The perils of bureaucratic perquisites.

Yesterday Dan Lack of NOAA gave a talk to the NCAR media fellows about his work on pollution from shipping, and told us something I found pretty flabbergasting. Last year the International Maritime Organisation, as part of a number of measures aimed at air pollution, decided to do something about the sulphur emissions from shipping by reducing the amount of sulphur dioxide permissible from 4.5% today to 0.5% in 2020. This would have great benefits; sulphate pollution, and associated particulate matter, cause significant health problems. According to a new paper in Environmental Science and Technology by Winebrake et al, if in 2012 the world’s shipping complied with this requirement, the associated sulphate pollution would cause 46,000 premature deaths; if that shipping used today’s higher sulphur fuels the death toll would be 87,000.

However, sulphur emissions from shipping have another effect: the sulphate aerosols that form from the gas make the oceans cooler by increasing the cloud cover above them, as the image at the top of this post shows. The effect is large enough that shipping cools the planet through sulphate aerosols much more than it warms the planet through greenhouse gas emissions. . .

Put another way (and I calculated these numbers myself, so please check and correct if you have the necessary skills) 0.3 W/m² is the radiative forcing you would expect if you dumped 47.5 billion tonnes of carbon (in the form of carbon dioxide) into the atmosphere, raising the concentration of CO2 from today’s 387 parts per million to 409 parts per million. That’s well over a decade’s worth of carbon emissions and an enormous amount of warming for the IMO to have committed the world to with no-one, as far as I can see, paying very much attention. (The most obvious environmental response to the IMO changes, from the Clean Air Task Force, was to applaud the health effects of the cuts in sulphur while deploring the lack of action on greenhouse gases and not mentioning the cooling issues at all. If you accept Dan Lack’s figure of just 0.06 W/m² for the total warming from shipping, that seems an odd omission.).

Now there are obviously complexities and caveats. This is just one modelling study — but its figures for the amount of cooling due to sulphur fit with those quoted by of others, such as Dan Lack. Taken at face value it would imply both that the total cooling effect of sulphur on clouds was probably greater than the IPCC best guess, and that sulphate from shipping was responsible for a disproportionate amount of it. But the IPCC’s guess has big error bars, and you would indeed expect sulphate from ships to be peculiarly effective — it gets sprayed into places where the clouds are very susceptible to such things. . .

Beyond preferring coastal controls to global controls I have no real policy case to make here. I’m aware that there is in general a trade off between air quality reasons for reducing sulphates and the possibility that their cooling effects can be climatically helpful. But the fact that this measure involves reducing sulphur emissions in places where they do no harm (the mid oceans) and where their cooling effects are greatly enhanced (by the presence of low clouds they can brighten) makes the question particularly pointed. I have no way to balance the advantages of reduced global warming against the advantages of decreased mortality. I don’t know who has. But I do think that it’s kind of extraordinary a regulatory change with this much effect on global warming could be made with so little apparent fuss.

And I also think this all makes the case for experiments with Latham-type techniques that brighten clouds to cool the seas even stronger than it already is. If, for good reason, we are actively reducing the amount of cooling provided by shipping, surely we should at least look at possible ways of putting it back?

In a business, even a very large business, this sort of thing can happen where narrow objectives have net negative consequences, but when done by regulation the effects are larger, longer lasting and less subject to rational reform. Those who see regulation as a first best option seem not to be aware of how things work in reality, mistaking reported results - which are shaved and fluffed to make regulators look good, or at least blameless, CYA - with actual results, which have the irritating habit of being realistic and comprehensive.

You get what you manage for whether you understand what that will be or not. If it happens to you, it's your fault, since you have the opportunity to act otherwise, and it is only by accepting responsibility for outcomes that you have any hope of success. You may get beat, but not because you didn't think it through and try hard.