The Great Barrier Reef and the prophets of doom

The severe global bleaching event of 1998 has not been repeated in a decade despite an ongoing increase in atmospheric carbon dioxide and oceanic surface temperatures have markedly decreased. Projections from highly dubious climate models are anything but certain.

"On present forecasts, the worst bleaching year we have had to date will be an average year by 2030. And it will be a good year by 2050."

This is an assertion based solely on an unqualified faith in the projections derived from unverified climate models which differ widely among themselves. These projections are also constantly changing with new "adjustments", are highly dependant on numerous uncertain assumptions and estimates, incorporate greatly simplified treatments of complex poorly understood phenomena and can be readily adjusted to produce a broad range of equally plausible projections. Most such models, in fact, predict little warming in the tropics but much greater increase at high latitudes.

"If we keep increasing greenhouse carbon dioxide, by 2050 at the very latest, the only corals left alive will be those hiding in refuges such as deep outer reef slopes. The rest of the Great Barrier Reef will be unrecognisable. Bacterial slime, largely devoid of life will be everywhere."

This isn't even supported by any model but might better be described as emotive dramatisation. Even the more extreme model projections only depict tropical oceanic warming still well within the limits that thriving reefs now tolerate in the Red Sea. Warmer water could also be expected to expand the geographic extent of reefs to higher latitudes.

"I cannot escape the conclusion that ocean acidification has played a major role in all five mass extinctions of the past."

"Cannot rule out the possibility …" would be the strongest statement sound science could support. It is entirely unclear whether past acidification episodes caused the mass extinctions or were simply one of a number of disastrous accompaniments to massive volcanic or impact events which were the primary cause of the extinctions.

Three widespread studies of reef coral calcification rates in South-East Asia, on the Great Barrier Reef and in the Caribbean, all found substantially increased calcification rates during the past half century: however, the reef catastrophists have now come up with a much smaller scale study that found reduced average calcification during a 16-year period encompassing two bleaching events in a few specimens from inshore reefs on the Great Barrier Reef. Much has been made from this barely detectable trend in a very limited, highly varied, sample. Without the tenuous suggestion of a link to global warming it is doubtful the study would have even found publication in a peer-reviewed journal.

During the Cretaceous period when vast marine carbonate beds were deposited carbon dioxide levels were far higher than anything projected in connection with anthropogenic emissions.

"Corals speak unambiguously about climate change. They once survived in a world where carbon dioxide from volcanoes and methane was much higher than anything predicted today. But that was 50 million years ago. The accumulation of carbon dioxide then took millions of years, not just a few decades. Then there was time enough for oceans to equilibrate."

Many current reef coral genera survived this event. The idea that the increase in atmospheric carbon dioxide associated with massive vulcanism or meteoritic impact events took millions of years is only a convenient but unlikely assumption.

"… the rate of carbon dioxide increase we are now experiencing has no precedent in all known geological history."