Cooling the Earth with geoengineering. The proposal on the UN table and the governments
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Climate, last resort. The umbrella could be opened, a very large umbrella, of course, enough to cool a large part of the planet. The summer metaphors end there. There geoengineeringespecially the “solar radiation modification” (Srm), which consists in making “shadow”, shielding the sun’s rays, reflecting them in space with, for example, artificial clouds, is on the table as an option of the United States Congress and also of the European Parliament and Council with a “joint communication” of the Commission and the High Representative for Foreign Affairs. In the same week, by the way. After an independent panel of experts convened by the United Nations Environmental Program in February published an analysis on the possible effects of “solar radiation modification” (alteration of solar radiation). In short, it is being taken seriously because, according to the analyzes proposed, it would be effective immediately in cooling the planet and would cost incredibly little.
The same is doing the Overshoot commission of the Paris peace forum, dedicated to strategies to reduce the risks of global warming. However, many scholars are skeptical if not against it, because it would be a leap in the dark, with feared consequences on the climate and still unpredictable “side effects”. A possibly even worse scenario than the one that the global warming has already put before our eyes. And that, in addition, could undermine the strategy of reducing emissions, which is already lame.
Thus the sun is blocked
It’s about blocking solar radiation, the amount of energy, heat, that comes to us from our star. The Earth would cool off with almost immediate effect. How you do it? Imitating Nature, therefore creating artificial ‘volcanic’ clouds. There are some famous examples that are usually done. The eruptions of Pinatubo (1991) and Tambora in 1815 which projected millions of tons of sulfur into the upper atmosphere. In both cases, in the immediately following periods, the global temperature dropped rapidly. A solution of Srm would therefore be to enter aerosols in the stratosphere (Stratospheric aerosol injection, Sia), a particulate matter that reflects part of solar radiation, using high-altitude aircraft.
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It is by far the most studied method and for which the immediate effects are known, precisely because they have already been observed with volcanoes, with the sands of the Sahara and also with emissions along the marine routes of boats. But we also know more. Suffice it to mention the American report (here the .pdf) which speaks of the eruption of Tambora Volcano to understand the level of skepticism with which these solutions are rightly viewed: “The eruption of Tambora cooled the Earth by 0.7°C and led to a ‘year without a summer’ (1816), precipitation patterns altered , interrupted monsoons, and led to floods that resulted in crop failures, famine, and the spread of disease. Understanding these and other potential negative impacts of SRM is as important as understanding the potential benefits.”
Among the hypotheses are also taken into consideration low-level marine cloud bleaching (Marine cloud brightening, Mcb). It has long been noted that, in satellite images, the oceans are streaked with bright white streaks of clouds that correspond to shipping lanes. They are the result of the suspension of tiny particles produced by ships. They reflect more sunlight back into space than normal clouds, and far more than the dark blue ocean. An aspect recently noted concerns precisely this point: in 2020 the legislation prohibited fuels for ships with a sulfur oxide percentage higher than 0.5% (previously it was 3.5%). The result is one better air quality: “A reduction in strokes, asthma, lung cancer and cardiovascular and pulmonary diseases is expected – reads the website of the International Maritime Organization https://www.imo.org/en/MediaCentre/PressBriefings/pages/34-IMO -2020-sulphur-limit-.aspx – Reducing sulfur emissions from ships will also help prevent acid rain and ocean acidification, benefiting crops, forests and aquatic species.”
Pollution or geoengineering
However this year the ocean temperature, especially the northern Atlantic and Pacific, is unusually high in the areas with the most shipping traffic. Some climatologists have correlated this anomaly with the precipitation of sulfur concentrations in the atmosphere whose cooling effect was well known, although there is no absolute certainty and other factors must be taken into account, including El Niño and the absence, also anomalous, of the Saharan sands carried by currents across the Atlantic. Even the finest dust particles in the desert are atmospheric particulates that shield and reflect sunlight.
