Origins and aimsThe IPCC developed from an international scientific body, the Advisory Group on Greenhouse Gases set up in 1985 by the International Council for Science, International Council of Scientific Unions, the United Nations Environment Programme (UNEP), and the World Meteorological Organization (WMO) to provide recommendations based on current research. This small group of scientists lacked the resources to cover the increasingly complex interdisciplinary nature of climate science. The United States Environmental Protection Agency and United States State Department, State Department wanted an international convention to agree restrictions on greenhouse gases, and the Conservatism in the United States, conservative Presidency of Ronald Reagan, Reagan Administration was concerned about unrestrained influence from independent scientists or from United Nations bodies including UNEP and the WMO. The U.S. government was the main force in forming the IPCC as an autonomous intergovernmental body in which scientists took part both as experts on the science and as official representatives of their governments, to produce reports which had the firm backing of all the leading scientists worldwide researching the topic, and which then had to gain consensus agreement from every one of the participating governments. In this way, it was formed as a hybrid between a scientific body and an intergovernmental political organisation. The United Nations formally endorsed the creation of the IPCC in 1988. Some of the reasons the UN stated in its resolution include :"[C]ertain human activities could change global climate patterns, threatening present and future generations with potentially severe economic and social consequences" :"[C]ontinued growth in atmospheric concentrations of "greenhouse" gases could produce global warming with an eventual rise in sea levels, the effects of which could be disastrous for mankind if timely steps are not taken at all levels." The IPCC was tasked with reviewing peer-reviewed scientific literature and other relevant publications to provide information on the state of knowledge about climate change.
OrganizationThe IPCC does not conduct its own original research. It produces comprehensive assessments, reports on special topics, and methodologies. The assessments build on previous reports, highlighting the latest knowledge. For example, the wording of the reports from the first to the fifth assessment reflects the growing evidence for a changing climate caused by human activity. The IPCC has adopted and published "Principles Governing IPCC Work", which states that the IPCC will assess: * the risk of Global warming, human-induced climate change, * its Effects of global warming, potential impacts, and * possible Climate change mitigation, options for prevention. This document also states that IPCC will do this work by assessing "on a comprehensive, objective, open and transparent basis the scientific, technical and socioeconomic information relevant to understanding the scientific basis" of these topics. The Principles also state that "IPCC reports should be neutral with respect to policy, although they may need to deal objectively with scientific, technical and socioeconomic factors relevant to the application of particular policies." Korean economist Hoesung Lee has been the chair of the IPCC since 8 October 2015, with the election of the new IPCC Bureau. Before this election, the IPCC was led by Vice-Chair Ismail El Gizouli, who was designated acting Chair after the resignation of Rajendra K. Pachauri in February 2015. The previous chairs were Rajendra K. Pachauri, elected in May 2002; Robert Watson (scientist), Robert Watson in 1997; and Bert Bolin in 1988. The chair is assisted by an elected bureau including vice-chairs and working group co-chairs, and by a secretariat. The Panel itself is composed of representatives appointed by governments. Participation of delegates with appropriate expertise is encouraged. Plenary sessions of the IPCC and IPCC Working group, Working Groups are held at the level of government representatives. Non-Governmental and Intergovernmental Organizations admitted a
Assessment reportsThe IPCC has published five comprehensive assessment reports reviewing the latest climate science, as well as a number of special reports on particular topics. These reports are prepared by teams of relevant researchers selected by the Bureau from government nominations. Expert reviewers from a wide range of governments, IPCC observer organizations and other organizations are invited at different stages to comment on various aspects of the drafts. The IPCC published its IPCC First Assessment Report, First Assessment Report (FAR) in 1990, a supplementary report in 1992, a IPCC Second Assessment Report, Second Assessment Report (SAR) in 1995, a IPCC Third Assessment Report, Third Assessment Report (TAR) in 2001, a IPCC Fourth Assessment Report, Fourth Assessment Report (AR4) in 2007 and a IPCC Fifth Assessment Report, Fifth Assessment Report (AR5) in 2014. The IPCC is currently preparing its IPCC Sixth Assessment Report, Sixth Assessment Report (AR6), which will be completed in 2022. Each assessment report is in three volumes, corresponding to Working Groups I, II, and III. It is completed by a synthesis report that integrates the working group contributions and any special reports produced in that assessment cycle.
