An Overview of Geoengineering

Zion Lights
Sunday, 18th August 2013

Zion Lights explores the use of geoengineering techniques in the battle against climate change.

There are few misunderstood words to rival that of 'geoengineering', large-scale human intervention to change the Earth's climate system. Contrary to popular belief, geoengineering is not a new idea - the Ancient Greeks and the Roman Empire sought to control the weather through appealing to the gods. Today the proposed methods are, in most cases, more effective than that, as they involve the use of modern science and technology.


The term 'geoengineering' was coined in the 1970s by an Italian physicist who described a method for 'disposal' of atmospheric CO2 through injection into sinking oceanic currents. However, until recently geoengineering has been absent from common dictionaries due to its absence from the common tongue. Recent media interest in the topic combined with growing public concern of climate change has changed a previously academic term to one in general use and in 2010 'geoengineering' entered the Oxford English Dictionary as 'the modification of the global environment or the climate in order to counter or ameliorate climate change'.

As you can probably tell, the OED definition is somewhat lacking in its description.

Further confusion is caused by the various names used for geoengineering which include but are not limited to 'climate modification', 'climate engineering', 'Earth systems engineering', 'planetary engineering, and 'climate remediation', all of which come with their own suggestions of what geoengineering is or aims to do.

Although there is debate surrounding the term, there is general consensus that for an action to constitute geoengineering it must be large in scale, although there is no definition of exactly what constitutes a 'large' venture. The issue is further complicated when you factor in the intentions behind the use of this technology, as geoengineering is normally considered to be a procedure of human intervention with the climate, however some argue that climate change itself is a form of inadvertent geoengineering that humans are undertaking without meaning to, with dangerous implications for us all.

Generally speaking, scientists use the term 'geoengineering' to refer to deliberate, positive intervention undertaken to reduce the effects of anthropogenic climate change. The OED may do well to update their definition to this one.

Types of Geoengineering

Sunlight Reflection Methods

Sunlight Reflection Methods (SRM) was previously known as Solar Radiation Management. The name was changed after it was decided that the original term was too emotively provocative, leading to wild theories connecting SRM to potential radiation exposure that still survive today.

In some cases the term 'geoengineering' is used synonymously with solar geoengineering proposals, as there are many different SRM techniques. Many people have heard of the 'cool roof' technique of painting the roofs of buildings and vehicles white in hot countries to reflect sunlight and reduce dependency on air conditioners, which is an SRM attempt to reduce the effects of global warming. Unfortunately there is no evidence yet that this harmless theory works. Take SRM a step further however and you reach a proposal to use pale coloured floating litter within certain stable oceanic gyres to create a deliberate garbage patch - and this is where things start to get murky. Other SRM proposals include using reflective aerosols or (atmospheric) dust to achieve a similar purpose as the painted roofs, or using stratospheric sulphur aerosols to modify the Earth's albedo with reflective or absorptive materials spread over portions of its surface. These techniques are considered extremely difficult to implement, however.

Other types of SRM include sending mirrors into space to deflect a percentage of solar sunlight into space, mining moon dust to create a shielding cloud, and adding reflective plastic sheets covering 67,000 square miles of desert every year for the next 60 years to reflect the Sun's energy. All of these techniques come with their own criticisms, potential risks, and estimated effectiveness. 

Carbon Dioxide Removal

The other type of geoengineering is known as Carbon Dioxide Removal (CDR), which as the name indicates involves the removal of CO2 from the atmosphere. CDR is generally viewed more favourably by environmental groups as it aims to deal with the root cause of climate change by removing greenhouse gases from the atmosphere, to the extent that some people argue it is not really geoengineering at all but a type of remedial carbon capture and storage required to counter anthropogenically-generated CO2 and therefore manmade climate change.

CO2 removal techniques aim to address the pressing issue of ocean acidification, which is also known as 'the second CO2'. When CO2 dissolves in water, it makes an acid called Carbonic Acid, which prevents corals and other animals from taking calcium out of the water to make shells and skeletons easily. Below a certain pH, molluscs and other sea life crucial to the ocean's ecosystem cannot make shells, which means that they cannot develop and live. If this becomes widespread, it will lead to the collapse of the entire oceanic ecosystem.

A CDR technique known as Bio-energy with carbon capture and storage, or BECCS, uses biomass to extract carbon dioxide from the atmosphere, and carbon capture and storage technologies to concentrate and store it in geological formations. Currently BECCS is the only CDR technology being deployed at full industrial scale. Other CDR techniques include artificial tree technology, which involves planting fake 'trees' which can remove significantly more CO2 from the air than real trees, ocean iron fertilization - the intentional introduction of iron to the upper ocean to stimulate a phytoplankton bloom, scrubbing towers, enhanced weathering to store thousands of years' worth of C02 emissions in, for example, specific types of rocks, and a method of carbon sequestration known as Biochar.

Again, all of these techniques come with their own criticisms, potential risks, and estimated ineffectiveness. To define geoengineering as effective or ineffective, dangerous or safe based on a single technique alone is inaccurate. Many anti-geoengineering groups do just this.


There is some speculation as to whether geoengineering in general can impact the carbon exchange processes between the atmosphere, biosphere, and oceans. The speed of different proposed techniques also varies greatly. For example most CDR geoengineering proposals act at a much slower rate than SRM proposals, which may make them ineffectual at moderating immediate climate changes, but they are also considered to be the most effective.

