Heron Island is a beautiful small island off the Queensland coast that sits on top of the southern part of the Great Barrier Reef.

There is a magnificent resort at one end and the Heron Island Research Station run by the University of Queensland at the other - which among other things is looking into the impact of global warming on the reef. 

We recently had a family holiday there which included a guided tour of the research station. 

Mainly rising sea temperatures and increasing acidity.

Same thing really, the main cause of global warming is the increasing emission of greenhouse gases, mainly carbon dioxide, and it is the absorption into the oceans of some of that carbon dioxide that causes the acidity level to increase.

The experiment started with 12 x 300-litre tanks filled with identical coral specimens, sea cucumbers and fish. No changes were made for four or five months until everything settled down. 

The tanks were divided into four groups of three tanks - to look at (A) how things were 100 years ago, (B) how things are now, (C) how things might be in 100 years if we continue to emit greenhouse gases as we are now and (D) how things might be in 100 years if we limit temperature increases to 2°C.  

By adjusting the acidity and the temperature in the tanks. A century ago the temperature and acidity levels were less – in 100 years they will be higher: a lot if we keep going as we are but less if we can limit greenhouse gas emissions enough to keep the temperature increase under 2°.

After a year they found that things were a bit better in the “100 years ago” tanks and healthy and okay in the “things as they are now” tanks.

However, in the "emissions as usual" tanks, things were as bad as could be - everything dead except some algae.

In the "under 2° increase" tanks things were not so bad. Some corals survived and some recovered during winter with lower temperatures. And maybe if it does take 100 years to get there, the corals will be able to adapt better than over the test year.

No, it's being run again with some refinements including to separate the impacts of increasing temperatures and increasing acidity. The results should be published by the end of this year.

According to the Australian Museum, when coral dies it “becomes wonderful habitat for worms and sponges which invade this new home by boring into the skeleton” so that the “coral becomes like honeycomb and increasingly fragile and more susceptible to being dislodged by storms” and ultimately  “the colourful and biodiverse reef becomes a dead reef which can no longer support all the fish and other animals which depend on live coral”. (Google "coral death aus museum")