CLIMATE TRENDS

• Rainfall
• Temperature
• Sea level
• Snow cover

WHAT IS HAPPENING TO OUR CLIMATE?

Observations of our past and current climate are essential for validation of the climate models we use to project future climate, and critical in our understanding of climate variability and drivers of climate change.

Causes of past climate change

One of the key challenges of climate change science is determining which climate patterns are due to naturally occurring climate variability and which ones are climate changes as a result of human activity.

To make this distinction, scientists undertake detection and attribution studies.

Detection demonstrates that the climate has changed in a statistically significant way, but doesn't offer any reasons for the change. Attribution establishes the most likely cause of the detected change.

Detection and attribution studies of Australian climate indicate that:

• Warming of climate is unequivocal.
• The widespread warming is very likely to be due to increased greenhouse gas concentrations in the atmosphere.
• A drop in rainfall in south-west Western Australia is likely due to a combination of increased greenhouse gas concentrations, natural climate variability, and land use change.
• The increased summer rainfall in north-west Australia may be due to increased aerosol particles in the atmosphere resulting from human activity, especially in Asia.
• Other apparent changes require further study. These include the ten year dry spell in South-eastern Australia and the apparent drying at south-east Queensland.

Climate over the long term

High quality instrumental climate records in Australia only extend back to the late 19th century, giving us a relatively short record of climate variability.

To understand the nature of our climate we need data that go back far beyond the instrumental record. Palaeo-records help us reconstruct the climate for periods when instrumental records did not exist.

Palaeo-records

Palaeo-records are natural archives of past atmospheric, terrestrial and marine environments. They include tree rings, cave deposits, corals, Antarctic ice cores, lake and marine sediments, sand dunes, coastal deposits and glacial deposits.

What palaeo-records tell us

Palaeo-records provide direct and indirect (proxy) evidence of atmospheric, terrestrial and marine conditions, including the causes of past greenhouse gas changes and their impact on global climate.

Direct evidence, such as air trapped in ice sheets, allows the reconstruction of the composition of our atmosphere over thousands of years, while proxy evidence of past climates can be obtained by examining the growth rate of trees or the chemical composition of fossils.

How we use palaeo-records

Palaeo-climate data allow us to test and improve our understanding of natural climate change and variability in Australia, as well as the processes driving climate change.

Palaeo-data can be used to validate the ability of climate models to simulate past climate, giving scientists confidence in predicting future climatic conditions.

The information provided by palaeo-research can help explain how and why our climate has changed in the past and, ultimately, help us to assess and plan for climate change in future.