There are a variety of proposals that involve using vertical ocean pipes to move seawater to the surface from the depths in order to reap different potential climate benefits. One idea involves using ocean pipes to facilitate direct physical cooling of the surface ocean by replacing warm surface ocean waters with colder, deeper waters. New research shows that these pipes could actually increase global warming quite drastically.

Source: Geoengineering proposal may backfire: Ocean pipes 'not cool,' would end up warming climate