The Times Australia
The Times World News

.
The Times Real Estate

.

Wondering what Australia might look like in a hotter world? Take a glimpse into the distant past

  • Written by Tim Flannery, Honorary fellow, The University of Melbourne
Wondering what Australia might look like in a hotter world? Take a glimpse into the distant past

Current concentrations of carbon dioxide (CO₂) in Earth’s atmosphere are unprecedented in human history. But CO₂ levels today, and those that might occur in coming decades, did occur millions of years ago.

Wouldn’t it be useful to go back in time and see what Australia looked like during those periods in the distant past? Well, scientists – including us – have done just that.

These studies, which largely involve examining sediments and fossils, reveal a radically different Australia to the one we inhabit.

The continent was warmer and wetter, and filled with unfamiliar plant and animal species. It suggests Australia may be much wetter, and look very different, in centuries and millennia to come.

ferns imprinted in rock
Studying fossils helps us understand past climates. Shutterstock[1]

Then and now: measuring CO₂

Atmospheric CO₂ is measured in “parts per million[2]” – in other words, how many CO₂ molecules are present in each million molecules of dry air.

The concentration of CO₂ influences[3] Earth’s climate. The more CO₂ present, the warmer it gets.

Right now, atmospheric CO₂ is about 420 parts per million. This concentration last occurred[4] on Earth between 3 million and 5 million years ago – a period known as the Pliocene.

If humanity keeps burning fossil fuels at the current rate, by mid-century CO₂ concentrations will be around 550 parts per million[5]. This level was last approached 14 million to 17 million years ago, in the mid-Miocene period.

In both these periods, Earth was warmer than it is today, and sea levels were far higher.

In the Pliocene, research[6] shows CO₂ was the cause of about half the elevated temperatures. Much of the rest was due to changes in ice sheets and vegetation[7], for which CO₂ was indirectly responsible.

In the mid-Miocene, the link between CO₂ and warmer temperatures is less certain. But climate modelling[8] does suggest CO₂ was the primary driver of temperature increases in this period.

By examining the plants and animals that lived in Australia during these epochs, we can gain insight into what a warmer Australia might look like.

Obviously, the Pliocene and mid-Miocene far predate humans, and CO₂ concentrations in the atmosphere in those periods increased for natural reasons, such as volcanic eruptions. Today, humans are causing the CO₂ increases, and it’s happening at a much faster rate than in the past.

Read more: Humanity is compressing millions of years of natural change into just a few centuries[9]

steam billows from chimneys
Today, humans are the cause of high CO2 levels in the atmosphere. Shutterstock

Australia in the Pliocene

The fossil and sediment record from the Pliocene period in Australia is limited. But the available data suggest[10] much of the continent – and Earth generally[11] – was more humid and warm than today. This helped determine the species that existed in Australia.

For example, the Nullarbor Plain, which stretches from South Australia to Western Australia, is today extremely dry. But studies[12] of fossilised pollen show during the Pliocene it was home to Gymea lilies, banksias and angophoras – plants found around Sydney today.

Similarly, the western Murray-Darling Basin is today largely saltbush and grassland. But fossil pollen records[13] show in the Pliocene, it was home to araucaria and the southern beech – rainforest trees found in high-rainfall climates[14].

And preserved remains of marsupials dating back to the Pliocene have been found near Hamilton in western Victoria. They include a dorcopsis wallaby[15] – the nearest living relative of which lives in New Guinea’s ever-wet mountains.

small grey wallaby
The nearest relative of the dorcopsis lives in New Guinea. Shutterstock

Hot and moist in the mid-Miocene

A rich fossil and sediment record exists from the mid-Miocene. Marine sediments off WA suggest[16] the west and southwest part of Australia was arid. In contrast, the continent’s east was very wet.

For example, the Riversleigh World Heritage area in Queensland is today a semi-arid limestone plateau. But research has found[17] in the mid-Miocene, seven species of folivorous ringtail possums lived there at the same time. The only place more than two ringtail possum species coexist today is in rainforests. This suggests the Riversleigh plateau once supported a diverse rainforest[18] ecosystem.

Similarly, McGraths Flat, near Gulgong in New South Wales, is today an open woodland. But mid-Miocene fossils from the site include[19] rainforest trees with pointed leaves that help shed water.

And mid-Miocene fossils from the Yallourn Formation, in Victoria’s Latrobe Valley, also include the remains[20] of rainforest plants. Before colonisation it supported eucalypt forests and grasslands.

This evidence of rainforest suggests far wetter conditions in the mid-Miocene than exist today.

Read more: If warming exceeds 2°C, Antarctica's melting ice sheets could raise seas 20 metres in coming centuries[21]

leaf in rainforest during downpour
Dry parts of Australia were once rainforest. Shutterstock

An uncertain future

You may be wondering, when climate change projections tell us Australia will be drier in future, why we are suggesting the continent will be wetter. We concede there is a real contradiction here, and it requires further research to unravel.

There’s another important point to note. While conditions in the Pliocene or Miocene can help us understand how Earth’s systems respond to elevated CO₂ levels, we can’t say Australia’s future climate will exactly replicate those conditions. And there are lags in the climate system, so while CO₂ concentrations in the Pliocene are similar to today’s levels, Earth hasn’t yet experienced the same extent of warming and rainfall.

