The Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body, set up at the request of member governments. It was first established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) and later endorsed by the United Nations General Assembly.
The aims of the IPCC are to assess scientific information relevant to:
- Human-induced climate change,
- The impacts of human-induced climate change,
- Options for adaptation and mitigation.
Working Groups of IPCC:
Each has two Co-Chairs, one from the developed and one from developing world, and a technical support unit.
- Working Group I: Assesses scientific aspects of the climate system and climate change.
- Working Group II: Assesses vulnerability of socio-economic and natural systems to climate change, consequences, and adaptation options.
- Working Group III: Assesses options for limiting greenhouse gas emissions and otherwise mitigating climate change.
The IPCC has published four comprehensive assessment reports reviewing the latest climate science, as well as a number of special reports on particular topics .The IPCC published its first assessment report in 1990,a second assessment report (SAR) in 1995, and a third assessment report (TAR) in 2001. A fourth assessment report (AR4) was released in 2007 and a fifth is due to be issued in 2014.
Working group 1 report: Observed Changes in the Climate System:
Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, 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.
In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years
It is very likely that the number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale.
It is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Australia.
There are likely more land regions where the number of heavy precipitation events has increased than where it has decreased. The frequency or intensity of heavy precipitation events has likely increased in North America and Europe.
Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010.
It is virtually certain that the upper ocean (0−700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971
More than 60% of the net energy increase in the climate system is stored in the upper ocean (0–700 m) during the relatively well-sampled 40-year period from 1971 to 2010, and about 30% is stored in the ocean below 700 m.
It is very likely that regions of high salinity where evaporation dominates have become more saline, while regions of low salinity where precipitation dominates have become fresher since the 1950s. These regional trends in ocean salinity provide indirect evidence that evaporation and precipitation over the oceans have changed
Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.
The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901 to 2010, global mean sea level rose by 0.19m [0.17 to 0.21].
Carbon and Other Biogeochemical Cycles:
The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification
The atmospheric concentrations of the greenhouse gases carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) have all increased since 1750 due to human activity. In 2011 the concentrations of these greenhouse gases were 391 ppm, 1803 ppb, and 324 ppb, and exceeded the pre-industrial levels by about 40%, 150%, and 20%, respectively.
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.