We have already observed changes to our climate that are more rapid than anything the earth has experienced for at least the last 1 800 years.
How has our climate changed?
The earth has warmed, on average, by about 0.7 °C since 1910 with nine of the ten warmest years on record occurring in the past decade. There has been an increase in heatwaves, fewer frosts, and a warming of the lower atmosphere and upper ocean.
Australian temperatures have increased by almost 0.9 °C over the last hundred years, which is slightly more than the global average.
Higher atmospheric concentrations of greenhouse gases, such as carbon dioxide, cause more heat to be trapped. As a result the lower atmosphere warms. This is known as the enhanced greenhouse effect.
Why has our climate changed?
Much of the warming since 1950 is due to human activities that have increased greenhouse gases. This is known as the enhanced greenhouse effect. Atmospheric carbon dioxide levels have increased by 35 per cent from pre-industrial times. Ice core records indicate this current level is higher than at any other time in the past 420 000 years.
What are the observed impacts of climate change?
The results of climate change can be readily observed, and include:
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retreat of glaciers and sea-ice
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a decline of 10-15 per cent of the Arctic sea ice extent and a 40 per cent decrease in its average thickness
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snow depth at the start of October has declined 40 per cent in the last 40 years in the Australian Alps
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an average sea level rise of 20 mm per decade over the last 50 years
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changes in mating and migration times of birds
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poleward and altitudinal shifts of plants and animals (especially in the Alpine zone)
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an increase in coral bleaching due to increased water temperature.
How will Australia’s climate change in the future?
Projections for Australia are for a hotter climate with more frequent extreme events. It is estimated that there will be:
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warming of 0.4-2 ºC by 2030 and 1-6 ºC by 2070 compared to 1990 (warming will not be the same everywhere but almost everywhere the climate will be different)
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more hot days over 35 ºC (up to three times as many by 2070) and a reduction in the number of frost days
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an increase in the frequency and duration of extreme events such as heavy rains, cyclones, floods, and droughts
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a rise in sea level rise of 9 to 88 cm by 2100 compared to 1990.
Read more about how CSIRO is Researching our climate and weather.
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