US cautiously opens door to research on blocking sunlight to fight climate change

Reflecting sunlight away from the Earth is seen as a potentially effective response to climate change and could yield benefits in a few years.

The White House on Friday released a congressionally mandated report on the prospects of using solar geoengineering—including reflecting sunlight away from the earth—to cool the atmosphere, possibly indicating the administration's openness to exploring such an avenue.

Once a controversial concept limited to science fiction, reflecting sunlight away from the earth—known as solar radiation modification (SRM)—could be a potentially effective response to climate change, and could be taken up in the near future as a subject of legitimate research.

However, some scientists say that such an exercise, if carried out, could give rise to unknown consequences arising out of an alteration of the chemical makeup of the atmosphere.

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What does the report say?

The report, released by the White House Office of Science and Technology Police (OSTP) in reponse to a mandate by Congress, was aimed at identifying "critical knowledge gaps" and scoping out "potential research areas that could improve understanding of risks and benefits posed by solar radiation modification."

Most notably, it stated that SRM "offers the possibility of cooling the planet significantly on a timescale of a few years" and acknowledged that "such cooling would tend to reverse many of the negative consequences of climate change."

Methods proposed include multiplying the amount of aerosols in the stratosphere to reflect sunlight away from the planet, increasing reflectivity of clouds over oceans, and reducing the amount of high-flying cirrus clouds that relfect solar radiation back to the planet.

An image showing the most discussed forms of SRM. Credit: White House

However, it also warned that undertaking such an exercise may give rise to "ramifications which are now poorly understood."

Given these uncertainties, the report called for rigorous research into SRM, including on the societal implications of introducing such technology.

"A program of research into the scientific and societal implications of SRM would enable better-informed decisions about the potential risks and benefits of SRM as a component of climate policy, alongside the foundational elements of greenhouse gas emissions mitigation and adaptation," the report urged.

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Why is it significant?

The White House, however, said that the report "does not signify any change in policy or activity by the Biden-Harris Administration" and that there was currently "no plans underway to establish a comprehensive research program" on SRM.

That said, Politico reported that the White House commenting on solar geoengineering at all was a remarkable feat, given how divisive the concept has been.

While some experts say that SRM could be the last line of defence against runaway climate change if greenhouse gas emissions aren't reduced, others warn that deployment of such technology could result in an atmospheric substance dependency, that, if disrupted, could lead to abrupt spikes in temperatures.

"The fact that this report even exists is probably the most consequential component of this release. This report also signals that the US government is supportive of well-governed research, including outdoor experimentation, which I think is quite significant," a top executive of Alliance for Just Deliberation on Solar Geoengineering, a non-profit engaged in the debate on solar geoengineering, was quoted as saying by Politico.

Interestingly, the White House also said that any potential research on SRM must be undertaken with "appropriate international cooperation," a statement that comes days after the European Union (EU) indicated its openness to exploring such an avenue.

"Guided by the precautionary principle, the EU will support international efforts to assess comprehensively the risks and uncertainties of climate interventions, including solar radiation modification and promote discussions on a potential international framework for its governance, including research related aspects," the European Council and European Parliament had said in a joint statement released on Wednesday.