Heating up: How rises in global temperature could damage the reef

As global surface temperatures rise, new research looks at the potential impact on Australia and its Great Barrier Reef.

The danger of Australia’s Great Barrier Reef experiencing another catastrophic heatwave similar to the recent shocking event is twice as likely if global average surface temperatures hit 1.5°C above pre-industrial conditions.

But it gets worse – the higher the temperature increase, the more severe the threat.

If we hit up to 2°C more than the pre-industrial world, then it almost triples the odds of another marine heatwave on par with the recent event that triggered mass coral bleaching.

Great Barrier Reef Turtle

A turtle swims over bleached coral at Heron Island on the Great Barrier Reef February 2016. Picture: XL Catlin Seaview Survey

This is just one of the findings from our research for the ARC Centre of Excellence for Climate System Science looking at how Australian extremes in heat, drought, precipitation and ocean warming will change in a warmer world.

We’ve already experienced about 1°C of global warming above a natural climate, resulting in more extreme weather events. Some of these events can be directly linked to climate change, for others the link is less clear. But this has meant more heatwaves and droughts – and a coral bleaching event on the Great Barrier Reef last year that has damaged much of the world’s largest coral reef.

So, how will these extremes change in future? If we experience more global warming do these extremes become more frequent?

These are the questions we’ve investigated in our study, published in Nature Climate Change.

THE PARIS AGREEMENT

The Paris Agreement of 2015 committed to: “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.”

It is vital we understand the differences in how climate extremes in Australia might change if we limit global warming to either 1.5°C or 2°C.

In our study we used state-of-the-art climate model simulations to examine the changing likelihood of different climate extremes under four different scenarios - a natural world without any human influences, the world of today, a 1.5°C world, and a 2°C world.

Great Barrier Reed

Death of a coral reef after bleaching. Picture: XL Catlin Seaview Survey

HEAT EXTREMES ARE HERE TO STAY

As part of our research, we looked hot Australian summers, like the “Angry Summer” of 2012/2013 which saw record-breaking high temperatures across the country.

We already know that human influences on the climate increase the chance of seeing hot summers like the Angry Summer. Our results show this trend continues into the future and with summers like these becoming more and more common. Historically hot summers like the Angry Summer would be cooler than normal if we reach 2°C global warming.

Read the full story in Pursuit