A startup says it’s begun releasing particles into the atmosphere, in an effort to tweak the climate

A startup claims it has launched weather balloons that may have released reflective sulfur particles in the stratosphere, potentially crossing a controversial barrier in the field of solar geoengineering.

Geoengineering refers to deliberate efforts to manipulate the climate by reflecting more sunlight back into space, mimicking a natural process that occurs in the aftermath of large volcanic eruptions. In theory, spraying sulfur and similar particles in sufficient quantities could potentially ease global warming.