As governments and researchers search for ways to slow global warming, one of the most controversial climate proposals under discussion involves reducing the amount of sunlight reaching Earth. But a new study suggests the approach could create risks far beyond the climate system itself.

The technique, known as stratospheric aerosol injection (SAI), has been proposed as a way to temporarily cool the planet by releasing reflective particles high into the atmosphere. These particles would bounce a portion of the Sun's energy back into space, potentially lowering global temperatures.

Supporters argue that the idea could buy valuable time as countries work to cut greenhouse gas emissions. Critics, however, have long warned that altering the atmosphere on a large scale may produce unintended consequences.

Researchers from Rutgers University are now highlighting another concern: aviation safety.

According to the study, the sulphur dioxide that would likely be used in large-scale SAI programs could remain suspended in the stratosphere for extended periods before eventually forming sulphate aerosols. Because commercial aircraft regularly operate near the lower stratosphere on some routes, scientists say the presence of these particles could expose aircraft and passengers to elevated concentrations of airborne pollutants.

Lead researcher Professor Alan Robock noted that conditions in the stratosphere differ dramatically from those closer to Earth's surface. Unlike lower layers of the atmosphere, where rain and weather systems help remove pollutants, particles released into the stratosphere can persist for much longer periods.

That persistence is one reason geoengineering remains one of the most debated ideas in climate science.

The latest findings add to a growing body of research examining the potential side effects of large-scale solar geoengineering. Previous studies have explored whether widespread deployment could alter rainfall patterns, influence regional weather systems, or create uneven climate impacts across different parts of the world.

The concept remains largely theoretical, and no global SAI program currently exists. Scientists continue to debate whether the potential cooling benefits outweigh the environmental, political and public-health risks associated with intentionally modifying the atmosphere.

Researchers estimate that millions of tonnes of sulphur dioxide would be required annually to produce a measurable cooling effect. While some climate models suggest such interventions could temporarily reduce global temperatures, experts caution that geoengineering would not address the root cause of climate change: the continued accumulation of greenhouse gases in the atmosphere.

For now, the debate over SAI highlights a broader question facing policymakers and scientists alike—whether humanity should attempt to engineer its way out of climate change, or focus entirely on reducing emissions before more drastic measures are considered.