Scope and preparation of the reportsThe IPCC does not carry out research nor does it monitor climate related data. Lead authors of IPCC reports assess the available information about climate change based on published sources. According to IPCC guidelines, authors should give priority to peer-reviewed sources. Authors may refer to non-peer-reviewed sources (the "grey literature"), provided that they are of sufficient quality. Examples of non-peer-reviewed sources include model results, reports from government agencies and non-governmental organizations, and industry journals. Each subsequent IPCC report notes areas where the science has improved since the previous report and also notes areas where further research is required. There are generally three stages in the review process: * Expert review (6–8 weeks) * Government/expert review * Government review of: ** Summaries for Policymakers ** Overview Chapters ** Synthesis Report Review comments are in an open archive for at least five years. There are several types of endorsement which documents receive: * Approval. Material has been subjected to detailed, line by line discussion and agreement. ** Working Group Summaries for Policymakers are ''approved'' by their Working Groups. ** Synthesis Report Summary for Policymakers is ''approved'' by Panel. * Adoption. Endorsed section by section (and not line by line). ** Panel ''adopts'' Overview Chapters of Methodology Reports. ** Panel ''adopts'' IPCC Synthesis Report. * Acceptance. Not been subject to line by line discussion and agreement, but presents a comprehensive, objective, and balanced view of the subject matter. ** Working Groups ''accept'' their reports. ** Task Force Reports are ''accepted'' by the Panel. ** Working Group Summaries for Policymakers are ''accepted'' by the Panel after group ''approval''. The Panel is responsible for the IPCC and its endorsement of Reports allows it to ensure they meet IPCC standards. There have been a range of commentaries on the IPCC's procedures, examples of which are discussed later in the article (see also IPCC Summary for Policymakers). Some of these comments have been supportive, while others have been critical. Some commentators have suggested changes to the IPCC's procedures.
AuthorsEach chapter has a number of authors who are responsible for writing and editing the material. A chapter typically has two "coordinating lead authors", ten to fifteen "lead authors", and a somewhat larger number of "contributing authors". The coordinating lead authors are responsible for assembling the contributions of the other authors, ensuring that they meet stylistic and formatting requirements, and reporting to the Working Group chairs. Lead authors are responsible for writing sections of chapters. Contributing authors prepare text, graphs or data for inclusion by the lead authors. Authors for the IPCC reports are chosen from a list of researchers prepared by governments and participating organisations, and by the Working Group/Task Force Bureaux, as well as other experts known through their published work. The choice of authors aims for a range of views, expertise and geographical representation, ensuring representation of experts from developing and developed countries and countries with economies in transition.
First assessment reportThe IPCC First Assessment Report (FAR) was completed in 1990, and served as the basis of the UNFCCC. The executive summary of the WG I Summary for Policymakers report says they are certain that emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases, resulting on average in an additional warming of the Earth's surface. They calculate with confidence that CO2 has been responsible for over half the enhanced greenhouse effect. They predict that under a "business as usual" (BAU) scenario, global mean temperature will increase by about 0.3 °C per decade during the [21st] century. They judge that global mean surface air temperature has increased by 0.3 to 0.6 °C over the last 100 years, broadly consistent with prediction of climate models, but also of the same magnitude as natural climate variability. The unequivocal detection of the enhanced greenhouse effect is not likely for a decade or more.
Supplementary report of 1992The 1992 supplementary report was an update, requested in the context of the negotiations on the UNFCCC at the Earth Summit (United Nations Conference on Environment and Development) in Rio de Janeiro in 1992. The major conclusion was that research since 1990 did "not affect our fundamental understanding of the science of the greenhouse effect and either confirm or do not justify alteration of the major conclusions of the first IPCC scientific assessment". It noted that transient (time-dependent) simulations, which had been very preliminary in the FAR, were now improved, but did not include aerosol or ozone changes.
