Climate engineering, the ambitious attempt to deliberately modify the Earth's climate to mitigate the effects of global warming, may have to deal with a new, unexpected adversary. Which? Solar eclipses.
The study conducted by an international team of researchers enriches our understanding of atmospheric dynamics, but raises crucial questions about the effectiveness and possible contraindications of geoengineering techniques.
Impact of eclipses on clouds
Recent scientific observations have revealed that during solar eclipses, a specific type of clouds, known as cumulus, tends to dissolve almost instantaneously over land areas. The disappearance of clouds, long observed only anecdotally, has now been scientifically documented.
The international team led by Victor Trees includes scientists from Delft University of Technology and the Royal Netherlands Meteorological Institute. I'll link it all here if you want to learn more.
This is a phenomenon that could have significant repercussions on any future attempt at climate manipulation.
Study methodology
The research addressed the challenges of measuring the effects of eclipses on clouds, overcoming the limitations of previous studies (which did not adequately consider the partial lunar shadow). Using an innovative method, the researchers were able to analyze data from previous eclipses, providing an accurate picture of how partial obscuration of the Sun affects the formation and dissipation of cumulus clouds.
The results – Cumulus clouds begin to disappear when only a small part of the Sun is obscured by the Moon, with effects that appear already with very limited solar obscurations (~15%). This phenomenon appears to be due to the reduction of sensible and latent heat fluxes from the Earth's surface to the lower atmosphere, caused by the decrease in Earth's surface temperature during the eclipse.
Eclipses and clouds, in simpler words
Imagine that the Sun is a giant lamp that heats a room (our Earth). Cumulus clouds are like cotton balls floating in this room, formed by heat rising from the floor. During a solar eclipse, it's as if someone begins to partially dim the lamp, reducing the heat in the room. Even if the lamp is covered only a little (~15%), the room starts to cool down.
The cotton balls (the clouds), which had formed thanks to the heat, begin to dissolve because the floor (the earth's surface) is no longer hot enough to send up enough "steam" to keep them together. Basically, when there is less heat rising from the ground, there isn't enough energy to keep the cumulus clouds forming, and so they start to disappear. This shows us how sensitive our clouds are to changing temperatures on Earth. Even with very small variations, such as those caused by a partial eclipse of the Sun.
Imagine if there were even more widespread dynamics at play, like those feared in some geoengineering projects.
We are very careful
In summary, the observation of rapid dissipation of cumulus clouds during solar eclipses raises important questions regarding climate engineering proposals. The potential reduction in cloud cover could, in fact, contradict the planet's cooling goals, given the role of clouds in reflecting sunlight and contributing to the Earth's heat balance. And it's not the first warning we've received, after that of MIT.
This is why we need to increase our understanding of atmospheric and climate dynamics before proceeding with any large-scale climate engineering intervention. Or we could end up making things even worse. And by a lot.
