A leading Kiwi climate scientist has a message for people wanting to visit Australia's Great Barrier Reef: see it now before it's too late.

Dr Jim Salinger said the "burning, drying and flooding" continent was now experiencing dramatic impacts from climate change.

"The iconic Great Barrier Reef, already badly damaged by global warming during three extreme heatwaves, in 1998, 2002 and 2016, is being yet damaged by a new bleaching event is under way now," said Salinger, currently an honorary research fellow at Otago University's Department of Geography.

"The extreme marine heatwave in 2016 killed two-thirds of the corals along a 700km stretch of the northern Great Barrier Reef, from Port Douglas to Papua New Guinea.

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"It caused dramatic change for the reef and that climate change is here now.

"The message is simple - visit it now otherwise if we see more diebacks of corals in the next few years, little if any action on emissions and inadequate progress on water quality, then an 'in danger' listing in 2020 as a World Heritage area."

Salinger said the past summer had brought prolonged and at times extreme heat over New South Wales, southern Queensland, South Australia and parts of northern Victoria.

The three heatwaves across January and early February saw unusually high daily maximum and minimum temperatures for at least three consecutive days over large parts of the country.

During these heatwaves, daily maximum temperatures across southeast Australia exceeded 40C over very large areas and were typically 8C to 12C above the January and February averages.

Many sites measured record runs of consecutive days of high temperatures above threshold values.

Climate scientist Dr Jim Salinger. Photo / File
Climate scientist Dr Jim Salinger. Photo / File

"In New South Wales, for example, Moree had 54 consecutive days of 35C or above from December 27 2016 to February 18 2017 - the previous record for New South Wales was 50 days at Bourke Airport," Salinger said.

"The Brisbane and Gold Coast areas continue to have runs of days above the mid and low 30C respectively, and it is now the end of March."

Salinger's comments follow a major study of the Great Barrier Reef published in the journal Nature this month, which reported how reducing pollution and curbing overfishing wouldn't prevent the severe bleaching that is killing coral at catastrophic rates.

In the end, the researchers say, the only way to save the world's coral from heat-induced bleaching was with a war on global warming.

Q&A: Can our oceans survive climate change?

As the impacts of climate change become ever clearer, our planet's oceans are bearing the brunt - absorbing most of the extra heat in our atmosphere.
But what will this mean for ocean ecosystems - and for how much longer can it continue? Science reporter Jamie Morton talked to Professor Arnold Dekker, the recently-retired research director in earth observation and informatics at Australia's CSIRO, and a guest speaker at this week's World Science Festival in Brisbane.

The world's oceans help regulate the planet's climate, and, in effect, life. Is there a simple way to briefly explain their big picture natural function?

To begin with, life evolved out of the oceans, after which colonisation of the terrestrial environment began.

The phytoplankton in the ocean did the major work of getting our atmosphere into a state where life on land became possible.

Ecosystems are gradually seeing the effects of CO2 being absorbed by oceans. Photo / 123RF
Ecosystems are gradually seeing the effects of CO2 being absorbed by oceans. Photo / 123RF

Essentially, nowadays the oceans that cover two thirds of our planet stabilise our climate by being a buffer and a sink for heat and for many of the gases humans emit into the atmosphere, as well as being the recipient of all our terrestrial runoff that ends up in our coasts.

Through evaporation, oceans also provide a major part of fresh water through cloud formation and rain.

The phytoplankton (algae) in the oceans play a significant role in metabolising carbon into their biomass, through photosynthesis, and are also the beginning of the food chain and an important factor for cloud formation.

The big question is, how much of this carbon sinks to the ocean floor and is gone forever out of the system?

The oceans absorb CO2 and this is causing increasing acidity.

So, as greenhouse gases trap more energy from the sun, the oceans are absorbing more heat, resulting in an increase in sea surface temperatures and rising sea level. What's the current state of play and how much more heat can our oceans absorb? And how is our understanding of what's happening improving?

