The United Nations says the speculative technology to reflect the Sun away from Earth needs to come into focus

A. said A new report from the United Nations was published on Monday.

Reducing greenhouse gas emissions is the only way to permanently slow global warming, but global efforts to reduce greenhouse gas emissions are “currently not on track to meet the Paris Agreement’s 1.5°C target,” the UN Environment Program said in a statement. A written statement accompanying the release of the report.

With the world not responding to climate change urgently enough, a “speculative array of technologies” for reflecting sunlight away from Earth has received more attention recently, the UN Environment Program said in a written statement accompanying the report. This class of technologies is often called solar radiation modulation (SRM) or solar geoengineering more broadly.

The report on these technologies, written by a panel of experts put together by the UN programme, advised that it was not currently a good idea to use them in an effort to respond to climate change.

However, “this view may change if climate action remains insufficient,” the report states, noting that it is time for careful consideration of both technologies and potential international governance.

A similar message came from a group of more than 60 scientists in an open letter also published (accidentally) on Monday.

The UN report said solar geoengineering “is the only known method that can be used to cool the Earth in a few years,” and would cost tens of billions of dollars annually per degree of cooling.

Although there is no technology to inject large amounts of aerosols into the upper atmosphere today, it is not seen as terribly complex: “No technical obstacles to supply have been identified,” the UN report states, and it could be “developed” in less than ten years.”

Scientists know it works quickly, citing the drop in the global average temperature after large volcanic eruptions that spewed large amounts of aerosols into the upper atmosphere. The United Nations study said that these observations of volcanic activity provide “strong evidence that the deliberate injection of large amounts of reflective particles into the stratosphere would rapidly cool the Earth.”

“If global warming at some point leads to outcomes that are widely viewed as intolerable (such as widespread famine, mass migration, mass deaths, and destruction of infrastructure), then deploying an operational SRM as part of a ‘planned’ emergency response may be able to mitigate some of these suffering in a few years’ time,” according to the report.

But technologies can also be dangerous.

For example, sulfur dioxide is usually suggested as an aerosol, but this practice can lead to acid rain, the report warned. It can also further deplete the ozone layer. Specifically, “the recovery of the Antarctic ozone hole could be delayed by two decades and the ozone hole could get deeper in the first decade of SAI” [stratospheric aerosol injection] The UN report said.

So solar geoengineering can be seen as a one-time opportunity to alleviate the extreme suffering and death caused by climate change.

Or sunlight reflection technology could become part of a long-term “phasing” strategy to buy more time to permanently and permanently reduce greenhouse gas emissions.

Regardless, experts acknowledge that we don’t know enough about the side effects of these techniques.

“We only have one atmosphere. We cannot risk doing more damage to it by taking an incomprehensible shortcut to repair the damage we have already done,” Inger Andersen, executive director of the United Nations Environment Programme, wrote in an introduction to the study.

Currently, there is not enough reliable information to make an informed decision.

“The review found that there is little information about the risks of SRM and limited literature on the environmental and social impacts of these technologies,” Andersen wrote. “Even as a temporary response option, widespread deployment of SRM is fraught with scientific uncertainties and ethical issues. The evidence base is simply not there to make informed decisions.”

In addition to the need for a rigorous scientific study, the report added that there is a need for a globally coordinated governance strategy for any potential use of solar geoengineering technology.

But the relatively low cost — it can be deployed for less than $20 billion per 1 degree Celsius of cooling per year — means it is “within reach” of many countries and organisations, opening up the possibility of “rogue deployment”, the report said.

The report said the United Nations could be a leader in global discussions of solar geoengineering talks, noting that a lack of international cooperation and governance is likely.

“One can assume that there will never be a universal consensus in the broader community on the deployment of SRM, which means that communities, nations, and communities that oppose the deployment of SRM will be swayed against their wishes, raising ethical and legal concerns,” the study said.