Global climate change projections
Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.
The IPCC concluded that Global-mean surface warming by the end of the 21st century is likely to exceed 1.5 °C relative to 1850–1900 for all RCPs except RCP2.6. It is likely to exceed 2°C for RCP6.0 and RCP8.5, and more likely than not to exceed 2°C for RCP4.5.
Warming will continue beyond 2100 under all RCPs except RCP2.6 (see figure). The global mean surface warming for 2081–2100 relative to 1986–2005 is projected to likely be 0.3°C to 1.7°C (RCP2.6), 1.1°C to 2.6°C (RCP4.5), 1.4°C to 3.1°C (RCP6.0), 2.6°C to 4.8°C (RCP8.5).
Warming will continue to exhibit interannual-to-decadal variability and will not be regionally uniform. There will be more hot days and fewer cold days over most land areas. Heat waves will occur with a higher frequency and duration. Occasional cold winter extremes will continue to occur.
Other IPCC findings include:
- Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast in precipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regional exceptions.
- The high latitudes and the equatorial Pacific Ocean are likely to experience an increase in annual mean precipitation by the end of this century under the RCP8.5 scenario. In many mid-latitude and subtropical dry regions, mean precipitation will likely decrease, while in many mid-latitude wet regions, mean precipitation will likely increase by the end of this century under the RCP8.5 scenario.
- Extreme precipitation events over most of the mid-latitude land masses and over wet tropical regions will become more intense and more frequent by the end of this century, as global mean surface temperature increases.
- The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation.
- It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow cover will decrease during the 21st century as global mean surface temperature rises. Global glacier volume will further decrease.
- Global mean sea level will continue to rise during the 21st century. Under all RCP scenarios, the rate of sea level rise will very likely exceed that observed during 1971 to 2010 due to increased ocean warming and increased loss of mass from glaciers and ice sheets. Global mean sea level rise for 2081–2100 relative to 1986–2005 will likely be in the ranges of 0.26 to 0.55 m for RCP2.6, 0.32 to 0.63 m for RCP4.5, 0.33 to 0.63 m for RCP6.0, and 0.45 to 0.82 m for RCP8.5. The collapse of marine-based sectors of the Antarctic ice sheet, if initiated, could cause global mean sea level to rise substantially above the likely range during the 21st century.
CMIP5 multi-model simulated time series from 1950 to 2100 for change in global annual mean surface temperature relative to 1986–2005. SOURCE: IPCC 2013
CMIP5 multi-model simulated time series from 1950 to 2100 for change in global annual mean sea level rise relative to 1986–2005. SOURCE: IPCC 2013
Further information (external links)Fifth Assessment Report: Summary for Policy Makers > IPCC