Serious concerns about Stardust's sunlight-reflecting particles

The American-Israeli startup Stardust Solutions previously raised $60 million to test its controversial “sun-reflecting” technology in the field. The company aims to cool the Earth by spraying sunlight-reflecting particles into the stratosphere. However, these plans have met with fierce opposition. The scientific community has expressed serious concerns about the unpredictable risks of these climate interventions. Researchers warn that a private company should not be allowed to control the global thermostat.

'Way too fast'

Global warming is forcing humanity to take drastic measures. Stardust Solutions has opted for an extremely radical approach. The startup plans to conduct its first outdoor experiments with its sunlight-reflecting technology as early as April 2026.

However, this commercial drive stands in stark contrast to the academic world’s approach. Traditional research into climate interventions is subject to strict, public oversight mechanisms. Stardust is not a fan of this cautious route.

Critics, including researcher Douglas MacMartin of Cornell University, believe that Stardust is moving far too quickly. They warn against exaggerated commercial claims and a total lack of transparency regarding the materials used. In their view, the development of a global thermostat simply has no place in the hands of a for-profit commercial entity.

Numerous risks

Moreover, scientists worldwide are expressing serious concerns about the safety of these sunlight-reflecting technologies. The method does not address the actual cause of climate change. It merely masks the symptoms of a warming Earth. Greenhouse gases continue to accumulate unabated in the atmosphere, while the artificial dust particles temporarily block sunlight. The worst-case scenario is known as the “termination shock.” Imagine that humanity sprays reflective particles into the air for decades and then suddenly stops doing so due to a conflict or financial collapse. The accumulated heat would then strike in a single, merciless blow. Global temperatures would skyrocket at an unprecedented rate. Vulnerable ecosystems and human societies would have absolutely no time to adapt to this abrupt heatwave. The consequences for global biodiversity and agriculture would be catastrophic in that scenario.

There is another problem. Artificially cooling the Earth via the stratosphere does not work the same way everywhere on the planet. The sprayed particles spread uncontrollably across the globe via strong winds. This leads to inevitable and drastic shifts in regional weather patterns. Local harvests could collapse entirely, causing prices of staple foods on the European and global markets to skyrocket.

Scientists also warn of the fundamental unpredictability of the technology. We simply do not understand the complex interactions of our climate system well enough to foresee the consequences. An intervention on this immense scale could trigger unforeseen chain reactions in the atmosphere. According to many academics, the risks of such large-scale experiments are too great.

A lack of international rules

The rapid rise of companies like Stardust exposes a painful problem. There is currently a glaring lack of binding, international regulations for geoengineering. In theory, large-scale climate interventions fall under a de facto moratorium imposed by the UN Convention on Biological Diversity. This international treaty stipulates that countries may not apply the technology on a large scale. However, it does not explicitly prohibit small-scale, commercial research. In practice, this creates a dangerous legal gray area. This vacuum inevitably attracts commercial cowboys.

It’s happened before

A notorious example of this is the American startup Make Sunsets. In the past, this company released weather balloons containing sulfur dioxide in Mexico without any permission or consultation with the local population. The Mexican government responded immediately with a strict total ban on such experiments within its borders.

To prevent such unilateral actions in the future, there is a growing call for firm, global agreements. Nearly six hundred leading academics and two thousand civil society organizations are now advocating for an international “Non-Use Agreement.” This treaty must permanently ban the development and outdoor testing of sunlight-reflecting technologies worldwide.