page_title: Intergovernmental Panel on Climate Change
section_title: "Hockey stick" graph
hierarchical_section_title: Intergovernmental Panel on Climate Change / Criticism of IPCC / "Hockey stick" graph
caption_attribution_description: Atmospheric carbon dioxide concentration and mean global temperature during the past 1000 years. Carbon dioxide levels (blue line, left-hand axis) are given in parts per million (volume), temperatures (red line, right-hand axis) in degrees centigrade.
context_page_description: The Intergovernmental Panel on Climate Change is a group of scientists chosen by governments and other large groups from around the world who study the way that humans are making the Earth heat up unnaturally. The group was established in 1988 by the World Meteorological Organization and the United Nations Environment Programme, two organizations of the United Nations.
  The IPCC shared the 2007 Nobel Peace Prize with former Vice President of the United States Al Gore who won for working on the same problems.
  A lot of IPCC work is publishing reports about the United Nations Framework Convention on Climate Change, an international agreement that human inventions and chemistry may make the Earth too hot to live on. The UNFCCC was the beginning of the Kyoto Protocol. Members of the IPCC read, write, and calculate as much as they can. Only member states of the WMO and UNEP may be members of IPCC.
  A lot of professors trust the IPCC work.
context_section_description: The IPCC Third Assessment Report showed a graph labeled "Millennial Northern Hemisphere temperature reconstruction" from a paper by Mann, Bradley and Hughes (MBH98) often called the "Hockey Stick Graph". This graph was different to the IPCC First assessment report which showed global temperature for the past 1000 years, and higher temperatures during the Medieval Warm Period. The graph was thought to show that temperatures between 1000 and 1900 were very different. This was criticized in an article by Stephen McIntyre and Ross McKitrick. In a 2006 letter to Nature, Bradley, Hughes and Mann claimed the original article had said that they could not be exact.
caption: The "hockey stick" temperature graph
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