Earth’s Missiles, Ready to Go?

by Eesha Khare

In 1991, an unusual phenomenon was observed following the volcanic eruption of Mount Pinatubo in the Philippines. After nearly 20 million tons of sulfur dioxide were launched into the stratosphere1—the second largest eruption of this century—the global temperatures dropped temporarily by 1°F. Amid the large-scale destruction, it seemed the Earth was fighting back.

The incident in Pinatubo was a learning opportunity for scientists worldwide. They realized that by manipulating various factors in the Earth’s environment they could work to fight the climate change slowly taking over the Earth. Since the 1950s, scientists have been working on a range of solutions to modify weather conditions. In the context of the Cold War in the 1940s, both the US and the Soviet Union worked on developing scientific techniques such as seeding clouds with substances, which allowed scientists to force more rain, create advantageous conditions for battle, and help agriculture in dry regions.2

This was the birth of geoengineering, or climate engineering, in which artificial modifications of the Earth’s climate systems are made in response to changing climate conditions.3 Geoengineering is focused on two main areas: carbon capture and solar radiation management. Since its advent, geoengineering has become a hot, controversial topic, as the risks and rewards of geoengineering solutions are slowly being detailed. On one hand, geoengineering solutions offer a promising approach to artificially reversing recent climate trends, especially in light of the Pinatubo eruption. Yet on the other hand, these same solutions present a number of risks regarding the side effects and controllability of geoengineering. As we move into the future, the need to counteract increasing climate disturbances is becoming even more pressing, making our search for a solution all the more important.


As previously stated, geoengineering solutions can be broken into two main areas: carbon capture and solar radiation management. Within each area, the stages of research are broken down into theory and modeling, subscale field-testing, and low-level climatic intervention. Of these, the latter two stages are seldom reached.3

Carbon capture techniques work to remove the amount of carbon dioxide in the atmosphere, thereby counteracting carbon dioxide emissions that result in the greenhouse effect. At the simplest level, there is a movement to encourage increased planting of trees, termed afforestation, in order to have trees consume carbon dioxide during their photosynthetic process. While initially economical and practical, afforestation would not produce very large reductions in temperature. According to a 1996 comprehensive study, researchers found that the average maximum carbon sequestration rate would be between 1.1 to 1.6 gigatons per year, compared to the 9.9 gigatons per year currently released into the atmosphere, a mere 11 to 16%.4 On top of that, annual sequestration rates would change year to year, as these rates are highly dependent on annual weather conditions. Furthermore, the location of tree planting is critical, as forests absorb incoming solar radiation. When planted at high latitudes, trees can actually lead to net climate warming.5

Some other techniques have focused on re-engineering plant life to capture carbon. This includes biochar, charring biomass and burying it so that its carbon content is kept in the soil, and bio-energy carbon capture, or growing biomass and then burn ing it to capture energy and store carbon dioxide. Many treatments have also focused on the ocean life, particularly the populations of phytoplankton that are responsible for nearly half of the carbon fixation in the world.6 Ocean fertilization, or adding iron to parts of the ocean to promote phytoplankton growth and subsequent carbon dioxide uptake, and ocean alkalinity enhancement, or adding limestone and other alkaline rocks to enhance carbon capture and counteract increasing ocean acidification, have also come up as possible techniques. However, the limiting factor is the lack of translation from small-scale ocean fertilization to larger-scale consequences.7

Solar radiation management is another broad category that has gained prominence over the past few years. In this technique, various measures are used to reflect some of the Sun’s energy back into space and thereby prevent the Earth’s temperature from rising. Albedo engineering, the main subset of this category, focuses on enhancing the albedo, or fraction of short-wave solar energy, reflected back into space. Harvard Professor David Keith is a strong advocate of achieving albedo engineering by launching sulfate particles above the ozone layer, mimicking the eruption and effects of Pinatubo. You would have to deliver nearly one millions tons of SO2 every year using balloons and rockets in order to see some effect. While the sulfur does not reduce the amount of carbon dioxide in the atmosphere, it helps offset its effects by reflecting solar radiation away from the earth. The cost is also quoted to be relatively inexpensive, at only $25-50 billion a year.8 Another solar radiation management technique is cloud whitening, where turbines are used to spray fine mist with necessary salt particulates into the low-lying stratosphere above the oceans, thus making them whiter and increasing scattering of light. While this technique would change precipitation patterns, it localizes the solution to the oceans,9 unlike the sulfate launch, which targets the whole stratosphere.