Second assessment report''Climate Change 1995'', the IPCC Second Assessment Report (SAR), was finished in 1996. It is split into four parts: * A synthesis to help interpret UNFCCC article 2. * ''The Science of Climate Change'' (WG I) * ''Impacts, Adaptations and Mitigation of Climate Change'' (WG II) * ''Economic and Social Dimensions of Climate Change'' (WG III) Each of the last three parts was completed by a separate Working Group (WG), and each has a Summary for Policymakers (SPM) that represents a consensus of national representatives. The SPM of the WG I report contains headings: # Greenhouse gas concentrations have continued to increase # Anthropogenic aerosols tend to produce negative radiative forcings # Climate has changed over the past century (air temperature has increased by between 0.3 and 0.6 °C since the late 19th century; this estimate has not significantly changed since the 1990 report). # The balance of evidence suggests a discernible human influence on global climate (considerable progress since the 1990 report in distinguishing between natural and anthropogenic influences on climate, because of: including aerosols; coupled models; pattern-based studies) # Climate is expected to continue to change in the future (increasing realism of simulations increases confidence interval, confidence; important uncertainties remain but are taken into account in the range of model projections) # There are still many uncertainties (estimates of future emissions and biogeochemical cycling; models; instrument data for model testing, assessment of variability, and detection studies)
Third assessment reportThe Third Assessment Report (TAR) was completed in 2001 and consists of four reports, three of them from its Working Groups: * Working Group I: The Scientific BasisTAR Working Group 1
Comments on the TARIn 2001, 16 national academy of sciences, science academies issued a joint statement on climate change. The joint statement was made by the Australian Academy of Science, the Royal Flemish Academy of Belgium for Science and the Arts, the Brazilian Academy of Sciences, the Royal Society of Canada, the Caribbean Academy of Sciences, the Chinese Academy of Sciences, the French Academy of Sciences, the German Academy of Sciences Leopoldina, German Academy of Natural Scientists Leopoldina, the Indian National Science Academy, the Indonesian Academy of Sciences, the Royal Irish Academy, Accademia dei Lincei, Accademia Nazionale dei Lincei (Italy), the Academy of Sciences Malaysia, the Royal Society of New Zealand, Academy Council of the Royal Society of New Zealand, the Royal Swedish Academy of Sciences, and the Royal Society (UK). The statement, also published as an editorial in the journal Science (journal), Science, stated "we support the [TAR's] conclusion that it is at least 90% certain that temperatures will continue to rise, with average global surface temperature projected to increase by between 1.4 and 5.8 °C above 1990 levels by 2100". The TAR has also been endorsed by the Canadian Foundation for Climate and Atmospheric Sciences, Canadian Meteorological and Oceanographic Society, and European Geosciences Union (refer to "Intergovernmental Panel on Climate Change#Endorsements of the IPCC, Endorsements of the IPCC"). In 2001, the US National Research Council (US NRC) produced a report that assessed Working Group I's (WGI) contribution to the TAR. US NRC (2001) "generally agrees" with the WGI assessment, and describes the full WGI report as an "admirable summary of research activities in climate science"., in IPCC author Richard Lindzen has made a number of criticisms of the TAR. , pp. 29–31. Available i
[...] the full [WGI] report is adequately summarized in the Technical Summary. The full WGI report and its Technical Summary are not specifically directed at policy. The Summary for Policymakers reflects less emphasis on communicating the basis for uncertainty and a stronger emphasis on areas of major concern associated with human-induced climate change. This change in emphasis appears to be the result of a summary process in which scientists work with policy makers on the document. Written responses from U.S. coordinating and lead scientific authors to the committee indicate, however, that (a) no changes were made without the consent of the convening lead authors (this group represents a fraction of the lead and contributing authors) and (b) most changes that did occur lacked significant impact.
Fourth assessment reportThe Fourth Assessment Report (AR4) was published in 2007. Like previous assessment reports, it consists of four reports: * Working Group I: The Physical Science Basis * Working Group II: Impacts, Adaptation and Vulnerability * Working Group III: Mitigation * Synthesis Report People from over 130 countries contributed to the IPCC Fourth Assessment Report, which took 6 years to produce. Contributors to AR4 included more than 2500 scientific expert reviewers, more than 800 contributing authors, and more than 450 lead authors.Press flyer announcing 2007 report
Response to AR4Several science academy, science academies have referred to and/or reiterated some of the conclusions of AR4. These include: * Joint-statements made in 2007, 2008 and 2009 by the science academies of Brazil, China, India, Mexico, South Africa and the G8 nations (the "G8+5"). * Publications by the Australian Academy of Science. * A joint-statement made in 2007 by the Network of African Science Academies. * A statement made in 2010 by the Inter Academy Medical Panel This statement has been signed by 43 scientific academies. The Netherlands Environmental Assessment Agency (PBL, ''et al.'', 2009; 2010) has carried out two reviews of AR4. These reviews are generally supportive of AR4's conclusions. Executive summary, in PBL (2010) make some recommendations to improve the IPCC process. A literature assessment by the US National Research Council (US NRC, 2010)Summary, p. 3
Climate change is occurring, is caused largely by human activities, and poses significant risks for—and in many cases is already affecting—a broad range of human and natural systems [''emphasis in original text'']. [...] This conclusion is based on a substantial array of scientific evidence, including recent work, and is consistent with the conclusions of recent assessments by the U.S. Global Change Research Program [...], the Intergovernmental Panel on Climate Change’s Fourth Assessment Report [...], and other assessments of the state of scientific knowledge on climate change.Some errors have been found in the IPCC AR4 Working Group II report. Two errors include the melting of Himalayas, Himalayan glaciers (see Intergovernmental Panel on Climate Change#Projected date of melting of Himalayan glaciers, later section), and Dutch land area that is below sea level.
