The Intergovernmental Panel on Climate Change (IPCC) is an international group within the United Nations (UN). Its purpose is to provide governments with scientific information to help develop climate policies. The World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) created the IPCC in 1988. The UN approved the IPCC's creation later that year. The IPCC has an office in Geneva, Switzerland, hosted by the WMO. It has 195 member countries that govern the IPCC. These countries choose a group of scientists to lead the IPCC's work during an assessment cycle, which usually lasts six to seven years. The group selects experts to prepare IPCC reports. Governments and observer organizations formally recommend these experts. The IPCC has three working groups and a task force that carry out its scientific work.

The IPCC informs governments about what is known about climate change. It does this by reviewing all scientific research on the topic, including natural, economic, and social impacts, risks, and possible solutions. The IPCC does not do its own research. It aims to be fair and thorough. Thousands of scientists and experts volunteer to review the research. They summarize key findings into "Assessment Reports" for policymakers and the public. Experts say this is the largest peer review process in science. The IPCC was the first of three global science policy groups. The next was the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES), created in 2012, and the Intergovernmental Science-Policy Panel on Chemicals, Waste and Pollution (ISPCWP), created in 2025.

Climate scientists and all member governments support the IPCC's findings. This shows the IPCC is a respected authority on climate change. Governments, organizations, and the media often use information from IPCC reports. These reports are important in the annual climate talks held by the United Nations Framework Convention on Climate Change (UNFCCC). The IPCC's Fifth Assessment Report influenced the Paris Agreement in 2015. The IPCC shared the 2007 Nobel Peace Prize with Al Gore for work on understanding climate change.

The seventh assessment cycle of the IPCC began in 2023. In August 2021, the IPCC released its Working Group I report on the physical science basis of climate change as part of the Sixth Assessment Report. The Guardian called this report the "starkest warning yet" about "major inevitable and irreversible climate changes." Many newspapers worldwide agreed with this description. In February 2022, the IPCC published its Working Group II report on impacts and adaptation. It released Working Group III's report on reducing climate change in April 2022. The Sixth Assessment Report ended with a Synthesis Report in March 2023.

During the Sixth Assessment Report, the IPCC published three special reports. The first and most important was the Special Report on Global Warming of 1.5°C in 2018. In 2019, the IPCC released the Special Report on Climate Change and Land, and the Special Report on the Ocean and Cryosphere in a Changing Climate. The IPCC also updated its methods in 2019. This made the sixth assessment cycle the most ambitious in the IPCC's history.

In January 2026, United States President Donald Trump announced that the United States would leave the organization.

Origins

The group that came before the IPCC was the Advisory Group on Greenhouse Gases (AGGG). Three organizations created the AGGG in 1986. These were the International Council of Scientific Unions, the United Nations Environment Programme (UNEP), and the World Meteorological Organization (WMO). The AGGG looked at scientific research about greenhouse gases. It also studied how the amounts of these gases were increasing. Climate science was becoming more complex and involved more areas of study. This small group of scientists did not have enough tools or support to cover all these topics.

The United States Environmental Protection Agency wanted an international agreement to limit greenhouse gas emissions. The Reagan administration was worried that scientists working on their own might have too much influence. Because of this, the WMO and UNEP formed the IPCC as a group made up of governments in 1988. Scientists join the IPCC as both experts and representatives of their countries. The IPCC creates reports supported by all top scientists in the field. All member governments must agree on these reports through a process called consensus. This means the IPCC works with both scientists and governments. Its job is to inform governments about what scientists know about climate change. It also looks at the effects of climate change and possible ways to address it. The IPCC does this by reviewing scientific studies that have been checked by other experts.

The United Nations approved the creation of the IPCC in 1988. A resolution from the General Assembly said human activities could change the climate. This could cause serious economic and social problems. It stated that rising levels of greenhouse gases could warm the planet. This warming could lead to rising sea levels. The effects on people would be very bad if action was not taken quickly.

Organization

The IPCC does not perform its own research. Instead, it creates detailed reports about what scientists know about climate change. It also writes reports on specific topics related to climate change and develops tools that help countries measure their greenhouse gas emissions and how much carbon is removed by natural processes like forests. These reports build on earlier studies and scientific papers. Over six major reports, the evidence about climate change has grown stronger, and these reports show that human activities are the main cause.

The IPCC follows rules called the "Principles Governing IPCC Work." These rules state that the IPCC will examine:
– the risks of climate change caused by human actions,
– the possible effects of climate change, and
– ways to prevent or reduce these effects.

IPCC reports are thorough, fair, open, and clear. They include all scientific, technical, and social information relevant to understanding climate change. The reports do not suggest specific policies but may discuss factors that influence policy decisions.

