Geoengineering: Can it help our planet keep its cool?
Box 1 | Geoengineering and climate change
To understand how geoengineering might work, we need to review the essentials of man-made global warming.
The sun is a major source of energy for changes on the earth's surface. About a third of the solar energy that arrives at the surface of the Earth is reflected back to space from clouds, dust in the atmosphere and the Earth’s surface. The Earth’s surface absorbs the remaining solar energy, warming up and causing it to emit thermal radiation. As thermal radiation is emitted back towards space, it is partially intercepted and absorbed by atmospheric molecules, including water vapour, carbon dioxide, methane and ozone. These gases re-radiate some of this energy back to the Earth. This effectively traps some of the heat in the lower levels of the atmosphere, warming it and profoundly influencing our weather and climate. This effect is called the greenhouse effect.
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| Geoengineering schemes to deliberately alter the Earth’s climate. (Image: IPCC 2007) |
This is no new phenomenon; the process has been at work for billions of years, making our planet habitable. Without this ‘greenhouse effect’ the surface of our planet would be 30 degrees colder than it is, frozen over and lifeless. But in the last century or so, the amounts of the key ‘greenhouse gases’ such as carbon dioxide and methane, have been rising due to human activities, including the burning of fossil fuels for energy. This has warmed the Earth more than normal, bringing with it other changes to Earth’s climate.
The obvious way to head off this danger is to reduce the amounts of greenhouse gases we produce. Such changes are more easily talked about than achieved, and are likely to take many years to have a significant effect. Hence the interest in geoengineering as another avenue of attack in case we fail to reduce greenhouse gas emissions sufficiently. Geoengineering would work by blocking some of the incoming energy from the sun or by removing some of the greenhouse gases from Earth’s atmosphere.
Boxes
Box 2. The two types of geoengineering
Box 3. Governing geoengineering
Related site
Enhanced greenhouse effect – a hot international issue
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Posted February 2010.