PLEA Network

28 January 2016, Climate Home, Scientists pour cold water on ocean geoengineering idea. One keenly-argued possible way of moderating the build-up of carbon dioxide in the atmosphere may not work, scientists have concluded. They say there is evidence that seeding the oceans with iron so that the algae that live there will multiply and devour more CO₂ − thus preventing it reaching the atmosphere and intensifying the human contribution to global warming – is not as promising a solution as its supporters hope. The extra iron can certainly stimulate the algae to grow more vigorously, but at a cost. More algae in one part of the oceans may mean there will be fewer in other areas, the researchers say. Report: Scientists warn against geoengineering as short-term climate fix. They report in Nature journal that the depths of the central Pacific Ocean contain ancient sediments that cast doubt on iron’s ability to slow the Earth’s steady temperature rise. In parts of the oceans that lack the iron that plants need, algae are scarce. Experiments have shown that dumping iron into these areas can encourage algal growth, so large-scale fertilisation could theoretically reduce atmospheric CO₂. The seafloor sediments the team studied show that, during past ice ages, more iron-rich dust blew from cold and barren landmasses into the oceans, apparently producing more algae in these areas and, presumably, a creating natural cooling effect. But the researchers say increased algal growth in one area can inhibit growth elsewhere, because ocean waters are always on the move and algae also need other nutrients, such as nitrates and phosphates. Read More here