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5 minutes reading time (1005 words)

Geoengineering - can it help address climate change?

Geoengineering-ClimateChange An alternative to reducing CO2 emissions and energy use?

"When a weather-controlling satellite system suddenly breaks down, a scientist must race against the clock to prevent a climate cataclysm on Earth." Geostorm - Currently on Netflix

You may be confused but this is not a film review! During the recent lockdown some may have watched the film Geostorm on Netflix. Essentially the film is an action and adventure sci-fi fantasy film loosely based on geoengineering. The idea being that if the climate of the planet gets out of control we can fix it through large scale intervention of the earths climate system by using satellites. It got me interested in the science behind geoengineering and large scale climate intervention and whether this might be an easier option than reducing CO2 emissions the energy efficiency route.

What is geoengineering? 

Geoengineering refers to large scale engineering programmes designed to manipulate the earth's climate and avert climate change. The two main branches are:

  • Solar geoengineering, which aims to control the amount of solar radiation reaching and being absorbed by the earth.
  • Carbon geoengineering, which aims to reduce greenhouse warming by reducing the quantity of carbon dioxide in the atmosphere. 

These are highly controversial areas, with proposals ranging from giant orbiting mirrors to reflect the sun's rays into space, injecting aerosols into the atmosphere, to chemically extracting carbon dioxide from the atmosphere. 

Is this mad science, or is there real merit in these proposals? Is there perhaps a mixture of both?

The cure might be worse than the cause 

Critics of solar geoengineering caution that the side effects of some proposals could be devastating. Possible outcomes include the disruption of global rain patterns and acceleration, rather than reduction, of global warming. On the other hand, advocates argue that such approaches can effectively reduce warming without harmful side effects, and both sides substantiate their positions through sophisticated computer models. 

There is no shortage of research on the subject. Both Oxford and Cambridge Universities have geoengineering programmes underway and, over recent years, more than 500 peer-reviewed papers on the subject have been published. However, so far, research funding has been relatively modest. Global research funding on geoengineering is just $10 million a year. So what are these proposals?

Reducing planetary albedo (solar radiation) 

Albedo is a measure of the amount of incident solar radiation that is reflected. A theoretical black body that absorbs all the radiation has an albedo of 0, and a body that reflects all of the incident radiation has an albedo of 1. In the real world, snow has an albedo of 0.9 and charcoal of 0.04. 

Several approaches concern reducing planetary albedo. These include:

Aerosol injection – injecting aerosols into the atmosphere from aeroplanes and balloons could potentially reduce albedo in a similar way to a volcanic eruption. The most likely aerosols would be sulphur dioxide, sulphuric acid, and hydrogen sulphide. While this could have an impact on rainfall patterns, recent climate computer models suggest that global warming could be reduced by up to 50% without significantly impacting rainfall. However, those aerosols are highly unpleasant pollutants which could fall back to earth as acid rain.

Marine cloud brightening – here the theory is that by spraying seawater into marine clouds, salt particles would seed further cloud formation "brightening" the clouds and increasing the amount of sunlight they reflect. However, it is difficult to see how this could be applied on a global scale.

Cloud reduction – while high cirrus clouds reflect sunlight, they also absorb infra-red radiation emitted by the earth's surface. The overall effect is to increase greenhouse warming. Injecting aerosol particles into these clouds could cause them to dissipate. However, there is a danger that seeding could cause clouds to thicken, thus exacerbating global warming.

Painting rooftops white – while this could impact cities, making them more comfortable to live an and possibly reducing air conditioning loads, the effect on global albedo and reduction of global warming would be insignificant.

Space reflectors 

Some geoengineering proposals appear to verge on science fiction; for instance, various scientists propose using orbiting space reflectors to reflect sunlight away from the earth. They claim that reducing sunlight reaching the surface by just 2% would reset global warming to pre-industrial levels. Perhaps surprisingly, such proposals are being taken seriously and are supported by authoritative bodies such as the EU and Nasa 

Carbon engineering using direct air capture 

As climate scientists attribute global warming to excess greenhouse gasses in the atmosphere, an obvious solution is simply to remove some it. A project that aims to do that is called Direct Air Capture technology run by the Carbon Engineering consortium.

The group has already demonstrated a pilot study in Canada and is currently planning to build an industrial-scale plant with the capacity to capture one million tons of carbon dioxide per year, the equivalent of 40 million trees. The extracted carbon dioxide would be stored safely deep underground. Bill Gates is one of the project backers as are several of the major oil companies.

Finally 

"Tinkering with our planetary system is not a silver bullet. It's an expression of political despair"

Doug Parr, Chief Scientist for Greenpeace
Is geoengineering a realistic way out of global warming, or is it just a little too crazy and dangerous to be taken seriously? Even if it were to provide benefits, it would do little to wean us off our addiction to fossil fuels. However, lurking amongst some of the more outlandish proposals could be some gems that might be worth pursuing. There appears to be sufficient scientific interest to suggest this could be the case. 

Perhaps to avert the kind of crisis that is becoming increasingly imminent, no stone should remain unturned as a last resort. But we shouldn't let it distract us from more down to earth approaches such as improving energy efficiency in all areas of life including UK commercial property building stock. 

It's been an interesting topic to research but back to the Energy Performance Certificates for me! If you haven't seen the film Geostorm it is worth a watch though.

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