The rapid increase in global CO2 concentration and temperature has raised the concern that the climate could reach a tipping point which could lead to rapid and massive climate change. Researchers have begin looking at options for climate engineering to mitigate the effects of rising greenhouse gas emissions in the short term.

A recent report Geoengineering the Climate by the Royal Society provides a detailed assessment options for mitigating the effects of global climate change. It divides geoengineering methods into two categories;

Carbon Dioxide Removal (CDR)
Removing CO2 from the atmosphere address the root cause of climate change, rising CO2 concentrations. These are beleived to be low risk, but work very slowly to reduce global temperatures.

Solar Radiation Management (SRM)
These methods are intended to reflect a small percentage of the sun’s light and heat away from the Earth. They do not address the root cause, rising CO2 levels, but act quickly, and so may be the only way to lower global temperatures quickly in the event of a climate crisis

The report recommends:

• Increased efforts towards mitigating and adapting to climate change.
• Considering CDR and SRM geoengineering methods as part of a wider package of options for addressing climate change.
• CDR methods should be regarded as preferable to SRM methods.
• Funding a 10 year geoengineering research programme at a level of the order of £10million per annum.
• That the Royal Society develop a code of practice for geoengineering research and recommendations for governance.

The SPICE project
The Stratospheric Particle Injection for Climate Engineering (SPICE) project, which is supported by the Engineering and Physical Sciences Research Council (EPSRC), the Universities of Bristol, Cambridge, Edinburgh, and Oxford, the Met Office, and Marshall Aerospace, was created to investigate one of these, solar radiation management (SRM) through the injection of reflective aerosol particles into the Earth’s upper atmosphere.

The proposed delivery system is a balloon tethered by a 25 km pipe that would allow fluids to be injected into the upper atmostphere. The first experiment, led by the University of Bristol, will hoist one end of a one kilometer long hose using a balloon, then pump a fluid up to it and spray it into the atmosphere. The first test will use water, but the intended materials would be sulphate aerosols of the type injected into the atmosphere from volcanic eruptions.

However, criticism has pushed the scheduled time for the experiment back by six months to allow for more public consultation.