One day we won’t need a Renewable Energy Target, because we’ll have good climate policy


David Blowers, Grattan Institute

Australia’s Renewable Energy Target (RET) has had a rough time in recent years. After a 2014 government review recommended it be abolished, both major parties eventually agreed to downsize the RET in 2015. But even with bipartisan support, investment in new projects has slowed to a trickle.

Endless politicking over the policy has damaged investor confidence, which shows only limited signs of recovery.

So how do we bring investor confidence back to the sector? We provide a solution in our latest report from the Grattan Institute: a healthy climate policy. A good climate policy, perhaps surprisingly, means that one day we won’t need the RET at all.

The problem with renewable energy

The RET mandates that 33 terawatt-hours of electricity must be generated from renewables by 2020. To meet the target, renewable generators such as wind and solar farms create Renewable Energy Certificates (REC) for each unit of electricity they produce. Electricity retailers are required to buy enough certificates from renewables to meet the target.

The income renewables receive from selling credits along with the income they receive from selling electricity provide the financial justification for renewable energy projects.

Renewables are long-lived investments – they need to earn revenue for many years to pay off the initial costs of building them. Renewables built to meet the target in 2020 need to prove they can generate revenue beyond this point in order to get finance to build them in the first place.

Allowing renewables to create RECs between 2020 and 2030 is a means to provide this revenue certainty. The problem is that, under current policy, renewables will not generate RECs beyond 2030. In investment terms, 2030 is fast approaching.

The problem can be solved, though. Revenue from selling RECs is not the only source of income for renewables. If the price of electricity after 2030 is high enough, renewables will not need the incentives provided by the RET.

Before July 2014 there was a good reason why the electricity price would be high after 2030: Australia had put a price on carbon.

Now that the carbon price has gone, both future electricity prices and government policy are less certain.

Beyond the RET, existing government policies do not provide any incentive for building more renewable generation. It is no wonder that the environment for investing in renewables, at least in the short term, is poor.

A blueprint for climate policy

But it can change. Our report outlines a climate change policy roadmap for Australia that both parties can embrace under their existing policies.

The report shows how the government’s climate change policy (the Emissions Reduction Fund, which pays polluters to reduce emissions) can be transformed over time to reduce emissions as well as attracting investment in clean technology.

For the electricity sector this involves changing the Emissions Reduction Fund initially to what is known as an intensity baseline scheme.

Under an intensity baseline scheme, big polluters, such as brown coal, are penalised. Emissions producers have to buy permits or credits for every unit of electricity they generate based on the amount of carbon in that electricity. But low or zero polluters earn credits for each unit of electricity they generate. They can then sell these credits.

Eventually, all businesses would have to buy permits for every unit of greenhouse gas they emit.

The upshot is that the cost of producing electricity from fossil fuels increases, while the cost for producing electricity from renewables goes down. In this way an intensity baseline scheme will encourage investment in new renewable energy.

Let the RET retire

This does not mean that once an intensity baseline scheme is introduced the RET no longer has a purpose and should be abolished. Existing investments in renewables have been made in good faith and should be protected from any change of policy.

Besides, the RET can operate alongside an intensity baseline scheme, providing additional revenue to projects if revenue from the intensity baseline scheme is insufficient. It will also protect existing investments in renewables that have been made in good faith.

But the RET should not be extended beyond its current timeframe (a target to 2020 and certificates credited to 2030). A robust intensity baseline scheme will provide incentives for renewable generation and should make an additional policy unnecessary.

As long as the baseline on emissions is tight enough, renewables should be enough to meet any emissions reduction target that Australia chooses to adopt. Setting a separate target might mean that Australia pays too high a cost to reduce its emissions.

Most importantly for the renewables industry and other industries, our roadmap provides a policy framework that both major parties can adapt and adopt. A bipartisan climate policy is vital to achieving the stability needed for businesses to invest in the low-emissions technologies this country needs if it is to transition successfully to a low-carbon economy.

For years, the renewables sector has lacked stability. This plan can bring it back.

The Conversation

David Blowers, Energy Fellow, Grattan Institute

This article was originally published on The Conversation. Read the original article.

