State of the Climate 2016 is the fourth in a series of reports produced by CSIRO and the Australian Bureau of Meteorology. It provides a summary of observations of Australia’s climate and analysis of the factors that influence it.

Full report

The Bureau of Meteorology and CSIRO play an important role in monitoring, archiving, analysing, interpreting and communicating Australia's observed and future weather and climate. This fourth, biennial State of the Climate report draws on the latest climate monitoring, science and projection information to describe changes in Australia's climate, and how it is likely to change in the future. Past climate changes and future projections paint a consistent picture of ongoing, long-term climate change interacting with underlying natural variability.

The described changes affect many Australians, particularly those changes associated with increases in the frequency or intensity of heat events, fire weather and drought. Australia will need to plan for and adapt to some level of climate change and this report will inform a wide range of economic, environmental and social decision-making by Australian governments, industry and communities. This report summarises newly available and extensive environmental intelligence which can be used in adaptation planning and assessment of local vulnerabilities.

Key Points

Australia

  • Australia's climate has warmed in both surface air temperature and surrounding sea surface temperature by around 1 °C since 1910.
  • By late this century, Australia's average temperature is projected to increase by 3–5 °C compared to a 1986–2005 baseline under the current global trajectory of greenhouse gas emissions, 1.5–2.5 °C for a medium emissions scenario or 0.5–1.5 °C for a low emissions scenario.
  • There has been, and will continue to be, an increase in the number of days with weather conducive to fire in southern and eastern Australia. The number of days is projected to double by the end of the century under a high emissions scenario.
  • May–July rainfall has reduced by around 19 per cent since 1970 in the southwest.
  • There has been a decline in rainfall of around 11 per cent since the mid-1990s over the April–October growing season in the continental southeast.
  • Winter rainfall is projected to decrease across southern Australia, by a median of 17 per cent with a range of 2–32 per cent under a high emissions scenario by the end of the century, relative to 1986–2005, with more time spent in drought.
  • Rainfall has increased across parts of northern Australia since the 1970s.
  • Extreme rainfall events are projected to increase in intensity by the end of the century across Australia under both medium and high emissions scenarios. That is, the wettest day of the year is projected to become wetter.
  • Oceans around Australia will warm further and acidification will continue.
  • Past and ongoing emissions commit us to further sea-level rise around Australia of around 6–19 cm by 2030, relative to the 1986–2005 baseline.

Global

  • Global average annual CO2 levels are steadily increasing; they reached 399 ppm in 2015, and the annual value for 2016 is expected to be higher than 400 ppm. Current levels are likely the highest in the past two million years.
  • 2015 was the warmest year on record for the globe since reliable global records began in 1880. Fifteen of the 16 warmest years on record have occurred in the last 15 years.
  • Globally averaged ocean temperatures and heat content are increasing. Observations reveal that this warming extends to at least 2000 m below the surface.
  • Global sea level has risen over 20 cm since the late 19th century with about one third of this rise due to ocean warming, and the rest from melting land ice and changes in the amount of water stored on the land.
  • The rise in mean sea level will amplify the effects of high tides and storm surges.

Why are Australia and the globe warming?

Energy comes from the Sun. In order to maintain stable temperatures at the Earth's surface, in the long run this incoming energy must be balanced by an equal amount of heat radiated back to space. Greenhouse gases in the atmosphere, such as carbon dioxide, act to increase the temperature of the Earth's surface and the atmosphere, by making it harder for the Earth to radiate this heat. Without any greenhouse gases, the Earth's surface would be much colder, with an average temperature of about -18 °C. For centuries prior to industrialisation the incoming sunlight and outgoing heat were balanced and global average temperatures were relatively steady.

Now, mostly because of the burning of fossil fuels and changes in land use, the concentrations of greenhouse gases in the atmosphere are rising and causing surface temperatures to increase. There is now an energy imbalance at the Earth’s surface of 0.65–0.80 Wm-2 (averaged globally). The atmosphere and oceans will continue to warm until enough extra heat can escape to space to allow the Earth to return to balance. Because carbon dioxide persists in the atmosphere for hundreds of years, further warming and sea-level rise is locked in.

Temperature

Australia's weather and climate are changing in response to a warming global climate system. Australia has warmed by around 1 C since 1910, with the most warming since 1950. the last three years, 2013-2015, were all in Australia's top five warmest years on record, with 2013 being the warmest. Warming will continue: by 2030, all modelled future scenarios are similarly warm, and the record high temperatures observed in 2013 would be an average year. After 2030, Australia's future temperature depends on when and how deeply emissions are cur globally.

The warmest year on record, 2013, will be considered cool after 2050. under the medium (blue) and high (orange) emission scenarios. The 2015 Paris Conference of Parties 21 (COP 21) agreement committed to limit global average warming to below 2 C, relative to pre-industrial temperatures. The relevant threshold on this graph for Australia is around 2.05 C. A stronger aspirational target was also agreed, with warming limited to 1.5 C - corresponding to 1.45 C on this graph.

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