A bright, hot sun in an orange-colored sky.

Reflecting solar heat could help cool Earth. Researchers ask: At what cost?

A lot of the climate technologies being developed try to reduce humans’ temperature-rising emissions on Earth. But some research projects are working toward out-of-this-world solutions that bounce heat and sunlight away from Earth and into space.

One example is a Purdue University invention: White paint that keeps building surfaces cooler and projects heat from Earth out into the universe. A University of Wisconsin researcher helped with another innovation — a passive cooling technology — that reflects light waves away from buildings and toward the sky.

Now, a University of Minnesota researcher is part of the Climate Intervention Biology Working Group that released a paper on the ecological effects of solar radiation modification technologies that reflect small amounts of sunlight back into space. Specifically, the research team examined a method called stratospheric aerosol intervention.

The innovation

Stratospheric aerosol intervention, or SAI, creates an aerosol cloud in the stratosphere to reduce the amount of incoming sunlight and radiation that reaches Earth. It puts tiny, reflective molecules in the atmosphere to bounce the solar radiation into space and prevent warming on Earth.

This method on its own doesn’t simply cool Earth by a degree or two. It is complex and potentially impacts numerous ecosystems and climate elements. For example, SAI could prompt shifts in rainfall and increases in surface ultraviolet rays.

The research team took a holistic approach by not examining SAI technology in a silo, but rather a broader view of how it works with other simultaneous real-world occurrences, such as soil absorption of carbon dioxide.

They studied whether reducing greenhouse gas emissions with this kind of geoengineering is overall beneficial or harmful to global biodiversity and ecosystem functions.

“We should only pursue geoengineering if its benefits strongly outweigh its downsides,” Jessica Hellmann, director of the University of Minnesota Institute on the Environment, said in a news release. “We are just starting to consider the risks and benefits of geoengineering, and it’s critical that we include ecosystems in cost-benefit studies.”

Why it matters

The Climate Intervention Biology Working Group’s study emphasizes that little is known about SAI and more research is needed to figure out if the method truly is viable for mitigating the effects of climate change.

But it is different from many other studies because it considers the more widespread and long-term effects of climate change interventions on ecology. It underscores the importance of looking at the big picture when developing and testing technology and creating a cost-benefit analysis.

The researchers encourage other scientists to put a greater focus on ecological impacts when studying climate solutions.

“I hope the paper can convince ecologists that research about nature’s responses to solar geoengineering is not just important, but also interesting — touching on core ecological questions about topics as varied as photosynthesis and animal migration,” said University of Minnesota alumnus Shan Kothari, who contributed to the study during his time at the university.

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