Exploring Climate Cooling

• Rising global temperatures increase the likelihood of crossing climate tipping points – abrupt and potentially irreversible shifts in the Earth’s climate system. While decarbonisation is the only sustainable way to reduce the risk of triggering these events in the long term, our current warming trajectory already makes a number of tipping points distinctly possible over the next century. 

• This has driven international interest into approaches to actively reduce global temperatures in the short term.

• There is a crucial need for objective and trustworthy science in this area to better understand these proposed approaches. Our programme intends to answer fundamental scientific questions on the feasibility and risks of cooling approaches.

Yes. In cases where essential scientific questions cannot be answered by modelling or indoor experiments alone, five projects will undertake carefully controlled outdoor experiments to responsibly gather crucial real-world data. 

Any outdoor experiment will only go ahead once independent environmental impact and legal assessments have been made, and if the results of these suggest that the experiments will be safe (the assessments will also be made publicly available before experiments start). These experiments will only go ahead after a period of meaningful public engagement with local communities, and will all be subject to oversight by the programme’s independent oversight committee.

Our programme funds five outdoor experiments:

• One project will explore the efficacy of rethickening arctic sea ice.

• Two projects will explore the effects of seawater spray on cloud reflectivity.

• One project will explore the effects of electric charge on cloud reflectivity.

• One project studies how milligram quantities of mineral dusts age in the stratosphere. In this controlled experiment, none of these materials will be released; all are returned to the ground for analysis by scientists.

Crucially, all ARIA-funded experiments will be time-bound, limited in size and scale, and their effects will dissipate within 24 hours or be fully reversible. Experiments can only proceed if they fully meet ARIA’s stringent governance requirements. ARIA is not deploying these technologies, and there is no risk of termination shock.

We’re also funding 4 projects that will monitor natural climate processes:

• Two projects will examine different aspects of the formation and properties of cirrus clouds, to better understand how these clouds influence the climate.

• One project will develop a lightweight and low-cost balloon system for collecting climate data from the high atmosphere.

• One project will use drones to study emissions from selected, regularly erupting volcanoes to better understand the effects that the emissions from these volcanoes have on the climate. 

Remaining projects will research computer modelling, public perception, ecological studies, governance, and ethics in the field of climate cooling.

• Any outdoor experiments will first be subject to an independent and publicly available environmental impact and legal assessment, as well as a co-design process with local communities. 

• The first outdoor experiments are expected to commence in early 2026, and will be a continuation of ice thickening experiments being conducted in Canada. The teams conducting this ice thickening have worked in these communities before and will comply with local regulations.

• Outdoor experiments in the UK will only take place if the appropriate community engagement work and the necessary assessments have taken place. No decisions have been taken yet on the locations for UK-based experiments. 

• The programme is funding up to three small, controlled, outdoor experiments planned to take place in the UK. The specific locations have not yet been decided. 

• These experiments will only go proceed:

  • Once independent environmental impact and legal assessments state that the experiments are safe and legal (these assessments will be publicly available).

  • After meaningful public engagement with the local communities.

  • After being subject to oversight by the programme’s independent oversight committee.

• All experiments are designed to be safe for humans, animals and the environment.  Their effects will dissipate within 24 hours, or be fully reversible. No toxic material will be released into the atmosphere.

• The three small, controlled experiments expected to take place in the UK are:

  • An experiment to explore the effects of seawater spray on cloud reflectivity. The first tests would be very small and not noticeable to the human eye, spraying seawater for just a few seconds to see the effect of the sprays on the size of the water droplets in the cloud (larger droplets give darker clouds and smaller droplets give brighter clouds). Later experiments (if the local community is supportive) might last for a few hours and be a few kilometres in size. This concept is a bit like the idea of using white paint on house roofs to reflect the sun and keep them cool. Do whiter clouds also reflect more sunlight? This experiment will help to answer that question, at least at a very small scale. 

  • An experiment to explore the effects of electric charge on cloud reflectivity. In a similar way to seawater spray, it might be possible to make clouds brighter by using static electricity (the same thing that makes your hair stand on end if you rub a balloon on your head). Do the water droplets in charged clouds form larger droplets more slowly due to charge repulsion, similar to the way that your hairs repel each other after you’ve rubbed the balloon on your head? This experiment will test out that theory over very small areas of approximately 100 m x 100 m, starting by looking at fogs as a type of easy-to-access low level cloud. The effects of any experiment on the fog would be small-scale and would dissipate in less than 24 hours. 

  • An experiment to study how milligram quantities of natural mineral dusts age in the stratosphere. This will take place in the US and/or UK. In the experiments, tiny (milligram, e.g. 1/1000th of a gram) quantities of naturally occurring mineral dusts will be secured to a tray inside the basket of a weather balloon. The weather balloon will then rise into the stratosphere. Once there, the tray will slide out from the basket to expose (but not release or disperse) the minerals to the stratosphere. After a set period of time, the tray will then retract into the basket and the balloon will descend to the ground, where the samples will be recovered and analysed by scientists. This allows scientists to understand how natural dusts age in the stratosphere without releasing any of the materials. 

