About Climate Change
Climate change is the shift in long term weather patterns across the earth. Large parts of the earth have become colder at some times and warmer at others.
Over thousands of years, the earth's climate changes in response to:
- changes in processes such as solar radiation
- deviations in the earth's orbit
- volcanic activity
- large-scale movements of the earth's crust
- continental drift, and
- changes in greenhouse gas concentrations.
While most of these changes are natural, much of the buildup in greenhouse gases is attributed to human activity.
The earth is surrounded by a layer of gases which insulate the planet, trapping heat from the sun. This is called the ‘greenhouse effect’ because the gases create an atmosphere similar to that found in a greenhouse. Without these natural gases earth would not be able to sustain life.
These gases are increasing in concentration as a result of practices such as coal burning and overuse of aerosol products. The temperature of the earth has warmed by nearly 1°C over the last 100 years and scientists predict this trend will continue.
Changes in our climate and an increase in extreme weather events are said to be caused by warming of the planet. A warmer earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans.
The first discoveries that helped explain recent climate change and global warming were in the 18th and 19th centuries:
- In 1753, Joseph Black discovered carbon dioxide.
- In 1827, Jean Baptiste Fourier suggested that an atmospheric effect kept the earth warmer than it would otherwise be - he used the analogy of a greenhouse.
- In 1896, Svante August Arrhenius proposed that carbon dioxide emissions from the burning of coal would increase the earth's greenhouse effect and lead to global warming.
Measuring climate change
From the late 1950s, carbon dioxide (CO2) measurements were taken on a mountain top in Hawaii. Over the next decade, these measurements confirmed that levels of CO2 in the atmosphere were rising year after year. In 1967, a computer simulation suggested that global temperatures might increase by more than 1°C, depending on CO2 levels.
Improved climate models developed over the next 20 years confirmed the link between CO2 emissions and global warming. Then an ice core from Antarctica revealed a link between carbon dioxide levels and temperature going back more than 100,000 years. The warnings from this evidence encouraged international action on climate change.
During the past 100 years, global average surface temperatures increased by about 0.75°C. Since 1910, the average temperature in Australia has risen by about 1°C. Although these increases sound small, they have a big impact on the world's climate.
Observations of our past and current climate are essential in assisting us to project future climate, and are critical in our understanding of both climate variability and the drivers of climate change.
Rainfall, temperature, sea levels and snow cover are the key indicators of climate trends.
Impacts of climate change
Climate change is one of the greatest social, economic and environmental challenges of our time. Human activity contributes significantly to climate change. This, in turn, is having an impact on Australia's:
- bushfire frequency
- cyclone frequency
- health (of both humans and animals)
These changes will affect current and future generations.
Global warming and climate change
The terms 'global warming' and 'climate change' are sometimes confused with each other, but there is a difference. Global warming is the gradual increase in the earth's average surface temperature due to greenhouse gases in the atmosphere, whereas climate change refers to the long term changes in climate, including average temperature and rainfall.
Greenhouse gases have always been a natural and necessary part of the atmosphere. The chemical properties of greenhouse gases mean that they strongly absorb and re-radiate the sun's warmth in the atmosphere. Because of this process, the earth's temperature is 33°C warmer than it would otherwise be, allowing life on earth to exist.
Water vapour is the most abundant greenhouse gas. The concentration of water vapour is highly variable and human activities have little direct impact on the amount of it in the atmosphere. The main greenhouse gases generated by human activity are carbon dioxide (CO2), methane and nitrous oxide. There are also manufactured gases such as chlorofluorocarbons (CFCs), halocarbons and some of their replacements that make a small contribution to global warming.
Over the last 800,000 years, the amount of carbon dioxide in the atmosphere has varied between approximately 172 and 300 parts per million (ppm). Since the 1700s, carbon dioxide levels have risen sharply to about 386 ppm. The extra carbon dioxide is largely responsible for the increase in global temperatures of about 0.75°C.
How will Australia be affected?
It is difficult to precisely predict what the impacts of climate change will be, as they vary with each region. The best estimates we have predict that by 2030 parts of Australia will face:
- a further 1°C of warming in temperatures
- up to 20 per cent more months of drought
- up to 25 per cent more days of very high or extreme fire danger
- increases in storm surges and severe weather events.
Australia is vulnerable to the effects of climate change. We are already the driest inhabited continent on earth, and are exposed to the dangers of extreme heat and drought. We are also home to many globally important and vulnerable ecological systems. Australians are overwhelmingly coastal dwellers. Our industries and urban centres face ongoing water limitations. Our economy, including food production and agriculture is under stress.
How will I be affected?
As an individual, you may find your home more exposed to extreme weather events, your food may be less plentiful, or your water will be more restricted and provided from recycled sources. You will also need to be aware of sustainably caring for our land and marine environments.