Here’s a drop of hope as regards dealing with global threat of climate change

Dr Richard Dixon is right to be concerned about the prediction of global warming of 5C by 2100 from cloud studies (Inside Environment, 23 June). It is also deeply concerning that melting permafrost and clathrates will accelerate this warming out of our control. It’s hard to see how civilisation will survive in these circumstances.

Perhaps the only relief will come from geoengineering (we are inadvertently experimenting with the climate and so a technical fix is called for). There are many options, some very expensive. But there is an economical one on our doorstep. The Marine Cloud Brightening scheme proposed by Prof Stephen Salter of the University of Edinburgh involves spraying fine water droplets to produce bright clouds which reflect more sunlight. It is calculated that spraying over only 3.3 per cent of the Earth’s surface, for example only in the North Atlantic, is enough to cool the planet by about 1 watt per square metre, dealing with about half the warming. Eventually this method could halt the increase in temperature and even lower it, reducing the dire effects that warming is already producing. This won’t solve all problems, but it would hold the temperature down while we try to reduce emissions and try to deal with ocean acidification. All Salter needs is support to get a trial started. Renewable energy and efficiency savings will never hack it. Dr Dixon’s concern regarding Scotland’s rising greenhouse gas emissions is justified. Even though Scotland alone cannot change the world ‘s climate, we should still be setting an example. He notes how burning gas to generate electricity needs to stop and that heating buildings is a major contributor. Odd, then, that his conclusion is that energy efficiency, renewables “and changing transport” would deal with it all.

What about the building heating problem he mentioned? That will require either an expensive shift to heating from electricity, for which at present there is insufficient generation capacity (new nuclear is required), or a change to using hydrogen instead of North Sea gas (methane). Transport also needs to shift to hydrogen; burning it produces nothing but water.

STEUART CAMPBELL Dovecot Loan, Edinburgh