Earth's climate has warmed
Both natural and human influences have affected climate over the past century, but it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.
The evidence that climate has changed over the past century includes temperature observations over land and sea, as well as measurements of rainfall, sea levels, and ocean acidity and salinity.
Over time, these measurements give us a picture of how climate has changed, both in Australia and globally.
The heat content of the world's oceans has increased during recent decades and accounts for more than 90 per cent of the total heat accumulated by the land, air and ocean since the 1970s. On a global scale, the ocean warming is largest near the surface, and the upper 75 m warmed by between 0.09°C and 0.13°C per decade over the period 1971–2010.
Changes in Australia
In Australia, surface temperatures on the land have been recorded at many sites since the mid to late 19th century. By 1910, Australia had a reliable and standardised network of thermometers and the data they produced have been extensively analysed by the Bureau of Meteorology and scientists at CSIRO, Australian universities and international research institutions.
This reveals that since 1910, Australia's annual-average daily maximum temperatures have increased by 0.8°C and the overnight minima by more than 1.1°C. Since the 1950s, each decade has been warmer than the one before. We've also experienced an increase in record hot days and a decrease in record cold days across the country.
Some years have been relatively cool due to effects such as La Niña, but overall the trend is clear and distinct: Australia has become warmer.
There has been a general trend towards increased spring and summer monsoonal rainfall across Australia’s north during recent decades, and decreased late autumn and winter rainfall across southern Australia.
Sea-surface temperatures around Australia have increased faster than the global average.