Pie in the sky

I've been looking forward to sinking my teeth into this post for a while - there are some weird and wonderful ideas out there.

Space-based methods of SRM are no doubt the most expensive options of geoengineering available. They're also highly risky. I have discussed in a previous post the risk of catastrophic failure causing rapid and catastrophic change in climate variables (Caldeira et al., 2013). Furthermore, once deployed, there's no going back. Once a space-based scheme has been deployed in orbit, there it will remain. At least until we work out how to safely remove it. Physicists and engineers are yet to discover how to remove 'space debris', which consists of defunct man-made objects that are no longer in operation but remain in orbit. The European Space Agency's e.Deorbit project is waiting for approval next month to be deployed in 2021 to remove a defunct ESA satellite. This would be a huge step in the 'Clean Space' initiative.

But what if it could buy us time whilst we work out how to swiftly reduce emissions, despite being risky and prohibitively expensive? Experiments are clearly limited in their capacity to determine outcomes, so we depend on the use of models (Sanchez and McInnes, 2015). Matthews and Caldeira (2007) state that modelling results show that cooling could begin within months of the implementation of orbital schemes, which would result in a cooling of several Kelvin within ten years. Therefore these approaches could be capable of preventing the collapse of climate-stabilising ice sheets, such as Greenland (Irvine et al., 2009).

Sunshades and solar mirrors:

(Source: Häggström) 

Early (1989) was the first to introduce the idea of orbital methods of climate management. He proposed using a Fresnel lens at the first Lagrange point of the Earth-Sun system - where the gravitational pull from the earth and sun are balanced to produce the centripetal force required for orbit. It would diffract sunlight and reduce the amount of radiation reaching earth. It has since been calculated that a diffraction grating need not be bigger than 1000 kilometres long to disperse the appropriate amount of light - the image above is gross overestimate of the size needed. These methods were since explored by the National Academy of Science (1992) and Angel (2006), who proposed placing a sunshade made up of multiple 'flyers' in orbit at the first Lagrange point.

Artificial planetary rings:

Earth ring concept, with shepherding satellites (Pearson et al., 2006) 

Alternatively, we could create artificial rings of particles to reflect and diffract light (Pearson et al., 2006) that would resemble something like Saturn's rings. Somewhat an eccentric idea, Struck (2007) recommended that we use particles of lunar dust in the moon's orbit. He argued that they would be the right size to scatter sunlight and the right colour of higher albedo to reflect radiation for about 20 hours a month.

... Is it feasible?

To quote Angel and Warden (2006):

"To make ten billion units of 14-meter squares in 30 years (10,000 days) would require manufacture and placement of a million units a day at L1. If there were 1,000 factories working in parallel, each factory would have to complete a unit in little more than a minute."

So, no. Not likely. We could always wait for the development of robotics, but this could take decades (McInnes, 2010).

What about the cost? Understandably, space mirrors and the like involve significant investment from design, to development, to implementation. It could cost up to $200 trillion dollars for the particle solar rings approach and $500 billion for deploying the spacecraft to implement it (Britt, 2005). Furthermore, It is unlikely that space-based schemes will take off (ha) without market incentives. This is why the development and implementation of space-based schemes remains a pipedream. The initial idea of a thin Fresnel lens was proposed almost 30 years ago, yet there has been little headway towards its realisation. Think of the booming industry of solar power in China: thanks to generous state incentives, solar manufacturing has risen at an annual rate of 2.4% between 2010 and 2015. Increased output has reduced prices significantly, making solar energy an increasing feasible option. If we can't convince the state, then companies will lack the ambition to pursue space-based projects.

Politically, more issues arise. The definition of "dangerous anthropogenic interference" by the UN Framework Convention on Climate Change (UNFCCC) is any activity that produces inadvertent climate effects (Robock, 2008). Space-based schemes of geoengineering are likely to fall into this category and therefore are unlikely to be investigated. There is also the issue of conlficting with current treaties. The Environmental Modification Convention (ENMOD) prohibits “military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage, or injury to any other State Party.” Therefore, any space-based scheme that has adverse impacts on regional climate would therefore violate the treaty (Robock, 2008).

However, let's consider the end goal: who and what are we trying to save? Would space-based schemes help protect human existence and the services we depend on? There are unknown impacts on vegetation growth and health. If the model results are true (Caldeira and Wood, 2008), then space-based schemes would likely reduce precipitation amount as well as sunlight (Bala, 2011), reducing primary productivity. Robock (2008) reminds us that reduction in solar radiation will not reduce the rates of ocean acidification from continued carbon emissions. This has implications for the entire oceanic biological chain, which in turn will impact us. Human health and prosperity thrives on healthy biological services. Thus, biological health should come first if we aim to protect human civilisation. And this ultimately leads us to carbon dioxide removal methods as the solution.

Space-based schemes would also threaten to undo all of the good work we have put in so far. It would reduce the potential for solar power and likely undermine the progress we have made in emissions mitigation through the likes of carbon taxation.

As someone with significant interest in climate dynamics and feedbacks, and without consideration of consequences, I wouldn't hesitate to be part of the experience of a worldwide experiment in orbital geoengineering. Think of what it could do for our scientific understanding of the field. But, rightly so, we live in a civilised world of economic and social rules, regulations and restrictions. The human desire for safety and stability will overrule any scientific ambition that could threaten that steady state.