Geoengineering: Can it help our planet keep its cool?
Box 2 | The two types of geoengineering
Geoengineering strategies can be divided into two broad groups. The first group of technologies, referred to collectively as carbon dioxide removal (CDR), involves the removal of greenhouse gases (especially carbon dioxide) from the atmosphere. The second type, solar radiation management (SRM), involves the blocking of incoming solar radiation to reduce Earth’s warming or enhancing the reflection of this radiation back to space.
Many people prefer CDR because it means returning greenhouse gas levels to previously recorded levels, so the impacts can be predicted more easily. Many techniques exist to do this. Some may be costly and take a long time to be effective. Others are likely to be less expensive but may also bring with them concomitant advantages to the management our landscapes. In general, they are likely to be accompanied by fewer risks when compared with many SRM options.
Compared with CDR, the effect of blocking solar radiation may be faster and in some cases cost less, but in most cases it would also carry higher risks. And it would be more of a holding operation, since we would not be addressing the issue of greenhouse gas levels. Those would continue to rise. Should SRM fail – it would have to be maintained over many years – we would suddenly be exposed to the effects of higher greenhouse gas levels. We would also not have addressed some of the ongoing consequences of rising carbon dioxide levels; for example, the oceans would have become more acidic, and the pattern of plant life on land would have changed, not necessarily for the better.
Indeed, both types could have unexpected effects on climate and ecosystems – we know from experience that nature can respond to change in unpredictable ways.
Boxes
Box 1. Geoengineering and climate change
Box 3. Governing geoengineering
Related sites
Geoengineering the climate: Science, governance and uncertainty (The Royal Society, UK)
Engineering the climate (Physics World, Institute of Physics)
External sites are not endorsed by the Australian Academy of Science.
Posted February 2010.