Geoengineering solutions are large-scale interventions to counteract the effects of climate change. The most established of solutions are carbon capture technologies, which seek to actively remove carbon from the atmosphere, e.g., carbon capture, utilization and storage (CCUS) or ocean alkalinity enhancement.  

Are geoengineering solutions the magic bullet?  There are three major issues impacting all geoengineering technologies: 

• They are very expensive 

• They largely ignore the root causes of climate change, which in some cases can further enable the root causes 

• They may have unintended and misunderstood impacts on the climate and ecologies  

I first remember learning about the term ‘geoengineering’ about 10 years ago at a lecture on ‘moon-shot solutions for climate change’ – my overall takeaway was that they were reckless, but inevitable. This inevitability has intensified as the world continues to be far off track of meeting climate goals, with a minimum six-fold increase in mitigation investment required to meet net-zero by 2030.  

The main categories of geoengineering solutions are:  

Carbon Dioxide Removal (CDR): Supported by the rapid post-2019 growth of the voluntary carbon market (VCM) many of these are in TRL 6-9 and commercializing stages. Solutions can be abiotic, including direct air capture, point source air capture and marine carbon dioxide removal, or biotic, including seaweed and algae farming, reforestation; some solutions also straddle both abiotic and biotic categories including enhanced rock weathering (ERW). 

Carbon removal is required to meet our climate goals, with many solutions being beneficial rather than dangerous for the climate and ecologies, e.g., diverse reforestation, sensitive to local ecologies can benefit biodiversity and local communities. CDR.fyi estimates that $3.3B has been spent on CO2 removal to date, amounting to just 0.12% of the 10 gigaton goal which will need to be removed annually by 2050. However, only 4.1% of carbon credit purchases have been delivered.  

Solar Radiation Modification (SRM): In very early stages of development, SRM seeks to reflect sunlight away from the earth and into space. Solutions include using large mirrors in the upper atmosphere or space; spraying sulphate aerosols into the stratosphere, or modifying clous, ice, and plants to make them more reflective.  

Weather Modification: This is a subcategory of SRM, as it seeks to change weather and precipitation without altering the climate. Solutions include cloud seeding, where small particles such as silver iodide are added to subfreezing clouds to initiate rainfall. This application was used to questionable success in the 2008 Beijing Olympics to reduce the risks of rain.   

Cloud seeding is in operation in the United Arab Emirates today to address water shortages and adapt to drought. In April, Dubai experienced record flooding after a year’s worth of rain fell in 24 hours which killed 20 people and caused over $1B in damage. Cloud seeding planes had been deployed the two prior days to the flooding. Although many were quick to lay blame on cloud seeding, experts say it would have had a ‘minor’ impact at best with climate change heat and nature being the real culprit making the rainfall 10-40% heavier.  

Cloud Seeding Innovations 

The negative public image hasn’t deterred some investors from cloud seeding. In May, Rainmaker, a developer of a cloud seeding system that incorporates radar validation, weather resistant drones, numerical weather modelling, and ‘sustainable’ cloud seeds, raised $6.3M in its first Seed round. Presented as an adaptation solution, Rainmaker utilizes drones, weather modelling, and radar algorithms, for delivery accuracy, better monitoring, optimizing, and demonstrating impact.     

Another start-up, Make Sunsets, is tackling solar radiation modification. With the approval of NOAA and FAA, Make Sunsets is deploying reflective, biodegradable ‘cloud’ balloons which release sulphur dioxide aerosols in the stratosphere (50km high) in the U.S. to offset the warming effect of the sun for a year. Make Sunsets’ ‘clouds’ include a flight tracking computer, camera, and a geolocating device to monitor and validate its flights.  

Make Sunsets’ 2024 Deployment 

In December 2022, Make Sunsets raised $750K in Seed funding from Pioneer Fund and Boost VC to launch their company and are currently pre-selling ‘offsets’ for $10 per tonne per year and claim to be able to achieve $0.01 per tonne per year once scaled. In December 2024, the company had undertaken 15 launches, and the company remains in pilot/testing phases.  

While sulphur dioxide in the atmosphere can both reflect sunlight and help clouds form to further reflect sunlight, it can also deplete the ozone layer, produce acid rain, alter precipitation patterns, and cause respiratory issues. However, varying the size of aerosol droplets and their chemical composition could shift the impact towards more favorable outcomes.  

NOAA and Indiana University have modelled the impact of widescale deployment of stratospheric aerosol injections (SAIs) in recent years.  They’ve found a diverse range of outcomes, from reducing rainfall in the tropics by 5-7% that were damaging crops and rainforests to shifting malaria from highland areas in East Africa to lowland areas in South Asia and Sub-Saharan Africa, as well as reducing surface temperatures. The sheer scale of these negative impacts could result in significant geopolitical unrest.  

Localized, intermittent SAI in a critical context may make sense. For example, in 2021 Southern Cross University and the Sydney Institute of Marine Science trailed SAI to shield the great barrier reef from bleaching events. After several iterations, they have now moved beyond ‘proof of concept’ and are continuing to monitor the response of the clouds.  

Looking Ahead 

It’s clear more research is needed, along with global regulatory and legal guidance, and agreements on such experiments. Although we see some early investment into start-ups, this is largely to fund pilots and research. I would expect to see more offset-style business models like Make Sunsets alongside the scaling of the VCM, but don’t expect certification providers such as Verra to work with these producers for a while due to their controversial nature.