In pictures: a close-up look at the Great Barrier Reef’s bleaching


Justin Marshall, The University of Queensland

These images are a selection of photos taken recently near Lizard Island off the north Queensland coast. They document the ongoing bleaching on the Great Barrier Reef as ocean temperatures continue to be driven upward by climate change.

The bleaching process

Before corals bleach, they are often a deep brown or khaki-green colour. These colours come from the symbiotic algae (sometimes called zooxanthellae) that co-exist with the coral polyp.

Before bleaching…
Justin Marshall/coralwatch.org, Author provided

During bleaching, as the symbiotic algae depart, you can see the beautifully coloured polyps. Sometimes polyps are transparent and we see only the white skeleton beneath. Other polyps may be brightly coloured, as seen here.

…during…
Justin Marshall/coralwatch.org, Author provided

But whether white or fluorescent, these corals are far from happy. Once the final stage of the bleaching process is reached, it is likely the coral has been stressed for days or weeks. From here on, it may recover slowly – by re-acquiring its symbiont friends – or it may die, having run out of energy in the absence of the symbiotic algae that provide it with carbohydrates.

What often happens next is that the coral is covered with a film of turf algae, which takes over the parts of the reef previously colonised by healthy coral.

… and after.
Justin Marshall/coralwatch.org, Author provided

Bleaching can be strangely beautiful

Unfortunately, what we are now seeing on the northern third of the Great Barrier Reef is the death of many of these beautiful organisms. But, as noted above, the bleaching can in some cases be weirdly beautiful, as the corals shed their algal cloaks and reveal themselves.

Bleached corals glow a striking shade of purple.
Justin Marshall/coralwatch.org, Author provided

These pictures show a variety of heavily bleached corals, with almost no remaining symbiotic algae. From this point it is a long, slow road to recovery – even those corals that survive will remain metabolically and reproductively compromised for months.

Purple-tinged bleaching.
Justin Marshall/coralwatch.org, Author provided
Pure white bleaching.
Justin Marshall/coralwatch.org, Author provided

The amazing colours are pigments present in the coral polyps themselves. They are often fluorescent – hence the day-glo appearance of some corals and their amazing fluorescence on torch-lit night dives.

Purple glow.
Justin Marshall/coralwatch.org, Author provided

Some healthy corals display such vivid blues and other colours naturally, not during a bleaching event. But these corals are rare. What we are seeing on reefs in northern Queensland is certainly bleaching.

Pink-tinged bleaching.
Justin Marshall/coralwatch.org, Author provided
Blue tips.
Justin Marshall/coralwatch.org, Author provided
Bleached colonies stand out starkly.
Justin Marshall/coralwatch.org, Author provided

Algal overgrowth

When the polyps die, macro or turf algae take over – a process that is already evident along parts of the 800 km of worst-affected Great Barrier Reef.

Non-symbiotic algae begin to take hold.
Justin Marshall/coralwatch.org, Author provided

Especially in warm or nutrient-rich waters, these algae outcompete any coral trying to settle or spread on the reef, taking over areas that corals previously dominated.

Algae growing on coral tips.
Justin Marshall/coralwatch.org, Author provided
A mix of starkly bleached coral and algal colonisation.
Justin Marshall/coralwatch.org, Author provided

Fish losing their homes

Not only is the turf algal community uglier than healthy coral, but it means the other species that depend on the coral lose their livelihoods too. Eventually, the reef structure itself breaks down, meaning that many fish species will need to move on or die.

That includes fish that feed on coral, such as this Okinawa goby…

An Okinawa goby on a coral colony.
Justin Marshall/coralwatch.org, Author provided

… and those that just use it for shelter, such as this black damselfish juvenile.

Juvenile black damselfish.
Justin Marshall/coralwatch.org, Author provided

The turquoise-blue chromis damselfish form huge clouds or schools over coral heads, and use coral branches for shelter when predators come along. The picture immediately below was taken before bleaching, while the one after that shows the fish on a bleached colony.

Before: chromis damselfish on a healthy reef.
Justin Marshall/coralwatch.org, Author provided
After: chromis damselfish on bleached coral.
Justin Marshall/coralwatch.org, Author provided

Anemones (which are close relatives of corals) are also prone to bleaching, which causes similar problems for the fish that use them for shelter.

