Giant mirrors positioned to reflect sunlight back into space may be needed to meet climate targets, according to a report from the United Nations. Solar radiation modification (SRM), also known as solar geoengineering, is among the proposals from the UN Environment Programme to use radical technology to avoid a climate emergency. “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...