Scientists say we don't know enough about the potential of using geoengineering to fight climate change Solar geoengineering is an unproven technique that could cool down the Earth by blocking out the sun, but there are huge unknowns and potential risks, say scientists. Social Sharing CBC Radio · Posted: Apr 23, 2021 5:17 PM ET | Last Updated: April 23 Solar geoengineering would involve injecting particles into the stratosphere to reflect sunlight back out into space, much like what happens naturally when volcanoes erupt.(SASTRAWAN GINTING/AFP via Getty Images) Quirks and Quarks17:19Understanding geoengineering - why we need to investigate last resort to tackle climate change