Advocates say reflecting solar radiation back into space can help cool a warming planet but opponents fear a devastating free-for-all
Aime Williams in Washington and Alice Hancock in Brussels SEPTEMBER 1 2023
On a Tuesday in August, Luke Iseman drove two hours east of Oakland in drought-stricken California to a remote spot where he launched a handful of balloons filled with sulphur dioxide and helium high into the sky.
From there, he used GPS to try to track the balloons as they rose into the stratosphere, the layer of Earth’s atmosphere that begins about 12km high and contains the ozone layer that protects the planet from solar radiation. Once there, they would burst and release the gas.
Iseman’s start-up, Make Sunsets, is piloting small-scale stratospheric aerosol injections: the sulphur dioxide released by the balloons oxidises to form an aerosol, or fine mist, of sulphate particles that deflect some of the sun’s radiation. So far it has launched 28, each the size of a small weather balloon. “The company’s mission is to cool the Earth as quickly as we safely can,” he says.
It is a rudimentary version of a niche climate solution broadly known as solar radiation management — the idea that the Earth can be cooled by reflecting some of the sun’s rays back into space. Other SRM techniques range from painting the world’s roofs white to putting giant mirrors into orbit.
“Pretty much every country that has a climate scientist is interested [in SRM],” says Daniele Visioni, assistant professor in the department of Earth and atmospheric sciences at Cornell University, although the majority of research is concentrated in the US and Europe.
Proponents argue that humanity’s lack of progress in curbing carbon emissions means society will increasingly need to look at more drastic ways to limit the worst effects of warming as well as trying to prevent further rises in global temperatures.
July was declared the hottest month ever recorded, according to Copernicus, the European Union’s Earth observation agency. The Intergovernmental Panel on Climate Change warned earlier this year that the average global temperature would reach 1.5C above pre-industrial levels “in the near term”. The 2015 Paris Agreement pledged to “pursue efforts to limit” the increase to that amount.
In its most recent report on SRM, the UN Environment Programme described the technology as the “only” way to cool the planet in the short term.
Pascal Lamy, a former director-general of the WTO who now chairs the Climate Overshoot Commission, a civil society group working on ways to mitigate the effects of exceeding the Paris Agreement target, says governments should “open the box” and research solar radiation management.
Pascal LAMY 