What to do with sulphur?

I was fortunate to be invited to attend CIGI 10 just outside Toronto, Canada. The annual “deep dive” policy discussion is held by the Centre for International Governance Innovation, a policy think-tank founded by Jim Balsillie, co-CEO of Research in Motion (a.k.a. Blackberry) and this year the focus was the global governance around the climate. While there was much discussion on bilateral vs. multilateral, UNFCCC or G20 and so on, one particular discussion focused on the role of sulphur in the atmosphere.

The discussion started with the current reality of sulphur being artificially pumped into the troposphere through the worldwide use of High Sulphur Fuel Oil (HSFO) in ships (and of course from other sources such as coal fired power stations not fitted with scrubbers). The combustion of this fuel powers much of the worlds ocean going fleet and the sulphur leaves the ship through the funnel. HSFO contains some 3.5% sulphur, so a modern container ship travelling from Shanghai to Southampton via the Suez Canal will eject about 30 tonnes of sulphur into the atmosphere, along with some 3,000 tonnes of CO2. The CO2 of course adds to the growing accumulation of this gas in the atmosphere, but the sulphur remains in the atmosphere for just a few weeks in aerosol form before dropping out. Nevertheless, as a result of all the marine activity and other sources of sulphur, there is a net suspension of sulphur in the atmosphere above us. The result of this is that it cools the atmosphere by scattering incoming radiation, offsetting some of the warming impact of CO2 and other greenhouse gases.

But sulphur also has a negative effect in terms of local and regional air quality so the International Maritime Organisation (IMO) has moved to limit sulphur in marine fuel. A recent analysis by Winebrake et al (2009) discusses the climate impact of the marine fuel sulphur specification reducing to 0.5% globally – a potential end goal of the current IMO limits. Whereas the global annual average cooling effect of shipping is currently some -0.6 W/m2 (compared to the current additional radiative forcing from post-industrial CO2 now approaching 2 W/m2), this is shown to reduce to -0.3 W/m2 in the case of a global 0.5% sulphur specification – in other words, another 0.3 W/m2 of warming.

But this was just the start of the discussion. The real issue was the potential role of sulphur in deliberately managing the global temperature – a practice more commonly referred to as geoengineering. Trying to do this at sea level and injecting sulphur into the troposphere has far less impact than doing the same in the stratosphere. For the same amount of surface cooling, approximately one twentieth the amount of sulphur is required at 25,000 metres because the half-life of the aerosol suspension is some 18 months at that height, rather than just the few weeks seen in the low atmosphere.

An indicative calculation has shown that a fleet of 150 aircraft injecting sulphur into the stratosphere on a continuous basis could potentially offset the warming associated with a doubling of CO2 in the atmosphere. The cost of this is estimated to be no more than $10 billion per annum and perhaps quite a bit less.

So began the real debate – the implications of being able to manage atmospheric warming for an amount so small that even some individuals could undertake the experiment, or perhaps a group such as the small island states in defense of their territory. For major emitters this would be a paltry sum, far less than some of the direct mitigation options. But if such a practice were undertaken, what then for the global endeavors to reduce emissions? Would we just give up trying? And while some amount of cooling might be achieved, phenomena such as ocean acidification would continue. Who should decide on such weighty issues and what if one nation or group of nations decided to conduct the practice unilaterally? One participant asked if the practice might even be in breach of Article 2 of the Framework Convention.

In the short time we had there was of course no resolution to the issues raised, but it was suggested that a global aerosol management framework was as important to the climate discussions as the greenhouse gas framework slowly being formulated or the CFC framework that exists under the Montreal Protocol. But no such framework is seriously under discussion. I won’t be so bold as to suggest answers to the questions raised, or even to attempt to list the dozens of other ethical and moral questions raised by this topic. But it certainly did provide a lively start to the Sunday morning portion of the conference!