The oceans do absorb more and more heat, but not only at the surface - something visible from satellites using thermal infrared - but also through transporting heat into the deeper waters that carry this heat thousands of kilometres in deep ocean currents.

This heat is not regularly distributed throughout the oceans; recent research has shown complex vertical and horizontal currents of relatively warmer Antarctic water going deep into the ocean and travelling north.

It may take 10 to hundreds of years for this deep water currents to travel these thousands of kilometres.

The ocean is also expanding due to this increase of heat - another contributor to global sea level rise next to melting land ice.

Our understanding is improving due to the way we can now monitor our environment, both from space using satellites that can measure salinity, temperature, waves, concentration and types of algae at the surface, fluorescence of algae, suspended matter, coloured dissolved organic matter, and various measures of transparency.

More sophisticated measures from these satellite based measurements are in development.

Next, research vessels have increasing capacity and capability to measure using flow through systems as well as lowering rosettes of equipment kilometres deep whilst continuously measuring many ocean variables.

Since the early 2000s, a massive programme has been launched using ARGO floats.

These are cylinders equipped with batteries, environmental sensors and satellite communications equipment.

These floats can sink hundreds to thousands of metres measure on their way down, float with underwater currents for days or weeks and then go to the surface at predetermined times, measure on the way up and then transmit all information to satellites that, in turn, convey this to information to labs around the world.

Coral communities are particularly threatened by climate change. Photo / 123RF
Coral communities are particularly threatened by climate change. Photo / 123RF

All of these measurements, coupled with atmospheric and ocean models, are vastly increasing our understanding of many of the ocean processes.

However, we need to remind ourselves we have only measured a fraction of what goes on due to the vast expanse of the oceans.

As to how much more our oceans can absorb, I can't answer what the current state of play is.

However, it's already impacting the frequency of coral reef bleaching, shifting algal species - or the beginning of the food chain - changing ocean currents and influencing El Nino and La Nina cycles.

The loss of coral communities due to ocean acidification is one emerging impact of climate change. Why is this so concerning and what does the world stand to lose here?

If we lose the world's coral reefs, we will lose and entirely unique and highly biodiverse ecosystem.

This would have major flow-on effects for biodiversity, as coral reefs often occur in nutrient-poor areas of the world and provide significant ecosystem functions, as well as services to us, like food and pharmaceuticals.

Moreover, there is an ethical aspect: are we happy with endangering an entire ecosystem?

Do we know the consequences of wiping out an ecosystem?

Are there unknowns? Of course there are.

How concerning, also, are current sea level rise projections - and heightened storm and cyclone projections - within this century?

Very.

Measurements are indicating that the global sea level rise is following or exceeding the worst case scenarios given in the latest [UN Intergovernmental Panel on Climate Change] reports.

The changes in the Arctic and Antarctic are not fully understood - especially in the Antarctic.

There are more and more indications the perceived or proclaimed stability of the Antarctic ice may not be so stable.

Are there any geo-engineering strategies that scientists are already exploring to lighten the burden on our oceans and address the amount of heat and CO2 they are absorbing? Are there any concepts or far-out ideas that may come into play in the future?

The only one I am aware of it the idea of fertilising the ocean's surface with nutrients to trigger algal blooms.

The idea comes from the effect of massive dust storms from the Sahara, or from the Australian continent triggering algal blooms in the surface of the oceans where the dust settles.

The idea of this is that the algae would use CO2 for photosynthesis and create algal biomass that, when the organisms die, would sink to the ocean floor and thus sequester carbon forever.

However, it seems that the dead algae are actually eaten by zooplankton and become part of the upper-layer food chain, therefore not sequestering large amounts of carbon at all.

In reality, we as a human race are unintentionally geo-engineering the oceans massively the wrong way by increasing greenhouse gases, as well as putting massive amounts of sediment, nutrients, herbicides, pesticides, organic micro-pollutants and heavy metals into our coastal waters.

In addition, we over-harvest many species of fish and crustaceans and other fauna - thereby upsetting the natural balance between species.

Jamie Morton was hosted at the World Science Festival by Brisbane Marketing.