IPCC review on climate change

RelatedNews

T&E: The price sensitivity of efficiency in shipping

UKHO: Understanding the S-100 transition

Headlines Statements from the report

The IPCC Report is produced by the Intergovernmental Panel on Climate Change (IPCC), which was established by the World Meteorological Organization and the United Nations Environment Programme in 1988 and confirmsthat it is extremely likely (95-100% probability) that most of the warming since 1950 has been due to human influence.

The Working Group I contribution to the IPCC’s Fifth Assessment Report (AR5) considers newevidence of climate change based on many independent scientific analyses from observations ofthe climate system, paleoclimate archives, theoretical studies of climate processes and simulationsusing climate models. It builds upon the Working Group I contribution to the IPCC’s FourthAssessment Report (AR4), and incorporates subsequent new findings of research. As acomponent of the fifth assessment cycle, the IPCC Special Report on Managing the Risks ofExtreme Events to Advance Climate Change Adaptation (SREX) is an important basis forinformation on changing weather and climate extremes.

Image Credit: IPCC WGI A5 – pg 27

For more information, please read WG1 Contribution to the IPCC Fifth Assessment Reporty Climate Change 2013: The Psysical Science Basis –Summary for Policymakers.

Key headline statements from the summary as follows:

Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented overdecades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level hasrisen, and the concentrations of greenhouse gases have increased.
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. Inthe Northern Hemisphere, 1983-2012 was likely the warmest 30-year period of the last 1400 years.
Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energyaccumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0-700 m) warmed from1971 to 2010, and it likely warmed between the 1870s and 1971.
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrinkalmost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (highconfidence
The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (highconfidence). Over the period 1901-2010, global mean sea level rose by 0.19 [0.17 to 0.21] m.
The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented inat least the last 800,000 years. CO2concentrations have increased by 40% since pre-industrial times, primarily from fossil fuelemissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emittedanthropogenic carbon dioxide, causing ocean acidification
Total radiative forcing is positive, and has led to an uptake of energy by the climate system. The largest contribution to totalradiative forcing is caused by the increase in the atmospheric concentration of CO2since 1750.
Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in theatmosphere, positive radiative forcing, observed warming, and understanding of the climate system
Climate models have improved since the AR4. Models reproduce observed continental-scale surface temperature patterns andtrends over many decades, including the more rapid warming since the mid-20th century and the cooling immediately followinglarge volcanic eruptions (very high confidence).
Observational and model studies of temperature change, climate feedbacks and changes in the Earth’s energy budget togetherprovide confidence in the magnitude of global warming in response to past and future forcing.
Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, inreductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for humaninfluence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observedwarming since the mid-20th century.
Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system.Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.
Global surface temperature change for the end of the 21st century is likely to exceed 1.5C relative to 1850 to 1900 for all RCPscenarios except RCP2.6. It is likely to exceed 2C for RCP6.0 and RCP8.5, and more likely than not to exceed 2C for RCP4.5.Warming will continue beyond 2100 under all RCP scenarios except RCP2.6. Warming will continue to exhibit interannual-todecadal variability and will not be regionally uniform.
Changes in the global water cycle in response to the warming over the 21st century will not be uniform. The contrast inprecipitation between wet and dry regions and between wet and dry seasons will increase, although there may be regionalexceptions
The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean andaffect ocean circulation.
It is very likely that the Arctic sea ice cover will continue to shrink and thin and that Northern Hemisphere spring snow coverwill 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 verylikely exceed that observed during 1971-2010 due to increased ocean warming and increased loss of mass from glaciers andice sheets.
Climate change will affect carbon cycle processes in a way that will exacerbate the increase of CO2in the atmosphere (highconfidence). Further uptake of carbon by the ocean will increase ocean acidification.
Cumulative emissions of CO2largely determine global mean surface warming by the late 21st century and beyond. Mostaspects of climate change will persist for many centuries even if emissions of CO2are stopped. This represents a substantialmulti-century climate change commitment created by past, present and future emissions of CO2.