Instead, we could intervene on the thickness of the cirrus clouds, clouds in the upper atmosphere that reflect the infrared radiations responsible for heating and the greenhouse effect towards the Earth. Little studied and not very practicable solution. As well as the very futuristic idea of placing one or more giant reflecting mirrors in space to directly block solar radiation before it enters the atmosphere. Artificial eclipses whose costs and, above all, feasibility, do not seem to be within the reach of current technologies.
Face to face with chaos
The analysis of the panel of experts chosen by the UN says two very important things. These methods, especially the first two (Sai and Mcb), would be effective immediately in reduce the temperature. The estimate of the studies cited by the report says that “continuous injection rates of 8-16 Tg (thousand tons ed) of sulfur dioxide (SO2) per year (roughly equivalent to the estimated amount emitted by Mount Pinatubo in 1991 alone) would reduce the global average temperature of 1°C”. At an all in all affordable price: $20 billion a year. But beware: we are only talking about temperature reduction. Problems related to the concentration of carbon dioxide such as ocean acidification would not be solved at all. Not to mention a much feared “psychological” effect: consider this a substitute for reducing greenhouse gas emissions. A mistake not to be made.
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The second point concerns the consequences of this geoengineering intervention on different scales. The global, regional and local effects. It is the real leap in the dark. The Earth, the atmosphere, the seas and the oceans form a chaotic system. Scientists are currently unable to predict what effects a sudden cooling triggered by one of these systems will have in the short, medium and long term. We start from what is defined as a climatic overcompensation in some areas, such as the tropics, which would cool rapidly unlike the poles. The change could modify the atmospheric and oceanic currents, disturbing the seasonality of phenomena such as monsoons, hurricanes, the North Atlantic oscillation and the Pacific oscillation, responsible for El Niño, the polar vortex. With potentially disastrous consequences.
“The model results indicate that a Sai implementation using highly reflective sulfates (which also absorb significant amounts of shortwave radiation) could cause a more intense phase of the North Atlantic Oscillation, with more precipitation and devastating flooding in parts of Northern Europe and severe droughts over parts of the Mediterranean”. Scenes we’re already getting used to, and that we’d like to avoid by falling from the frying pan into the fire.
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The use of sulfur compounds could mean acid rain and damage or delay in repairing the ozone layer. In some equatorial and tropical areas changes in the spread of diseases are expected. “Modeling studies indicate that if Sai were distributed on a scale sufficient to prevent sea level rise or preserve large ice sheets in Antarctica And Greenlandthe negative effects described above would be pronounced”. The unpredictability of what could be triggered, putting a hand on the mechanisms that govern the climate, would have another feature that worries analysts: its effects could be unleashed anywhere. And as with the global warming, the poorest countries could be the ones to suffer the most. For this reason, UN, American and European documents underline that the study of these solutions, their possible application and governance must be managed with international coordination .
To give an idea of the difficulty that arises, suffice it to say that the US analysis itself underlines how processes on a micrometric scale are involved (one thousandth of a millimetre, chemical processes and those of aerosol particles, particulate matter), up to the global one, with the influence on atmospheric currents and the Earth’s climate. Here the famous metaphor of the butterfly flapping its wings and unleashing a storm on the other side of the world comes in handy. The White House itself, in the report, underlines that its drafting was requested by Congress and does not imply any decision regarding solar radiation management. There is skepticism, in short.
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The fact is that geoengineering would aim to change the climate, which we have already done, in the opposite direction of what we have caused so far. We are seeing the effects of the first (unintentional) human intervention and they are not pleasant. Rather, they are very often catastrophic and difficult to predict. Will turning the switch in the opposite direction help or have we already opened a Pandora’s box? The White House calls for a “risk vs risk” analysis, meaning that at a certain point it will be necessary to decide whether it is worth taking a leap in the dark, hoping that the side effects will not be more disastrous than the “zero” scenario, i.e. without this geoengineering intervention. But at that point all that would be left was to rely solely on reducing emissions and safeguarding forests. Efforts that, it seems, are not having great success.
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