance is growing and in 2025 its 10-year average reached a record high, indicating that global temperatures could increase at even higher rates in the future.
This is among the headline findings of the latest “indicators of global climate change” (IGCC) report, published in the journal Earth System Science Data, which tracks changes in the climate system on an annual basis.
The report, now in its fourth iteration, has been produced by dozens of scientists from around the world.
Its findings are designed to fill the gap between Intergovernmental Panel on Climate Change (IPCC) science reports, which are published every 5-7 years.
In this article, we unpack the IGCC report, which explores how human activity is driving a growing energy imbalance and why monitoring systems to track global climate are so crucial.
(For more on previous IGCC reports, see Carbon Brief’s coverage in 2023, 2024 and 2025.)
Greenhouse gas emissions remain at an all-time high
Global greenhouse gas emissions are continuing to increase, mostly as a result of the use of fossil fuels. However, deforestation, agriculture and industrial processes also play an important role.
Over the most recent decade (2015-24), emissions stood at the equivalent of 54.6bn tonnes of carbon dioxide equivalent (GtCO2e) per year. In 2024, the most recent year for which we have complete data, emissions reached 56.8GtCO2e.
As the chart below shows, these emissions have pushed up atmospheric levels of CO2, methane and nitrous oxide. In 2025, concentrations of these gases reached 425.6 parts per million (ppm), 1936.3 parts per billion (ppb) and 339.4ppb, respectively.
This represents a rise of 3.8%, 3.8% and 2.2%, respectively, since the 2019 levels reported in the IPCC’s sixth assessment report (AR6).
At the same time, declines in emissions of aerosols such as sulphur dioxide, partly as a result of efforts to tackle air pollution, are increasing the Earth’s energy imbalance. This is because aerosols have a cooling effect on the Earth’s climate, counteracting warming from CO2 and other greenhouse gas emissions.
(Tackling sulphur dioxide, alongside other particulate emissions, remains critical because the immediate health and environmental damage they cause far outweighs their short-term cooling effect on the climate.)
The Earth’s energy imbalance is rising rapidly
The Earth’s energy imbalance has long been recognised as a key indicator of how the climate is being affected by human activities.
However, it is only in the last few decades that scientists have been able to record temperature changes deep enough in the ocean to accurately quantify it.
Earth’s energy imbalance measures how quickly excess heat is accumulating in every part of the Earth system, primarily in the ocean, but also in land, ice and atmosphere.
Through this accumulation of heat, the energy imbalance influences the rate of sea level rise and ice melt across the world, as well as increasing the frequency and intensity of extreme weather events, such as storms, floods and droughts.
Without human influence, the Earth’s energy imbalance would be close to zero.
But, as greenhouse gas emissions have built up in the atmosphere, the imbalance has been growing since the 1970s. Recent increases to Earth’s energy imbalance have outpaced those projections made by climate models — indicating the planet could see more warming than expected in the future.
As the right-hand chart below shows, the imbalance is now at a record high, having more than doubled over the past two decades.
It has increased by around 40% since 2019, from an average 0.79 watts per square metre (Wm2) over 2006-18, according to IPCC AR6, to 1.12Wm2 over 2013-25.
The left-hand chart shows how heat is accumulating in the ocean (blues), ice (grey), land (orange) and atmosphere (purple).
Global temperature rise
The excess heat building up in the climate system from the energy imbalance is pushing up global temperatures at a record rate of 0.27C per decade.
We estimate that human-induced warming – the amount of observed global surface
temperature increase attributable to both the direct and indirect effects of human activities – reached 1.37C in 2025. This has risen from 1.0C in 2017, as reported in IPCC AR6.
While natural variability in the climate system – such as El Niño or La Niña events – can also influence temperatures year-to-year, the upward temperature trend we are seeing is being driven by the persistent imbalance in energy.
We now expect global temperatures to exceed the Paris Agreement limit of 1.5C above pre-industrial levels around the year 2030.
This is significant because 1.5C has been identified as the critical dividing line between manageable climate risks and catastrophic, potentially irreversible damage to global ecosystems and human societies.
