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Two Main Categories of Geoengineering

What are the two main categories of geoengineering?
© Adam Smith Centre

Two Main Categories

There are two main categories of geoengineering. One is shading the earth from solar radiation, of which the shroud of sulphates in the stratosphere is emerging as the quickest, most effective, and least costly. The other is to remove more CO2 or other greenhouse gases from the atmosphere.

These are two main categories of geoengineering:

  • Carbon Dioxide Removal (CDR) – taking carbon dioxide out of the atmosphere
  • Solar Radiation Management (SRM) – reflecting sunlight to cool the planet

Carbon Dioxide Removal (CDR)

The Intergovernmental Panel on Climate Change (IPCC) has already stated that it considers CDR to be a necessary mitigation pathway. The anticipated role of CDR in mitigating the effects of climate change has important implications for its regulation.

CDR technologies aim to take carbon dioxide out of the atmosphere, creating essentially “negative emissions,” to lower atmospheric greenhouse gas concentrations and reduce warming.

Carbon dioxide removal is the more direct and less risky of the two groupings, and it addresses excess CO2. The most commonly cited modes of CDR are afforestation (planting new forests) and reforestation (restoring forestland). These methods leverage photosynthesis, a naturally occurring process, to take up carbon dioxide.

Solar Radiation Management (SRM)

SRM technologies aim to reflect incoming sunlight away from the Earth with clouds or other reflective substances, thereby reducing the warming of the atmosphere.

One reason why climate scientists believe SRM can possibly work is because of Mount Pinatubo’s eruption. This volcanic eruption happened on June 15 1991, in the northwest of the Philippines. It produced a gas cloud that reached the stratosphere. The cloud itself lowered the Earth’s temperature for four years. Sulphur dioxide in the cloud created particles which spread around the Earth. These then reflected some of the sun’s rays into space. Climate scientists have since looked back to mimic the effects of this phenomenon to lower global warming.

© Adam Smith Centre
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Climate Change and Public Policy

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