UK experiments to reflect sunlight one step closer

Controversial experiments exploring the science around reflecting sunlight with an aim to bring about global cooling have been announced.

The Advanced Research and Innovation Agency (ARIA) - a government backed body - is funding nearly £60m that could allow real-world experiments, including in the UK.

As part of the Exploring Climate Cooling programme, projects in Solar Radiation Modification (SRM) will involve trying to thicken Arctic sea ice and make clouds more reflective.

But, critics have real concerns about the impact of SRM on weather patterns and our health, seeing it as a distraction to drastic de-carbonisation.

Global average temperatures in 2024 were running at 1.6C above pre-industrial levels, temporarily exceeding the target set out by the 2015 Paris Agreement.

Current trajectories show the world passing 1.5C of long-term warming by the end of the early 2030s.

While extreme weather is a consequence of climate change there are concerns of abrupt and potentially irreversible shifts in the climate system.

Some of these shifts or so-called tipping points, such as a collapse of the Atlantic Meridional Overturning Circulation might be closer to happening - within the next century – than we'd like.

While every effort should still be made to reduce global emissions, there is a growing scientific community looking at geo-engineering, specifically SRM.

Geo-engineering is the process of artificially modifying the atmosphere and climate.

SRM techniques which try to mimic the natural cooling that occurs after the eruption of volcanoes releasing ash and gases, are some of the most controversial.

ARIA programme director Mark Symes said "there is a critical missing gap in our knowledge on the feasibility and impacts of SRM and to fill that gap requires real-world outdoor experiments".

The agency announced on Wednesday it will fund five projects that could lead to real-world experiments.

These include research into thickening Arctic sea ice to make it more reflective, Marine Cloud Brightening (MCB) and Stratospheric Aerosol Injection (SAI).

Outdoor experiments on sea ice thickening could take place as soon as this winter.

They will also fund a modelling based project that would investigate mirrors or shades deployed into space.

One proposed MCB experiment is to spray a fine mist of natural sea water into the atmosphere from a coastal location in the UK.

The hope is that it would brighten existing cloud and increase its reflectivity.

Another funded SAI project could involve sending a small amount of natural mineral dust contained within a weather balloon high into the atmosphere to see how it responds in that environment. No dust would be released.

ARIA stress that "before any outdoor experiment takes place there will be a full and transparent public consultation with necessary environmental assessments taken place".

And any outdoor experimentation "will only occur after robust oversight measures which won't include the release of any toxic materials".

But Raymond Pierrehumbert, Professor of Planetary Physics at Oxford University is "extremely worried" about SRM.

"People want a Plan B if we don't reduce global emissions. But there really is no Plan B, it just kicks the can down the road because [solar geo-engineering] doesn't take away the carbon dioxide in the atmosphere".

Studies have shown that SRM could cause strong warming high above the tropics, changing large-scale weather patterns, warming the polar regions and altering rainfall patterns around the world.

For example it's been shown that brightening cloud off the coast of Namibia in south-west Africa could induce drought over South America, affecting the Amazon rainforest - often referred to as the 'lungs of the planet'.

While global average temperatures may be reduced, the weather or climate in certain regions of the world may get worse.

For SAI techniques, new aircraft would be needed capable of flying at an altitude of 12 miles, spreading sunlight reflecting aerosols such as sulphur.

However, in a study, external published in Earth's future, scientists at University College London, show that SAI could be achieved using existing aircraft injecting aerosols at an altitude of 8 miles high instead.

To inject at this lower altitude three times more aerosol would be needed to be as effective and it would strongly increase side-affects such as acid rain.

Public perception of such techniques is also going to be challenge, primarily due to the widely known conspiracy theory of 'chemtrails'.

Incorrect suggestions that condensation trails - water vapour created from aircraft jet engines - is evidence of SRM and weather modification is happening at large-scale today.

Currently there is no international regulation of geo-engineering so private companies or governments are essentially able to do what they like.

Because of the potential for modifications in one area having an impact across the globe, experts are calling for an international framework to regulate geo-engineering techniques such as SRM.

For example, a US start-up company – Make Sunsets – is commercialising SRM.

Offering 'cooling credits' for a fee, a hydrogen and sulphur dioxide filled balloon is launched and rises to 12 miles before popping and releasing the gas into the stratosphere. They claim 1g of this gas offsets one ton of carbon dioxide a year.

As a direct result of these balloons being released in Baja, California, Mexico looked at banning solar geo-engineering in 2023.

And one SRM project run by Harvard University called SCoPEX was cancelled in 2023 after strong opposition to the plan of launching a high-altitude balloon in Sweden that would have monitored the results of releasing aerosols into the stratosphere.

Last week the Florida House of Representatives approved a bill to bar geo-engineering and weather modification activities in the state. Adding to the growing number of other states in the US who have also passed bills, including Tennessee which passed it into law in April 2024.

Professor Pierrehumbert is "worried about ARIA and the [really dangerous] precedent it will set"

"Now the UK is pouring nearly £70 million into this and opening the door to outside experimentation, then that's just going to open the floodgates to other countries that may have fewer controls".

But Sarah Hunter, Chair of ARIA's Ethics and Social Responsibility Committee said "this cooling programme is a vital piece of research, and the thoughtful governance and engagement plans in place mean we can make progress in this field in a responsible way".