Heat accumulating throughout the Earth system
While heat is accumulating throughout the Earth system, it is not being distributed evenly around the globe.
Since the 1970s, around 90% of this heat has been taken up by the ocean, affecting marine ecosystems, ocean circulation patterns, sea level rise and climate extremes.
For example, the number of marine heatwave days – periods of unusually high sea surface temperatures – has more than tripled globally since the early 1990s. The year 2025 alone saw 65 days of marine heatwaves – meaning they occurred, on average, more than one day a week.
Meanwhile, the cryosphere – the portion of the Earth made up of frozen water, including glaciers, ice sheets and permafrost – is experiencing widespread ice loss and thawing in response to the growing energy imbalance. This affects ecosystems, sea level rise and infrastructure in polar and high-latitude regions.
Rapid warming has also resulted in record extreme temperatures over land, with average maximum temperatures for any single day over 2016-25 around 1.92C above pre-industrial levels). This is an increase of almost half a degree compared to the previous decade (2006-15).
Sea level rise and the energy imbalance
Sea level rise provides one of the clearest long-term signals of a changing planet.
It is closely linked to Earth’s energy imbalance. As heat accumulates in the ocean, water expands, raising sea levels. Meanwhile, a warming land and atmosphere means addition of water to the oceans through melting of glaciers and ice sheets, also adding to sea level rise.
Over the long-term, sea levels have been rising, on average, at a rate of around 1.8mm per year since 1901, totalling a record 23cm in 2025. This is increasing the risk of coastal flooding, erosion and habitat loss in many low-lying areas around the world.
This rise can be seen in the left-hand chart below, which shows observed global sea level changes from tide gauges (grey and blue dashed lines) and satellites (red dashed lines) since 1901. The solid lines indicate the average across multiple datasets.
Sea level rise is accelerating consistent with the observed increase in Earth’s energy imbalance. Over 2006-25, sea levels have risen at a rate of 3.67mm per year – more than double the rate of 1.69mm per year seen over 1976-95.
This increasing rate is shown in the right-hand figure below, which shows four successive overlapping 20-year periods and the most-recent decade.
(Last year’s transition from El Niño to weak La Niña conditions affected global rainfall patterns and led to a small and temporary fall in global average sea level in 2025. This explains the slight decrease in rate of sea level rise for the most recent decade, which is affected more than the 20-year period 2006-25.)
The bigger picture
Despite greenhouse gas emissions not increasing as rapidly as in the 2000s, this year’s IGCC findings continue to show how far and how fast the climate is changing due to human activity.
A significant increase in decarbonisation efforts in the second half of this decade is required to slow down the rate of human-caused warming and limit the escalation of climate risks and impacts.
These findings, like many others produced by scientists across the globe, rely on international expertise, partnership and the maintenance and availability of global climate datasets and the global observing programmes that underpin them.
This year’s edition of IGCC used more than 40 global datasets produced by research teams around the world, including the NASA satellite record of the Earth’s energy imbalance and the ARGO deep ocean float network.
However, a number of long-term monitoring programmes could be threatened by funding decisions made by governments around the world, most notably the Trump administration in the US.
Local meteorological data and weather balloon measurement programmes in many countries have declined in recent years, especially in Africa, the west Pacific and South America. This reduces scientists’ ability to monitor and understand key indicators of climate change.
This is not just an issue for climate science. Many of these observations are key to weather forecasts and systems that provide early warning for extreme weather. For example, media reports have suggested that recent reductions in weather balloon measurements in Alaska led to a lack of warnings for a recent winter storm.
The continuity and integrity of the climate observations that scientists use to understand how the climate is changing depends on effective and sustained coordination by international organisations, such as the Global Climate Observing System, the World Meteorological Organization and World Climate Research Programme.
Without this data and its coordination, future assessments will be much more difficult at a time when urgent climate action is needed.
The post Guest post: How a record-high ‘energy imbalance’ is driving global warming appeared first on Carbon Brief.
Guest post: How a record-high ‘energy imbalance’ is driving global warming
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