Fifth assessment reportThe IPCC's Fifth Assessment Report (AR5) was completed in 2014. AR5 followed the same general format as of AR4, with three Working Group reports and a Synthesis report. The Working Group I report (WG1) was published in September 2013. Conclusions of AR5 are summarized below: ;Working Group I: * "Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia". * "Atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years". * Human influence on the climate system is clear. IPCC (11 November 2013): D. Understanding the Climate System and its Recent Changes, in
Representative Concentration PathwaysProjections in AR5 are based on "Representative Concentration Pathways" (RCPs). The RCPs are consistent with a wide range of possible changes in future anthropogenic greenhouse gas emissions. Projected changes in global mean surface temperature and sea level are given in the main Representative Concentration Pathways, RCP article.
Sixth assessment reportThe sixth assessment report is scheduled to be released in the first half of 2022. Its three working groups are titled ''The Physical Science Basis''; ''Impacts, Adaptation and Vulnerability'' and ''Mitigation of Climate Change''. They are all currently scheduled for publication in the second half of 2021.
ArchivingPapers and electronic files of certain working groups of the IPCC, including reviews and comments on drafts of their Assessment Reports, are archived at th
Special reportsIn addition to climate assessment reports, the IPCC publishes Special Reports on specific topics. The preparation and approval process for all IPCC Special Reports follows the same procedures as for IPCC Assessment Reports. In the year 2011 two IPCC Special Report were finalized, the Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) and the Special Report on Managing Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX). Both Special Reports were requested by governments.
Special Report on Emissions Scenarios (SRES)The Special Report on Emissions Scenarios (SRES) is a report by the IPCC which was published in 2000. The SRES contains "climate change scenario, scenarios" of future changes in emissions of greenhouse gases and sulfur dioxide. One of the uses of the SRES scenarios is to project future changes in climate, e.g., changes in global mean temperature. The SRES scenarios were used in the IPCC's Third and Fourth Assessment Reports. The SRES scenarios are "baseline" (or "reference") scenarios, which means that they do not take into account any current or future measures to limit greenhouse gas (GHG) emissions (e.g., the Kyoto Protocol to the United Nations Framework Convention on Climate Change). SRES emissions projections are broadly comparable in range to the baseline projections that have been developed by the scientific community.
=Comments on the SRES= There have been a number of comments on the SRES. Parson ''et al.'' (2007) stated that the SRES represented "a substantial advance from prior scenarios". At the same time, there have been criticisms of the SRES. The most prominently publicized criticism of SRES focused on the fact that all but one of the participating models compared gross domestic product (GDP) across regions using market exchange rates (MER), instead of the more correct purchasing-power parity (PPP) approach. This criticism is discussed in the Special Report on Emissions Scenarios#MER and PPP, main SRES article.
