Geoengineering: Reducing solar radiation (SRM)

To start with, I will introduce you to the method or idea of Geoengineering. It is a very controversial topic, but at the same time a topic, which increased strongly its importance over the last few years. In general, it is a method to reduce climate change. There are two main ideas behind this method, reducing climate change by reducing CO2 (Carbon Dioxide Removal, CDR) and reducing climate change by reducing solar radiation (Solar Radiation Management, SRM).

In this post, I will focus on the methods of reducing solar radiation. According to Caldeira et al 2013 the idea of SRM is a mathematical solution. There is a certain input of solar radiation per square meter. By increasing CO2, there will be more solar energy (warmth) left in our atmosphere. If we double the amount of CO2, it will be an increase of about 1,7%. The main idea of SRM methods is now to reduce this additional amount of energy by increasing the albedo of the earth and therefore increasing the reflection of the incoming solar radiation and decreasing the absorption.

Figure 7: Caldeira et al 2013

As you can see in the picture above, there are different approaches to reduce solar radiation.

a)    Space-based approaches: The idea of installing a large “glass shield” in space between the sun and the earth or mirrors or small particles into the orbit to increase the reflection of solar radiation. A massive intervention in our system earth, which consequences could just be guessed and which expenses would be exorbitant. (Caldeira et al 2013)

b)   Stratospheric aerosol-based approaches: The increase of the atmospheric albedo by injecting aerosol particles. The success of this method is already be proven by accident. The eruption of the volcano Mount Pinatubo in 1991 released sulphur aerosols into the atmosphere and cooled our climate. There also was a first experiment to this method, SPICE, but it got shut down, because the public opinion to this topic was too controversial. In particular, concerning all the unknown side effects, which could appear and again the exorbitant expenses. (Stilgoe 2015)

c)    Marine cloud brightening: A method to brighten and add clouds, which would increase reflection. Again not all side effects of this method are known and it would just delay climate warming for about 25 years. (Caldeira et al 2013)

d)   Surface albedo enhancement (water): Our planet is covered by two thirds with water, so the easiest thing to increase the global albedo, would be to increase the water (ocean) albedo, especially water albedo is in general very low. But the expenses and environmental impacts of approaches like that are difficult to calculate. (Royal Society 2009)

e)    Surface albedo enhancement (rural areas): There are different approaches in this area, starting with covering desserts and ending by planting brighter crops. Again the ecological impact would be immense and the increase of the albedo not even that big. (Royal Society 2009)

f)     Surface albedo enhancement (urban areas): The use of different building material, brighter colours, for example white rooftops. The benefit of this method would also be to save energy for air conditioning, but the global impact would be quite small and the governance would be difficult. (Royal Society 2009)

The problem of SRM methods is mainly the unknown side effects or the impacts to our environment and the mostly exorbitant expenses.

In addition, at my opinion, it is morally not right. We, as humans, are harming our climate system by producing CO2 and instead of just reducing it; we are trying to change the whole system, which could harm our system even more. We are not trying to fix the cause of our problems; we are just fighting the symptoms, which I think, is the wrong way. Even CDR methods, which I will explain to you in my next post, are not the solution.