Australia has two decades to avoid the most damaging impacts of climate change

Iain Stewart, ClimateWorks Australia

The long-awaited special report on the science underpinning the Paris Agreement goal of limiting global warming to 1.5℃ has been released today by the Intergovernmental Panel on Climate Change.

It tells us that hitting this goal will be challenging, but not impossible. And it highlights the benefits of hitting the target, by pointing out that global warming will be vastly more damaging if allowed to reach 2℃.

Read more:
The UN’s 1.5°C special climate report at a glance

The report says that for a 66% chance at limiting global warming to 1.5℃, an additional 550 billion tonnes of carbon dioxide (or its equivalent) can be emitted globally from the beginning of 2018. Increasing the risk to a 50% chance at limiting global warming to 1.5℃, that figure becomes 750Gt CO₂e.

Based on previous calculations, Australia’s fair share of the global carbon budget is roughly equivalent to 1%. That would put Australia’s remaining carbon budget at 5.5Gt and 7.5Gt for a 66% and 50% chance, respectively.

The simplified trajectory below shows that Australia would therefore need to reach net zero greenhouse emissions by 2038 for a 66% chance of limiting global warming to 1.5℃, and by 2045 for a 50% chance.

ClimateWorks Australia, Author provided

In practical terms, this gives Australia two decades to deliver on our part, for a good chance of avoiding the most devastating impacts of a warming climate. Globally, we must reach net zero greenhouse emissions by 2047 for a 66% chance of limiting global warming to 1.5℃, and by 2058 for a 50% chance. Australia will have to hit net zero before it is achieved globally because we currently have among the highest per person emissions, so our decarbonisation trajectory needs to be steeper.

But Australia’s emissions are rising

From 2006 to 2013, Australian emissions decreased, but they have since begun to rise again. As shown in ClimateWorks Australia’s recently released report, Tracking Progress, we are not yet on track meet our current Paris commitment of cutting emissions by 26-28% relative to 2005 levels by 2030. Nor are we on track to reach net zero.

Yet our research also showed we have the potential to get back on track. There have been recent periods when sectors of our economy have cut carbon at or near the pace required to achieve net zero emissions by 2050.

Read more:
Australia is not on track to reach 2030 Paris target (but the potential is there)

Reaching net zero from here will require rapid, economy-wide action, including:

  • increasing the share of renewable electricity
  • improving energy efficiency
  • electrifying transport and industry where possible
  • switching to lower-emission fuels such as gas
  • land use changes (reforestation, reduced land clearance, and best practice farming).

There are already many examples of these kinds of approaches. For example, since 2010, solar photovoltaic prices have fallen by around 70% and battery prices by around 80%, while uptake rates have surpassed expectations. This has been the result of research, investment, government incentives, shifting consumer preferences, and economies of scale.

Consumers are beginning to embrace trends such as electric vehicles and 3D printing, and we can expect more technological disruptions throughout the economy such as building optimisation, smart grids, and solar-hydrogen, which all have the potential to reduce emissions significantly.

The goal is still in reach (just)

The new IPCC report is adamant that the goal of limiting global warming to 1.5℃ is still achievable – despite previous fears that it is already out of reach. Yes, it is tight, but the challenge is in going faster, not the lack of solutions.

Crucially, the report also points out that 2℃ of global warming would be vastly more damaging than 1.5℃, and that 2℃ cannot be treated as a “safe” limit.

At 2℃, the report predicts it is “very likely that there will be at least one sea-ice-free Arctic summer per decade”. In contrast, holding warming to 1.5℃ rather than 2℃ would protect an extra 10.4 million people from rising sea levels.

Some of these people are our neighbours in Pacific Island nations, many of which are implementing some of the most ambitious climate policies in the world. For low-lying countries and island states, the reality is “1.5 to stay alive”.

Australia’s climate at stake

Closer to home, the impacts of climate change on Australia will continue to manifest themselves in extreme weather events such as droughts, floods and bushfires. Increasing impacts are expected to extend to water, food and even border security, creating the potential for millions of climate refugees in our region before the end of the century.

