Geoengineering is seen by some as a quick and easy way out of global warming, and by others as dangerous, unpredictable and just another excuse not to cut carbon emissions. But what actually is it? Well, there is no generally accepted definition, but anything that can be classed as a large-scale scheme to manipulate the effects of global warming would probably fit the bill. There are a variety of ways this manipulation can be done, however most methods can be split into two categories: solar radiation management and greenhouse gas remediation. In other words, reducing the amount of sunlight reaching the Earth, or soaking up greenhouse gasses from the atmosphere.
The first category includes techniques intended to increase the albedo (or reflectivity) of the Earth, for example sending billions of aluminised reflective balloons into the atmosphere, or positioning a giant mirror in space that would act as a sunshade between the Sun and the Earth. One of the most noteworthy of these types of proposals is one that aims to inject up to two metric tons of sulphuric aerosols into the atmosphere, which would then act as condensation nuclei and influence the micro-physical and optical properties of clouds. This is the idea of Dutch Professor Paul Crutzen, who won the Nobel Prize for Chemistry in 1995 when he and his colleagues discovered the cause of the hole in the ozone layer. Mount Pinatubo has already shown that this method would succeed in reducing the average global temperature; after it’s eruption in 1991, sunlight reaching the Earth was reduced by 10% and temperatures decreased by 0.5°C over the globe, staying at their new level for 3 years on average. However, ozone destruction also increased substantially and the average precipitation worldwide dropped significantly in the 16 months following the eruption.
The second major type of geoengineering method involves enhancing natural “carbon sinks”. Fertilising the oceans with iron to stimulate phytoplankton growth falls into this category, as does reforestation. These processes aim to attack the rising levels of greenhouse gases, and hopefully lock them away for years to come.
There are plenty of advantages to geoengineering. For instance, a lot of the methods that decrease the amount of sunlight hitting the earth would be very cheap to implement – it would be possible to create a new ice age for around 0.01% of the USA’s gross domestic product by decreasing global temperatures. Also, the changes resulting from applying geoengineering methods would appear much more quickly than any changes arising from cutting emissions, suggesting that it may be a good way to buy the Earth some time while we wait to see the results of emissions cuts.
Criticisms are also easy to come up with. It has been argued that these techniques will only put off the inevitable, and while doing so risk making politicians and others complacent about emissions cuts. What’s more, little detailed research has been done into some of these methods, so there may be unintended consequences that we know nothing about at present. For example, reducing solar input could result in lowering crop yields, which could cause famine.
In an ideal world, to combat global warming we would cut emissions by the 60-80% needed to stabilise the concentration of CO2 in the atmosphere. However, from 2001 to 2002 emissions actually increased by 2% and this trend doesn’t look set to change much in the near future. Soon, some geoengineering methods may become necessary to stop drastic climate heating before it’s too late.