Net-zero is not enough to stop climate catastrophe, Professor Stephen Salter warns

Professor Stephen Salter of Edinburgh University told The National that in addition to reducing emissions, the world would have to deal with the harmful effects of those already in the atmosphere as well as get rid of carbon dioxide more rapidly.

He has been working on the engineering for the late physicist John Latham’s proposal to make clouds that would reflect the sun’s energy back into space which would stop the polar ice caps melting and counteract other damaging effects of global warming.

However, the UK’s Department for Business, Energy and Industrial Strategy (BEIS) has so far rejected pleas for funding for the work Professor Salter has been developing for nearly 20 years. He is worried it will share the same fate as his famous Edinburgh Duck, the world’s first practical wave energy converter, which he believes was sabotaged by consultants working for the UK’s Atomic Energy Authority (UKAEA).

“I am worried something similar will happen,” he said. “The engineering is pretty nearly done but I have not had any money at all to do it and the trouble is that people think all we need to do is stop emitting.

“Yet there is no sign at all that we can stop emitting – if you look at the atmospheric concentrations they are going up and up.

“Even if we could reduce carbon emissions to zero, the concentration of atmospheric greenhouse gases will be what we have now, plus what we will be emitting between now and the zero-emission date, minus the amount taken up by the oceans. This means that typhoons, floods, droughts, bushfires, sea-level rise, Arctic ice loss and damage to coral will all be worse, perhaps much worse than now.

“We have to get rid of the emissions, we have to do some direct cooling and we also have to get rid of carbon dioxide more rapidly than doing it naturally.

“All three things have got to be done and what you mustn’t do is assume you can do just one of them which is what our politicians are saying. Net-zero is not nearly enough.”

Outside of government, many scientists are in favour of pursuing Salter’s work, including Professor Sir David King, head of the Climate Crisis Advisory Group.

“It might depend on a change of political views for it to go ahead which is frustrating but Sir David King has got a lot of clout,” said Salter.

He is also having talks with European groups as he believes EU funding might be an option despite Brexit.

“We would have to have an EU partner but that should be possible,” he said.

Salter’s project involves building unmanned hydrofoil ships that would spray very small drops of sea water into the air at, for example, the Arctic Circle. The water would evaporate, leaving a tiny grain of salt which would act as a nucleus for a cloud to form. This would reflect the sun’s rays back into space, cooling the area directly underneath the cloud.

Work by Sean Twomey on the reflectivity of clouds, showed that reflectivity depends on the size distribution of the cloud drops. A large number of small drops reflects more than the same amount of liquid water in larger ones. Salter first started work on the project back in 2004 when he was approached by Professor John Latham, who had worked out how much water would have to be sprayed over the world’s oceans to cancel global warming and was amazed at how little was needed – about 10 cubic metres of water a second for the whole of the world.

At the time Salter was working on ways to create rain in drought stricken lands.

“John heard about this and asked if I could make the spray for his cloud idea. I told him that would be no problem which wasn’t quite true as I have been working on it since then but we are nearly there. The way we want to do it is to have a bunch of wind powered ships cruising round the oceans to places we think would be best. The movement through the water will generate some energy which we can use to filter the water to get rid of the plankton and then pump it through tiny holes in a silicon wafer.”

He said the method is now well established and all that is required now is to build the ships and find out precisely where to use them.

“I want to use ships that fly in the water on hydrofoils rather than float,” said Salter. “At one time that was thought too fanciful but now half the boats that sail round the world in the Vendee Globe Race are using hydrofoils. I also want to have them unmanned which people thought was crazy when I first started this but now we have road vehicles which are driverless.”

Salter estimates the cost of each boat, which would last around 25 years, would be £4m which he says is cheaper than holding worldwide climate conferences. About 300 boats in the right place at the right time would be needed, rising to a few thousand to undo the damage if the world continues to use fossil fuels.

“That is certainly manageable – the Americans built nearly 100,000 planes in 1944,” he pointed out.

“He is now at the stage of writing contract specifications which he intends to send out to different factories capable of producing what is needed. Because we can do this in lots of different factories that are already making similar components we could do it very quickly,” said Salter.

Some environmentalists are against the idea on the grounds that it distracts attention from reducing carbon emissions and that it could have unpredictable effects on the climate but he believes the method is both safe and urgently needed.

“As well as reducing emissions we will have to remove greenhouse gases, probably with help from phytoplankton, and also do direct cooling a soon as we can and hopefully ramp it down as emissions reduce,” said Salter.