(Increasing the reflective power of the Earth's atmosphere)BY: Dr. Ron Nielsen, 2006
Albedo enhancement would be a controlled geoengineering project.
It is not suggested to do it immediately but rather to study it carefully in order to assess not only its technical and financial feasibility but more importantly its possible effect on the environment.
The current critical global trends associated with human activities already shape the future of our planet in a negative way and it would be irresponsible to undertake a geoengineering project, however well intended it might be, if it would make it all even worse.
On the other hand, in order to change the already advanced progression of the threatening trends we probably have no choice but take radical remedial steps.
How to do it
How to construct the protective shield in the stratosphere?
How much of reflective material we would have to deposit?
How long would it take to construct the shield?
The material deposited in the stratosphere has a limited lifetime of 1-2 years.
How much we would have to add to compensate for the natural loss?
How much would it cost to construct and maintain the required stratospheric shield?To deploy an albedo enhancing material in the stratosphere we could use rockets or balloons.
To compensate for the removal of human-made aerosols from the lower parts of the Earth's atmosphere (the troposphere) we would have to construct a protective shield in the stratosphere containing 2 million tonnes of reflective aerosols.
I have found that the simplest and cost-effective way of constructing and maintaining the protective shield would be to deposit 1 million tonnes per year if the residence time of reflective material is 2 years or 2 million tonnes per year if the residence time is 1 year.
We would have to do it virtually indefinitely, or at least for as long as human-made greenhouse gases remain in the atmosphere.
If we decided to do it by rockets, we would have to use 67-133 rocket launchers (the lower number is for the residence time of 2 years and the higher number for 1 year) working round the clock, 250 days per year. (I exclude weekends and public holidays).
We would have to launch 2-4 million rockets per yeas (8,000-16,000 shots per working day).
The estimated cost, using 1992 prices, would be US$23-45 billion per year.
If in addition we would also like to protect ourselves from the continuing increase in global warming between now and say 2050 caused by our continuing use of fossil fuels and the resulting continuing increase in the concentration of carbon dioxide, we would have to increase the thickness of the protective shield to between 4 and 6 million tonnes.
The uncertainty is dictated by the uncertainty of predicting the increase of global warming between now and 2050.
To construct and maintain such a shield, we would have to deploy 2-6 million tonnes of reflective material per year, using 133-400 rocket launchers working round the clock, 250 days per year.
The number of launched rockets would be 4-12 million per year (16,000-48,000 per working day) and the ongoing cost would be US$45-135 billion per year.
Of course, if we go beyond 2050 and if our emissions of greenhouse gases increase, our efforts to protect ourselves from the increased global worming would be even more complex and costly.
Is it safe?
Is such a geoengineering project environmentally safe?
The short answer to this question is that we do not know.
We have to study and assess the possible environmental risks.
We can do it both theoretically and by experimentation.
The risks will depend not only on the amount of the reflective material we would have to deposit in the stratosphere but also on the type of the material.
If the material is chemically neutral the risk might be small.
However, even chemically neutral material might provide an environment for harmful chemical reactions between atoms and molecules, which are already present in the stratosphere.
If the deposited material is chemically active, the risk might be greater.
For instance, if we deposit sulphur, we would have to explore its possible chemistry in the stratosphere.
For instance, we would have to make sure that it would not contribute substantially to the destruction of the ozone layer.
Furthermore, we would have to understand how sulphur compounds interact with the atmospheric components when they are being removed from the stratosphere by natural processes and what environmental and health problems they might be causing.
Volcanic eruptions that deposit large quantities of sulphur into the stratosphere seem to indicate that there are no environmental risks.
However, we do not know what might happen if we maintain large quantities of sulphur in the stratosphere for a long time.
The first step is to assess as carefully as possible that the proposed geoengineering project is safe.
If we then decide to go ahead with the project but discover later that it causes environmental problems, we could stop the project without causing much damage to the environment.
In 1-2 years, the deployed material would be removed from the stratosphere by natural processes and the stratosphere would be restored to its original condition.
Not a permanent solution
It should be stressed that albedo enhancement of the Earth's atmosphere is not a solution to global warming.
It is only a temporary solution designed to give us a breathing space while we work on such issues as developing clean fossil fuel technology, alternative sources of energy to replace fossil fuels, and more efficient methods of energy consumption.