The UK government’s “high-risk” research funding agency last week announced that it will invest £57m ($76m) in a new solar geoengineering research programme.
“Solar geoengineering” refers to methods that aim to address some of the impacts of a warming climate by reflecting away more sunlight from the Earth.
The programme, spearheaded by the Advanced Research and Invention Agency (Aria), will fund 21 projects globally.
This includes small-scale outdoor experiments, involving attempts to thicken Arctic sea ice and brighten clouds above Australia’s Great Barrier Reef to reflect away sunlight.
The news was reported breathlessly by the UK media, with some outlets conjuring images of the government one day “dimming the sun” or trying to modify the weather and others focusing on the “secretive” nature of Aria and its research.
The reaction was even more exaggerated on social media, where anonymous accounts seized upon the news to spread misinformation about existing “secret” government schemes to “control” the weather.
At the same time, the programme – first reported last year – has sparked legitimate debate among climate scientists, who have long held diverging views on whether more research funding should be channelled into solar geoengineering.
Below, Carbon Brief explains what the new solar geoengineering research programme consists of and explores the social and ethical concerns surrounding the technology.
- What is the UK’s new solar geoengineering research programme?
- How does this compare to past solar geoengineering efforts in the UK and globally?
- Why do some scientists say solar geoengineering research is needed?
- Why are there social and ethical concerns around solar geoengineering?
What is the UK’s new solar geoengineering research programme?
Solar geoengineering is a term used to describe a group of hypothetical technologies that could, in theory, counteract temperature rise by reflecting more sunlight away from the Earth’s surface. (It is also sometimes called “solar radiation modification”.)
The most commonly proposed idea is to introduce reflective aerosols high up into the stratosphere, which would lower global temperatures in a similar way to a volcanic eruption.
Other ideas include deliberately modifying clouds to make them more reflective or sending giant mirrors into space.
The proposals may sound futuristic, but the notion of engineering the climate in order to limit sunlight has been debated by scientists and politicians for more than 50 years.
However, these debates have always proved controversial, meaning – apart from studies based on computer simulations – little field research into solar geoengineering has been carried out. (See: How does this compare to past solar geoengineering efforts in the UK and globally?)
Aria’s new research programme aims to invest £57m in 21 solar geoengineering research projects globally.
This – along with a separate £10m scheme from the UK Research and Innovation body – means the UK is now one of the world’s biggest funders of solar geoengineering research.
Announcing the details of the scheme, Aria said its motivation for launching the research programme was “the possibility of encountering damaging climate tipping points”.
Out of the £57m, around £24.5m ($33m) will be spent on “controlled, small-scale outdoor experiments”, according to Aria.
These include attempts to thicken Arctic sea ice, brighten clouds above Australia’s Great Barrier Reef and to float weather balloons containing natural minerals high in the stratosphere, which will be retrieved after “hours or weeks”.
All outdoor experiments will be “scrutinised” by an oversight committee chaired by Prof Piers Forster, a leading climate scientist who is the founding director of the Priestley Centre for Climate Futures at the University of Leeds.
In a note released alongside news of the research funding, the oversight committee said it does “not exist to legitimise this programme”, adding:
“We advise Aria on the risks and benefits of supporting proposed creator projects and how best to work with and across creator teams to support learning and to help ensure that findings are contextualised and communicated appropriately alongside [climate] mitigation and adaptation options.”
Aria is a “high-risk, high-reward” government research agency that was formally established through an act of parliament in 2023.
It was originally conceptualised by Dominic Cummings, a controversial former adviser of then prime minister Boris Johnson.
According to Nature, Aria was modelled on the “famed US Defense Advanced Research Projects Agency, or DARPA, which helped to pioneer some of the world’s most consequential technologies, including the internet and personal computers”.
In its recent coverage, the Daily Telegraph described Aria as a “secretive government unit”.
Aria itself has said that it aims to be fully transparent about its solar geoengineering programme, which was its motivation for publicly announcing its spending on the 21 projects involved.
How does this compare to past solar geoengineering efforts in the UK and globally?
As mentioned above, the idea of solar geoengineering has been debated for more than 50 years. However, its controversial nature has meant that, until now, very few field experiments have been carried out.
In 2010, there was an attempt to carry out field research in the UK by the Stratospheric Particle Injection for Climate Engineering (SPICE) project, which was headed by Dr Matthew Watson at the University of Bristol and involved scientists from the University of Oxford, the University of Cambridge and the University of Edinburgh.
The project aimed to “investigate the effectiveness” of solar geoengineering, in part by releasing the equivalent of a bathtub of water high into the atmosphere above Norfolk.
However, it was met with fierce opposition by some campaign groups. In 2012, the team ended the project, citing issues with intellectual property and discomfort with the current lack of regulation and governance of solar geoengineering research.
(Watson is one of the recipients of Aria’s new research programme. His team has been awarded £4.3m ($5.7m) to build specialised drones to study emissions from regularly erupting volcanoes in Guatemala, Montserrat and Chile.)
Outside of the UK, another high-profile solar geoengineering experiment headed by researchers at Harvard University, called the Stratospheric Controlled Perturbation Experiment (Scopex), was also forced to disband following public disapproval.
In the private sector, a US start-up called Make Sunsets has begun releasing high-altitude balloons containing sulphur dioxide into the stratosphere, in an attempt to geoengineer the planet. It funds its activities by selling “cooling credits”.
