Coral reefs, as they were 50 years ago, will not be found anywhere on Earth by the middle of the century, even if December's Climate Change Conference (COP21) in Paris is "wildly successful," an expert has warned.
The stated aim for the COP21 climate conference is to limit a temperature increase to less than 2 degrees Celsius by the end of the century.
Speaking at the Goldschmidt conference in Prague, Professor Peter F Sale from the University of Windsor, Canada spelled out the stark choice facing climate scientists in the run-up to the Paris conference later this year.
"Even if Paris is wildly successful, and a treaty is struck, ocean warming and ocean acidification are going to continue beyond the end of this century," said Sale.
"This is now serious; I find it very unlikely that coral reefs as I knew them in the mid-1960s will still be found anywhere on this planet by mid-century. Instead, we will have algal-dominated, rubble-strewn, slowly eroding limestone benches," said Sale.
"I see little hope for reefs unless we embark on a more aggressive emissions reduction plan.
"Aiming for CO2 at 350ppm, or a total warming of around 1 degrees Celsius is scientifically defendable, and would give reefs a good chance; a number of coral reef scientists have called for this," he said.
A goal of stabilising CO2 at less than 350ppm is also environmentally cautious.
Getting to 2 degrees Celsius or so, overshooting along the way, is unwise, self-defeating, and may have far more serious consequences than are dreamed of by politicians happily negotiating minimalist responses to climate change, researchers said.
"As well as CO2 emissions, we must also deal with our other insults to the oceans. We have lost 90 per cent of our commercial fish biomass since the 1940's, we are polluting coastal waters, and the great majority of marine protected areas are not being protected," Sale said.
"Either we agree limits, which means the end of the' high seas', or we let large parts of the seas die," said Sale.
"Knowing what we are doing, do we have the ethical right to eliminate an entire ecosystem from this planet? It's never been done before. But watching as our actions lead to the loss of all coral reefs on the planet is like removing all rainforests. I don't believe we have that right," Sale said.
"This is a global emergency, which requires us to decarbonise within the next 20 years, or face temperatures that will eliminate ecosystems like coral reefs, and indeed many systems that humans depend on," said Professor Ove Hoegh-Guldberg, Coordinating Lead Author of section on 'The Ocean' within the latest IPCC (Intergovernmental Panel on Climate Change) report.
"At the same time, dealing with non-climate stresses will be vitally important - we must buy time by building resilience in Earth's biological systems, given that even more stringent activities will still result in much warmer and more acidic oceans, than today," Hoegh-Guldberg said.