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.
The plight of the Great Barrier Reef has been dear to my heart for years, and agonising to watch unfold.
Make no mistake, the time to do something to protect a significant proportion of it was back in the 90s, about the time of the Kyoto agreement. Instead, we dropped the ball on global warming and have showed no inclination to pick it up other than some idle curiosity and a kick down the road at the Paris agreement a little less than 18 months ago. Far too little, far too late - even if humans were to disappear from the planet today, the Reef as a functioning entity is now committed to an inexorable process of ecosytem extinction, and will be 90% gone by the end of the century.
Every year of continuing as we have sees disappearing more of the possibility of salvaging something of the remaining 10%. We have to stop kidding ourselves that if we act soon we can make it all better. We can't. All that we can do is to make it so that there's something left for the future to work with, to in turn leave something for their future to perhaps rebuild what we've destroyed.
...close to my heart...
We are nowhere near as angry about this and other environmental disasters as we should be. Our world is disintegrating and we are lucky if politicians even consider the reports before doing little to nothing about them.