An introduction to geoengineering

Geoengineering has been termed "the deliberate large-scale manipulation of the planetary environment to counteract anthropogenic climate change" (The Royal Society 2009).  Although I'm aware of certain techniques being developed to mitigate climate change over the past decade or so; I didn't realise there were quite so many technologies being innovated and tested.  I find the paper produced by the Royal Society in 2009 is referenced in lots of the papers and articles I'm reading about this subject and it provides a good summary of the main geoengineering proposals. 

Large-scale methods being developed to save the planet fall into two main categories - carbon dioxide removal (CDR) and solar radiation management (SRM).  The main difference between the two is that SRM techniques are concerned with reflecting or deflecting solar energy mainly in the stratosphere, thus reducing the amount of thermal energy reaching the atmosphere and to Earth.  In contrast, CDR techniques actually remove the amount of carbon dioxide in the atmosphere to cool the Earth by allowing infrared waves to exit more easily.  Below I found some diagrams summarising some of the methods being developed:

(Kerr 2006)

Overall SRM tend to be more favourable in terms of readiness and effectiveness.  However, these can be considered as more short-term techniques as they only limit or decrease global temperatures.  Studies suggest SRM produces unintentional environmental effects in the way of altering global weather patterns and ocean currents, which could produce ill-effects in some parts of the globe.  More research is required into the effects SRM will have upon global climate patterns, their sustainability and other potential risks .
CDR tends to be considered safer; but obviously a greater deal of research and refinement is required in order to be employed on a global scale.  Effectiveness of CDR techniques is considered to be lower, but this may be due to the fact removing carbon dioxide from the atmosphere will take years or decades before global temperatures reduce noticeably.

(Maynard 2009)

CDR techniques may be more acceptable in some societies due to the fact they have less associated risks.  Additionally they are more sustainable in the way they actually remove the carbon dioxide currently residing in the atmosphere - CDR techniques coupled with reducing emissions may be the key to fixing the climate due to the fact they are sustainable.  However, the extent of the error bars provided on the diagram above illustrating uncertainties show how much more work needs to be applied in terms of developing and refining the methods we already have available, therefore the future is still uncertain.

This aside, although geoengineering is obviously going to be a big part of the future in terms of mitigating climate change; I think it is also very important to continue to promote public awareness of the issue and to continue efforts to reduce greenhouse gas emissions as opposed to just applying technology to try to cool the planet.  Geoengineering creates moral issues in terms of lessening the pressure of emissions reductions, but I'll look at this debate another time.