Has a well-meaning international effort to cut pollution from ships contributed to a sudden warming of the waters in the north Atlantic this year? That is the extraordinary claim made this week in an article in Science magazine, the journal of the American Association for the Advancement of Science. It asserts that limits on the sulphur content of fuels used by ships have helped reduce sulphur pollution from those vessels by 80 per cent – but at the inadvertent cost of reducing cloud formation over the oceans and so speeding global warming.
Previously, well-used corridors of the Atlantic Ocean were covered with ‘ships tracks’ – yellowish, elongated clouds which followed the paths of passing ships. Now, the clouds have been diminished, and the waters are exposed to the full power of the sun, resulting in record sea surface temperatures. As Michael Diamond of Florida State University puts it, ‘It’s as if the world suddenly lost the cooling effect from a fairly large volcanic eruption each year.’ Sulphur Dioxide emissions from the eruption of Mount Pinatubo in the Philippines in June 1991, for example, have been claimed to have reduced global temperatures by 0.3 Celsius for three years.
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The world is better off without the air above the oceans polluted with sulphur. It was sulphur emissions from coal-burning power stations which was responsible for acid rain. Yet the theory that ocean-warming has been exacerbated by a fall in clouds generated by ships’ exhausts has rekindled the question: should we be employing ‘geo-engineering’ in order to try to combat climate change?
The idea has been around a long time. Experiments in cloud-seeding by spraying silver iodide or other chemicals into the atmosphere have been carried out since the 1940s – with conflicting claims as to their success. But in recent years there has been a revival in fantastical ideas of engineering the climate. In 2015 the US National Academy of Sciences looked into the possibility of cooling the Earth by interfering with the ‘albedo’ of the Earth’s atmosphere – albedo being the proportion of solar energy absorbed, where 0 is total absorption and 1 total reflection. This could be achieved, it suggested, by regularly injecting aerosol-forming gases into the stratosphere. This, the report concluded, could help moderate temperatures in the Earth’s surface by “at least an order of magnitude less than the cost of decarbonising the global economy”. However, it also concluded that “proposed albedo modification approaches introduce environmental, ethical, social, political, economic, and legal risks associated with intended and unintended consequences”. The unintended consequences, it suggested, could consist of damage to the ozone layer, changes in patterns of precipitation and increased growth in forests.
It was damage to the ozone layer, after all, which led to the banning of CFC gases in aerosol sprays, fridges and other products in the 1980s – it would be somewhat perverse now if we went back to spraying aerosols into the stratosphere which could cause damage to the ozone layer. Incidentally, the removal of man-made aerosols from the atmosphere has been claimed by some to be responsible for the sharp increase in global temperatures in the 1980s and 1990s.
In other words, the National Academy of Sciences concluded that while it might be cost-effective to try to limit global warming by tinkering with the Earth’s albedo, it was associated with the same kind of risks of global warming itself. If it is going to change rainfall patterns, causing flooding in some places and drought in others, isn’t that exactly the kind of thing which we are told we risk from rising carbon dioxide concentrations in the atmosphere?
Cloud-seeding experiments died a similar death, in Britain at least, after being blamed for the Lynmouth flood disaster of 1952, when nine inches of rain fell on parts of Exmoor in 24 hours, resulting in a torrent of water washing away part of the town and the loss of 35 lives. In spite of official denials that cloud-seeding experiments were underway at the time, documents later revealed that Operation Cumulus – a cloud-seeding experiment by the RAF – had indeed been taking place in Southern England between 4 and 15 August 1952 – the latter date being the day of the Lynmouth flood. Put like that, it sounds damning – except that Operation Cumulus was being conducted over Bedfordshire – 150 miles away from Exmoor. Operation Cumulus does, however, appear to have come to an abrupt halt after the Lynmouth flood – suggesting that those in charge feared its consequences. That the experiments were conducted by the RAF rather than a civilian body does also say something: that cloud-seeding was seen in Britain as much as a potential weapon as a useful means of say, alleviating drought. The practice is, however, still carried out by US ski resorts hoping to increase snow cover and by the Chinese – who are reported to have used it to deflect rain from the 2008 Beijing Olympics.
Cloud-seeding, at least, takes place in the lower atmosphere. To conduct experiments into changing the Earth’s albedo by spraying materials into the stratosphere would have much further-reaching consequences, with the potential for generating global conflict. There is already a political movement demanding climate reparations for historic greenhouse gas emissions. That should give a clue as to what would lie in store in the event of efforts to geo-engineer our way out of global warming.