One technique involves releasing particles of sulphur dioxide high up in the stratosphere. Another involves trying to brighten the clouds over the sea by spraying salt water off the back of ships. Both are potential methods of solar radiation modification (SRM), a type of solar geoengineering aimed at trying to reflect more sunlight away from Earth, thus helping to reverse the effects of global warming.

While SRM has attracted attention and investment in recent years, it remains a controversial – and some argue, dangerous – idea.

The Conversation Weekly podcast is running two episodes about geoengineering. In the first part, we heard from scientists working on different potential geoengineering technologies on why they believe they’re worth exploring. In this second episode, we hear the case against SRM from researchers pushing a non-use agreement for solar geoengineering, who explain why they’re so worried about this technology.

Chukwumerije Okereke is professor of global governance and public policy at the University of Bristol in the UK, and co-director of the Center for Climate Change and Development at Alex Ekwueme Federal University in Nigeria. In recent years, he’s become a prominent critic of solar geoengineering technologies:

I think they’re untested, they’re risky,........

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