Thursday, January 31, 2013

Climate Changes

Climate change is correctly regarded as one of the greatest threats to humanity in the 21st century and with many of the world’s governments reluctant to reduce greenhouse gas emissions it looks unlikely that we will be able to stop global temperature rises over the coming decades by reduction and substitution alone.

Geoengineering may offer another route to preventing excessive global temperature rise; geoengineering is a branch of engineering that intentionally manipulates earth system processes. A promising technique known as stratospheric aerosol injection (SAI) would reflect incoming solar radiation thereby lowering surface temperatures, in other words it would create global dimming to counter balance global warming.

SAI would inject sulfide gases such as sulfuric acid, hydrogen sulfide or sulfur dioxide by highflying artillery aircraft into the stratosphere. Estimations by the Council of Foreign Relations state, “one kilogram of well placed sulfur in the stratosphere would roughly offset the warming effect of several hundred thousand kilograms of carbon dioxide”.

There are both many positives and many negatives to SAI.
Possible positives include:

- Cost, estimated at costing between $25-50 billion a year it works out over a 100 times cheaper than producing the same temperature change by reducing CO2 emissions.
- Technological feasibility, all the technology for this to work exists.
- Natural process, volcanoes naturally do this same process.
- Speed of action, temperatures would change quickly after the sulfur is injected as the solar radiation is reflected back into space.
- Efficacy, SAI has the potential to completely control the temperature change by adding more or less as required. Factors such as delivery, distribution and lifespan of the aerosols do still need more research to be fully addressed.

Possible negatives include:

- If stopped after many years of use the short lived aerosols would no longer work after a few years leaving the world to heat very quickly as all the longer-lived carbon that it had been offsetting would take effect heating the world very quickly.
- Drought, as risk of monsoon failure in Asia/ Africa.
- Ozone depletion
- Tarnishing the sky, the potential to affect the appearance of the sky resulting in a whitening effect.
- Ecosystems, plant growth may be affected and an increase in ocean acidification due to acid rain.

As the results of climate change are increasingly felt around the world, SAI may provide a get out of jail free card but the cost in doing so could trigger many other problems in the process. More research and modeling is needed before SAI is seriously considered.

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