Proposals to fight the impact of the climate crisis at the poles, from giant underwater curtains to scattering glass beads across the ice, have been dismissed by a group of scientists as an unimaginably expensive and dangerous distraction. Geoengineering, which includes blocking sunlight with airborne particles and thickening ice with pumped seawater, has become highly divisive among scientists. Its proponents argue that, with cuts in carbon emissions going far too slowly, exploring options for emergency brakes would be valuable.