The year 2025 has seen exceptionally dry conditions in many parts of the UK.
At the time of writing, a large area of England is officially “in drought” and hosepipe bans are in force for more than 8m households.
This follows severe drought episodes in the summers of 2022 and 2018 – which raises the question of whether these events are part of a pattern towards a drier future.
However, the intervening periods between these drought events have been associated with major floods.
There is good reason to assume this “hydrological volatility” could be linked to climate change.
Writing for Carbon Brief in 2020, we explored how climate change might be impacting UK river flooding.
Here, we revisit this theme – but ask whether global warming is driving a long-term trend towards increasing drought severity in the UK.
To do so, we draw from the findings of a 2023 Environment Agency report, a chapter of which we authored and has now been accepted for publication in a peer-reviewed journal.
Key findings include:
- Future projections indicate hydrological droughts will become more severe in the UK, especially over the months of April to September, due to hotter, drier summers.
- However, observations from the past 50 years – and longer where records allow – do not provide evidence of worsening drought.
- This apparent conflict is largely because natural climate variability can obscure underlying trends driven by climate change.
- An increasingly variable climate in the UK means planners still need to prepare for more severe droughts, as well as more floods.
The 2025 hydrological drought
Droughts are complex events that vary in duration, time of year, location and severity.
They are often categorised into different types. For example, a meteorological drought is defined by a lack of rainfall – whereas agricultural drought is a period when there is not enough water for crops to grow.
Here, we are focusing on hydrological drought, which is when a lack of rainfall results in less water in streams, lakes, rivers and reservoirs.
In particular, we look at deficits in river flow. It is through dwindling river flows that droughts have some of their greatest impacts on society and the environment.
Over March-July of this year, flows for many UK rivers were at their lowest level on record. Hosepipe bans have been introduced by water companies, while the Environment Agency has imposed restrictions on extracting water from rivers and warned of widespread environmental impacts, such as fish die-offs and algal blooms in rivers, streams and lakes.
The map below shows how a significant number of rivers in the UK this spring saw exceptionally low flows (marked by a dark red circle) or notably low flows (marked by an orange circle) compared to the 1991-2020 average. This includes many rivers in northern parts of Great Britain – which is typically wetter the south-east.
The graphs on the right, meanwhile, show how flows in the River Derwent and the River Wye (black line) in 2025 have been at equivalent levels, or lower, than in major past droughts (red, green and orange lines). This includes the record-breaking drought of 1976 (orange line), often used as a benchmark.
How is climate change going to affect droughts in the UK?
Globally, climate change causes an intensification of the hydrological cycle. This means that both wet and dry extremes – floods and droughts – are likely to become more frequent and severe.
One way of understanding the impact of climate change on hydrological drought is to use rainfall and temperature projections from climate models to drive hydrological models that simulate how the flow of water through river catchments could change in the future.
There are numerous studies that provide such projections of UK drought. (A summary of these can be found in the chapter on modelling in the 2023 Environment Agency report, linked above.)
Across these studies, river flow models generally show that, in the future, the UK should expect lower summer river flows, increasing drought severity and decreasing minimum flows – in other words, the lowest flows in each year will get lower.
The graphs below show projections of changing low flows for a selection of UK rivers from the 1980s to the 2080s over consecutive 30-year moving averages (1983-2012, 1984-2013 and so on, through to 2050-79).
These projections are based on the “enhanced future flows and groundwater” (Eflag) dataset, which provides simulated river flows for 200 catchments around the UK, using four river flow models. These are driven by the “regional” projections from the Met Office’s UK Climate Projections 2018 (UKCP18), a 12-member climate model “ensemble” which uses the very-high-emission RCP8.5 scenario.
(For more on why this regional data is only available under this pathway, read Carbon Brief’s in-depth Q&A on UKCP18.)
The multiple lines on each plot – which indicate different projections for low flows – show the uncertainties arising from the different climate model runs and river flow models used.
The charts reveal that, across all rivers and different future trajectories, the trend points in the same direction – towards diminishing minimum flows. This suggests a drier future across the UK, most notably in the summer.
Past trends in drought
Given these projections, we would expect to see a similar trend of decreasing minimum flows emerging in observational data over the last few decades.
However, our research concludes that there is little compelling evidence for any evidence of a widespread worsening of UK droughts over the last half century – yet.
The maps below show how river flows have changed since 1965 across the UK for very low (Q95), medium-low (Q70) and median (Q50) flows.
For much of the north and west of the UK, the lowest flows in each year have, in fact, increased since 1965 (blue triangles). In the south and east of the country, there are decreases (inverted red triangles), but it is a mixed picture. Overall, the number of statistically significant trends is modest.
But, while these river flow records span more than 50 years, this is still a relatively short timeframe.
As a result, we also explored much longer records, including “reconstructed” river flows, which stretch back to 1890. Here, too, we find there is no consistent trend towards worsening drought over these long periods.
In fact, our research shows how trends in the last 50 years are often unrepresentative of longer-term changes. Some of the apparent decreasing trends from the maps above disappear when a longer view is taken.
Mismatch between past trends and future projections
There is a clear contradiction between future projections and past trends. We do not yet see much evidence of the drier future that climate models project.
However, this apparent contradiction is unsurprising once uncertainties inherent in both future projections and historical observations are considered.
Future projections are highly uncertain and span a wide range of possibilities – as shown by the multiple lines in the Eflag graphs above.
Caution is needed in interpreting trends in observations, too. While 50 years seems a reasonably long period, trends can be influenced by variability associated with natural atmospheric and oceanic circulation patterns.
