Query: The claim that 97 percent of scientists believe humans are causing climate change has been debunked by the "head" of the United Nations Intergovernmental Panel on Climate Change.

Relevant passages:
Attribution of recent climate change <=SEP=> Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth , commonly known as ` global warming ' . The effort has focused on changes observed during the period of instrumental temperature record , when records are most reliable ; particularly in the last 50 years , when human activity has grown fastest and observations of the troposphere have become available . The dominant mechanisms are anthropogenic , i.e. , the result of human activity . They are :  increasing atmospheric concentrations of greenhouse gases  global changes to land surface , such as deforestation  increasing atmospheric concentrations of aerosols .   There are also natural mechanisms for variation including climate oscillations , changes in solar activity , and volcanic activity .   According to the Intergovernmental Panel on Climate Change ( IPCC ) , it is `` extremely likely '' that human influence was the dominant cause of global warming between 1951 and 2010 . The IPCC defines `` extremely likely '' as indicating a probability of 95 to 100 % , based on an expert assessment of all the available evidence .   Multiple lines of evidence support attribution of recent climate change to human activities :  A basic physical understanding of the climate system : greenhouse gas concentrations have increased and their warming properties are well-established .  Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual .  Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included .  Natural forces alone ( such as solar and volcanic activity ) can not explain the observed warming .   The IPCC 's attribution of recent global warming to human activities is a view shared by the scientific community , and is also supported by 196 other scientific organizations worldwide ( see also : scientific opinion on climate change ) .

Scientific consensus on climate change <=SEP=> There is currently a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.  Nearly all actively publishing climate scientists (97–98%) support the consensus on anthropogenic climate change, and the remaining 2% of contrarian studies either cannot be replicated or contain errors.

Intergovernmental Panel on Climate Change <=SEP=> The Intergovernmental Panel on Climate Change ( IPCC ) is a scientific and intergovernmental body under the auspices of the United Nations , set up at the request of member governments , dedicated to the task of providing the world with an objective , scientific view of climate change and its political and economic impacts . 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 through Resolution 43/53 . Membership of the IPCC is open to all members of the WMO and UNEP .  The IPCC produces reports that support the United Nations Framework Convention on Climate Change ( UNFCCC ) , which is the main international treaty on climate change . The ultimate objective of the UNFCCC is to `` stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic -LSB- i.e. , human-induced -RSB- interference with the climate system '' . IPCC reports cover `` the scientific , technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change , its potential impacts and options for adaptation and mitigation . ''   The IPCC does not carry out its own original research , nor does it do the work of monitoring climate or related phenomena itself . The IPCC bases its assessment on the published literature , which includes peer-reviewed and non-peer-reviewed sources .   Thousands of scientists and other experts contribute ( on a voluntary basis , without payment from the IPCC ) to writing and reviewing reports , which are then reviewed by governments . IPCC reports contain a `` Summary for Policymakers '' , which is subject to line-by-line approval by delegates from all participating governments . Typically this involves the governments of more than 120 countries .   The IPCC provides an internationally accepted authority on climate change , producing reports which have the agreement of leading climate scientists and the consensus of participating governments . The 2007 Nobel Peace Prize was shared , in equal parts , between the IPCC and Al Gore .