Intergovernmental Panel on Climate Change

The IPCC receives funding through a dedicated trust fund, established in 1989 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO). The trust fund receives annual cash contributions by the WMO, UNEP, and IPCC member governments; payments are voluntary and there is no set amount required. Administrative and operational costs, such as for the secretariat and headquarters, are provided by the WMO, which also sets the IPCC's financial regulations and rules.[31] The Panel is responsible for considering and adopting by consensus the annual budget.

The 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.[5][34] According to IPCC guidelines, authors should give priority to peer-reviewed sources.[5] Authors may refer to non-peer-reviewed sources (the "grey literature"), provided that they are of sufficient quality.[5] Examples of non-peer-reviewed sources include model results, reports from government agencies and non-governmental organizations, and industry journals.[5] 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:[5]

• 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,[35] while others have been critical.[36] Some commentators have suggested changes to the IPCC's procedures.[37]

Each 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.[38]

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.

Already in the Fifth Assessment Report, the IPCC had enhanced its communications activities, for instance by making the approved report and press release available to registered media under embargo before the release,[52] and expanding its outreach activities with an outreach calendar.[53] At the start of the Sixth Assessment Report cycle, the IPCC held an Expert Meeting on Communication in February 2016, bringing together members of the old and new Bureau and Technical Support Units with communications experts and practitioners. This meeting produced a series of recommendations.[54] Many of these were taken up subsequently by the IPCC, such as bringing people with communications expertise into the Working Group Technical Support Units, and considering communications questions early on in the preparation of reports.

This increasing professionalism in IPCC communications was followed by a significant increase in the media coverage of some IPCC reports such as the Special Report on Global Warming of 1.5ºC in 2018 and "Climate Change 2021: The Physical Science Basis" (the Working Group I contribution to the Sixth Assessment Report) in 2021, as well as public interest reflected in the youth and other movements that emerged in 2018.[55]

The importance of IPCC reports for public awareness of climate change and related policymaking has led to number of academic studies of IPCC communications. The journal "Climatic Change" published a "Topical Collection" on IPCC communications with contributions from communications scientists and IPCC insiders, launched at the annual climate conference COP26 in Glasgow.[56][57]

Papers and electronic files of certain working groups of the IPCC, including reviews and comments on drafts of their Assessment Reports, are archived at the Environmental Science and Public Policy Archives in the Harvard Library, as well as on the IPCC website.

In 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.[58]

The Special Report on Emissions Scenarios (SRES) is a report by the IPCC which was published in 2000.[59] The SRES contains "scenarios" of future changes in emissions of greenhouse gases and sulfur dioxide.[60] 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[61] and Fourth Assessment Reports.[62]

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).[63] SRES emissions projections are broadly comparable in range to the baseline projections that have been developed by the scientific community.[64]

This report[65] assesses existing literature on renewable energy commercialisation for the mitigation of climate change. It was approved in 2011 and covers the six most important renewable energy technologies in a transition, as well as their integration into present and future energy systems. It also takes into consideration the environmental and social consequences associated with these technologies, the cost and strategies to overcome technical as well as non-technical obstacles to their application and diffusion.

More than 130 authors from all over the world contributed to the preparation of IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (SRREN) on a voluntary basis – not to mention more than 100 scientists, who served as contributing authors.

The report[66] was approved in 2011. It assesses the effect that climate change has on the threat of natural disasters and how nations can better manage an expected change in the frequency of occurrence and intensity of severe weather patterns. It aims to become a resource for decision-makers to prepare more effectively for managing the risks of these events. A potentially important area for consideration is also the detection of trends in extreme events and the attribution of these trends to human influence.

More than 80 authors, 19 review editors, and more than 100 contributing authors from all over the world contributed to the preparation of the 594-page report.

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".[67] 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".[67]

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".[67][68] Meeting the Paris target of 1.5 °C (2.7 °F) is possible but would require "deep emissions reductions", "rapid",[68] "far-reaching and unprecedented changes in all aspects of society".[69] 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.[70][67][71]

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.[72]

The "Special Report on the Ocean and Cryosphere in a Changing Climate" (SROCC) was approved on 25 September 2019 in Monaco.[73] 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.[74]

Within the IPCC the National Greenhouse Gas Inventory Programme develops methodologies to estimate emissions and removals of greenhouse gases.[75] Originally undertaken by IPCC Working Group I in collaboration with the Organization for Economic Co-operation and Development and the International Energy Agency, the programme has been managed since 1998 by the IPCC's Task Force on National Greenhouse Gas Inventories (TFI) [76] whose Technical Support Unit is hosted by Japan's Institute for Global Environment Strategies . The objectives of the National Greenhouse Gas Inventory Programme 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.

