Solar geoengineering 'could be safe'

Posted by Kate Taylor

Solar geoengineering can be safely tailored to manage specific risks like the loss of Arctic sea ice, says a group of researchers keen to persuade the world that such techniques aren't necessarily a disaster waiting to happen.

By increasing the concentrations of aerosols in the stratosphere or by creating low-altitude marine clouds, such projects would scatter incoming solar heat away from Earth's surface, reducing the effects of climate change.

However, critics say that such a global intervention would have unequal effects around the world and could result in unforeseen consequences that could be a lot worse than the problem they're designed to prevent.

The answer, says Gordon McKay, professor of Applied Physics at the Harvard School of Engineering and Applied Sciences (SEAS), lies in a new model designed to maximise the effectiveness of solar radiation management while decreasing the risks.

"We can be thoughtful about various tradeoffs to achieve more selective results, such as the trade-off between minimizing global climate changes and minimizing residual changes at the worst-off location," he says.

The study focuses on the feasibility of using solar geoengineering to counter the loss of Arctic sea ice.

"There has been a lot of loose talk about region-specific climate modification. By contrast, our research uses a more systematic approach to understand how geoengineering might be used to limit a specific impact," says McKay.

"We found that tailored solar geoengineering might limit Arctic sea ice loss with several times less total solar shading than would be needed in a uniform case."

Generally speaking, greenhouse gases tend to suppress precipitation, and cutting the amount of sunlight absorbed by Earth wouldn't bring this precipitation back. Both greenhouse gases and aerosols affect the distribution of heat and rain on this planet - but change the temperature and precipitation in different ways in different places.

The researchers suggest that varying the amount of sunlight deflected away from Earth both regionally and seasonally could combat some of this problem.

"While more work needs to be done, we have a strong model that indicates that solar geoengineering might be used in a far more nuanced manner than the uniform one-size-fits-all implementation that is often assumed," writes the team.

"One might say that one need not think of it as a single global thermostat. This gives us hope that if we ever do need to implement engineered solutions to combat global warming, that we would do so with a bit more confidence and a great ability to test it and control it."