Special report on renewable energy sources and climate change mitigation (SRREN)Thi
Special Report on managing the risks of extreme events and disasters to advance climate change adaptation (SREX)Th
Special Report on Global Warming of 1.5 °C (SR15)When the Paris Agreement was adopted, the UNFCCC invited the Intergovernmental Panel on Climate Change to write a special report on "How can humanity prevent the global temperature rise more than 1.5 degrees above pre-industrial level". The completed report, Special Report on Global Warming of 1.5 °C (SR15), was released on 8 October 2018. Its full title is "Global Warming of 1.5 °C, an IPCC special report on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty". The finished report summarizes the findings of scientists, showing that maintaining a temperature rise to below 1.5 °C remains possible, but only through "rapid and far-reaching transitions in energy, land, urban and infrastructure..., and industrial systems". Meeting the Paris target of is possible but would require "deep emissions reductions", "rapid", "far-reaching and unprecedented changes in all aspects of society". In order to achieve the 1.5 °C target, CO2 emissions must decline by 45% (relative to 2010 levels) by 2030, reaching net zero by around 2050. Deep reductions in non-CO2 emissions (such as nitrous oxide and methane) will also be required to limit warming to 1.5 °C. Under the pledges of the countries entering the Paris Accord, a sharp rise of 3.1 to 3.7 °C is still expected to occur by 2100. Holding this rise to 1.5 °C avoids the worst effects of a rise by even 2 °C. However, a warming of even 1.5 degrees will still result in large-scale drought, famine, heat stress, species die-off, loss of entire ecosystems, and loss of habitable land, throwing more than 100 Million into poverty. Effects will be most drastic in arid regions including the Middle East and the Sahel in Africa, where fresh water will remain in some areas following a 1.5 °C rise in temperatures but are expected to dry up completely if the rise reaches 2 °C.
Special Report on climate change and land (SRCCL)The final draft of the "Special Report on climate change and land" (SRCCL)—with the full title, "Special Report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems" was published online on 7 August 2019.
Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC)The "Special Report on the Ocean and Cryosphere in a Changing Climate" (SROCC) was approved on 25 September 2019 in Monaco. Among other findings, the report concluded that sea level rises could be up to two feet higher by the year 2100, even if efforts to reduce greenhouse gas emissions and to limit global warming are successful; coastal cities across the world could see so-called "storm[s] of the century" at least once a year.
Methodology reportsWithin IPCC the National Greenhouse Gas Inventory Program develops methodologies to estimate emissions of greenhouse gases. This has been undertaken since 1991 by the IPCC WGI in close collaboration with the Organisation for Economic Co-operation and Development and the International Energy Agency. The objectives of the National Greenhouse Gas Inventory Program are: * to develop and refine an internationally agreed methodology and software for the calculation and reporting of national greenhouse gas emissions and removals; and * to encourage the widespread use of this methodology by countries participating in the IPCC and by signatories of the UNFCCC.
Revised 1996 IPCC Guidelines for National Greenhouse Gas InventoriesThe 1996 Guidelines for National Greenhouse Gas Inventories provide the methodological basis for the estimation of national greenhouse gas emission inventory, emissions inventories. Over time these guidelines have been completed with good practice reports: ''Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories'' and ''Good Practice Guidance for Land Use, Land-Use Change and Forestry''. The 1996 guidelines and the two good practice reports are to be used by parties to the UNFCCC and to the Kyoto Protocol in their annual submissions of national greenhouse gas inventories.
2006 IPCC Guidelines for National Greenhouse Gas InventoriesThe 2006 ''IPCC Guidelines for National Greenhouse Gas Inventories'' is the latest version of these emission estimation methodologies, including a large number of default emission factors. Although the IPCC prepared this new version of the guidelines on request of the parties to the UNFCCC, the methods have not yet been officially accepted for use in national greenhouse gas emissions reporting under the UNFCCC and the Kyoto Protocol.
Other activitiesThe IPCC concentrates its activities on the tasks allotted to it by the relevant WMO Executive Council and UNEP Governing Council resolutions and decisions as well as on actions in support of the UNFCCC process. While the preparation of the assessment reports is a major IPCC function, it also supports other activities, such as the Data Distribution Centre and the National Greenhouse Gas Inventories Programme, required under the UNFCCC. This involves publishing default emission factors, which are factors used to derive emissions estimates based on the levels of fuel consumption, industrial production and so on. The IPCC also often answers inquiries from the UNFCCC Subsidiary Body for Scientific and Technological Advice (SBSTA).
Nobel Peace PrizeIn December 2007, the IPCC was awarded the Nobel Peace Prize "for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change". The award is shared with Former U.S. Vice-President Al Gore for his work on climate change and the documentary ''An Inconvenient Truth''.
