Evidence of climate change globally and in Australia
Observed changes globally
The US National Oceanic and Atmospheric Administration (NOAA) monitors many climate indicators using tens of thousands of instruments around the world to track the major components of Earth’s climate system, including the atmosphere, land, ice and oceans.
NOAA's observations on global climate from State of the Climate in 2011 include:
- warm temperature trends continue - four independent datasets show 2011 was among the 15 warmest since records began in the late 19th century
- overall, glaciers around the world continued to lose mass - loss from Canadian Arctic glaciers and ice caps were the greatest since measurements began in 2002
- the average rate of global sea level rise is 3.2 millimetres per year, give or take 0.4 mm; rising seas are reshaping the world’s coastlines and affecting some of the most densely populated areas on Earth
- sea surface temperature and ocean heat content rise - even with La Niña conditions occurring during most of the year, the 2011 global sea surface temperature was among the 12 highest years on record
- the Arctic continued to show more rapid changes than the rest of the planet - sea ice shrank to its second smallest 'summer minimum' extent on record during 2011
- ocean salinity trends continue - continuing a trend that began in 2004 and similar to 2010, oceans were saltier than average in areas of high evaporation, including the western and central tropical Pacific, and fresher than average in areas of high precipitation, including the eastern tropical South Pacific, suggesting that precipitation is increasing in already rainy areas and evaporation is intensifying in drier locations.
Intergovernmental Panel on Climate Change (IPCC) and observed changes
The Intergovernmental Panel on Climate Change (IPCC), formed by the World Meteorological Organisation and the United Nations Environment Programme, reviews the scientific evidence for climate change and summarises these findings in regular assessment reports.
The IPCC released its Fourth Assessment Report (AR4) in November 2007. The report provides evidence from all continents and most oceans that many natural systems are being affected by regional climate changes, particularly temperature increases.
Warming of the climate is unequivocal, as is evident from observations of:
- increases in global average air and ocean temperatures
- widespread melting of previously stable snow and ice fields
- rising global average sea level.
The IPCC Working Group I assesses the physical scientific components of the climate system and climate change, including changes in greenhouse gases in the atmosphere; and observed changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets, and sea and ocean levels. Direct Observations of Recent Climate Change is a summary of observed changes globally, as described in Climate Change 2007: Working Group I: The Physical Science Basis (based on scientific literature available to the authors in mid-2006).
Work is under way on the Fifth Assessment Report. The three Working Group reports will be finalised by April 2014 and the Synthesis Report by October 2014.
Observed changes in Australia
Australia was one of the few places in the world to have cooler than average temperatures in 2011. Despite the slightly cooler conditions, the country’s 10-year average temperatures continue to rise, with 2002–11 likely to rank in the top two warmest 10-year periods on record for Australia, at 0.52ºC above the long-term average (Australian Bureau of Meteorology 2012).
Surface temperatures in Australia rose by just under 1ºC over the 100 years from 1910 to 2009 (CSIRO 2011).
The frequency of extreme cold weather has decreased across most of Australia, while that of warm weather has increased, with the number of days with record hot temperatures increasing each decade over the past 50 years (CSIRO 2011).
Sea surface waters surrounding Australia ‘warmed by about 0.9ºC since 1900, with about 0.4ºC of that warming [occurring] in the past 50 years’ (CSIRO 2011). There is regional variation in sea surface temperatures around Australia. Over the 20th century, the strongest warming occurred in the south-eastern coastal regions of the continent. The warmest 10-year-averaged sea surface temperatures in the Australian region since 1910 were recorded in 2002-11 (Australian Bureau of Meteorology 2012).
Between 1993 and 2009, sea level has risen 1.5-3 millimetres per year in the south and east of Australia and 7–10 mm each year in the north and west (CSIRO/BoM 2010).
In the past 50 years, total rainfall on the Australian continent has been relatively stable, but its distribution has changed significantly: ‘Rainfall decreased in south-west and south-east Australia, including all the major population centres’ (CSIRO/BoM 2010).
Page last updated: 23 November 2012