Anemones are prone to bleaching too.
Justin Marshall/coralwatch.org, Author provided
Searching for shelter.
Justin Marshall/coralwatch.org, Author provided

Here are some more before and after photos, showing the effects of bleaching on the anemones that species such as clownfish use as a refuge.

Before: fish living on a healthy anemone.
Justin Marshall/coralwatch.org, Author provided
After: fish on a bleached anemone.
Justin Marshall/coralwatch.org, Author provided

Living with coral… or without it

When I saw the coral this perky little blenny is sitting in, I was convinced I was looking at a healthy colony! Maybe Lizard Island was not 100% bleached after all.

Unfortunately, closer examination shows that the coral head has died and a thin film of algae covers the branches. The little blenny is farming his patch and cropping the algae so that it does not become overgrown.

A blenny on the reef.
Justin Marshall/coralwatch.org, Author provided
Tending the algae.
Justin Marshall/coralwatch.org, Author provided

One-third of all marine life spends at least part of its life cycle on a reef. What happens when these reefs disappear?

Current predictions are that coral reefs worldwide could be gone within 25 years. How much will be left after this global bleaching event? How much will be left for future generations?

Given the globally accepted link between carbon emissions, climate change and reef bleaching, the decision to approve the Carmichael coal mine in Queensland right next to the Great Barrier Reef really is adding insult to injury.

The continued loss of the Great Barrier Reef is an environmental tragedy and a huge blow to all Australians who cherish this natural wonder and to the tourists who flock here to see the reef – particularly after seeing David Attenborough’s new documentary on it.

Further afield, coral bleaching is a potential humanitarian crisis in countries that rely on reefs for food and basic livelihoods. Let’s not forget that when Australia burns or sells coal it is contributing to this global problem as well.

The Conversation

Justin Marshall, ARC Laureate Fellow, The University of Queensland

This article was originally published on The Conversation. Read the original article.

New climate science centre doesn’t make up for CSIRO cuts: experts


James Whitmore, The Conversation

Hobart will be home to a new climate science research centre in plans announced by the CSIRO. The centre, which will focus on climate measurement and modelling, will be staffed by 40 climate scientists and guarantee research for ten years.

In February 2016, CSIRO chief executive Larry Marshall announced broad job cuts at the organisation. The latest announcement reduces the total job losses from 350 to 275.

Around 75 positions will still be lost within the CSIRO’s Oceans and Atmosphere division, which is responsible for climate science, from around 420 full-time staff.

The cuts were widely criticised by climate scientists in Australia and overseas.

The new centre will be housed within the Oceans and Atmosphere division. It will be overseen by a new National Climate Science Advisory Committee, including experts from the CSIRO and the Bureau of Meteorology, answering to federal Industry Minister Christopher Pyne. Environment Minister Greg Hunt will help establish the committee.

Chief Scientist Alan Finkel, who has previously urged CSIRO to ensure climate science is maintained, has welcomed the announcement.

CSIRO research fellow John Church said the new centre was “a step forward from where we were a few weeks ago”.

“But it’s only 40 people so it’s significantly less than we had previously. I don’t see how that few people are going to deliver on what Australia’s requirements are,” he said.

Church said the ten-year research guarantee was longer than most CSIRO research cycles.

“I would hope that with such commitment maybe it will be possible to grow the areas over that time frame,” he said.

He also welcomed co-ordination across the CSIRO, the Bureau of Meteorology and universities under the advisory committee.

However, Matthew England, a researcher at the ARC Centre of Excellence for Climate System Science at UNSW Australia, said he was “worried about the very small size of the centre”.

“Forty staff is woefully low in number. Equivalent centres overseas house five to ten times this number, even in nations not nearly as vulnerable to climate change as Australia is. [It is] great to set up a centre – now we need it to house real capacity.

“CSIRO management needs to get realistic about what this centre needs and how important it is for the nation,” he said.

Sarah Perkins-Kirkpatrick, also at UNSW Australia, said there were “small positives” but “it seems like they’ve [CSIRO] basically rebranded what they were doing in the first place”.

“They’re just shuffling people around. I fail to see how they can operate a national climate centre with just 40 staff.”

