"During 2002, not during an El Nino, warmer-than-normal summer water temperatures were right on top of the GBR, and a large area of the reef bleached."
I would have to say that since they only have reliable data for 1-200 years, this represents a blip in a sliver. That means it has happened before, and the reefs recovered.
"If sea surface temperatures trend warmer than normal over the next decades, there will be coral death and coral reef changes due to this trend. Combined with the other more damaging factors (which I cited in the post to which you replied), this is predicted to lead to significant coral reef degradation."
Agreed. Notice the bold that I used for emphasis, those are still pretty big ifs given our relative lack of historical sea temps in the areas.
"If 2% of the money spent on global warming programs was spent on better sewage treatment plants for coastal areas in Third World and island nations, a lot of the stress on coral reefs would be reduced, and the reefs would then be better able to cope with any warming-related stress."
Exactly. Global warming is the least proved theory of reef degradation. If we concentrated our efforts (read: $$$$) on precisely the proven problems you mentioned, we'd save the reefs, save our cars and air conditioners, save our money, and save our sanity.
Unfortunately, there's no reason to think that there have been warmer water temperatures over the last 200 years, because the world was definitely recovering from the Little Ice Age through the 19th century (1800s) and this century has had a warming trend. I don't know if anyone has studied coral reef changes during the "Medieval Warm Period" that occurred 900-1300 or so. That would be the last time that global temperatures were comparable to today.
Corals are good temperature recorders, though; there should be some data... (Google searching, be right back)
More than some data. Ohmigod. http://www.aims.gov.au/pages/auscore/auscore-08-6b.html
If you are REALLY interested, here's the whole Bibliography page: http://www.aims.gov.au/pages/auscore/auscore-08.html
Can't find a short article about it, though. Feel free to wade through these references; a few of them look interesting.
Exactly. Global warming is the least proved theory of reef degradation. If we concentrated our efforts (read: $$$$) on precisely the proven problems you mentioned, we'd save the reefs, save our cars and air conditioners, save our money, and save our sanity.
The one thing worth noting is that due to the potential for warming sea surface temperatures and the effects on the GBR (which have been observed), warming-related bleaching may be one of the most important threats to the GBR, because it's not heavily impacted by nearby human habitation and much of it is an ecological preserve. Reefs in many other places would benefit from what I've already described; the GBR may be in better shape now, but if global warming really kicks in (and it's certainly not clear if that will happen), then every reef, including the GBR, will be affected.