The 1996 Guidelines for National Greenhouse Gas Inventories provide the methodological basis for the estimation of national greenhouse gas emissions inventories.[77] 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.

The 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.[78] 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.[79] Further material was provided in the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.[80]

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Al Gore's Nobel Peace Prize acceptance speech

In 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.[83]

In October 2022, the IPCC and the IPBES shared the Gulbenkian Prize for Humanity, because the two intergovernmental organisations "produce scientific knowledge, alert society, and inform decision-makers to make better choices for combatting climate change and the loss of biodiversity". [84]

Some critics have contended that the IPCC reports tend to be conservative by consistently underestimating the pace and impacts of global warming,[93] and report only the "lowest common denominator" findings.[94]

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.[95][96]

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.[97][98]

Greg Holland from the National Center for Atmospheric Research, who reviewed a multi-meter sea level rise study by 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."[99]

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".[100]

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.[101]

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, a climate scientist, from the IPCC chairmanship, and to have him replaced by Rajendra Pachauri, who was seen at the time as more mild-mannered and industry-friendly.[102][103]

Michael 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.[90] It has become more important to provide a broader exploration of uncertainties.[90] Others see as well mixed blessings of the drive for consensus within the IPCC process and ask to include dissenting or minority positions[104] or to improve statements about uncertainties.[105][106]

The IPCC process on climate change and its efficiency and success has been compared with dealings with other environmental challenges (compare Ozone depletion and global warming). In case of the Ozone depletion, global regulation based on the Montreal Protocol has been successful. In case of Climate Change, the Kyoto Protocol failed.[107] The Ozone case was used to assess the efficiency of the IPCC process.[108] The lockstep situation of the IPCC is having built a broad science consensus while states and governments still follow different, if not opposing goals.[109] The underlying linear model of policy-making of the more knowledge we have, the better the political response will be is being doubted.[109][110]

According to Sheldon Ungar's comparison with global warming, the actors in the ozone depletion case had a better understanding of scientific ignorance and uncertainties.[111] The ozone case communicated to lay persons "with easy-to-understand bridging metaphors derived from the popular culture" and related to "immediate risks with everyday relevance", while the public opinion on climate change sees no imminent danger.[111] The stepwise mitigation of the ozone layer challenge was based as well on successfully reducing regional burden sharing conflicts.[108] In case of the IPCC conclusions and the failure of the Kyoto Protocol, varying regional cost-benefit analysis and burden-sharing conflicts with regard to the distribution of emission reductions remain an unsolved problem.[107] In the UK, a report for a House of Lords committee asked to urge the IPCC to involve better assessments of costs and benefits of climate change,[112] but the Stern Review, ordered by the UK government, made a stronger argument in favor to combat human-made climate change.

Since 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.[113] However, there has generally been a steady evolution of key findings and levels of scientific confidence from one assessment report to the next.[114]

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.[115] 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,[116] and added, "that means you better start with intervention much earlier".[117]

Scientists 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.[118] Concerns have been raised that the large uncompensated time commitment and disruption to their own research may discourage qualified scientists from participating.[119]

In 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.[120]

In February 2010, in response to controversies regarding claims in the Fourth Assessment Report,[121][122] five climate scientists – all contributing or lead IPCC report authors – wrote in the 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 moderated "living" Wikipedia-IPCC.[123][124] Other recommendations included that the panel employ a full-time staff and remove government oversight from its processes to avoid political interference.[125]

The 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."[126]

In 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.[127][128] The IAC panel, chaired by Harold Tafler Shapiro, convened on 14 May 2010 and released its report on 1 September 2010.[120][129]

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:

1. establish an executive committee;
2. elect an executive director whose term would only last for one assessment;
3. encourage review editors to ensure that all reviewer comments are adequately considered and genuine controversies are adequately reflected in the assessment reports;
4. adopt a better process for responding to reviewer comments;
5. working groups should use a qualitative level-of-understanding scale in the Summary for Policy Makers and Technical Summary;
6. "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
7. implement a communications plan that emphasizes transparency and establish guidelines for who can speak on behalf of the organization.[130]

The panel also advised that the IPCC avoid appearing to advocate specific policies in response to its scientific conclusions.[131] 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".[132]

Various scientific bodies have issued official statements endorsing and concurring with the findings of the IPCC.

• Joint 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".[86]
• 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..."[133]
• 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."[134]
• 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".[135]
• International Council for Science (ICSU). "...the 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".[136]
• 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".[137]
• 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".[138]
• 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".[139]
• Royal Meteorological Society, in response to the release of the Fourth Assessment Report, referred to the IPCC as "The world's best climate scientists".[140]
• 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".[141]