A major concern regarding the effectiveness of using geoengineering to tackle climate change is that the most effective geoengineering proposals to address the 'second CO2', i.e. ocean acidification, also come with the most risks. Appraisals of geoengineering are mostly conducted using methods such as calculations, computer modelling, and weighing up expert reviews and opinions from specialist scientists. The implementation of one form of geoengineering must also be weighed against the effectiveness of it, which results in a lot of stabbing in the dark. In some cases there are no straightforward answers. For example, large-scale afforestation is thought to be one of the least effective carbon geoengineering proposals, and one that would take a lot of time, but because it also poses the lowest risk, it might be most effective to implement the technique while still developing data on the more complex options.

The CDR technique Biochar is unique in that it addresses multiple crucial issues relating to climate change. Biochar is currently being studied for carbon sequestration to produce negative carbon dioxide emissions, through carbon sinking. Biochar is a high-carbon, fine-grained residue which today is produced through a thermal decomposition process. It increases soil fertility, agricultural productivity, and can store large amounts of greenhouse gases in the ground, potentially reducing or stalling the growth in atmospheric greenhouse gas levels.

A commonly misunderstood fact about geoengineering is that scientists argue that it holds all the answers, or that it can triumph over continued increasing emissions. In fact they propose geoengineering techniques as accompanying strategies to other methods, not as a general answer to halting climate change.


The purported risks of different methods of geoengineering are limited to the aforementioned limitations of analysing their effectiveness. Therefore results can also vary wildly, for example the professed risks of space reflectors vary from very low, to low, to moderate, to high, depending on the scientists you speak to. It is generally accepted in the scientific community that more transparency is needed in these areas to determine why the results differ so much.

On the other hand, stratospheric aerosols, which are considered to be the most effective method of geoengineering, also come under the most scrutiny, as they are deemed to be high risk due to the risk of ozone depletion if high enough quantities of aerosols drift to, or are deposited in, polar stratospheric clouds before the levels of CFCs and other ozone destroying gases fall naturally to safe levels.

In summary, there are no easy or straightforward answers in the geoengineering debate, and there are many angles to consider before rejecting or claiming the use of any SRM or CDR technology.

Financial Cost

Analysts have concluded that many geoengineering proposals would be cheap to implement, since the benefits outweigh the costs of slowing down climate change. Some geoengineering techniques, such as cool roof techniques, certainly cost very little to implement, which is one potential reason to implement the technology even if there is currently little evidence to prove its effectiveness.

However, the seemingly low costs of geoengineering have fuelled concerns about the ease with which any government or agency might be able to employ them.


There is controversy relating to the potential power of geoengineering technology. Just as the atomic bomb was used for warfare purposes, geoengineering is vulnerable to unethical political motives. This technology could be used to serve as weapons of mass destruction, to create droughts or famines in order to attack enemies in war, or to create favourable conditions for battlefield conditions to take place. Although much of this may sound like heightened speculation, it is recognised within the scientific community, particularly since the controversy surrounding proposed use of geoengineering during the Vietnam War led to the signing of the United Nations (UN) international treaty, the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (ENMOD) (UN, 1976).

Controversy also surrounds the legality of geoengineering in relation to potentially risky methods such as deploying stratospheric aerosols. Treaties such as the Long-Range Transboundary Air Pollution Convention and the 1990 amendment to the Clean Air Act would not allow this geoengineering technique to be implemented. Some people argue that the 1977 UN ENMOD treaty makes any type of geoengineering illegal, however the treaty has a specific preservation of the right to use such techniques for peaceful purposes. It is clear however that should this technology be implemented worldwide, a new legal framework may be necessary before geoengineering is widely established.

A more general criticism surrounding geoengineering is that the concept alone creates a moral hazard by suggesting a quick-fix method of climate change prevention. This may also reduce the political and popular pressure for emissions reduction, which is currently unsustainable and will sooner or later have to be tackled.


We rely on science to predict earthquakes, tornadoes, asteroids that might plummet into our planet, and other potential dangers to the Earth and the species that live on it. Now science tells us that time is running out for preventing unstoppable climate change. As in other times of impending catastrophe, humans will inevitably look to science for the solution to climate change, or at least for methods that might buy us more time to deal with it. Scientists accept that geoengineering can only play a part in this area, though it is not yet known how small or large this part may be.

Although there are legitimate known and unknown risks involved with various geoengineering techniques, there are also known and unknown impacts that will accompany the progression of climate change on our planet. I will leave you then to weigh up the odds on either side of the debate yourself, and to decide for yourself where you stand on this issue. Hopefully from reading this article you have surmised that there are no clear answers when it comes to geoengineering, except that perhaps we all need to start putting more pressure on our governments to act on climate change, paying more attention to our personal carbon footprints, and doing what we can to reduce the size of them.

(Some of this article is based on the following research - as well as other sources).

Further resources 

More from Zion Lights:

The truth about fracking - 8 fracking myths debunked

Should cloning be used to bring back extinct species?

Nicholas Stern on climate change and the alternative route to mitigation

Watch: How to green the world's deserts and reverse climate change: hope for the future