As a wealthy, emissions-intensive country with abundant natural resources, in a region highly vulnerable to climate impacts, Australia should take its Paris climate targets very seriously. Australia has the means to become a regional leader in climate action, positioning ourselves as a “clean energy superpower” and helping our neighbours work towards becoming carbon-neutral.

Read more:
Lack of climate policy threatens to trip up Australian diplomacy this summit season

There are many examples within Australia of commitments already made to reach net zero emissions. States and territories representing 80% of Australia’s emissions – along with the federal opposition – have committed to reaching net zero emissions by 2050. Tasmania has already reached net zero. The ACT has legislated to do so by 2045.

Other organisations have also pledged to go carbon-neutral or use 100% renewable energy, including multinational companies, major cities such as Melbourne, Sydney and Adelaide, and universities.

These initiatives prove that setting targets for emissions reduction actually ignites action. The IPCC’s new report sets us perhaps the most important target of all: the world must hit net zero emissions by mid-century if we are to stand a good chance of avoiding the worst impacts of global warming.The Conversation

Iain Stewart, Analyst, ClimateWorks Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.


Target Earth: how asteroids made an impact on Australia

File 20180320 31627 hln2cf.jpg?ixlib=rb 1.1
Gosses Bluff impact crater in the Northern Territory.
NASA’s Earth Observatory

Andrew Glikson, Australian National University

Our planet has had a few close encounters with asteroids of late.

Asteroid 2018 CC came within about 184,000km of Earth on February 6 this year. A few days later asteroid 2018 CB came within 64,000km, which is less than one-fifth the distance of Earth to the Moon.

Animation showing how asteroid 2018 CB passed closely by Earth on February 9. (NASA/JPL-Caltech)

Thankfully, both asteroids were relatively small (estimated between 15m and 40m). Neither posed a risk to Earth (this time), but Earth has not been so lucky in the past.

Read more:
Ancient asteroid impacts yield evidence for the nature of the early Earth

Research in Australia and other countries indicates that, in the distant geological past, asteroids as large as Eros (about 34.4km long and 11.2km wide) have impacted Earth. These have triggered major changes in the structure and evolution of the crust and mantle, as I’ve written about before.

Asteroid Eros.

The impact of asteroids on the Australian continent and marine shelves is examined more closely in my new book, Asteroid impacts, crustal evolution and mineral systems, with special reference to Australia, co-authored by Franco Pirajno.

In the firing line

The terrestrial planets of the inner solar system – Mars, Earth, Venus and Mercury – are all affected by asteroids deflected from the asteroid belt, located between Mars and Jupiter, and by comets falling off the Kuiper belt beyond Neptune.

The cratered surface of Mercury.
NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Many of these impact craters are clearly seen on Mars and Mercury as well as on our Moon. Venus too has its craters, but its thick atmosphere obscures these.

When Earth is viewed from space, it displays little or no cratering despite also being located in the trajectory of these asteroids and comets.

Earth doesn’t look very cratered from space.

But this impression is apparent rather than real. Many of the impact scars are covered or masked due to the dynamic nature of Earth and the oceans that extend over some two-thirds of the planet’s surface. The masking processes include the accretion and subduction of tectonic plates as well as intensive erosion processes.

It was not until about 1981 that the scientific community began to recognise the significance of extraterrestrial impacts for the mass extinction of species about 66 million years ago, which wiped out the dinosaurs and many other groups.

The American scientists Louis and Walter Alvarez and their colleagues had unearthed a telltale iridium-rich sedimentary layer around the 66 million-year-old Cretaceous-Tertiary boundary at Gubbio, Italy. The element iridium, typically enriched in asteroids, is a signature within sediments for material from a meteorite impact.

The discovery re-established the idea that catastrophes shaped much of Earth’s history, a theory originally promoted by the French zoologist Georges Cuvier.

Impacts on the Earth

Beyond forming craters, the impact of large asteroids on Earth resulted in the formation of structural domes due to elastic rebound of the crust. Examples include the Vredefort dome in South Africa and the buried Woodleigh dome under and east of Shark Bay in Western Australia.

