Mixing the oceans proposed to reduce global warming

Could nutrients from the deep help remove carbon dioxide from the air?

Quirin Schiermeier

Could mighty pumps be installed in the ocean to mix up the waters and cool the planet? At least some scientists and businessmen believe so — but the idea is controversial.

In a letter to the editor published in Nature this week¹, James Lovelock and Chris Rapley suggest that this deus ex machina could be an "emergency treatment for the pathology of global warming". Large vertical pipes could, they say, be used to mix nutrient-rich waters from hundreds of metres down with the more barren waters at the surface. This could cause algal blooms at the surface, which would consume carbon dioxide (CO₂) through photosynthesis. When the algae die, some of this carbon could sink into deep waters. The algae may also produce chemicals that spur cloud formation, further cooling the planet.