CriticismsThere is Intergovernmental Panel on Climate Change#Endorsements of the IPCC, widespread support for the IPCC in the scientific community, which is reflected in publications by other scientific bodies and experts. However, criticisms of the IPCC have been made. Since 2010 the IPCC has come under yet unparalleled public and political scrutiny. The global IPCC consensus approach has been challenged internallyEvaluation, characterization, and communication of uncertainty by the intergovernmental panel on climate change—an introductory essay Climatic ChangeAn Interdisciplinary, International Journal Devoted to the Description, Causes and Implications of Climatic Change, Gary Yohe and Michael Oppenheimer
Projected date of melting of Himalayan glaciersA paragraph in the 2007 Working Group II report ("Impacts, Adaptation and Vulnerability"), chapter 10 included a projection that Himalayan glaciers could disappear by 2035 : ''Glaciers in the Himalaya are receding faster than in any other part of the world (see Table 10.9) and, if the present rate continues, the likelihood of them disappearing by the year 2035 and perhaps sooner is very high if the Earth keeps warming at the current rate. Its total area will likely shrink from the present 500,000 to 100,000 km2 by the year 2035 (WWF, 2005).'' This projection was not included in the final summary for policymakers. The IPCC has since acknowledged that the date is incorrect, while reaffirming that the conclusion in the final summary was robust. They expressed regret for "the poor application of well-established IPCC procedures in this instance". The date of 2035 has been correctly quoted by the IPCC from the WWF report, which has misquoted its own source, an International Commission on Snow and Ice Hydrology, ICSI report "Variations of Snow and Ice in the past and at present on a Global and Regional Scale". Rajendra K. Pachauri responded in an interview with ''Science''.
Overstatement of effectsFormer IPCC chairman Robert Watson (scientist), Robert Watson said, regarding the Himalayan glaciers estimation, "The mistakes all appear to have gone in the direction of making it seem like climate change is more serious by overstating the impact. That is worrying. The IPCC needs to look at this trend in the errors and ask why it happened". Martin Parry, a climate expert who had been co-chair of the IPCC working group II, said that "What began with a single unfortunate error over Himalayan glaciers has become a clamour without substance" and the IPCC had investigated the other alleged mistakes, which were "generally unfounded and also marginal to the assessment".
Emphasis of the "hockey stick" graph. File:Ipcc7.1-mann-moberg-manley.png, Comparison of MBH99 40-year average from proxy records, as used in IPCC Third Assessment Report, IPCC TAR 2001 (blue), with IPCC First Assessment Report, IPCC 1990 schematic Figure 7.1.c (red) [based on Lamb 1965 extrapolating from central England temperatures and other historical records]; central England temperatures to 2007 shown from Jones ''et al.'' 2009 (green dashed line). Also shown, Moberg ''et al.'' 2005 low frequency signal (black). The IPCC Third Assessment Report, third assessment report (TAR) prominently featured a graph labeled "Millennial Northern Hemisphere temperature reconstruction" based on a 1999 paper by Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes (MBH99), which has been referred to as the "hockey stick graph". This graph extended the similar graph in :File:IPCC 1996 SAR Figure 3.20.png, Figure 3.20 from the IPCC Second Assessment Report of 1995, and differed from a schematic in the MWP and LIA in IPCC reports, first assessment report that lacked temperature units, but appeared to depict larger global temperature variations over the past 1000 years, and higher temperatures during the Medieval Warm Period than the mid 20th century. The schematic was not an actual plot of data, and was based on a diagram of temperatures in central England, with temperatures increased on the basis of documentary evidence of Medieval Wine from the United Kingdom, vineyards in England. Even with this increase, the maximum it showed for the Medieval Warm Period did not reach temperatures recorded in central England in 2007. p. 36 The MBH99 finding was supported by cited reconstructions by , , and , using differing data and methods. The Jones et al. and Briffa reconstructions were overlaid with the MBH99 reconstruction in Figure 2.21 of the IPCC report.