Cuts to other CSIRO divisions, particularly land and water, would also affect climate science, she said.

But she welcomed a commitment to maintain CSIRO support for ACCESS, the model used to develop climate projections and weather forecasts for Australia.

She called for a national government-funded centre separate from the CSIRO, perhaps modelled on the UK Hadley Centre, which works alongside the UK Met Office.

Steven Sherwood, director of the UNSW Climate Research Centre, said the cuts still represent a decrease in research investment. He said the UK Met Office generated at least A$6 of economic benefit for the UK per dollar spent on it.

“So, from a broad perspective, we appear to be downsizing an activity that was probably already underfunded even from a purely economic perspective.”

Comments compiled with the assistance of the Australian Science Media Centre.

The Conversation

James Whitmore, Editor, Environment & Energy, The Conversation

This article was originally published on The Conversation. Read the original article.

Rising carbon dioxide is greening the Earth – but it’s not all good news


Pep Canadell, CSIRO and Yingping Wang, CSIRO

Dried lake beds, failed crops, flattened trees: when we think of global warming we often think of the impacts of droughts and extreme weather. While there is truth in this image, a rather different picture is emerging.

In a paper published in Nature Climate Change, we show that the Earth has been getting greener over the past 30 years. As much as half of all vegetated land is greener today, and remarkably, only 4% of land has become browner.

Our research shows this change has been driven by human activities, particularly the rising concentration of carbon dioxide (CO₂) in the atmosphere. This is perhaps the strongest evidence yet of how people have become a major force in the Earth’s functioning.

We are indeed in a new age, the Anthropocene.

How do you measure green?

Plants play a vital role in maintaining Earth as a habitable place, not least through absorbing CO₂. We wanted to know how people are affecting this ability.

To do this, we needed to know how much plants are growing. We couldn’t possibly measure all the plants on Earth so we used satellites observations to measure light reflected and absorbed from the Earth’s surface. This is a good indicator of leaf area, and therefore how plants are growing.

We found consistent trends in greening across Australia, central Africa, the Amazon Basin, southeast United States, and Europe. We found browning trends in northwest North America and central South America.

Updated figure to 2015. Source: http://sites.bu.edu/cliveg/files/2016/04/LAI-Change.png

We then used models to figure out what was driving the trends in different regions.

A CO₂-richer world

Plants need CO₂ to grow through photosynthesis. We found that the biggest factor in driving the global greening trend is the fertilisation effect of rising atmospheric CO₂ due to human activity (atmospheric concentration grew by 46 parts per million during the period studied).

This effect is well known and has been used in agricultural production for decades to achieve larger and faster yields in greenhouses.

In the tropics, the CO₂ fertilisation effect led to faster growth in leaf area than in most other vegetation types, and made this effect the overwhelming driver of greening there.

A warmer world

Climate change is also playing a part in driving the overall greening trend, although not as much as CO₂ fertilisation.

But at a regional scale, climate change, and particularly increasing temperature, is a dominant factor in northern high latitudes and the Tibetan Plateau, driving increased photosynthesis and lengthening the growing season.

Greening of the Sahel and South Africa is primarily driven by increased rainfall, while Australia shows consistent greening across the north of the continent, with some areas of browning in interior arid regions and the Southeast. The central part of South America also shows consistent browning.

A nitrogen-richer world

We know that heavy use of chemical nitrogen fertilisers leads to pollution of waterways and excess nitrogen which leads to declining plant growth. In fact, our analysis attributes small browning trends in North America and Europe to a long-term cumulative excess nitrogen in soils.

But, by and large, nitrogen is a driver of greening. For most plants, particularly in the temperate and boreal regions of the Northern Hemisphere, there is not enough nitrogen in soils. Overall, increasing nitrogen in soils has a positive effect on greening, similar to that of climate change.

A more intensively managed world

The final set of drivers of the global greening trend relates to changes in land cover and land management. Land management includes forestry, grazing, and the way cropland is becoming more intensively managed with multiple crops per year, increasing use of fertilisers and irrigation.

All of this affects the intensity and time the land surface is green.

Perhaps surprisingly, felled forests don’t show as getting browner, because they are typically replaced by pastures and crops, although this change has profound effects on ecosystems.

