Global mean near-surface air temperature has risen by around 0.85˚C from 1880 to 2012 and at 0.12˚C per decade since 1951.
The IPCC (2013) concluded,
“It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century” and “Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes.”
Natural forcings (e.g. solar variations and volcanic aerosols) and intrinsic climate variability have had little effect on the warming since 1951.
Global mean temperatures
Projected to rise from 0.3-1.7˚C under RCP2.6* to 2.6-4.8˚ C under RCP8.5 by 2081-2100, compared to the climate of 1986-2005.
Warming is projected to be stronger over land than oceans and strongest over the Arctic.
Hot days and heat waves are projected to become more frequent and cold days less frequent.
Projected changes in rainfall
Much less spatially uniform than projected warming. Rainfall is generally projected to increase at high latitudes and near the equator and decrease in regions of the sub-tropics, although regional changes may differ from this pattern. Rainfall extremes are projected to become more intense and more frequent in most regions.
Global mean sea level
Projected to increase by 26-55 cm for RCP2.6 and 45-82 cm for RCP8.5 by 2080-2100 relative to 1986-2005. Global sea level rise is driven mainly by ocean thermal expansion and melting from glaciers and ice caps.
- CSIRO and Bureau of Meteorology (2015). Climate Change in Australia. Information for Australia’s Natural Resource Management Regions: Technical Report. CSIRO and Bureau of Meteorology, Australia.
*Projected changes have been prepared for four Representative Concentration Pathways (RCPs) used by the latest IPCC assessment (CMIP5).
RCP2.6 – requiring very strong emission reductions from a peak at around 2020 to reach a carbon dioxide (CO2) concentration at about 420 parts per million (PPM) by 2100
RCP4.5 – slower emission reductions that stabilise the CO2 concentration at about 540 ppm by 2100
RCP8.5 – assumes increases in emissions leading to a CO2 concentration of about 940 ppm by 2100.