Modify the clouds to cool the planet

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The main suggestions are to reduce CO2 emissions and increase carbon sequestration, all in the hope of reducing the effects of climate change and, more precisely, global warming. Scientists working in the field of geoengineering are exploring other strategies that can also make an important contribution to this effort.

On the one hand, some scientists want to imitate nature by injecting particles into the stratosphere, others propose sweeping a certain type of sky clouds. The main goal is the same: to help stop global warming on the planet. The authors of the articles published in Science underline that, before proceeding, it is necessary to study very well the possible secondary effects of these measures, since they manipulate in an artificial way in the sky.

“These are things that have not been put into practice and which, for now, theoretically work and theoretically make sense”, said Alfredo Rocha, a professor in the Department of Physics and the Center for Environmental and Marine Studies at the University of Aveiro. The proposed injection of sulphate particles into the stratosphere is not surprising and is based on a natural phenomenon, he said. “When there are very strong volcanic eruptions, such as that on Mount Pinatubo in the Philippines in 1991, there is an injection of sulphate particles into the stratosphere that reflect solar radiation and prevent it from entering the planet, there the Earth ceases to heat so much”.

All the models presented in the study suggest that this artificial intervention can mitigate changes caused by greenhouse gases in global temperature and extreme precipitation. But researchers at the Max Planck Institute for Meteorology in Germany and the US National Center for Atmospheric Research warn that this action may slow down the hydrological cycle and consequently reduce rainfall and water availability. One of the main issues is related to the number of particles that need to be injected to achieve the desired effect without harm.

Another, has to do with the costs of this operation: “Assuming a scenario of aggressive mitigation and a large-scale catch that could start as late as 2040, it would be necessary to inject sulfate for 160 years to limit the increase in temperature on the planet to 2 ° Celsius – such an adventure could cost more than 17 billion euros per year”.

There are many types of clouds and they have different effects, so the researchers at the Institute of Atmospheric and Climatic Science in Switzerland are the cirrus. Clouds that look like thin rags of cotton that form at an altitude that can reach 10 kilometers (almost in the stratosphere) and which are made of ice crystals. “They are clouds that are situated high above and practically transparent. Solar radiation passes through the cirrus, but absorbs a lot of radiation emitted by the Earth into space and then emits to the surface again”.

“This will heat the Earth’s surface as it warms up more carbon dioxide or water vapor in the atmosphere”, explained Alfredo Rocha. Scientists want to decrease the thickness and quantity of these clouds in the sky. But how? Creating artificial clouds with molecules that attract moisture.

“In terms of science, I find it very interesting to change the area and thickness of cirrus clouds. Basically, it is changing the way the cloud is formed. Instead of just being liquid particles that have frozen, it is to introduce solid particles around which the water vapor will deposit and freeze”, said the UA professor. “Clouds of another type are created, and with another thickness and eventually lower, they descend a little. They will be cirrus modified by human action”.

The authors of the article also warn that if the manufacture of these artificial clouds is not done in the right way, the effect may be the opposite of what is desired and instead of helping to cool the planet, we can rather warm it.

“You have to be careful. We can do an evil to the atmosphere and then we cannot correct”, said Alfredo Rocha, adding that these proposals are promising, but they have to be well studied. “Reducing emissions and reducing CO2 in the atmosphere is something that will take a long time to produce an effect.

Some of these new measures are likely to be able to reduce the effects of climate change much more quickly. It is necessary to evaluate the relationship of the benefit of a remedy and its side effects.

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