Former Harvard physicist, Russell Seitz, wants to trap bubbles in the ocean water, by increasing the sunlight submerged in the bubbles and thereby whiten the water. This process would result in undershine, similar to the previously proposed ideas of brightening roofs to offset the CO2 in the air and increase the reflectivity of the air. Again, his solution proposes a series of technical challenges but still highlights the core principles of the geoengineering movement.

One of the main challenges in such work is that creating the climate engineering solutions at a small scale for testing is very difficult, if not near impossible. This raises the question—can we really test geoengineering? Cambridge University Professor Hugh Hunt works to answer that exact question, and in 2011, he tried to launch a small-scale experiment of dispersing sulfur dioxide over Norfolk as a part of the SPICE (Stratospheric Particle Injection for Climate Engineering) consortium in the UK.10 Even this experiment was met with high levels of resistance and ultimately stopped before it could be carried out. Since then, a number of other interesting projects have been developed, such as an ice protector textile coated over a small glacier in the Swiss Alps to reflect light and slow ice melt.11


The radical and far-reaching geoengineering solutions presented in this article have raised a number of technical and political issues among the research and local community. For example, while sulfate aerosols would last for a couple of years, a number of concerns have been raised about the side effects of acid rain and ozone damage. However, beyond the technical problems, geoengineering solutions have also become extremely controversial in the political space, as political leaders are forced to deal with the debate over usage of these techniques. From a policy standpoint, opponents of geoengineering fear that introducing such solutions would disincentivize governments and corporations from reducing anthropogenic carbon dioxide emissions, the root of this environmental problem.11 They argue that “technofixes,” or technical solutions to social problems, are falsely appealing, as they do not provide real solutions to the social and political environment causing these problems.12 Further, they also worry that the reduced cost and speed of implementation may result in certain countries adopting solar radiation management techniques without consulting other neighbors and thereby indirectly affecting international policy through their national measures. It is clear that, with the increasing likelihood of the need to implement geoengineering solutions, developing a new national and international policy framework is necessary for further action.


It is clear that, with the increasing fluctuations in Earth’s climate, rapid training of natural resources, and scaling degree of globalization, solutions to preserve and protect the Earth’s environment are not just desirable, but extremely necessary. While geoengineering presents promising solutions, it also raises a number of economic, political, and environmental concerns that will likely prevent its full-scale integration. While many geoengineering solutions will likely continue being contested and therefore underdeveloped, it is worth noting that taking a greater focus in specific carbon-capture based technologies, such as chemically catalyzed reactions for “carbon”-fixation, would enable the same level of climate impact without the side effects. Although challenges abound, the development of carbon capture technology must be the next step in this fight to save this planet.

Eesha Khare ‘17 is a junior in Leverett House, concentrating in Engineering Sciences.

Works Cited

  1. Diggles, M. The Cataclysmic 1991 Eruption of Mount Pinatubo, Philippines. U.S. Geological Survey Fact Sheet 113-97.
  2. Victor, D.G. et al. The Geoengineering Option. Foreign Affairs. Council on Foreign Relations. March/April 2009.
  3. What is Geoengineering? Oxford Geoengineering Programme. 2015.
  4. Land Use, Land-Use Change and Forestry. Intergovernmental Panel on Climate Change.
  5. Arora, V.K.; Montenegro, A. Nat. Geoscience 2011, 4, 514-518.
  6. Chisholm, S. W. et al. Science. 2001, 294(5541), 309-310.
  7. Strong, A. et al. Nat. 2009, 461, 347-348.
  8. Crutzen, P. J. Climatic Change 2006, 77(3–4), 211–220.
  9. Morton, O. Nat. 2009, 458, 1097-1100.
  10. Specter, M. The Climate Fixers. The New Yorker [Online]. May 14, 2012.
  11. Ming, T. et al. Renewable and Sustainable Energy Reviews 2014, 31, 792-834.
  12. Hamilton, C. Geoengineering Is Not a Solution to Climate Change. Scientific American [Online]. March 10, 2015.

Categories: Fall 2015

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