“There are lots of scientific questions about this approach, but it is more appealing to some people than other methods, especially since we already have clouds, and making them a little brighter seems rather innocuous,” Hurrell said.

Why is solar geoengineering controversial? 

While reflecting the sun’s rays away from the Earth could help stabilize or even reduce global temperatures, it’s a Band-Aid that doesn’t fix the actual problem. 

“It doesn’t lower concentrations of carbon dioxide in the atmosphere – in fact, some argue it could even be used as a deterrent to doing the things we must do, like quickly and dramatically reducing emissions,” Hurrell said. “There’s a concern that it could give policymakers an idea that we could manipulate the climate system in some way, which in turn could be a disincentive for decarbonizing.” 

And then there’s the more obvious critique. 

“You’re talking about playing with nature, right?” Hurrell said. “But a counterargument is: We’ve created a problem, we’ve put greenhouse gases into the atmosphere, causing climate change. We’ve already played with nature, and we are not doing nearly enough of the things we need to do to fix the problem we have created.” 

Hurrell is careful to point out that he and others are not advocating to deploy SRM, but simply that climate policy should be based on sound science, and so the science to establish the benefits and risks of these approaches  needs to be accelerated. 

Hurrell and his collaborators model the potential impacts of pumping aerosols into the upper atmosphere to combat climate change, especially on weather and climate, but he emphasizes the need to expand those studies into possible impacts on  agriculture, terrestrial and marine ecosystems, and even human and animal health. 

Then there’s the question of who actually gets to determine the global temperature if SRM was ever used. 

“Who gets to determine the setting of the global thermostat? There are very tricky geopolitical and ethical issues that need to be studied and addressed as well,” he said. “Whether or not SRM should be a tool in our toolbox to combat climate change will require a broad and inclusive conversation among the public, social and political scientists, ethicists, physical climate researchers and others.” 

How do CSU scientists work together to explore different ways of combating climate change?

Just last year, the United Nations Environmental Programme issued a report looking into solar radiation modification – something Hurrell said is evidence that climate intervention is becoming more mainstream and an opportunity for CSU researchers to continue to distinguish themselves. 

“Our team here at Colorado State is one of the top groups in the world examining proposed SRM approaches, and we’ve been on the leading edge of this research over the last several years,“ Hurrell said. 

CSU does not do field work into SRM aerosol injection – instead, researchers use climate models to study its potential benefits and risks. This also presents the opportunity for collaboration across not only the atmospheric science department, but across the entire university. 

“What excites me is the potential we have here at Colorado State to address issues around SRM in a holistic way, in particular by leveraging our considerable strengths in weather and climate science, data science, climate and societal change, human and animal health, agriculture, terrestrial ecosystems and political science, and so much more,” Hurrell said. “CSU has an ability to advance understanding in ways that few institutions can.” 

This potential to make a difference in the fight against climate change gives Hurrell hope. 

“The future is in our control. As an optimist, I remain very hopeful that we will ultimately do what we need to do to mitigate climate change and reduce carbon dioxide concentrations to more acceptable levels. In the meantime, however, we need to determine whether or not SRM could be part of the solution space,” he said.