The greening trends in southeast China and the southeastern United States are clearly dominated by land cover and management changes, both regions having intensive cropping areas and also reforestation.

Although this management effect has the smallest impact on the greening trend presented in this study, the models we used are not suitable enough to assess the influence of human management globally.

The fact that people are making parts of the world greener and browner, and the world greener overall, constitutes some of the most compelling evidence of human domination of planet Earth. And it could be good news: a greening world is associated with more positive outcomes for society than a browning one.

For instance, a greener world is consistent with, although it does not fully explain, the fact that land plants have been removing more CO₂ from the atmosphere, therefore slowing down the pace of global warming.

But don’t get your hopes up. We don’t know how far into the future the greening trend will continue as the CO₂ concentration ultimately peaks while delayed global warming continues for decades after. Regardless, it is clear that the benefits of a greening Earth fall well short compared to the estimated negative impacts of extreme weather events (such as droughts, heat waves, and floods), sea level rise, and ocean acidification.

Humans have shown their capacity to (inadvertently) affect the word’s entire biosphere, it is now time to (advertently) use this knowledge to mitigate climate change and ameliorate its impacts.

The Conversation

Pep Canadell, CSIRO Scientist, and Executive Director of the Global Carbon Project, CSIRO and Yingping Wang, Chief research scientist, CSIRO

This article was originally published on The Conversation. Read the original article.

19th century weather data is helping climate scientists predict the future


Linden Ashcroft, Universitat Rovira i Virgili; Howard Bridgman, University of Newcastle, and Ken Thornton, University of Newcastle

The 19th-century English historian Lord Acton famously advised people to live in both the future and the past, and said “those who do not live in the past cannot live in the future”.

It may seem a stretch to apply this famous quotation to climate research, but we can’t possibly understand how the climate will change in the future without first understanding how it changed in the past.

Australia’s official climate record, kept by the Bureau of Meteorology, begins in 1910. But historical climate records kept before the development of national meteorological organisations are valuable tools for improving our understanding of what has happened in the past.

They also put the present into a long-term context, and improve climate models used to predict the future.

What can old numbers really tell us?

One thing historical records can help us understand is extreme weather events – the aspect of climate change that has people most concerned. How can we prepare cities and buildings for storms in the future without understanding what previous storms have done?

It is true that historical observations have reliability issues and are sometimes hard to compare to modern observations, which are recorded in a standard way. However, old weather records can still tell us a lot about year-to-year changes, and there are many ways to minimise reliability problems.

There are several climate and weather analysis products that recreate how the atmosphere behaved over time. In the Southern Hemisphere, these climate tools are generally uncertain until the mid-20th century, due to a lack of – you guessed it — long-term data.

Historical records can also help us hone climate models for predicting the future. Some of the atmospheric and oceanic features that dominate our climate have cycles that can last several decades. This means that modern climate data starting in the 20th century may only capture one or two cycles of a particular feature, making it hard to train climate models on the full range of our climate variability.

Historical weather records are also important for past climate analysis. Extracting the climate signal from tree rings, ice cores, or documentary data, requires instrumental climate records for comparison. The longer the climate records are, the better this comparison will be.

What exists for Australia?

In the past few years, concerted efforts at the Bureau of Meteorology and several universities have been able to recover and analyse a large amount of historical climate data for Australia. Most of these observations come from Australia’s southeast, as this is the region that was first colonised by Europeans.

There are now studies that explore temperature, rainfall and atmospheric pressure variability in southeastern Australia back to the 1860s. Several studies have even rescued data from 1788.

With these newly recovered observations, we have learned a lot about Australia’s climate in the 19th century, as well as the early years of English colonisation. But there is still a lot we don’t know.

In particular, the majority of our old weather data come from coastal locations, where the weather is more sensitive to local factors rather than large-scale features such as the El Niño–Southern Oscillation (ENSO).

A rare opportunity

In 2011, some weather diaries were donated to the University of Newcastle and University of New England. The diaries contain 45 years of daily handwritten weather observations of a Mr Algernon Belfield taken on his 8,000-hectare property, Eversleigh, near Armidale in northern New South Wales.

