There is a widespread belief, cultivated at least in part by Prof Ove Hoegh-Guldberg that global warming has resulted in more coral bleaching.
Given the interest in the subject, I have copied the following comment from Dr Walter Starck, from yesterday's rather long and tedious thread:
"Bleaching events result from extended periods of calm weather during which mixing from wave action ceases and surface water becomes exceptionally warm. Such warming is especially marked in very shallow water such as on reef flats. At the same time the absence of waves also eliminates the wave driven currents that normally flush the reef top. Bleaching conditions require at least a week or more of calm weather to develop and this may happen every few years, only once in a century, or never, depending on geographic location. On the outer GBR it is uncommon due to ocean swell and currents even in calm weather. In the mid-shelf and inshore areas it is much more common due to the absence of swell and reduced currents.
Characteristic bleaching scars and isotope temperature records from coral cores commonly show evidence of past bleaching events going back thousands of years. There is no evidence for a recent increase in frequency and/or severity of bleaching events and nothing to link extended periods of calm winds with global warming.
In past geologic periods when global climate was warmer than at present corals enjoyed greater latitudinal distribution. The most likely effect of a warming climate on reefs would seem to be an expansion of their geographic distribution and there is some evidence this is already happening. In Florida recent growth of coral has occurred farther north than it did a few decades ago and in the same areas sub-fossil corals indicate previous such advances in the recent geologic past.
Hoegh-Guldberg has found an attractive GW niche in the well established guild of GBR doomscryers. It has provided notoriety, acclaim and generous research support. Whether his prophesies will stand up to the reality test remains to be seen. Based on the track record of science based doomscrying his odds don't look too good. In fact sheep's entrails and tea leaves seem to produce better results, probably because they at least incorporate some element of intuitive judgment."
Last year Walter wrote a review titled 'Threats to the Great Barrier Reef', published by the IPA, it can be downloaded by clicking here.
This picture was taken at the Great Barrier Reef by Roger Steene:
I've already agreed with the three Australian researchers whose paper Phil cited above that the fundamental research question that remains to be answered is, 'Can organisms and ecosystems accommodate, acclimatise to or adapt to rising temperatures faster than ocean temperatures may rise?'
I also agree with the researchers that 'the response of corals, coral reefs and other significant reef organs to climate variability will be complex.'
I do not believe that these research findings support CSIRO's unqualified assertion, stated as a matter of certainty, that an increase of 1-2 deg. C over an unspecified period into the future, would mean that '58-81% of the GBR is bleached every year.'
This argues for Walter Starck's presciption for
'Open, objective, rational, evidence-based analysis.'
I agree with bambam that, considering the size and importance of the GBR, we are scratching for both LOCAL science and scientists. But I find it encouraging that the authors of the McNeil et al papers recently published in Geophysical Research Letters come from three different Australian research institutions.
I for one don't want to see research of this calibre picked off by 'any bunch of would be experts in the media' - or even by the expert at another institution whose position in 1999 was 'that corals have no defences against factors bringing about bleaching.' (I don't know what Prof. H-G's present stance is, but I'm not impressed with his statements in press releases over the past few months).
Phil raves on Hockey Stick. Snore - grizzle.
More maths errors asserted.
http://timlambert.org/category/science/mckitrick/
Read the comments including Wag The Dog
http://illconsidered.blogspot.com/2006/03/hockey-stick-is-broken.html
Amman and Wahl 2006 are in press.
http://www.cgd.ucar.edu/ccr/ammann/millennium/refs/WahlAmmann_ClimChange2006.html
Anyone any wiser?
Ian should admit to the possibility of severe degradation of the GBR
Ian; its time you conceeded, we know precious little about reefs from sitting on a stool in Canberra.
Phil; whats your interest in CA? It's just another ho hum blog, unauthorised bleating lot.
Did any of them actually do anything Phil?
BTW seems you have the edge in our seawater Ph debate. Mine was all about slops!
Bambi would like to see Dr Starck's explanation of the stark death events which have just occurred in the Caribbean. These events have presumably occurred in the '25% of reefs globally [which] have been estimated to be heavily impacted' which Walter Starck referred to above.
He said that 'Whether this situation will improve or grow worse in the future is unclear. There is evidence in both directions.'
Neither he nor I has said or implied that corals can't bleach permanently.