Fact Sheet

Human activities are changing the climate

Atmospheric greenhouse gas exceeds pre-industrial levels

Since the Industrial Revolution (about 1750), global carbon dioxide (CO2) concentration has risen 37 per cent, methane 150 per cent and nitrous oxide 18 per cent.

The increase in CO2 concentration is primarily due to fossil fuel use and land-use change, while increases in methane and nitrous oxide are primarily due to agriculture.

The CO2 concentration in 2008 of 383 parts per million (ppm) is much higher than the natural range of 172 to 300 ppm that has existed for the past 800 000 years.

Human activities changing climate

There is a greater than 90 per cent likelihood that most of the global warming since the mid 20th century is due to increases in greenhouse gas emissions from human activities.

The physical and chemical processes involved are well understood and documented, and the likelihood of observed warming being due to natural causes alone is less than five per cent.

About half of the rainfall decline in south-western Australia since the 1950s is likely to be due to increases in greenhouse gases.

The intensification of the Sub-Tropical Ridge (a ridge of high pressure over southern Australia) is associated with about 70 per cent of the recent rainfall decline in south-eastern Australia, and this is highly likely to be linked to global warming.

Evidence of human influence also has been detected in ocean warming, sea-level rise, continental-average temperatures, temperature extremes and wind patterns.

This conclusion is consistent with the observed melting of glaciers and ice sheets.