Simon Bradshaw | Climate Council calls code blue on Australia's ocean crisis

We are up on a northern part of the Great Barrier Reef for the launch of Code Blue: Our Oceans in Crisis - the Climate Council's first comprehensive report on climate change and our oceans.

It was a stark reminder of just how much hangs in the balance - what we are losing, but what we still can and must fight to save.

We saw healthy patches of reef, some of which have been lovingly tended by marine scientists and assisted in their recovery. But we also saw vast tracts that can only be described as coral boneyards - areas that have never recovered from successive marine heatwaves.

The truth is our Great Barrier Reef, and indeed our ocean at large, is in very serious trouble. As we head into another El Nino summer, there are well-founded fears of another devastating mass bleaching event.

More than half-a-billion people worldwide depend on coral reefs for their food, livelihoods, and the protection of their coastlines. Tragically, the damage to tropical coral reefs is but one aspect of a much larger crisis affecting our oceans. A crisis brought on by climate change, driven by the burning of coal, oil and gas.

The vast majority - around 93 per cent - of the extra heat we have trapped by burning fossil fuels has ended up in the ocean. It's an astonishing amount of energy - equivalent to detonating five Hiroshima atomic bombs every second, or enough energy to boil Sydney Harbour every eight minutes.

This has consequences. More frequent and severe heatwaves are pushing coral reefs and other critical marine ecosystems to the brink. Ice sheets are melting at an accelerating rate, driving up sea levels and displacing coastal communities. The ocean circulations and currents that distribute heat, rainfall and nutrients around the planet are slowing and may even be headed for collapse.

The potential impacts of these abrupt changes are truly profound.

All life depends on the water cycle that starts in the ocean. The ocean and the atmosphere form a coupled system that shapes the Earth's climate, creating the stable conditions that have enabled advanced human societies to develop. Humans also need the ocean in other fundamental ways: every second breath we take comes from oxygen produced by the ocean. Even if we live thousands of kilometres inland, our weather is shaped by what is happening in our oceans.

The ocean's enormous capacity to absorb heat may have masked the true extent of the damage. But today these changes are coming back to bite us. This year is almost certain to register as the Earth's warmest year on record, and Australia faces yet another climate reckoning with a devastatingly early start to our fire season, and warnings of worse to come.

Put simply, the global dance between the ocean and the atmosphere underpins life as we know it.

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The latest observations suggest we are perilously close to dangerous tipping points for our ocean that could trigger millennia of irreversible sea level rise and the collapse of the ocean circulations and marine ecosystems upon which we depend for our very survival.

We ignore these warnings at our peril. There is only one solution to our climate and ocean crises, and that is to leave our fossil fuels in the ground and get our emissions plummeting. Fast. Australia must aim to reduce its emissions by 75 per cent below 2005 level by 2030, and reach net zero by 2035. And we must urgently update our outdated national environment law so that it takes account of the dangers of climate change and puts a halt to the reckless expansion of our fossil fuel industries.

In hospital emergency rooms, a code blue is called when a life-threatening event is under way. We are calling a code blue for our oceans today, because the crisis in our oceans threatens all life as we know it - including our own.