If climate change is not prevented by reducing CO2 emissions, scientists want to use technical interventions to cool the world down again. One concept wants to create large clouds over the seas.
The best way to stop climate change would be to reduce CO2 emissions until carbon balance is achieved. Then no more CO2 is released than is simultaneously bound by plant growth.
But the world is far from that. Instead of less, more and more CO2 is being blown into the atmosphere. The greater the doubt that efforts to save the climate are sufficient, the more interesting other approaches become. They promise a shortcut on the long road to stabilizing the climate.
Science writer Tim Smedley presents some of these visions in his book Clearing the Air: The Beginning and the End of Air Pollution. They all have one thing in common: Not less, but more technology should bring the climate back on track. Instead of restoring the natural conditions of the years before 1950, they want to artificially recreate a climate – a world climate that is cooler.
Less sun, less heat
The starting point for many considerations is the eruption of the Pinatubos volcano in the Philippines in 1991. It ejected particles ten kilometers high. This veil of dust had a noticeable cooling effect, keeping out the sun’s rays. This discovery led to several concepts. The most exotic idea is some kind of gigantic parasols in space that could partially shade the earth.
Technically less complex models tie in with the role of ice and clouds. About 30 percent of the sun’s rays are currently reflected back into space off white surfaces. If the bright area is reduced – for example due to the melting of ice – this increases the climate increase even more.
The open sea, on the other hand, reflects only 6 percent of sunlight and absorbs 94 percent. As long as there are no clouds over the water. Marine stratocumulus clouds reflect a good portion of solar radiation, and they also cool the sea. So what if it were possible to create more and whiter clouds?
It has been known since the 1970s that ships leave a cloud trail behind them. The dirt from their chimneys acts as a condensation nucleus. Water droplets collect around the particles. In the 1990s, Stephen Salter, a professor at the University of Edinburgh, and the atmospheric scientist John Latham worked together. Your suggestion amounts to some kind of cloud ships. They work like a snow cannon, but of course they are not supposed to produce snow, but white clouds.
Cloud Cannons on the Sea
Of course, the soot from the ship’s diesel should not be used as a condensation nucleus. Salter and Latham want to use salt particles that can be extracted from seawater. Technically, the project is more complex than initially expected because seawater clogs the spray systems and especially the valves in the long term. Nevertheless, these ships would not be a high-tech project, but simply constructed.
The pair’s latest design is an unmanned sailing ship that pumps an ultra-fine mist of sea salt towards the clouds. The now retired professor is quite optimistic. Salter told Tim Smedley, “If we sprayed like 10 cubic meters per second, we could undo all the damage we’ve done to the world so far.”
300 boats could reduce temperatures worldwide by 1.5 degrees. At the same time, the targeted use of some ships could at least mitigate the formation of hurricanes if they specifically reduce the heating of the sea water. Stephen Salter promises the same for phenomena like El Niño.
A cloud ship fleet of small autonomous sailing ships still looks pretty natural. Other researchers dream of injecting chemicals into high layers of the air so that a veil would form, reflecting the sun’s rays there long before they even reached the lower layers.
These techniques promise a real prospect of significantly reducing climate gain at comparatively very low cost. Nevertheless, projects of this kind are controversial and are rarely added via laboratory tests. Why is that?
experiment with an uncertain outcome
On the one hand, there is clear opposition from climate researchers and activists. They fear that the fight against the increase in CO2 in the atmosphere will no longer be vigorously fought if there are alternative, cheaper and more convenient methods. Then more and more fossil fuels would continue to be burned. Instead of struggling with an expensive global energy transition, one would rather fog the seas with clouds, create haze in the outer atmosphere and possibly also hang shadow sails of gold in space.
Even if the project were to succeed, it would be anything but a natural world climate in a natural balance. The fear is that once geoengineering has started on a large scale, there is no way it will ever stop.
The second reason for rejection lies in the technology itself: the research can only predict partial consequences of the interventions. But no one can predict the full impact of these interventions on a system as complex as the global climate. No one will dispute that more clouds mean more solar reflection. But hardly anyone can guarantee that the desired cooling would be the only effect of the measure and that forced cloud formation over the oceans would otherwise have no effect. Rainfall could change, air currents could seek new paths. Perhaps we would soon be living in a kind of headlock under a dense cloud cover.
Source: Tim Smedley, “Clearing the Air: The Beginning and the End of Air Pollution”, Justice and responsibility in climate and energy policy, Royal Society “Navy cloud brightening“