Here’s a video from the Guardian on the current status of the reef:
This is going to take a while. If there is a major bleaching event every year for a few years, the reef could essentially die off right away, but most likely, there will still be a few years where coral can spread, and a few years that are not too bad. So one must adjust expectations.
Let me put this a different, perhaps cynical but probably realistic, view. In about four years from now, there will be some bone-headed global warming denier standing on a boat off shore in Australia, showing us a section of really nice, well preserved, ecologically healthy reef. That person will tell us that climate scientists predicted that the Great Barrier Reef would be dead by now, but look, it isn’t!
The truth is that the reef is already severely damaged, and will recover only if water temperatures in the area cool down. That is not going to happen. A very likely scenario is that the living reef becomes a very limited phenomenon, so you will always be able to find a bit here or there that looks good, but the vast majority of the reef will not be alive.
Once a large area of the reef is dead — meaning specifically that the thin growth layer on the coral formation’s surface, where the living coral are, is dead — it will begin to dissolve and erode. The total dissolution and erosion of the geological structure is impossible, it will simply become a giant fossil. But, the minimum depth of the reef formation will increase to the point where there won’t be much sunlight, so recovery will be even less likely. Reefs start in shallow water, and then grow upwards as sea level rises (as it did in the past). The Great Barrier Reef is located on formerly dry land. With future sea level rise moving the sea surface up, and erosion of a dead coral structure pushing the surface of the reef down, we will reach a situation where the current location of the Great Barrier Reef is simply not a place a coral reef of this kind can exist, even if the sea temperatures and other conditions improve.
Personally, I don’t see any hope, medium and long term, for this natural feature. I think we need to preserve optimism where it is realistic, but very much avoid it when it isn’t. I’m not sure where we are at this time in relation to this particular outcome of human greenhouse gas pollution. I don’t see how two bad years in a row are not going to be followed by two more bad years in a row, given the steady increase in sea temperatures. However, climate systems to vary in the region, maybe it is possible. Maybe in three years we’ll be looking at a remarkable recovery. But, it is almost positively certain that over the next decade or two the frequency of bad years will go up and the best years will become unlivable for most of the coral.