A H Belfield at Eversleigh
Belfield Family

A pastoralist, amateur meteorologist and astronomer, Belfield took these meticulous weather observations every morning at 9am from June 1877 until August 1922, a month before his death.

His observations continued through the period of the 1891 shearers’ strike, the Boer War, Australia’s Federation, the First World War and the Centennial and Federation droughts.

Belfield’s diaries also span the period that inspired Dorothea Mackellar’s famous ode to Australia, My Country.

The last few decades of the 19th century were indeed times of “droughts and flooding rains”, thanks to a string of La Niña and El Niño phases of ENSO.

Belfield weather diaries
Ken Thornton (Author)

Belfield’s steady hand captured the weather at Eversleigh during a time of dramatic variability before the impact of human-induced climate change, in a region where the climate is highly correlated with ENSO.

His detailed records, therefore, provide us with a unique opportunity to uncover more about this period in our climate history than ever before.

The handwritten records are scanned but need to be transcribed into a digitised format. We are looking for volunteers to help us with this important task of recovering our climate history. If you are interested, please contact us here, to help shed light on Australia’s past, present and future climate.

The Conversation

Linden Ashcroft, Senior Researcher, Universitat Rovira i Virgili; Howard Bridgman, Conjoint Professor, University of Newcastle, and Ken Thornton, Affiliate, Cultural Collections, University of Newcastle

This article was originally published on The Conversation. Read the original article.

Burning fossil fuels is responsible for most sea-level rise since 1970


Aimée Slangen, Utrecht University and John Church, CSIRO

Global average sea level has risen by about 17 cm between 1900 and 2005. This is a much faster rate than in the previous 3,000 years.

The sea level changes for several reasons, including rising temperatures as fossil fuel burning increases the amount of greenhouse gases in the atmosphere. In a warming climate, the seas are expected to rise at faster rates, increasing the risk of flooding along our coasts. But until now we didn’t know what fraction of the rise was the result of human activities.

In research published in Nature Climate Change, we show for the first time that the burning of fossil fuels is responsible for the majority of sea level rise since the late 20th century.

As the amount of greenhouse gases we are putting into the atmosphere continues to increase, we need to understand how sea level responds. This knowledge can be used to help predict future sea level changes.


CSIRO

Measuring sea level

Nowadays, we can measure the sea surface height using satellites, so we have an accurate idea of how the sea level is changing, both regionally and in the global mean.

Prior to this (before 1993), sea level was measured by tide gauges, which are spread unevenly across the world. As a result, we have a poorer knowledge of how sea level has changed in the past, particularly before 1960 when there were fewer gauges.

Nevertheless, the tide gauge measurements indicate that global mean sea level has increased by about 17 cm between 1900 and 2005.

What drives sea level rise?

The two largest contributors to rising seas are the expansion of the oceans as temperatures rise, loss of mass from glaciers and ice sheets, and other sources of water on land. Although we now know what the most important contributions to sea-level rise are, we did not know what is driving these changes.

Changes in sea level are driven by natural factors such as natural climate variability (for example El Niño), ongoing response to past climate change (regional warming after the Little Ice Age), volcanic eruptions, and changes in the sun’s activity.

Volcanic eruptions and changes in the sun affect sea level across years to decades. Large volcanic eruptions can cause a temporary sea-level fall because the volcanic ash reduces the amount of solar radiation reaching the ocean, thus cooling the ocean.

Humans have also contributed to sea level rise by burning fossil fuels and increasing the concentration of greenhouse gases in the atmosphere.

Separating the causes

We used climate models to estimate ocean expansion and loss of mass from glaciers and ice sheets for each of the individual factors responsible for sea level change (human and natural). To this we added best estimates of all other known contributions to sea level change, such as groundwater extraction and additional ice sheet contributions.

We then compared these model results to the observed global mean 20th century sea-level change to figure out which factor was responsible for a particular amount of sea level change.

Over the 20th century as a whole, the impact of natural influences is small and explains very little of the observed sea-level trend.

The delayed response of the glaciers and ice sheets to the warmer temperatures after the Little Ice Age (1300-1870 AD) caused a sea-level rise in the early 20th century. This explains much of the observed sea-level change before 1950 (almost 70%), but very little after 1970 (less than 10%).