• We expect up to three small experiments to take place outside the UK. Like the UK-based experiments, these will only proceed once independent environmental impact and legal assessments have been made (publicly available) and there has been meaningful public engagement with the local communities. All are subject to oversight by the programme’s independent oversight committee. All are designed to be safe for humans, animals and the environment, with effects dissipating within 24 hours, or being fully reversible. No toxic materials are released into the atmosphere.

• The three small, controlled experiments are:

  • An experiment to explore whether or not the Arctic sea can be re-thickened in order to limit sea ice loss. This will take place in Canada. The experiment involves pumping seawater on top of Arctic ice during the cold polar winter, where it freezes rapidly. The experiments will start small (0.1 square km) and (if the communities are supportive) will grow to between 0.5 and 1 square km in size.
  • An experiment to explore the effects of seawater spray on cloud reflectivity. This will take place over the Great Barrier Reef in Australia and will use a very similar approach to REFLECT in the UK. The two teams will work closely with each other to share their learnings. This Australian project is a continuation of work to cool and shade the Great Barrier Reef, originally funded by the Australian Government’s Reef Restoration and Adaptation Program.
  • An experiment to study how milligram quantities of natural mineral dusts age in the stratosphere. This will take place in the US and/or UK. In the experiments, tiny (milligram, e.g. 1/1000th of a gram) quantities of naturally occurring mineral dusts will be secured to a tray inside the basket of a weather balloon. The weather balloon will then rise into the stratosphere. Once there, the tray will slide out from the basket to expose (but not release or disperse) the minerals to the stratosphere. After a set period of time, the tray will then retract into the basket and the balloon will descend to the ground, where the samples will be recovered and analysed by scientists. This allows scientists to understand how natural dusts age in the stratosphere without releasing any of the materials.

Before any experiment, the project team will engage directly with local communities to explain plans and adjust them based on feedback. An independent environmental impact and legal assessment will also be conducted and made publicly available before the experiment begins.

Computer modelling and indoor testing are essential first steps to establish the basic science of earth cooling approaches. However, these methods are simplifications and cannot fully answer some important questions. To better understand potential impacts and effects in real-world conditions, and to improve models, controlled, small-scale outdoor experiments may be necessary. We only consider small-scale outdoor experiments where there is a crucial need for real-world data to answer key scientific questions and improve our models.

All activities funded comply with all local, national and international regulations. Our independent Oversight Committee – composed of international climate and technology experts – will also support ARIA's leadership in the effective governance of outdoor experiments. They scrutinise experiment plans, provide expert recommendations, and can ask for modifications to the planned experiments before they are carried out.  

No. The first outdoor experiment is expected to commence in early 2026 – this is the continuation of an experiment in northern Canada to assess if sea ice can be thickened by pumping sea water on top of it during the cold polar winter.

Yes. All funded experiments comply with local, national, and international regulations. Before any outdoor experiment, an independent environmental impact and legal assessment is conducted and made publicly available.

Yes. All the experiments are designed to be safe and must meet strict safety rules for humans, animals and marine life. None of the experiments will release anything toxic into the environment. All of the experiments have been designed so that the effects dissipate within 24 hours or are fully reversible. Environmental impact assessments will be undertaken by independent experts and published before any experiment begins.

No noticeable effect on weather or seasons will occur. Independent environmental impact assessments are performed before and after any outdoor experiment to ensure no lasting environmental impact. All experiments use non-toxic materials, are limited in size, scale, and duration, ensuring effects dissipate within 24 hours or are fully reversible.

No. Experiments involve no toxic materials and will not reflect enough sunlight to have any effect on plants or crops growing.

• No. ARIA’s funded experiments are not designed to block or dim the sun, or carry out large-scale climate modification. Our programme focuses strictly on foundational research, modelling, and where necessary, carefully controlled, small-scale outdoor experiments to investigate fundamental scientific processes. 

• While a number of ARIA's funded outdoor experiments will examine if clouds can be made slightly more reflective for short periods (a few hours), these experiments will be strictly confined in size and time, and should have no effect noticeable to the human eye.

No, ARIA does not fund any research that releases toxic materials into the atmosphere.

Two experiments (UK and Australia) will spray natural seawater into the sky to measure its effect on cloud reflectivity. Any cloud effect will be tiny, brief (dissipating within 24 hours), and should not be noticeable to the human eye. Another experiment will launch weather balloons (US and/or UK) with secured milligram amounts of natural mineral dusts into the stratosphere. All the materials will be returned to the ground for recovery and analysis by scientists. Crucially, no materials will be released.  

No, ARIA does not, and has never, funded the Stratospheric Aerosol Transport and Nucleation (SATAN) project. It was conceived and developed by other actors prior to ARIA’s Exploring Climate Cooling programme.

• We are not funding the deployment of climate cooling approaches, nor are we funding research to facilitate the deployment of such technologies.

• ARIA will only conduct experiments at research scale and for very short periods of time to find out if any of the suggested approaches work (and what their effects are) in a controlled manner.