‘Termination shock’: trust our expert warnings on geoengineering’s planetary risks | Raymond Pierrehumbert, Julia Slingo, Michael Mann and Valerie Masson-Delmotte

A series in the Guardian recently declared “it’s time to talk about geoengineering.” So let’s talk about it. And let us start with some simple truths about this cluster of techno-optimistic “quick fixes” which purport to somehow offset our slow progress towards zeroing out planet-warming carbon emissions. Solar geoengineering proposals – reducing sunlight – have received the most attention, but a host of desperate schemes have been proposed in an effort to “fix” the disruption of climate caused by the growing burden of carbon dioxide human activities add to the atmosphere. Many threaten the most sensitive aspects of polar environments , extending even to wildly expensive proposals to dam the Bering strait . If implemented, geoengineering schemes would put Earth’s physical climate in a dangerously precarious state, and introduce a major new destabilizing technology to an already turbulent political climate. The essential thing to understand is that carbon dioxide, once emitted, is only very slowly removed from the atmosphere. A sizable share of it will still be keeping Earth dangerously hot millennia from now . Solar geoengineering proposals involve injection of substances whose effect, by contrast, decays in a matter of years. Some might think this is an advantage of solar geoengineering. We can turn it on and off quickly when the damage it is doing to our planet becomes clear, right? Wrong. …