The trends towards increasing river flows in the north and west are consistent with changes in the North Atlantic Oscillation (NAO) – the atmospheric pressure system that influences the UK’s weather on year-to-year and decade-to-decade timescales.
There is a growing list of drivers of drought variability, including the El Niño-Southern Oscillation (ENSO) and the role of the influx of freshwater into the North Atlantic due to the melting of the Greenland ice sheet.
In a recent paper, we highlighted that long-term trends in low river flows for many UK catchments may not be detectable for decades due to being obscured by natural climate variability.
This is shown by the plot below, which illustrates how projected trends of very low river flows over the 21st century (red line) contrasts with the estimated range of historical river flow variability (dashed lines). (The grey shading shows the range of different climate models.)
It shows that for some catchments – for example, the Lambourn River in south-east England – significant trends do not emerge until the 2050s.
Part of the mismatch between historical observations and climate projections for UK summer is due to a run of wet summers from the late 2000s onwards. This climate variability has ‘masked’ an underlying trend that could eventually emerge and bring a more worrisome consistency with the projections of climate models.
That this masking has often entailed living with an excess of water, in the form of widespread, damaging flooding, only highlights the challenges water managers face.
A drier and wetter future
Further research is required into how different types of hydrological drought will evolve.
We are confident we will see more droughts in April-September, typically associated with heatwaves, as in 2025, 2022 and 2018. This is because warming temperatures – which, unlike rainfall trends, are certain – will exacerbate droughts.
The increased likelihood of hot, dry summers also means more rapid-onset “flash droughts”, which have impacts on soil moisture as well as river flows.
As such, the droughts of recent years should be interpreted as a warning that hotter temperatures will worsen drought impacts.
However, we are much less confident that we will see more long, multi-annual droughts driven by dry winters that fail to replenish reservoirs and aquifers, such as those seen in 1988-93, 2005-06 and 2010-12. This is because climate models generally predict wetter winters for the UK. (These multi-annual droughts have, historically, posed some of the greatest challenges to water management.)
Nevertheless, climate variability means that even if winters get wetter, there will always be runs of dry years. This is a cause for concern, as the greatest problems occur when wet winters combine with dry summers. (It was the dry winter of 1975-76 which made the 1976 drought so severe).
Our finding that it is difficult to confirm whether droughts are, overall, becoming more severe offers little comfort to water managers preparing for the future.
Our research offers a number of recommendations for water planners trying to navigate this complexity. This includes using large climate model “ensembles” to test the resilience of water supply systems to different types of droughts. Although model projections are uncertain, they provide a way to assess the UK’s vulnerability to a range of future outcomes.
Furthermore, the hydrological volatility of the recent past indicates the importance of preparing for both a drier and wetter future in the UK.
The UK is known for its variable weather, but it will have a future climate that is even more variable and extreme.
The post Guest post: Is climate change making UK droughts worse? appeared first on Carbon Brief.
Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
Greenhouse Gases
DeBriefed 6 March 2026: Iran energy crisis | China climate plan | Bristol’s ‘pioneering’ wind turbine
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Energy crisis
ENERGY SPIKE: US-Israeli attacks on Iran and subsequent counterattacks across the Middle East have sent energy prices “soaring”, according to Reuters. The newswire reported that the region “accounts for just under a third of global oil production and almost a fifth of gas”. The Guardian noted that shipping traffic through the strait of Hormuz, which normally ferries 20% of the world’s oil, “all but ground to a halt”. The Financial Times reported that attacks by Iran on Middle East energy facilities – notably in Qatar – triggered the “biggest rise in gas prices since Russia’s full-scale invasion of Ukraine”.
‘RISK’ AND ‘BENEFITS’: Bloomberg reported on increases in diesel prices in Europe and the US, speculating that rising fuel costs could be “a risk for president Donald Trump”. US gas producers are “poised to benefit from the big disruption in global supply”, according to CNBC. Indian government sources told the Economic Times that Russia is prepared to “fulfil India’s energy demands”. China Daily quoted experts who said “China’s energy security remains fundamentally unshaken”, thanks to “emergency stockpiles and a wide array of import channels”.
‘ESSENTIAL’ RENEWABLES: Energy analysts said governments should cut their fossil-fuel reliance by investing in renewables, “rather than just seeking non-Gulf oil and gas suppliers”, reported Climate Home News. This message was echoed by UK business secretary Peter Kyle, who said “doubling down on renewables” was “essential” amid “regional instability”, according to the Daily Telegraph.
China’s climate plan
PEAK COAL?: China has set out its next “five-year plan” at the annual “two sessions” meeting of the National People’s Congress, including its climate strategy out to 2030, according to the Hong Kong-based South China Morning Post. The plan called for China to cut its carbon emissions per unit of gross domestic product (GDP) by 17% from 2026 to 2030, which “may allow for continued increase in emissions given the rate of GDP growth”, reported Reuters. The newswire added that the plan also had targets to reach peak coal in the next five years and replace 30m tonnes per year of coal with renewables.
ACTIVE YET PRUDENT: Bloomberg described the new plan as “cautious”, stating that it “frustrat[es] hopes for tighter policy that would drive the nation to peak carbon emissions well before president Xi Jinping’s 2030 deadline”. Carbon Brief has just published an in-depth analysis of the plan. China Daily reported that the strategy “highlights measures to promote the climate targets of peaking carbon dioxide emissions before 2030”, which China said it would work towards “actively yet prudently”.
Around the world
- EU RULES: The European Commission has proposed new “made in Europe” rules to support domestic low-carbon industries, “against fierce competition from China”, reported Agence France-Presse. Carbon Brief examined what it means for climate efforts.
- RECORD HEAT: