Climate Change

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In this section:

How does the climate change naturally?
What’s carbon got to do with climate?
How do scientists measure climate change?
What can we do about climate change?

Major climate change occurs when the Earth’s average temperature rises or falls by 5 to 10 degrees centigrade. That’s enough to affect most systems that support life on the planet. A rise in average temperature increases the energy in weather systems, causing stronger winds, intense storms and floods. Sea levels rise because the warming ocean expands and ice on landmasses melts into the oceans. The climate has changed many times in the Earth’s history. Most climate scientists believe that humans are causing major climate change now by increasing the amount of a gas called carbon dioxide in the air. Every time we burn coal, oil or gas for energy we add more carbon dioxide to a ‘blanket’ of gases around the Earth that keeps the planet warm.

The earth has a blanket of greenhouse gases around it that trap heat from the sun.
How carbon dioxide affects climate

Earth’s climate has changed before

The fossil record suggests that about 90% of all plant and animal species became extinct when the climate changed 251 million years ago. Scientists think that temperatures rose at the time as a result of massive amounts of carbon dioxide being released from volcanic activity in Siberia. Only adaptable plants and animals survived when the conditions changed. All plants and animals have a particular range of environmental conditions that make life possible for them. Those with a narrow range are very sensitive to climate change.

A stone fossil of a sea creature which has large eyes and a body with thirteen segments.
Trilobites became extinct about 250 million years ago.
A fossil ammonite
Ammonites were probably driven to extinction by climate change. Their closest living relative today is the nautilus.

People can adapt to survive climate change

People left footprints in the mud beside Lake Mungo in western NSW 20 000 years ago. The lake once covered about 135km and teemed with fish, yabbies and mussels. Human skeletons and fossils confirm that the lake nourished Aboriginal people for at least 25 000 years. But around 14 000 years ago the climate warmed and the lake dried up. People had to adapt and find food elsewhere. Lake Mungo is now a dry lake bed, but descendants of those early people live on in the region.

A dry lake bed with deep ridges caused wind and water erosion.
Lake Mungo is located in Western New South Wales, about 50 kilometres east of the Darling River.

How will climate change affect us?

The calm climatic conditions of the last 10 000 years have allowed agriculture and human civilisation to flourish. But scientists advise that life will be less predictable if we let global warming continue. Australia’s climate includes extreme events like droughts and floods but a warming climate will make those events even more extreme. As well as destroying homes and infrastructure, extreme weather events will disrupt supplies of fresh fruits and vegetables.

Hurricane Irene's Gentle Caress, by captainkickstand, on Flickr
This photo was taken by William Kurtz when Hurricane Irene hit the USA in 2011. You can join our Flickr group to display your own photos of extreme weather events.


The supply of seafood will change. All of us who eat fish or other seafood will be affected. When carbon dioxide from the air dissolves in sea water, the water turns into weak acid. This is bad news for all the little sea creatures with shells because acid destroys their shells and reduces their chance of survival. All the animals that rely on the shelled animals for food also suffer. Humans are part of this food web so we are affected too.
A chart showing how energy flows through sixteen species of animals and two people who are all linked in an ocean food web.
No more prawns on the barbie! High acid levels in the ocean make it very hard for sea creatures to build calcium carbonate shells. These include corals, clams, prawns and plankton that form the base of the ocean food web. Without their shells they will simply disappear.

Sea levels will rise as ice sheets melt and oceans expand. This will affect billions of people around the world. A model of Sydney Opera House and Circular Quay showing which parts would be under water if the sea level rose by 10 metres.
This model shows how the coastline of Sydney city would change if sea levels rose 10 metres. Scientists expect sea levels to rise by up to 2 metres this century. If the Greenland icesheet melts completely then sea levels will rise by at least an extra 7 metres. Model: Gift of Modelcraft, Sydney.

Is there debate about climate change?

There is clear evidence that Earth’s climate is warming and most working climate scientists agree that humans are causing that change. Scientists constantly assess the best available information and test the evidence. They create models to predict how climate change will affect us and, according to them, there is no time to waste debating whether human-induced climate change is real. You can learn more from The Science of Climate Change, Questions and Answers, published by the Australian Academy of Science.

Is it a matter of belief or fact?

Belief is something that you can have in religion or other social system that makes your life more meaningful. It’s a matter of faith and is a very personal decision that isn’t based on scientific evidence.

But climate change is not a matter of belief. Climate scientists base their reports and estimates on scientific evidence. It doesn’t matter to Nature whether politicians or other people believe in climate change. The evidence shows that the temperature of the earth and the concentration of carbon dioxide in the atmosphere are both rising and are likely to continue whether we believe it or not.

Scientific ideas aren’t always popular

Between 300 and 400 years ago two scientists, Copernicus and Galileo, proposed that the Earth travels around the Sun. Their idea was criticised by the Church because it challenged what people believed hundreds of years earlier when the Bible was written. The Church was very powerful and the two men were punished for their theories. It wasn’t until 1998 that the concept was formally accepted by the Church. This is an example of the clash that can occur when scientific evidence doesn’t fit with people’s ideas and belief systems. In this case it wasn’t a life and death matter. Unfortunately human-induced climate change is. We don’t have 400 years to wait for everyone to agree that it’s true.


A model showing where our galaxy's planets and moons are in relation to the Sun.
This model of our solar system was made in the 1800s to show how all the planets, including the Earth, revolve around the Sun. Powerhouse Museum collection, H1700-2