A technical workshop conducted last week by marine scientists and hosted by the Zoological Society of London (ZSL), the International Programme on the State of the Ocean (IPSO), and the Royal Society concluded that temperature-induced mass coral bleaching began killing many of the world’s coral reefs and their ecosystems when global atmospheric CO2 exceeded 320ppm (parts per million), about 20% below today’s levels.
360ppm is the level at which reefs “cease to be viable in the long term,” according to coral reef specialist Professor John E.N. Veron of the Center for Marine Studies, University of Queensland. Atmospheric concentrations of CO2 currently stand at approximately 385ppm, depending on the part of the world in which the atmosphere is sampled.
In addition to temperature-induced bleaching, coral reefs in many parts of the world are under stress from overfishing, destructive fishing, coastal pollution, and sedimentation.
A joint statement issued by conference participants declared:
To ensure the long-term viability of coral reefs, atmospheric carbon dioxide level must be reduced significantly below 350ppm... In addition to major reductions in CO2 emissions, achieving this safe level will require the active removal of CO2 from the atmosphere.
The Earth’s atmospheric concentrations of CO2 reached 320 ppm in the mid-1960s, and 360ppm in the mid-1990s. The joint statement will be submitted to the United Nations Framework Convention on Climate Change (UNFCCC) ahead of December's climate policy negotiations in Copenhagen.