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Australia's affinity for the ocean is renowned, but it is likely to be dramatically disrupted, according to the latest report from the UN's Intergovernmental Panel on Climate Change (IPCC).
Key points:
- The UN's IPCC releases a new report on the world's oceans and frozen areas in a changing climate
- Australia can expect to see extreme coastal flooding every year and a 20 per cent decline in our fisheries over the next 80 years
- Scientists say the changes "can be minimised" if global warming is kept to less than 2C on pre-industrial levels
Eighty-five per cent of the population lives within 50 kilometres of the ocean — we fish, surf, swim and bask in coastal life, but beneath the sea's surface, the story is far from idyllic.
Oceans cover more than 70 per cent of Earth's surface and are made up of a mixture of water, salt, organic materials, particulates and atmospheric gasses.
They help to produce half of the planet's oxygen and contain important food sources.
So, what happens in the oceans has ramifications for life on Earth — specifically what we breathe and what we eat.
On Wednesday, the IPCC released its Special Report on Oceans and Cryosphere (or frozen areas) in a Changing Climate, finding that since the 1970s, these vast blue expanses have absorbed 90 per cent of excess heat in the climate.
Recently, the world's oceans have also had to work overtime to suck up excess pollution caused by humans and it's taking its toll.
Oceans are warming faster than before, causing ice sheets, permafrost and glaciers to rapidly melt.
As they do, they risk releasing toxins and harmful gasses, which would further heat the planet.
And as the ice melts, the excess water is pushing up sea levels and diluting important surface layers, forcing change within the ecosystems that reside there.
Experts warn that unless significant and coordinated changes are made to limit global warming, the world's oceans and frozen areas will undergo unprecedented changes that will be devastating to human life.
What has the report found?
The report is the most definitive scientific account yet of current observations and predictions about what oceans and cryosphere will look like if global warming is capped to under 2 degrees Celsius — and what we will face is if isn't.
"While sea level has risen globally by around 15 centimetres during the 20th century, it is currently rising more than twice as fast — 3.6 mm per year — and accelerating," the IPCC report reads.
The report also concluded sea levels would continue to rise for centuries, and could surge by up to 60cm by the year 2100, even if greenhouse gas emissions were sharply reduced and global warming was limited to well below 2C.
If emissions continue to rise rapidly, those levels could rise by up to 110cm by the end of this century.
Driving the expansion of our oceans is the rapid thawing of ice in Greenland and the Arctic.
It is not known whether the melting of ice sheets is reversible, although that is likely to be a major area of focus for researchers in the coming years.
"Our oceans have changed," said Nathan Bindoff, a report co-author, and one of the world's leading climate scientists.
"They've moved from one climate that we knew about, to a new one."
The Australian scientist is also a professor of physical oceanography with the University of Tasmania and CSIRO.
"The global ocean has warmed unabated since 1970, and the rate of warming has doubled since 1993, so we are totally convinced the oceans are warming up," Professor Bindoff said.
"We're committed to quite a lot of change in the climate system regardless of which pathway we take; the high emissions pathway is definitely much more impactful."
Marine heatwaves have also doubled in frequency since 1982 and they're becoming more intense.
While this means the threat of coral bleaching is more persistent, heatwaves can also affect entire ecosystems and reduce seagrass cover, kelp forests and mangroves.
Sea level rise and changes to marine ecosystems are already being seen by some of Australia's closest neighbours, especially Pacific Island nations.
Last month, Pacific leaders urged Australia to do more to cut emissions.
Closer to home, concerns about the impacts of climate change have also been addressed in a speech prepared for Australia's Defence Force chief.
What does this mean for Australia?
Rising sea levels are changing how oceans act, and are leading to an increase in the frequency of extreme sea level events during high tides and severe storms.
Associate Professor Nerilie Abram is with the Australian National University and is also a coordinating author of the IPCC report.
"The report is a wake-up call," she said.
She said countries like Australia needed to prepare for unavoidable coastal changes, and the sooner communities adapted, the better they would cope.
"Australia depends on the ocean that surrounds us for our health and prosperity," Ms Abram said.
"Australia's coastal cities and communities can expect to experience what was previously a once-in-a-century extreme coastal flooding event at least once every year by the middle of this century — in many cases much more frequently."
She also predicted Australian fisheries — and the food they produce — would decline by more than 20 per cent within the next 80 years if global warming could not be capped.
As oceans become more acidic, it also becomes harder for species like oysters, mussels and other shelled organisms to survive.
Changes to their habitats means some fish may have to seek out new homes, which could transform the world's existing fishing zones.
Action taken now will influence what happens to our oceans
"The future state of the ocean depends very strongly on which emission pathway the planet takes; if you take the low pathway, there's quite a lot of these changes which can be minimised," Professor Bindoff said.
A low emissions pathway would be one where humans could lower emissions enough to cap global warming to less than 2C above pre-industrial levels.
Only leaders who agreed to do so were invited to speak.
Australia's Prime Minister Scott Morrison did not attend the summit.
The IPCC's findings are designed to be used by world leaders attending future climate and environment negotiations, including the UN Framework Convention on Climate Change Conference in December.
Scientists say it's imperative leaders acted immediately because even if the world reached zero net emissions tomorrow, the planet would continue to warm due to a lag.
The Australian Conservation Foundation chief Kelly O'Shanassy said the IPCC report should prompt governments around the world to act.
"This is a stark warning from the world's best scientific minds that climate change is harming our oceans, meaning more coral bleaching, more storms that lead to flooding and more bushfire-fuelling El Ninos if our pollution keeps rising," she said.
Federal Environment Minister Sussan Ley office also sent through a statement in response to the report.
"The report highlights the importance of addressing emissions and Australia is committed to meeting its international targets," the statement read.
"Australian scientists made key contributions to the report and we are working closely with scientists through the CSIRO and the Australian Institute of Marine Science to study and mitigate climate impacts.
"Australia is a world leader in the protection and sustainable use of the ocean and we are investing in world-leading marine science."
Topics: climate-change---disasters, government-and-politics, climate-change, environment, oceans-and-reefs, australia
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