Fact SheetThe observed increases in global average temperatures cannot be explained by natural factors alone. Human activities are changing the climateGreenhouse gas emissions from human activities are more than 90 per cent likely to have caused most of the global warming since the mid-20th century. Greenhouse gases are a natural part of the atmospherePage 1 of 3 Greenhouse gases are a natural part of the atmosphere, trapping and re-radiating energy from the Earth’s surface. The natural greenhouse effect maintains a surface temperature that can support life. The main greenhouse gases are water vapour, carbon dioxide (CO2), methane, nitrous oxide, halocarbons and tropospheric ozone. Greenhouse gas concentrations (excluding water vapour) often are expressed as a carbon dioxide equivalent (CO2-e). Changes in land-use can either reduce or increase the amount of heat absorbed by the Earth’s surface. Many other natural and human factors affect the climate. Natural variability such as the El Niño cycle and variations in solar activity can affect the temperature, while large volcanic eruptions can lead to cooling. Changes in land-use can either reduce or increase the amount of heat absorbed by the Earth’s surface. Airborne particles (aerosols) have a net cooling effect. < Prev Page1 2 3 Next Page > Share this CSIRO content using: |
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