Solar Radiation Management Overview
Solar radiation management, according to the Solar Radiation Management Government Initiative (SRMGI 2018), is an approach to theoretically remove some effects climate change has on the Earth by reflecting incident sunlight back out into space. The effects of solar radiation management are to not reduce the amount of greenhouse gas concentrations in the atmosphere as the previous method (carbon dioxide removal) mentioned, however, instead this method paves ways to reduce rising global temperatures. There are many ways in which solar radiation management could be implemented which include space-based and surface-based operations.
Solar Radiation Management: Space-Based Operations
Space-based solar radiation management, as the name indicates, takes place in outer space. Space-based operations would be an attempt to block portions of sunlight before it reaches the Earth’s atmosphere. According to Pluijm (2017), solar radiation management would help to offset the warming effects of greenhouse gases by allowing the Earth to absorb decreased amounts of solar radiation. Reflecting solar radiation can be done through one way which is the utilization of space mirrors (see Figure 2). Reflecting solar radiation using space mirrors was first proposed by, according to Kaufman (2012), Lowell Wood of Lawrence Livermore National Laboratory. Wood proposed the use of an enormous mirror or a multitude of mirrors to deflect sunlight back into space. Wood calculated that even by deflecting a mere one percent of sunlight would significantly reduce the effects of climate change. The space mirror in question would have to be enormous and roughly have an area slightly smaller than Greenland, at six hundred thousand square miles. Launching something like this would be nearly impossible due to not only the size, but the cost. An effective way to implement this device would be to build it in space, which may risk the lives of the engineers who build it. Also, a mirror this size would be extremely difficult to maintain. Debris from broken satellites, small meteorites, comet tail debris, and other facts would make this a nightmare to maintain and build. Thankfully, other measures have been investigated.
According to Kaufman (2012), another option was proposed in 2002 by a space consulting firm known as Star Technology and Research. This option explored the idea of creating a network of steerable mirrors that would orbit Earth’s equator. According to the calculations, this network could lower the average global temperature by as much as three degrees Celsius (or 5.4 degrees Fahrenheit), while at the same time, using onboard solar panels to harness the energy captured and sending that energy to a facility on Earth. However, a major problem arises within the idea itself. To obtain the effect of dropping the average global temperatures by three degrees Celsius, the president of Star Technology and Research Jerome Pearson, according to Kaufman (2012) stated that it would take nearly five million spacecrafts to generate such a result, which means, in terms of repairs, approximately one hundred thirty-seven of these spacecrafts would need replaced or repaired daily. Since both these ideas are most likely unrealistic with modern day technology, we must explore other ideas (Kaufman, 2012).
Solar Radiation Management: Surface-Based Operations
Many ideas have been investigated to help reduce the effects of climate change. Idea that have been discussed include changing the color of rooftops on a multitude of structures and by adding reflective sheets in desert areas.
Solar Radiation Management: Reflective Rooftop Colors
In recent studies, according to Biello (2014), painting rooftops white may offset the effects of global warming (see Figure 2).
According to Georgescu et al (2013), by painting rooftops white, we can reflect more sunlight back out into space, which, in turn, can offset warming due to urban expansion. Urban expansion is currently contributing to the effects of global warming. The albedo of a surface is, according to the National Snow and Ice Data Center, a non-dimensional, unitless quantity that represents how well a surface can reflect sunlight. The albedo of a surface ranges from zero to one; zero being a black surface which completely absorbs incident radiation and one being a white surface which completely reflects incident radiation As more buildings and other structures replace forests and trees, the average temperature in that area rises due to the urban heat island effect. The urban heat island effect is an urban area that is much warmer than the surrounding rural areas due to increased human activity. According to models developed by the Environmental Protection Agency (EPA), the amount of urban areas within the United States may increase by as much as one million square miles by 2100.
The idea of implementing the color changes would have, at least, some effect on the average global temperature rise. For example, according to Biello (2014), New York City contains one hundred square kilometers of black-colored rooftops. These black-colored rooftops allow the heat to be absorbed, thus making New York City hotter. As part of the Cool Roofs project, volunteers in NYC have been changing the color of the rooftops from black to white to enhance the reflection of sunlight to produce a cooling effect. However, according to Biello (2014), only five hundred square meters of roof have been painted thus far, which amounts to less than one percent of NYC’s rooftops. This idea, although intriguing and possibly effective, proves to be a hard-to-achieve method due to lack of support from communities. However, another method has been discussed recently.
Solar Radiation Management: Reflective Sheeting in Desert Areas
The implementation of adding reflective sheeting in desert areas seems like a radical idea, however since desert regions receive large amounts of sunlight, adding reflective sheeting in these areas may help reduce the effects of global warming. By adding reflective sheeting to deserts, the albedo can be altered. By adding reflective sheets within desert regions, we can effectively raise the albedo, thus allowing for the reflection of more sunlight. However, due to increased carbon dioxide levels within Earth’s atmosphere, this method, although reducing incoming solar radiation by 1.74 watts per meter squared, would not mitigate the Arctic shrinkage (see Figure 3), which is one of the major effects resulting from global warming.
Overall, many ideas have been discussed to increase the reflection of sunlight back into outer space, however most of the ideas are either too expensive, nearly impossible to achieve, or do not counteract varying effects of climate change. However, the next blog will focus on ways to increase cloudiness in particular regions, which may help reduce global temperatures as well as deflect sunlight away from the ice caps and other ice-covered regions on planet Earth.
Cool Roofs Might Be Enough to Save Cities from Climate Overheating (Biello, 2014)
Could Space Mirrors Stop Global Warming (Kaufman, 2012)?
Editor’s Vox: Good Night Sunshine: Geoengineering Solutions to Climate Change (Pluijm, 2017)?
Fix for Global Warming? Scientists Propose Covering Deserts with Reflective Sheeting
Solar Radiation Management Governance Initiative
What is the Urban Heat Island Effect?