IPCC Fifth Assessment Report on Climate Change: Global Warming Attributable to Human Influence

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The report shows that the Greenland Ice Sheet is shrinking. Photo: Christine Zenino

The IPCC report shows that the Greenland Ice Sheet is shrinking. Photo by Christine Zenino

The Intergovernmental Panel on Climate Change (IPCC) released the summary of its fifth report on 27 September 2013. The panel, which was established under the auspices of the World Meteorological Organization and United Nations Environment Program in 1988, is a scientific body whose role is to evaluate the range of climate research produced worldwide and to present ‘a clear scientific view’ upon the current state of knowledge.

The IPCC Fifth Assessment Report: The Key Points

The most recent report is, to say the least, extensive: More than 850 authors and reviewers were involved in the program, which covered over 9,200 pieces of research into differing aspects of climate change, including both direct observation and computer modelling. With such a wide range of research the results will not always be in agreement, but the summary published by the panel was unequivocal in at least some of its conclusions.

Human influence on the climate system is clear” the summary begins. “This is evident in most regions of the globe.” That influence, which the panel describe as “unprecedented over decades to millennia”, is manifested in many elements of the climate system. In particular, the report identifies:
• The oceans are warming: The researchers are “virtually certain” that the upper ocean has warmed considerably in the past forty years and probably since the 1870s.
• Ice sheets in Greenland and Antarctica have lost mass in the past 20 years and there has also been loss of sea ice and shrinkage of glaciers on land.
• The rate of sea level change is increasing.
• Levels of atmospheric carbon dioxide, a greenhouse gas, are increasing; a proportion of this is reabsorbed into the ocean, resulting in increasing ocean acidification.

Climate Change Implications

The key points outlined above (there are others) are not just significant in themselves. Various aspects of the Earth system are closely interlinked so that changes in one area may have impacts, or feedbacks, elsewhere. Those impacts may be positive (increasing the extent of the original change) or negative (working to reduce the extent of that change); or they may cause alternative changes in another part of the system.

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