Conservative nature of IPCC reportsSome critics have contended that the IPCC reports tend to be wikt:conservative, conservative by consistently underestimating the pace and impacts of global warming, and report only the "lowest common denominator" findings. On the eve of the publication of IPCC's Fourth Assessment Report in 2007 another study was published suggesting that temperatures and sea levels have been rising at or above the maximum rates proposed during IPCC's 2001 Third Assessment Report. The study compared IPCC 2001 projections on temperature and sea level change with observations. Over the six years studied, the actual temperature rise was near the top end of the range given by IPCC's 2001 projection, and the actual sea level rise was above the top of the range of the IPCC projection. Another example of scientific research which suggests that previous estimates by the IPCC, far from overstating dangers and risks, have actually understated them is a study on projected rises in sea levels. When the researchers' analysis was "applied to the possible scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC), the researchers found that in 2100 sea levels would be 0.5–1.4 m [50–140 cm] above 1990 levels. These values are much greater than the 9–88 cm as projected by the IPCC itself in its Third Assessment Report, published in 2001". This may have been due, in part, to the expanding human understanding of climate. Greg Holland from the National Center for Atmospheric Research, who reviewed a multi-meter sea level rise study by James Hansen, Jim Hansen, noted "''There is no doubt that the sea level rise, within the IPCC, is a very conservative number, so the truth lies somewhere between IPCC and Jim.''" In reporting criticism by some scientists that IPCC's then-impending January 2007 report understates certain risks, particularly sea level rises, an AP story quoted Stefan Rahmstorf, professor of physics and oceanography at Potsdam University as saying "In a way, it is one of the strengths of the IPCC to be very conservative and cautious and not overstate any climate change risk". In his December 2006 book, ''Hell and High Water: Global Warming'', and in an interview on Fox News on 31 January 2007, energy expert Joseph Romm noted that the IPCC Fourth Assessment Report is already out of date and omits recent observations and factors contributing to global warming, such as the release of greenhouse gases from thawing tundra. Political influence on the IPCC has been documented by the release of a memo by ExxonMobil to the Bush administration, and its effects on the IPCC's leadership. The memo led to strong Bush administration lobbying, evidently at the behest of ExxonMobil, to oust Robert Watson (scientist), Robert Watson, a climate scientist, from the IPCC chairmanship, and to have him replaced by Pachauri, who was seen at the time as more mild-mannered and industry-friendly.
ProceduresMichael Oppenheimer, a long-time participant in the IPCC and coordinating lead author of the Fifth Assessment Report conceded in ''Science Magazine's State of the Planet 2008–2009'' some limitations of the IPCC consensus approach and asks for concurring, smaller assessments of special problems instead of the large scale approach as in the previous IPCC assessment reports. It has become more important to provide a broader exploration of uncertainties. Others see as well mixed blessings of the drive for consensus within the IPCC process and ask to include dissenting or minority positionsLessons from the IPCC: do scientific assessments need to be consensual to be authoritative?
Outdatedness of reportsSince the IPCC does not carry out its own research, it operates on the basis of scientific papers and independently documented results from other scientific bodies, and its schedule for producing reports requires a deadline for submissions prior to the report's final release. In principle, this means that any significant new evidence or events that change our understanding of climate science between this deadline and publication of an IPCC report cannot be included. In an area of science where our scientific understanding is rapidly changing, this has been raised as a serious shortcoming in a body which is widely regarded as the ultimate authority on the science. However, there has generally been a steady evolution of key findings and levels of confidence interval, scientific confidence from one assessment report to the next. The submission deadlines for the Fourth Assessment Report (AR4) differed for the reports of each Working Group. Deadlines for the Working Group I report were adjusted during the drafting and review process in order to ensure that reviewers had access to unpublished material being cited by the authors. The final deadline for cited publications was 24 July 2006. The final WG I report was released on 30 April 2007 and the final AR4 Synthesis Report was released on 17 November 2007.Rajendra Pachauri, the IPCC chair, admitted at the launch of this report that since the IPCC began work on it, scientists have recorded "much stronger trends in climate change", like the unforeseen dramatic melting of polar ice in the summer of 2007, and added, "that means you better start with intervention much earlier".
Burden on participating scientistsScientists who participate in the IPCC assessment process do so without any compensation other than the normal salaries they receive from their home institutions. The process is labor-intensive, diverting time and resources from participating scientists' research programs. Concerns have been raised that the large uncompensated time commitment and disruption to their own research may discourage qualified scientists from participating.
Lack of error correction after publicationIn May 2010, Pachauri noted that the IPCC currently had no process for responding to errors or flaws once it issued a report. The problem, according to Pachauri, was that once a report was issued the panels of scientists producing the reports were disbanded.Associated Press, "U.N. climate chief welcomes review, defends work", ''Japan Times'', 16 May 2010, p. 5.
Proposed organizational overhaulIn February 2010, in response to controversies regarding claims in the AR4, Fourth Assessment Report, five climate scientists – all contributing or lead IPCC report authors – wrote in the journal ''Nature (journal), Nature'' calling for changes to the IPCC. They suggested a range of new organizational options, from tightening the selection of lead authors and contributors, to dumping it in favor of a small permanent body, or even turning the whole climate science assessment process into a Internet Forum#Moderators, moderated "living" Wikipedia-IPCC. 100211 nature.com 100211 theaustralian.com.au Other recommendations included that the panel employ a full-time staff and remove government oversight from its processes to avoid political interference.
