Intergovernmental Panel on Climate Change

The IPCC receives funding through a dedicated trust fund, established in 1989 by UNEP and the 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.[30] The Panel sets the annual budget.

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 ("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]

Authors prepare drafts of a full report divided into chapters, a technical summary of this report, and a summary for policymakers. [5]

There are generally three stages in the review process:[5] Expert review, government/expert review and government review of: summaries for policymakers, overview chapters and the synthesis report. Review comments are in an open archive for at least five years.The report is completed at sessions of the responsible working group and panel, where government representatives review the Summary for Policymakers in dialogue with the authors who have drafted it.

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, the Synthesis Report Summary for Policymakers is approved by the Panel).
• Adoption - Endorsed section by section (and not line by line) (the Panel adopts Overview Chapters of Methodology Reports and the 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 working group approval).

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.[35]

The choice of authors by the Bureau 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. The Bureau also seeks a balance between male and female authors and a balance between those who have worked previously on IPCC reports and those new to the process.

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 labour-intensive, diverting time and resources from participating scientists' research programs.[36] Concerns have been raised that the large uncompensated time commitment and disruption to their own research may discourage qualified scientists from participating.[37]

In addition to comprehensive assessments of climate change, the IPCC publishes Special Reports on specific topics proposed by governments or observer organizations. The preparation and approval process for all IPCC Special Reports follows the same procedures as for IPCC Assessment Reports. Details of recent examples follow.

The Special Report on Emissions Scenarios (SRES) is a report by the IPCC which was published in 2000.[51] The SRES contains "scenarios" of future changes in emissions of greenhouse gases and sulphur dioxide.[52] 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[53] and Fourth Assessment Reports.[54]

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).[55] SRES emissions projections are broadly comparable in range to the baseline projections that have been developed by the scientific community.[56]

This report assesses existing literature on renewable energy commercialisation for the mitigation of climate change.[57] 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 report on a voluntary basis – not to mention more than 100 scientists, who served as contributing authors.

The report was approved in 2011.[58] 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 this report.

Within the IPCC the National Greenhouse Gas Inventory Programme develops methodologies to estimate emissions and removals of greenhouse gases.[71] 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) [72] 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 IPCC has started preparations for a methodology report on short-lived climate forcers to be completed in the seventh assessment cycle.

The 1996 Guidelines for National Greenhouse Gas Inventories provide the methodological basis for the estimation of national greenhouse gas emissions inventories.[73] 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 an update to these emission estimation methodologies, including a large number of default emission factors (a factor estimating the amount of emissions for an activity).[74] The IPCC prepared this new version of the guidelines on request of the parties to the UNFCCC,[75] and the methods were officially accepted for use in national greenhouse gas emissions reporting under the UNFCCC and the Kyoto Protocol at the 2013 United Nations Climate Change Conference.[76] Further material was provided in the 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.[77]

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,[80] and expanding its outreach activities with an outreach calendar.[81] 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.[82] 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.[83]

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.[84][85]

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.[86]

Some critics have contended that the IPCC reports tend to be conservative by consistently underestimating the pace and impacts of global warming,[87] and report only the "lowest common denominator" findings.[90] In 2007 Stefan Rahmstorf, professor of physics and oceanography at Potsdam University, stated: "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".[91] IPCC reports are intended to inform policymakers and others about the state of knowledge on climate change by assessing the findings of the thousands of scientific papers available on the subject at a given time in a process with multiple drafts and reviews. Individual publications, including those appearing just after the release of an IPCC report, may have different conclusions, leading to criticism that the IPCC is either overly alarmist or excessively conservative. New findings are reflected in the next assessment. [92] [93]

A potential political influence on the IPCC has been documented by the release of a memo by ExxonMobil to the Bush administration in the United States in 2002, 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.[94]

Governments form the membership of the IPCC, and are the prime audience for IPCC reports. IPCC rules gives them a formal role in the scoping, preparation and approval of reports. [95] For instance governments take part in the review process and work with authors to approve the Summary for Policymakers of reports. But some activists have argued that governments abuse this role to influence the outcome of reports. [96]

The IPCC came under unprecedented media scrutiny in 2009 in the run-up to the Copenhagen climate conference. This followed the leak of emails from climate scientists (so called "Climatic Research Unit email controversy"), many of whom were IPCC authors of the Fourth Assessment Report which was published in 2007. The discovery of an error in this report about the projected date for melting of Himalayan glaciers in early 2010 put the IPCC under further pressure.[97] Scientific bodies upheld the general findings of the Fourth Assessment Report and the IPCC’s approach.[98][99] But the Chair of the IPCC and UN Secretary-General invited the InterAcademy Council to carry out an independent review of IPCC procedures (see below).[100]

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.[100][101] The IAC panel, chaired by Harold Tafler Shapiro, released its report on 1 September 2010.[102] The panel made seven formal recommendations for improving the IPCC's assessment process. The IPCC implemented most of the review's recommendations by 2012, including the introduction of a protocol to handle errors in reports.[103][104] Others included strengthening the science-review process and improving communications, but the IPCC did not adopt the proposal to appoint a full-time executive secretary.[102][105]

Michael Oppenheimer, a long-time participant in the IPCC and coordinating lead author of the Fifth Assessment Report, conceded some limitations of the IPCC consensus approach and asked for concurring, smaller assessments of special problems instead of the large scale approach as in the previous IPCC assessment reports.[89] Others see "mixed blessings" of the drive for consensus within the IPCC process and ask to include dissenting or minority positions[106] or to improve statements about uncertainties.[107][108]

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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.[117]

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". [118]