I don’t quite know how to react.
The call to at least consider audacious geo-engineering steps that would fill the stratosphere with globe-cooling aerosols to check global warming got louder last week. In Science, Tom M. L. Wigley of the National Center for Atmospheric Research, in Boulder, Colo., writes that reducing carbon dioxide emissions is the long-term solution to global warming but that nearer term engineering of the atmosphere might provide “additional time to address the economic and technological challenges faced by a mitigation-only approach” (DOI: 10.1126/science.1131728). Last month, Nobelist Paul J. Crutzen of the Max Planck Institute for Chemistry, in Mainz, Germany, made headlines with an essay in the journal Climatic Change calling for more research into the pros and cons of injecting sulfate-based aerosols into the stratosphere as a sunlight-reflecting, cooling foil to global warming (C&EN, Aug. 7, page 19).
The paper is still not out for public consumption, because “YOUR INSTITUTIONAL SUBSCRIPTION DOES NOT INCLUDE THIS ITEM:” (How an organization that is funded wholly by government (taxpayer) money can publish in journals that make you pay to read their contents is the subject of a different rant). Nevertheless, this modeling effort builds on Crutzen’s earlier essay which I just finished reading.
Sulfate particles reflect incoming solar radiation, reducing the amount of light incident on earth and lowering the average temperature. This has been known for years, and I am sure every aerosol scientist has thought “Well, if there was some way of putting particles in the atmosphere to reflect more light, this whole global warming thing would just go away”. But the obvious issue with this approach is that sulfates in the troposphere are nasty, they cause acid rain, haze, increased mortality, etc. Crutzen expands on this further.
The great advantage of placing reflective particles in the stratosphere is their long residence time of about 1–2 years, compared to a week in the troposphere. Thus, much less sulfur, only a few percent, would be required in the stratosphere to achieve similar cooling as the tropospheric sulfate aerosol (e.g., Dickinson, 1996; Schneider, 1996; NAS, 1992; Stern, 2005). This would make it possible to reduce air pollution near the ground, improve ecological conditions and reduce the concomitant climate warming. The main issue with the albedo modification method is whether it is environmentally safe, without significant side effects
Which I guess is the key question, let alone the practicalities of introducing and maintaining 5.3 Tg (terra grams or million metric tonnes) of sulfur in the stratosphere successfully. This is a 10% increase from the current emissions of 55 Tg/year, so I guess it is not a terribly large number. Crutzen estimates that it will cost 25-30 billion dollars per year to have a loading of 1-2 Tg (to combat the most optimistic global warming scenario), though he cites a personal communication with someone at the National Academy of Sciences in 1992. This number is bogus, how do you know what something will cost if you don’t know how you’re going to do it? Crutzen has some ideas…
Locally, the stratospheric albedo modification scheme, even when conducted at remote tropical island sites or from ships, would be a messy operation. An alternative may be to release a S-containing gas at the earth’s surface, or better from balloons, in the tropical stratosphere
In other words, speculation at this point in time. The bottom line is this, the idea is not revolutionary, heck, even I thought of this in the mid 90s when I was doing sulfate aerosol work. The mechanics of how this will be done without causing some unforeseen other major issue is the real question that will take years to answer. Meanwhile, this silly personal virtue called conservation still works, look at this graph (from an NY Times article through the Washington Monthly), if Cali can do it, so can you.