The uncertainty comes down to the complexities of the climate system. Some components, such as air temperature, respond to increased CO₂ levels relatively quickly. But other components will require centuries or millennia to fully respond. For example, ice sheets over Greenland and Antarctica are kilometres thick and as big as continents, which means they take a long time to melt.

So, even if CO₂ levels remain high, we shouldn’t expect a Pliocene-like climate to develop for centuries or millennia yet. However, every day we add CO₂ to Earth’s atmosphere, the climate system moves closer to a Pliocene-like state – and it cannot be easily turned around.

References

  1. ^ Shutterstock (www.shutterstock.com)
  2. ^ parts per million (gml.noaa.gov)
  3. ^ influences (www.lyellcollection.org)
  4. ^ last occurred (research.noaa.gov)
  5. ^ around 550 parts per million (www.theworldcounts.com)
  6. ^ research (www.sciencedirect.com)
  7. ^ vegetation (www.jstor.org)
  8. ^ climate modelling (agupubs.onlinelibrary.wiley.com)
  9. ^ Humanity is compressing millions of years of natural change into just a few centuries (theconversation.com)
  10. ^ suggest (www.researchgate.net)
  11. ^ Earth generally (www.sciencedirect.com)
  12. ^ studies (www.pnas.org)
  13. ^ fossil pollen records (www.sciencedirect.com)
  14. ^ high-rainfall climates (onlinelibrary.wiley.com)
  15. ^ dorcopsis wallaby (researchers.mq.edu.au)
  16. ^ suggest (www.science.org)
  17. ^ research has found (www.researchgate.net)
  18. ^ diverse rainforest (www.researchgate.net)
  19. ^ include (www.science.org)
  20. ^ include the remains (www.researchgate.net)
  21. ^ If warming exceeds 2°C, Antarctica's melting ice sheets could raise seas 20 metres in coming centuries (theconversation.com)

Read more https://theconversation.com/wondering-what-australia-might-look-like-in-a-hotter-world-take-a-glimpse-into-the-distant-past-227058

The Times Features

Best Deals on Home Furniture Online

Key Highlights Discover the best deals on high-quality outdoor furniture online. Transform your outdoor space into a stylish and comfortable oasis. Explore a wide range of d...

Discover the Best Women's Jumpers for Every Season

Key Highlights Explore lightweight jumpers for spring and summer, ensuring breathability and ease. Wrap up warm with cozy wool jumpers for the chilly autumn and winter season...

Uncover the Elegance of Gorgeous Diamond Tennis Necklaces

Key Highlights Diamond tennis necklaces are a timeless piece of jewelry that exudes elegance and sophistication. They feature a continuous line of brilliant-cut diamonds, cre...

Dental Implants vs. Dentures: Which Is Better for You?

When it comes to replacing missing teeth, two of the most common options are dental implants and dentures. Both have their advantages and disadvantages, so choosing between them ...

What Neck Pain Really Means (And Why It’s More Than Just Poor Posture)

Neck pain is often brushed off as something temporary — a tight spot after a long day at the desk or a poor night’s sleep. But when the discomfort keeps returning, it could be a ...

The Work of Gosha Rubchinskiy: Fashion, Culture, and Youth

From Designer to Cultural Architect Gosha Rubchinskiy is not just a fashion designer—he's a cultural force. Born in Moscow in 1984, Rubchinskiy began his career in fashion in t...

Times Magazine

The Essential Guide to Transforming Office Spaces for Maximum Efficiency

Why Office Fitouts MatterA well-designed office can make all the difference in productivity, employee satisfaction, and client impressions. Businesses of all sizes are investing in updated office spaces to create environments that foster collaborat...

The A/B Testing Revolution: How AI Optimized Landing Pages Without Human Input

A/B testing was always integral to the web-based marketing world. Was there a button that converted better? Marketing could pit one against the other and see which option worked better. This was always through human observation, and over time, as d...

Using Countdown Timers in Email: Do They Really Increase Conversions?

In a world that's always on, where marketers are attempting to entice a subscriber and get them to convert on the same screen with one email, the power of urgency is sometimes the essential element needed. One of the most popular ways to create urg...

Types of Software Consultants

In today's technology-driven world, businesses often seek the expertise of software consultants to navigate complex software needs. There are several types of software consultants, including solution architects, project managers, and user experienc...

CWU Assistive Tech Hub is Changing Lives: Win a Free Rollator Walker This Easter!

🌟 Mobility. Independence. Community. All in One. This Easter, the CWU Assistive Tech Hub is pleased to support the Banyule community by giving away a rollator walker. The giveaway will take place during the Macleod Village Easter Egg Hunt & Ma...

"Eternal Nurture" by Cara Barilla: A Timeless Collection of Wisdom and Healing

Renowned Sydney-born author and educator Cara Barilla has released her latest book, Eternal Nurture, a profound collection of inspirational quotes designed to support mindfulness, emotional healing, and personal growth. With a deep commitment to ...

LayBy Shopping