The impacts also caused major seismic activity and faulting, large tsunami events, ejection of masses of particles and dust, and – as mentioned earlier – in some instances the mass extinction of species due to rapid environmental changes.

The asteroid impact record on Earth is thus to a large extent concealed and the subject of an extensive search using structural, geophysical, geochemical and other methods.

Since many impact records are covered by the oceans or were eroded, old stable parts of the Earth crust, named “cratons”, are the best places to look. This is where the scars of ancient asteroid impacts are preserved and can be found, including craters and their deep-seated roots and rebound dome structures.

Australian impacts

The criteria applied for recognition of asteroid impact structures and meteorite craters allowed the identification of at least 38 confirmed impact structures on the Australian continent and surrounding continental shelf.

There are an additional 43 examples of exposed and buried circular ring and dome features, many of which are of possible or probable impact origin.

The red circles show confirmed impact structures, green circles are impact craters, the yellow circles are possible-to-probable ring structures, red outer rings are impact structures larger than 100km in diameter, and outer white rings are impact structures less than 50km.
Google Earth/Andrew Glikson, Author provided

Examples of exposed confirmed impact structures include Gosses Bluff in the southern Northern Territory, Shoemaker in central Western Australia, and Acraman and Lawn Hill in northwestern Queensland.

A Google Earth image of the central ring of the Gosses Bluff impact structure, central Australia, Northern Territory. It is 14km in diameter and was formed around 142 million years ago.

A Google Earth image of the Shoemaker impact structure, Nabberu Basin, in Western Australia. It is 30km in diameter and was likely formed around 1,630 million years ago.

A Google Earth image of the centre of the Acraman impact structure in southern South Australia. It is 90km in diameter and was formed around 590 million years ago.

A Google Earth image of the centre of the Lawn Hill impact structure in northwestern Queensland. It is is 18km in diameter and was formed more than 515 million years ago.

The impact record of Australia thus includes exposed impact structures, buried impact structures, meteorite craters and geophysical ring anomalies of unproven origin.

Examples of large geophysical multi-ring features – total magnetic intensity anomalies, circular gravity anomalies and seismic domes – include probable buried twin impact structures in the Warburton Basin in northeast South Australia, a confirmed buried impact structure at Woodleigh in WA, and confirmed buried impact structures at Tookoonooka and Talundilly in the Eromanga Basin in southwest Queensland.

Seismic tomographic (identified 3D images) anomalies of the Warburton twin structures, South Australia, representing probable impact structures, and the Woodleigh impact structure, Western Australia.
Saygin and Kennett 2010/Andrew Glikson, Author provided

Fallout of asteroid impacts

Structures and craters caused by asteroid impacts are not the only thing we find. In the Australian landscape there are also the rock fragments and melt drops derived from clouds ejected from the impact craters.

The melt drops, condensed from impact-ejected vapour, are termed “microkrystites”. These are recognised by their radiating quench (cooling) textures and abundance of platinum group element anomalies.

Impact condensate spherules (called microkrystites) from the 2.63 billion-years-old Jeerinah Impact layer, central Pilbara Craton, Western Australia.
Bruce Simonson, Author provided

In at least one instance the evidence suggests that an impact by a cluster of large asteroids resulted in an abrupt transformation of crustal structure on the Pilbara, northwestern Australia, as well as the Barberton greenstone belt in South Africa, from a granite/greenstone system to semi-continental crustal environment.

Read more:
World’s largest asteroid impact site could be right here in Australia

Between 3.26 and 3.24 billion years ago these impacts caused a sharp tectonic uplift and magmatic activity, leading to to an onset of semi-continental crustal conditions.

Thus, far from being free from impacts, the Australian landscape has been shaped many times over millions and billions of years by asteroids falling to Earth.

The ConversationAs studies of Australian impact structure and impact ejecta progress, the critical role of asteroid impacts in the early evolution of the Earth and in the development of the Australian continent are becoming clearer.

Andrew Glikson, Earth and paleo-climate scientist, Australian National University

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

Noise Pollution: Squids and Octopuses

The following link is to an article that looks into how noise pollution impacts squids and octopuses. An enlightening article on an issue that is becoming clearer all of the time.

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