The price of uncertainty: geoengineering climate change through stratospheric sulfate

With thanks to Clive Hamilton for his talk.

Stratospheric sulfate seems to be one of the most promising geoengineering methods to combat climate change. It involves the injection of  hydrogen sulfide (H2S), sulfur dioxide (SO2) or other sulfates, into the stratosphere. Similar to what happens after major volcanic eruptions, this would reflect off part of the sun’s energy and cool the Earth, counterbalancing the effect of greenhouse gases (see for instance the “Year without a Summer” that followed the 1815 eruption of Mount Tambora).

It is probably the best geoengineering solution to climate change, in that it’s likely to work, should be technically feasible, can be done by a single nation if need be (no need for global consensus), and is likely to be very cheap – especially in comparison with cutting emissions. But it has a few drawbacks:

  1. It will have unpredictable effects on the weather across the globe.
  2. We can’t really test it – the test would be doing it, on a global scale.
  3. We wouldn’t know if it worked until we’d had about a decade of temperature measurements.
  4. Once started, it’s extremely dangerous to stop it – especially if carbon emissions keep rising.

So, should we do it? Narrow cost-benefit analysis suggests yes, but that doesn’t take into account the uncertainty, the unknown unknowns – the very likely probability that things will not go as expected, and that we’ll have difficulty dealing with the side effects. This includes the political side effects when some areas of the globe suffer more than others from this process.

How bad does global warming have to get before we consider this type of nearly irreversible geoengineering? If we had to choose between this and cutting emissions, how high would the cost of cutting have to go before we sprang for this instead? In short, what price do we put on avoiding uncertainty on the global scale? Can we estimate a dollar amount, or some alternative measure of the cost – quality-adjusted life years, or some other human-scale estimate? Or is this an illusionary precision, and do our intuitions and qualitative arguments (precautionary principle?) give us a better estimate of whether we should go ahead with this?

To 1750 – or beyond?

At the current Conference of the Parties in Durban, Libya proposed an ambitious scheme which, it claims, will not only halt, but reverse global warming.   (See

 Effectively, the “Libyan Climate Change Initiative” will turn the Sahara desert, and perhaps the Arabian and other deserts, into a giant wind-farm.  But not your average of wind-farm.  This wind-farm is one which first creates wind out of solar power and then uses it to drive giant wind turbines.   Continue reading

Geoengineering, Science, Consequentialism and Humility

The Uehiro Centre has recently hosted Clive Hamilton who was visiting from the Centre for Applied Philosophy and Public Ethics at Charles Sturt University. Hamilton is well known for his work on the politics of climate change. While here he presented a paper on the ‘Ethical Foundations of Climate Engineering’, which he has now been revised and is available at his website:

Climate engineering is also known as ‘geoenginering’ and the ethics of geoengineering has recently been discussed in a joint paper by several members of the Uehiro Centre who take a view that Hamilton strongly disagrees with:

 Hamilton’s paper is an attack on consequentialist justifications for geoengineering – attempts to use technology to try to manipulate the Earth’s climate in order to ameliorate the effects of climate change. He sees such attempts as part and parcel of a world view which springs from the Scientific Revolution. He tells us that: ‘The consequentialism of climate ethics is built on an unstated (and mostly unrecognized) understanding of the natural world, one that grew out of the Scientific Revolution in the 17th Century and the European Enlightenment philosophy that went with it.’ According to Hamilton, people who are in the grip of this scientific world view, including consequentialist philosophers, lack ‘humility in the face of nature’. The ground for this humility is, ‘… acceptance of our limitations in the face of the superior power, complexity and enigmatic character of the earth’. Hamilton sees the presumption that we might be able to ‘master’ nature as fundamentally misguided: ‘Climate engineering represents a conscious attempt to overcome resistance of the natural world to human domination …’, however, ‘… the sheer complexity and unpredictability of the natural world resists attempts at total mastery’.

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The ethics of geoengineering – comments welcome

Should we encourage or avoid large scale environmental manipulation, for example in order to reduce climate change?

Measures such as carbon dioxide capture or ocean iron fertilisation have the potential to mitigate global warming, but what ethical issues are raised by these technologies? How should we take into account the potential risks of such measures, and how should they be weighed against the risks of inaction?

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