Several Japanese residents invested in a U.S. venture touting to cool the Earth by spreading aerosols in the sky and artificially blocking sunlight despite international criticism, revealing the reality of an overheated environmental business with unclear effects, the Mainichi Shimbun has learned.

Make Sunsets Inc., based in South Dakota, began operations in 2023 with funds from well-known U.S. investors and others. The company launches balloons filled with sulfur dioxide (SO2), which explode in the stratosphere 20 kilometers above the ground. The SO2 chemically transforms into aerosols, creating artificial clouds. The firm claims that these clouds block sunlight and cool the Earth. The idea was apparently inspired by the fact that the Earth is cooled by giant volcanic eruptions.

Make Sunsets has been calling for investment in the product, modeled after carbon credits, which are used to trade greenhouse gas emissions. However, such methods have been criticized around the world on the grounds that they have not been scientifically evaluated and have side effects, but there is no international framework to regulate them.

The startup's co-founder, Andrew Song, 38, said in an interview with the Mainichi Shimbun that more than 100 launches had been made so far, releasing a total of 73 kilograms of SO2. Based on previous studies simulating volcanic eruptions, Song estimated that his company had offset the greenhouse effect equivalent to that caused by 73,000 metric tons of carbon dioxide (CO2). However, this is a very small amount compared to global emissions at some 36.8 billion tons in 2022.

On its website, Make Sunsets solicits investment by selling its own "cooling credits," which it says will offset greenhouse gas emissions by spraying SO2. One credit is priced at $10, which the firm claims is enough to offset the greenhouse effect caused by 1 ton of CO2 per year.

According to Song, 650 people have purchased credits so far, 16 of whom live in Japan. There are also 155 regular buyers, and purchases are made not only by individuals but also corporate managers.

The company, however, has been under intense scrutiny from the scientific community because spraying aerosols into the air could lead to environmental pollution and unexpected climate change.

Following Make Sunsets' preliminary balloon launch experiment in northwestern Mexico in 2022, the Mexican environment and natural resources ministry announced in January 2023 that it would ban large-scale spraying of aerosols in the country. The ministry criticized the company, saying that it had not made a prior notification, that it did not grasp the results of the experiment and that the balloon had been neither monitored nor recovered.

Despite this criticism, Make Sunsets has continued its project. Song insisted that if the sun's energy is cut by about 1 to 2% by releasing 2 million tons of SO2 into the stratosphere every year, the current global warming can be offset. However, the results have not been monitored, and there is no evidence that the spraying so far has cooled the atmosphere.

One researcher in Japan commented, "The spraying technique itself is simple, so it was expected that such people would emerge. There should have been some rules to stop them."

'Carbon credit' system

Under the system, reductions in CO2 and other greenhouse gases emitted by companies and local governments are certified as "credits" and traded. Organizations can convert their credits, or excess emission allowances, into money or purchase them to offset their own emissions. It is known as one of the economic tools to achieve a decarbonized society.

(Japanese original by Mayumi Nobuta, Tsukuba Local Bureau)