Building a wall in the sky might help climate change. It might also create new problems
Credit: Ben Birchall/PA Archive/PA Images   

I’m an optimist on climate change. Big drops in the price of renewable energy fill me with confidence that we will end our damaging dependency on fossil fuels.

There is, however, an alternative approach. Instead of reducing our greenhouse gas emissions we could, it is argued, embark on a programme of activities designed to cancel out their impact on the global climate. This is known as geoengineering. A number of reports this year have suggested that the Trump administration is interested in the concept. For instance, here’s Ian Johnston for the Independent:

“A controversial plan to create a ‘wall in the sky’ to reflect sunlight could win support from the Trump administration because it appears to offer a way to keep burning fossil fuels while reducing global warming, campaigners have said.

“A team of Harvard University scientists led by Professor David Keith plans to begin a trial of a so-called ‘geoengineering’ project next year.”

I guess that Trump will want to prioritise his ‘wall along the ground’; but if we were to build a ‘wall in the sky’ against climate change, how would we go about it? 

Writing for Project Syndicate, Barbara Unmussig explains the basics of geoengineering – and also why it’s such a terrible idea:

“Each of the engineered technologies being discussed carries dangers and uncertainties. For example, the only way to test the effectiveness of solar radiation management (SRM) on a global scale would be to carry out experiments in the environment – either by spraying particles into the stratosphere, or by artificially modifying clouds. While such tests would be designed to determine whether SRM could reflect enough sunlight to cool the planet, experimentation itself could cause irreversible damage. Current models predict that SRM deployment would alter global precipitation patterns, damage the ozone layer, and undermine the livelihoods of millions of people.”

Here’s a useful rule-of-thumb: if it sounds like something a Bond villain would do, then don’t do it. Blocking out the sun to change the temperature of the world surely qualifies. 

Are there any less alarming forms of geoengineering? The main alternative to SRM is CDR – carbon dioxide removal. This sounds reasonable, taking out of the atmosphere the extra we’ve dumped into it. The devil, though, is in the detail:

“Some CDR approaches are already prohibited, owing to concerns about possible environmental consequences. For example, fertilization of oceans with carbon-sequestering plankton was banned by the London Protocol on marine pollution in 2008. Parties to that decision worried about the potential damage to marine life.”

Other CDR techniques are available. For instance, Barbara Unmussig introduces us to ‘BECCS’ – which stands for bio-energy with carbon capture and storage. What you do is plant a fast-growing crop species and burn the harvest in a power station equipped with CCS. The captured carbon is then stored underground so that it never reaches the atmosphere. Because plants grow by absorbing carbon dioxide from the air, the net emissions of the whole process are, in theory, negative. 

Great stuff, but there’s a catch:

“In order for BECCS to achieve emissions limits set by the Paris agreement, between 430 million and 580 million hectares (1.1 billion to 1.4 billion acres) of land would be needed to grow the required vegetation. That is a staggering one third of the world’s arable land.”

Who needs food anyway?

By releasing colossal quantities of carbon dioxide into the atmosphere we’re already conducting a hugely dangerous experiment on the only planet we’ve got to live on. Trying to put things right by conducting further such experiments is to multiply the risks we’re running. 

We need to return to the fundamentals of conservatism – such as ‘first do no harm’, ‘prevention is better than cure’ and ‘if something cannot go on forever, it must stop’. Innovation is giving us the tools to stop the great carbon experiment – and, in the process, also generate the energy we need without polluting our lives. 

Compared to building a ‘wall in the sky’ that sounds like a pretty good deal.