Space mirrors could be one way to cool Earth, a new UN report claims

A report from the United Nations says that to meet climate goals, it might be necessary to set up big mirrors that reflect sunlight into space.

One of the radical ideas the UN Environment Programme put forward to stop a climate emergency is solar radiation modification (SRM), also called solar geoengineering. This comes in light of other efforts by some researchers to release hundreds of grams of sulfur dioxide into the stratosphere from balloons to produce a similar cooling effect.

“SRM is the only known approach that could be used to cool the Earth within a few years,” the report, compiled by an expert panel of climate scientists, stated.

“Climate model simulations consistently show that SRM could offset some of the effects of increasing greenhouse gases on global and regional climate, including carbon and water cycles, but there could be substantial residual or overcompensating climate change at the regional scales,” it concluded.

The report concluded that additional research is required to comprehend geoengineering technologies' environmental and social effects. Injecting large aerosols into the upper atmosphere to block out the sun was one of the other technologies mentioned in the report.

It's not the first time space mirrors have been suggested to lessen the worst effects of climate change. Andrew Yang, a former candidate for president of the United States, devised a plan to fix the planet in 2019.

His plan to put huge, foldable space mirrors in orbit would cost $4.86 quadrillion and take about twenty years to implement. The United Nations said that the world's efforts to cut greenhouse gas emissions are not on track to meet the 1.5°C goal set by the Paris Agreement.

The head of the United Nations Environment Programme, Inger Andersen, said that SRM shouldn't be seen as a replacement for current goals to cut emissions. “It does not remove carbon from the atmosphere. Nor will SRM improve the environment or tackle the root causes of climate change,” she said.

“Our best bet for a prosperous and equitable future remains [to put] in the unavoidable hard work to achieve climate stability by reducing greenhouse gas emissions, to create a pollution-free planet and societies that live in harmony with nature.”

However, other scientists warn that such mirrors would only address one aspect of climate change—the warming caused by solar radiation. Other effects of greenhouse gas emissions, like making the oceans more acidic, would still happen. So, depending only on space mirrors could make it harder to reduce greenhouse gas emissions.

Deploying giant space mirrors could have unintended consequences for the Earth's climate system. For example, mirrors could change how clouds, rain, and wind move, affecting the weather and climate on a local, regional, or global scale.

So, while using big mirrors in space to cool the Earth may seem appealing, it's essential to consider the bad things that could happen first.