Threat of abrupt climate change

In only a century human activity has increased greenhouse gas warming influence by over a third, causing a rate of warming that is unprecedented in Earth’s unimaginably long history. Today the rate of increase itself is accelerating. Worrying self-reinforcing feedback processes are now underway in the Arctic that climate scientists warn could spiral out of control and spread to the whole planet. Earth’s climate might undergo a step-change in only the next few decades or even years, altering conditions so much that human civilisation as we know it becomes no longer viable. So now scientists and engineers are debating methods of intervening, including reducing atmospheric greenhouse gases, and cooling the Earth’s surface by increasing its albedo (reflecting more sunshine out to space).

Even if atmospheric greenhouse gas emission reduction and removal are scaled up quickly, at least one expert on sea level rise (John Englander) is now saying we should expect sea level rise over 1m over the next half-century, and quite likely a few metres. Therefore, direct planetary cooling is now increasingly thought to be needed.


Enhancing Mother Nature’s cooling processes

Iron Salt Aerosol

The safest and most cost effective method of providing rapid cooling and greenhouse gas depletion is looks likely to be tropospheric dispersion of Iron Salt Aerosol. The initial proposal is to double the existing level of Iron Salt Aerosol (ISA) and concentrate it in the polar regions. This would:

  • provide rapid cooling with marine cloud brightening and ocean brightening
  • quadruple the natural methane depletion rate
  • sequester 6Gt CO2/yr, most of it deep into the ocean
  • reduce other powerful warming agents such as tropospheric ozone and black/brown carbon aerosols

The first order cost estimate is $1/tonne CO2 equivalent removed.

See:    Brief Summary     Full Summary      Australian Iron Salt Aerosol Website


Planetary-wide cooling

Stratospheric Aerosol Injection of sulphates (SAI) appears to be the cheapest, quickest method of reducing radiative forcing. It works by blocking out about 2% of the suns rays all over the Earth. However risks include worsening existing droughts and causing new ones, reducing agricultural yields, suppressing forestry growth and damaging the ozone layer.  Some scientists worry that further massive intervention may then be needed to correct these side effects. In his book The Madhouse Effect, Climate scientist Prof Michael Mann likens stratospheric sulphate spraying to the children’s song There was an old lady who swallowed a fly, which ends “There was an old lady who swallowed a horse. She’s dead of course.”

On the other hand, the risks of inaction could be even worse. Rising sea levels inundating coastal conurbations around the world, and seasonal loss of irrigation from disappearing mountain glaciers, are both likely to lead to social unrest and increased geopolitical stress, even conflict.

Stratospheric Aerosol Injection’s main proponent David Keith proposes early testing with very small-scale applications, in order to study and quantify the various effects. Since SAI mimics the release of natural volcanic sulphate release, the effects are known to be temporary. The cooling effects of Mount Pinatubo’s massive eruption in 1991 lasted just two years.

Other deliberate cooling proposals include Iron Salt Aerosol (which also removes greenhouse gases, see below), Marine Cloud Brightening, Marine Permaculture Arrays and creating plumes of Nanobubbles in the oceans. These proposals are still in their infancy and need further funding for research and development.


Buoyant Flake Ocean Fertilisation

Another reasonably scalable carbon dioxide removal proposal is very slowly to fertilise barren, sun-drenched areas of the ocean with trace minerals delivered by floating flakes: Buoyant Flake Ocean Fertilisation

Other Drawdown Technologies

Many other interesting methods for removing atmospheric greenhouse gases are described in Drawdown, a book edited by Paul Hawken, some of which are featured as game changers in Food, Agriculture and Forestry


Other organisations promoting climate restoration solutions

Foundation for Climate Restoration

Climate Restoration Foundation



Some people worry that if these methods successfully compensate for carbon intensive economic activity, there will be reduced motivation to rein in greenhouse gas emissions, a condition they describe as ‘moral hazard’. In addition they say it is morally wrong to carry out large-scale experiments on planet Earth.


Need for research

However, having already inadvertently carried out a very dangerous experiment on Earth’s atmosphere, experts are now saying it is time to begin seriously researching the safest methods, to avoid total catastrophe.


Who will pay?

This is a thorny question especially for planetary cooling, because there is no profit to be made, only prevention of bad things happening at indeterminate times in the future. Nation states have evolved mechanisms to fund prevention of future ‘bads’, such as defence budgets. However, the global community has only weak funding mechanisms, such as voluntary pledges. All too often pledges are not honoured.

recently proposed funding source is the reinsurance industry. It is a globalised industry and will suffer directly as climate impacts become increasingly disastrous. It therefore has has the most direct interest in seeing planetary intervention programs succeed. Funds would be obtained by placing a premium on fossil fuel extraction. Fossil fuel companies would have to pay this premium or be uninsured, and therefore unable to operate.

Of course, this would place a cost on energy which we would all end up paying, and economies would suffer as a result, at least a little. It’s a hard choice. No doubt there would be push-back from the fossil fuel companies and their shareholders. In a way, it’s the same old problem – that mankind has become overly reliant on ‘borrowing from the future’. This proposal will only be successful if it receives sufficient government support. And governments cannot enact policies without sufficient public support.



Careful governance will be needed to ensure that experimentation and any deployment of intervention techniques are safe, fair, effective and economic. The Oxford Principles are an example of a proposed ‘geoengineering governance’ framework.

Next: Money and Capitalism