Our climate is changing, largely due to the observed increases in human activities such as the burning of fossil fuels (coal, oil, and natural gas), agriculture and land clearing. Changes over the 20th century include increases in global average air and ocean temperature, widespread melting of snow and ice and rising global sea levels. The extra heat in the climate system has other impacts such as affecting atmospheric and ocean circulation, which influences rainfall and wind patterns.
Another serious impact of the increasing concentration of atmospheric carbon dioxide is ocean acidification. Around a quarter of the carbon dioxide produced by humans is absorbed by the oceans. As the carbon dioxide dissolves in sea water it forms a weak carbonic acid, making the ocean more acidic. There are early indications that some marine organisms are already being affected by ocean acidification.
The global average air temperature has increased by around 0.85 degrees Celsius since 1880.[i] The observed increase in temperatures has occurred across the globe, with rising temperatures recorded on all continents and in the oceans. World Meteorological Organization records show that the decade of 2001-10 was the world’s warmest decade on record, and that the 2000s were warmer than the 1990s which in turn were warmer than the 1980s. In Australia, average air temperatures have increased by around 0.9 degrees Celsius since 1910, and each decade has been warmer than the previous decade since the 1950s.[ii]
Scientists agree that the worst effects of climate change can largely be avoided if carbon dioxide emissions are reduced to an acceptable level.
- Australian Academy of Science report The Science of Climate Change: Questions and Answers
- Bureau of Meteorology
- Climate Commission
- Intergovernmental Panel on Climate Change (IPCC)
- Joint Science Academies
- National Aeronautics and Space Administration (NASA)
- Potsdam Institute for Climate Impact Research
- The Royal Society
- CSIRO climate change website
- CSIRO climate response blog