A 2.7-Tonne Iceberg has been suspended over Sydney Harbour, just metres from the foot of the Opera House in a stark piece of commentary on climate change.

The performance piece "Thaw" is part of the Sydney Festival, and for the next three days will have an aerialist performing atop it for ten hours a day.

READ MORE: Novak Djokovic has visa cancelled just days before Australian Open

"They're out in the Sydney summer sun on a freezing block of ice, so it takes a lot of time to train them in that not only from an aerial safety perspective but also an impact on the body perspective," artistic director Joshua Thomson told 9News.

As the hot days stretch on, the huge chunk of ice will melt, and is intended to start a conversation about what is happening to glaciers around the world.

Watch the full story above.