Reframing of scientific researchThe 2018 report ''What Lies Beneath'' by the Breakthrough – National Centre for Climate Restoration urges the IPCC, the wider UNFCCC negotiations, and national policy makers to change their approach. The authors note, "We urgently require a reframing of scientific research within an existential risk-management framework."
InterAcademy Council reviewIn March 2010, at the invitation of the United Nations secretary-general and the chair of the IPCC, the InterAcademy Council (IAC) was asked to review the IPCC's processes for developing its reports. The IAC panel, chaired by Harold Tafler Shapiro, convened on 14 May 2010 and released its report on 1 September 2010. The IAC found that, "The IPCC assessment process has been successful overall". The panel, however, made seven formal recommendations for improving the IPCC's assessment process, including: # establish an executive committee; # elect an executive director whose term would only last for one assessment; # encourage review editors to ensure that all reviewer comments are adequately considered and genuine controversies are adequately reflected in the assessment reports; # adopt a better process for responding to reviewer comments; # working groups should use a qualitative level-of-understanding scale in the Summary for Policy Makers and Technical Summary; # "Quantitative probabilities (as in the likelihood scale) should be used to describe the probability of well-defined outcomes only when there is sufficient evidence"; and # implement a communications plan that emphasizes transparency and establish guidelines for who can speak on behalf of the organization. The panel also advised that the IPCC avoid appearing to advocate specific policies in response to its scientific conclusions. Commenting on the IAC report, ''Nature News'' noted that "The proposals were met with a largely favourable response from climate researchers who are eager to move on after the media scandals and credibility challenges that have rocked the United Nations body during the past nine months".
EndorsementsVarious scientific bodies have issued official statements endorsing and concurring with the findings of the IPCC. * Joint national academy, science academies' statement of 2001. "The work of the Intergovernmental Panel on Climate Change (IPCC) represents the consensus of the international scientific community on climate change science. We recognise IPCC as the world's most reliable source of information on climate change and its causes, and we endorse its method of achieving this consensus". * Canadian Foundation for Climate and Atmospheric Sciences. "We concur with the climate science assessment of the Intergovernmental Panel on Climate Change (IPCC) in 2001 ... We endorse the conclusions of the IPCC assessment..." * Canadian Meteorological and Oceanographic Society. "CMOS endorses the process of periodic climate science assessment carried out by the Intergovernmental Panel on Climate Change and supports the conclusion, in its Third Assessment Report, which states that the balance of evidence suggests a discernible human influence on global climate." * European Geosciences Union. "The Intergovernmental Panel on Climate Change [...] is the main representative of the global scientific community [...] [The] IPCC third assessment report [...] represents the state-of-the-art of climate science supported by the major science academies around the world and by the vast majority of scientific researchers and investigations as documented by the peer-reviewed scientific literature". * International Council for Science (ICSU). "...the IPCC Fourth Assessment Report, IPCC 4th Assessment Report represents the most comprehensive international scientific assessment ever conducted. This assessment reflects the current collective knowledge on the climate system, its evolution to date, and its anticipated future development". * National Oceanic and Atmospheric Administration (US). "Internationally, the Intergovernmental Panel on Climate Change (IPCC)... is the most senior and authoritative body providing scientific advice to global policy makers". * United States National Research Council. "The IPCC Third Assessment Report'] conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue". * Network of African Science Academies. "The IPCC should be congratulated for the contribution it has made to public understanding of the nexus that exists between energy, climate and sustainability". * Royal Meteorological Society, in response to the release of the IPCC Fourth Assessment Report, Fourth Assessment Report, referred to the IPCC as "The world's best climate scientists". * Stratigraphy Commission of the Geological Society of London. "The most authoritative assessment of climate change in the near future is provided by the Inter-Governmental Panel for Climate Change".
See also* United Nations Framework Convention on Climate Change * Kyoto Protocol * 4 Degrees and Beyond International Climate Conference * Avoiding dangerous climate change * Indian Network on Climate Change Assessment * Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services * List of authors from Climate Change 2007: The Physical Science Basis * Post–Kyoto Protocol negotiations on greenhouse gas emissions * Robust decision making
Sources* . Statemen