The company has been banned in Mexico, where it previously launched balloons, and is currently being investigated by the US Environmental Protection Agency.
According to the online publication SRM360, funding for solar geoengineering has increased from $34.9m in 2010-14 to $112.1m in 2020-24. The vast majority of funding is concentrated in global-north countries and about half of all funding comes from philanthropic sources.
This week, scientists and policymakers are meeting in Cape Town, South Africa for the largest summit to date on the scientific, social and political implications of solar geoengineering.
Countries have agreed to a de facto moratorium on large-scale solar geoengineering under the Convention on Biological Diversity, a UN treaty that aims to protect biodiversity. (However, it is not legally binding.)
Why do some scientists say solar geoengineering research is needed?
Scientists agree that cutting global greenhouse emissions as soon as possible is key to tackling climate change.
But global emissions are still rising – and the prospect of limiting global warming to 1.5C above pre-industrial levels, the ambition of the landmark Paris Agreement, without first “overshooting” the target is fast vanishing.
This has led some scientists to call for more research into solar geoengineering ideas, including through small-scale experiments and trials.
Research based on computer modelling indicates that artificially cooling the planet by releasing reflective aerosols into the stratosphere using specialised planes could be effective at offsetting a range of climate impacts, such as more intense heatwaves and flooding, melting sea ice and higher tropical storm risk.
(One solar geoengineering scientist has estimated that halving global warming with reflective aerosols would involve a specialised fleet of about 100 planes releasing 1m tonnes of sulfuric acid each year by 2070.)
However, this type of solar geoengineering would not address rising CO2 levels, which are causing oceans to become more acidic and crops to become less nutritious, among other issues.
Some scientists have raised concerns that, if aerosols were used to address global warming, the world could be left at risk of a “termination shock”. That is, if aerosols were released and then suddenly stopped – as a result of political disagreement or a terrorist attack, for example – global temperatures could rapidly rebound.
This sharp temperature change could be “catastrophic” for wildlife, modelling studies have suggested. However, other research argues that the likelihood of a termination shock has been “overplayed” and that measures could be put in place to ensure that the risk is minimised.
There is also a risk that deploying aerosols from just one spot on Earth could cause uneven impacts for people. One research paper based on modelling found that releasing aerosols in just the northern hemisphere could lead to a decrease in rainfall – and, therefore, an enhanced drought risk – in India and the African Sahel.
Ultimately, advocates of solar geoengineering research tend to argue that the only way to understand more about the efficacy and risks of the technology is to study it further, whereas opponents say more research could be a “slippery slope” towards deployment.
Why are there social and ethical concerns around solar geoengineering?
As well as scientific uncertainties, experts have long warned that solar geoengineering poses large social, ethical and governance challenges.
Some scientists and campaigners are fundamentally opposed to the idea of manipulating the climate further in order to try to repair some of the damage caused by fossil-fuel emissions.
Writing in the Guardian, climate scientists Prof Raymond Pierrehumbert and Dr Michael Mann described Aria’s research programme as “like using aspirin for cancer”.
Indigenous groups have strongly opposed the idea of solar geoengineering and its research, often arguing it goes against their beliefs about living in harmony with nature.
Some scientists and campaign groups also believe that solar geoengineering could be viewed by politicians and the public as a quick “technofix” to climate change. If more research and development is channelled into these techniques, they argue, people may start to backpedal on their promises to cut their emissions.
This is often referred to as the “moral hazard” dilemma.
But other researchers have urged caution on this idea. One reason for this is that social experiments conducted with members of the public have found little evidence of the moral hazard problem existing in practice.
Advocates of solar geoengineering research say it should be viewed as a “supplement” to climate mitigation efforts rather than a “substitute” or “quick fix”.
However, many experts and commentators have pointed out that the technology presents a very large global governance challenge.
A fair and just deployment of solar geoengineering would require agreement between countries, experts have reasoned. At present, it is difficult to picture a global forum that could garner such collaboration, they say.
Prof Alan Robock, a professor in the department of environmental sciences at Rutgers University, summarised this issue neatly in a conversation with Carbon Brief in 2018, when he said:
“You’re asking if the world can come together and agree on geoengineering without agreeing on mitigation. I think the answer is for us to agree on mitigation. Paris is the first step, the pledges made there aren’t enough but have got to increase.”
Another concern is the “free-driver problem”, an idea that refers to the potential for a single country, group or even individual to unilaterally deploy solar geoengineering, even if it might cause negative impacts for others. This concern arises from the fact that solar geoengineering would be relatively cheap to carry out.
It has been argued that the free-driver problem poses a larger concern than ever in today’s increasingly polarised world, where lone politicians and billionaires hold large amounts of power.
These serious social and governance issues prompt some experts to say solar geoengineering should not be researched at all, but others to say it should be researched to try to address concerns.
Out of Aria’s £57m for solar geoengineering research, around £2.8m ($3.7m) is earmarked for governance and ethics projects.
In its latest assessment for how the world can address climate change, the world’s authority on climate science, the Intergovernmental Panel on Climate Change (IPCC), notes that there is “high agreement” among research papers that solar geoengineering “cannot be the main policy response to climate change and is, at best, a supplement to achieving sustained net-zero”.
The assessment also notes that solar geoengineering “may introduce novel risks for international collaboration and peace”.
The post Factcheck: How the UK is – and is not – studying solar geoengineering appeared first on Carbon Brief.
Factcheck: How the UK is – and is not – studying solar geoengineering
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.