The human factor

The largest contributions to sea-level rise after 1970 are from ocean thermal expansion and the loss of mass from glaciers in response to the warming from increasing greenhouse gas concentrations. This rise is partly offset by the impact of aerosols, which on their own would cause a cooling of the ocean and less melting of glaciers.

The combined influence of these two factors (greenhouse gases and aerosols) is small in the beginning of the century, explaining only about 15% of the observed rise. However, after 1970, we find that the majority of the observed sea-level rise is a direct response to human influence (nearly 70%), with a slightly increasing percentage up to the present day.

When all factors are considered, the models explain about three quarters of the observed rise since 1900 and almost all of the rise over recent decades (almost 90% since 1970).

The reason for this difference can be found either in the models or in the observations. The models could underestimate the observed rise before 1970 due to, for instance, an underestimated ice sheet contribution. However, the quality and number of sea level observations before the satellite altimeter record is also less.

Tipping the scales

Our paper shows that the driving factors of sea-level change have shifted over the course of the 20th century.

Past natural variations in climate were the dominant factor at the start of the century, as a result of glaciers and ice sheets taking decades to centuries to adapt to climate change.

In contrast, by the end of the 20th century, human influence has become the dominant driving factor for sea-level rise. This will probably continue until greenhouse gas emissions are reduced and ocean temperatures, glaciers and ice sheets are in equilibrium with climate again.


John will be on hand for an Author Q&A between 4 and 5pm AEST on Tuesday, April 12, 2016. Post your questions in the comments section below.

The Conversation

Aimée Slangen, Postdoctoral research fellow, Institute for Marine and Atmospheric Research, Utrecht University and John Church, CSIRO Fellow, CSIRO

This article was originally published on The Conversation. Read the original article.

David Attenborough says the Great Barrier Reef is in ‘grave danger’ – it’s time to step up


Ove Hoegh-Guldberg, The University of Queensland and Tyrone Ridgway, The University of Queensland

Over three weeks, Australians have been taken on an incredible journey through the biology, beauty and wonder of the Great Barrier Reef, guided by Sir David Attenborough.

As individuals who have had the privilege of working on the Reef for much of our lives, the wonderful storytelling, exquisite photography and stunning production of the Great Barrier Reef with David Attenborough has been inspiring. It’s a great reminder of how lucky we are to have this wonder of nature right on our doorstep.

Particularly special has been the wonderful black-and-white footage of Sir David’s first visit to the Reef in 1957, a trip down memory lane. His attachment and fascination with the Reef are hard to dismiss.

However, as the curtain closes on this wonderful series, Sir David concludes that the Reef that he visited nearly 60 years ago is very different from today.

Research backs up this personal experience. The Australian Institute of Marine Science has shown that the Great Barrier Reef has lost around 50% of its coral cover between 1985 and 2012.

A reef in peril

The Great Barrier Reef is in grave danger. The twin perils brought by climate change – an increase in the temperature of the ocean and in its acidity – threaten its very existence. – Sir David Attenborough

As this television series has aired in Australia, an underwater heatwave has caused coral bleaching on 93% of the reefs that make up the Great Barrier Reef. Up to 50% of corals in the worst-affected regions may die as a result of this bleaching.

We should not be too surprised. Reef scientists have been warning about this for decades. In 1998, the warmest year on record at the time, the world lost around 16% of its coral reefs in the first global-scale mass coral bleaching event.

Before the current bleaching, the reef bleached severely in 1998 and 2002, with a substantial bleaching event in 2006 around the Keppel Islands. Outside these events, there has been moderate mass bleaching on the reef since the early 1980s (particularly 1983 and 1987), although never to the extent and intensity that we are witnessing today.

Rising sea temperatures

The current bleaching event has drawn widespread media coverage. One of the arguments we have seen raised is that coral bleaching is natural – and that the reef will bounce back as it always has, or even adapt to warming seas.

It is true that certain coral species, and even certain individual colonies within the same species, do perform better than others when stressed by warmer-than-normal sea temperatures. However, the extent of these differences is only 1-2℃. Given that even moderate climate change projections involve temperatures 2-3℃ higher than today, these differences offer little comfort for reefs like the Great Barrier Reef in a warmer world.

