Is Blocking Out Sunlight to Reduce Global Warming Viable?


One of the more unique propositions for controlling global warming is to block out solar radiation with the strategic spraying of tiny reflective particles into the upper atmosphere. Recently, Asfawossen Asrat of Addis Ababa University and Andrew Parker, a Fellow at Institute for Advanced Sustainability Studies, spoke with The Conversation about the risks and opportunities such an approach would carry.

According to the experts, solar radiation management is the idea that blocking out a small amount of sunlight could reduce some of the risks of global warming. Though the idea may sound like science fiction, it is seriously being considered by climate scientists. The process involves spraying reflective particles, like sulfur dioxide, into the upper atmosphere where they would reflect away some of the energy of the sun before it reaches Earth’s lower atmosphere. An alternative approach involves spraying sea water into clouds at low altitude, where the tiny droplets would function as nuclei to form whiter, more reflective clouds.

Computer modeling of the potential impacts has been done, and a few small-scale experiments have been run outdoors, including one experiment in America on ‘marine cloud formation’ and an experiment in Russia on ‘reflective aerosols’. Scientists at Harvard announced plans to conduct another small scale experiment this year in order to understand how adding aerosols to the atmosphere might impact atmospheric chemistry.

Is Blocking Out Sunlight to Reduce Global Warming Viable?

While solar radiation management will not reduce greenhouse gas emissions, it could buy more time by reducing some of the risks of global warming until emissions are under control. Asrat and Parker say that even if dramatic cuts were made to carbon emissions, at a quick pace, the Earth would continue to warm for decades to come. Much of the reason this happens comes from the fact that carbon dioxide stays in the atmosphere for a long time. Solar radiation management, therefore, is currently the only known way to stop the rise of global temperatures in the near future. It has the potential to stop effects of global warming like rising temperatures and sea levels.

Due to how vast and interconnected the climate is, solar radiation management could also possess risks from unseen and undesired effects, say Asrat and Parker. For instance, if sulfur dioxide was used as a reflective aerosol, it might delay the regeneration of the ozone layer. It also has the potential to impact precipitation, in some areas, depending on how it is used. There is also some concern over possible health effects due to the inhalation of sulfur dioxide, which is known to cause lung problems. Finally, there are effects which are just impossible to predict due to how complex the planet’s climate is.

The risks and rewards of solar radiation management will have to be carefully weighed and thoroughly explored if the system is intended to be put to use.