Stratospheric sulfate aerosols

This is a solar radiation management technique; and from what I've been reading this idea seems very promising.  A previous post of mine summarised the technique to have high effectiveness - the technology is also developed and ready to be implemented.  There were however concerns over safety and cost.  Luckily I found some facts to rubbish these allegations:
- Crutzen (we all know and trust him because he termed the anthropocene) estimated the technique to be x100 cheaper than cutting CO2 emissions ($25–50 billion a year).
- Sulfur injections into the stratosphere are a natural phenomena (i.e volcanic eruptions) and there is substantial evidence these cool the planet.

Basically the science behind it is, injecting a sulfide gas (H₂S or SO₂ mainly) into the stratosphere.  In fact any aerosols scatter sunlight, but sulfides are advantageous as they can be introduced as gases (Katz 2010) meaning particles don't clump together, hence enhancing the albedo effect. Once up there, the particles scatter incoming solar energy before it reaches the surface.  Apparently, reducing solar input by just 2% balances out the effect on global temperatures of a doubling of CO₂ (The Royal Society 2009).

There is some debate surrounding the most effective and feasible way of inserting the gases at such a great height.  Currently, it has been proposed this could be achieved by aircraft, military guns or high-altitude balloons.  This aspect is important, as the lifespan of aerosols in the trophosphere is short due to them being washed out.  Additionally, more research is required into where on Earth they should be delivered in order for them to be evenly distributed around the globe.

Unfortunately there are some risks and side effects associated with this method of solar radiation management, including:

• Acceleration of ozone depletion
• Increase in drought severity
• Possibly only short-lived
• Requires continuous injections of sulfides
• Altering the appearance of the sky and sunsets
• Dry fallout of particles

However more work is required in order to examine these side effects more thoroughly.  I think a disadvantage of this method is that as it is not widely used (yet), and studies into the effects are heavily based upon modelling; which contain errors.  I'm going to look at a paper which investigates one of these associated negative effects (the amount of sulfur deposition to the Earth's surface) using modelling to further evaluate this technique.  At the moment though if I had $25-50 billion I'd definitely pay for this!


Also this is good, 20 reasons why geoengineering may be a bad idea.  But it still didn't change my mind!  I don't think emission mitigation is going to be enough to help us in the future.  Personally I'm not bothered if the sky looks a little whiter, as long as it keeps the world cooler!