The observation that corals grow in warm areas of the globe is a demonstration that corals can and do adapt to local temperatures. However, the time frames involved are hundreds of years, not a single decade. Current rates of warming are much faster than anything for tens of millions of years, which makes the prospect of evolution keeping pace with a changing ocean even more improbable.

Mass bleaching is a new phenomenon that was first reported in the early 1980s. Before this, there are no reports of corals bleaching en masse across any coral reef or ocean region.

Experts are in agreement that mass coral bleaching and death on the Great Barrier Reef is driven by climate change resulting from human activities (mainly burning fossil fuels). This is the conclusion at the heart of the latest consensus of the United Nations scientific report.

Rising sea temperatures coupled with strong El Niños are unfortunately pushing corals to their thermal tolerance limits and beyond. It only takes a temperature increase of 1-2℃ to disrupt the special relationship between corals and tiny marine algae that live inside their tissue, resulting in bleached corals.

In fact, as CO₂ concentrations rise, sea temperatures will continue to climb – increasing the likelihood that mass coral bleaching events will become more frequent and more destructive. Recent research has shown that near-future increases in local temperature of as little as 0.5℃ may lead to significant degradation of the Great Barrier Reef.

Rising temperatures are not the only climate threat. Cyclones are predicted to become stronger (if less frequent) in a warmer world. Since 2005 there have been eight cyclones on the reef of category 3 or above – more than previous decades. We would argue this is evidence that these predictions are already coming true and form part of our current reality.

Heat stress is not just affecting corals on the Great Barrier Reef either. We are seeing reports of bleaching across all of Australia’s coral real estate (Coral Sea, Torres Strait, Kimberley, North West Shelf), the South Pacific and the central and western Indian Ocean.

It is likely only a matter of time before we start to see reports of bleaching from other coral reefs around the world. We are indeed dealing with changing times and a global issue.

It’s not too late to act

It’s not too late to act – but we will need very deep and significant action to occur within three to five years or face a collapse of ecosystems like the Great Barrier Reef.

Climate change is just one of the threats facing the Great Barrier Reef. Fortunately, it is not too late to give the reef a fighting chance.

Ove Hoegh-Guldberg on the future of the reef

However, it does require strong, immediate and decisive action from our political leaders.

In the lead-up to the federal election, we believe that four major steps are required by our leaders to ensure a future for the Reef:

  1. Mitigate: we need to – as per the Paris Agreement – keep average global surface temperature increases to below 2.0°C, and hopefully 1.5°C in the long term. This means we must adopt a pathway that will bring our greenhouse gas emissions to zero over the next few decades. Our leaders must live up to the global agreement that they committed to in Paris at COP21.

  2. Invest: we need to ultimately close our coal mines and stop searching for more fossil fuels. The experts tell us that we must leave 80% of known fossil fuels in the ground. Let’s invest in coral, renewables and the planet, and not in coal, emissions and ecosystem collapse.

  3. Strengthen: we need an urgent and concerted effort to reduce other non-climate change threats to build the resilience of the reef so it can better withstand the impacts of climate change over the coming years.

  4. Integrate: Australian and Queensland governments have begun a process to address declining reef health through the Reef 2050 Long-term Sustainability Plan. This plan has a strong focus on coastal water quality. The 2050 Reef Plan and its resourcing will need to consider climate change – especially given that it is likely to make achieving the objectives of the plan even more challenging and impossible (if no action). Otherwise we run the risk of ending up with a great plan for improving water quality by 2050 but no Great Barrier Reef.

We hope that Sir David Attenborough will help inspire Australians to demand action from their political leaders to ensure that this natural wonder of the world continues to inspire, employ, educate and generate income for generations to come.

It seems fitting to end with Sir David’s closing words with a call to our political leaders and fellow Australians:

Do we really care so little about the earth upon which we live that we don’t wish to protect one of its greatest wonders from the consequences of our behaviours?

After all, it is our Great Barrier Reef – let’s keep it great.

Or at least let’s fight to keep it.

The Conversation

Ove Hoegh-Guldberg, Director, Global Change Institute, The University of Queensland and Tyrone Ridgway, Healthy Oceans Program Manager, Global Change Institute, The University of Queensland

This article was originally published on The Conversation. Read the original article.