The IPCC has the following structure:
– IPCC Panel: Meets about twice a year and can meet more often to approve reports. It oversees the IPCC’s work, budget, and structure. It also approves IPCC reports. The Panel is the main decision-making body.
– Chair: Elected by the Panel. Leads the IPCC and represents it.
– Bureau: Elected by the Panel. Has 34 members from different regions. It guides the Panel on scientific and technical matters and leads the IPCC’s three Working Groups and Task Force.
– Working Groups: Each group has two co-chairs, one from a developed and one from a developing country. They produce reports on different aspects of climate change:
– Working Group I: Studies the science of climate change. Co-Chairs: Robert Vautard (France) and Xiaoye Zhang (China).
– Working Group II: Examines how climate change affects people and nature, and how to adapt. Co-Chairs: Bart van den Hurk (Netherlands) and Winston Chow (Singapore).
– Working Group III: Focuses on ways to reduce greenhouse gas emissions (called "mitigation"). Co-Chairs: Katherine Calvin (United States) and Joy Jacqueline Pereira (Malaysia).
– Task Force on National Greenhouse Gas Inventories: Creates tools to measure emissions. Co-Chairs: Takeshi Enoki (Japan) and Mazhar Hayat (Pakistan).
– Executive Committee: Includes the Chair, Vice-Chairs, and co-chairs of Working Groups and Task Force. It handles urgent issues between Panel meetings.
– Secretariat: Manages daily activities, supports the Chair and Bureau, and serves as a contact point for governments. Supported by UNEP and WMO.

The current IPCC Chair is Jim Skea, a British energy scientist. He has led the IPCC since July 2023. Previous chairs include Hoesung Lee (Korea, 2015), Rajendra K. Pachauri (India, 2002), Robert Watson (United States, 1997), and Bert Bolin (Sweden, 1988).

The IPCC Panel includes government representatives who attend meetings. Non-governmental and international organizations can attend as observers. Meetings are by invitation only. For example, the 48th Panel meeting in 2018 had about 500 people from 130 countries, including 290 government officials and 60 observers. Media can attend opening ceremonies but not other meetings.

The IPCC is funded by a trust fund created in 1989 by UNEP and WMO. Governments, along with UNEP, WMO, and other organizations, voluntarily contribute money. The WMO covers the secretariat’s costs and sets financial rules. The Panel decides the annual budget.

In 2021, the IPCC’s budget was about six million euros, funded by 195 UN member states. Major contributors included the United States, Japan, France, Germany, and Norway. Some countries, often developing ones, help by hosting IPCC meetings. In 2022, the budget was slightly less than eight million euros.

The IPCC works based on decisions made by UNEP and WMO, which created the IPCC. It also supports the UNFCCC. Its main tasks include preparing reports and managing data through the Data Distribution Centre.

The IPCC has a "Gender Policy and Implementation Plan" to ensure equal participation and respect for all genders in its work. It aims to provide equal opportunities for everyone involved.

To improve communication, the IPCC made reports and press releases available to media before public release for the Fifth Assessment Report. It also held an Expert Meeting on Communication in 2016, where recommendations were made, such as including communication experts in Working Groups and addressing communication early in report writing. These steps led to more media coverage, especially for the 2018 Special Report on Global Warming of 1.5°C and the 2021 report on climate science. This increased public interest, including youth-led movements in 2018.

IPCC reports help raise public awareness and guide policy decisions. This has led to academic studies on how the IPCC communicates its findings.

The IPCC stores its reports and electronic files on its website. These include feedback from reviewers on draft reports. The Environmental Science and Public Policy Archives at Harvard Library also keeps copies.

Assessment reports

From 1990 to 2023, the IPCC created six major reports that reviewed the latest climate science. The IPCC also made 14 special reports about specific topics. Each main report has four parts: contributions from each of the three working groups and a synthesis report. The synthesis report combines the working group contributions and any special reports made during that time.

The IPCC does not do research. It does not track climate data. Instead, it reviews scientific papers and results from other groups. The IPCC sets a deadline for including scientific papers in a report. Papers published after this deadline are not included. However, the key findings and confidence levels in the science improve with each new report. Each report explains where science has improved since the last one and where more research is needed.

The First Assessment Report was published in 1990 and updated in 1992. New editions of the IPCC Assessment Reports were released about every six years.

Each country appoints a representative who helps the IPCC choose people to work on the reports. The IPCC Bureau uses these lists to pick authors, but it can also select others based on scientific skill, diverse viewpoints, and other factors like geography, experience, and gender. Authors can be researchers, people from the private sector, or experts from NGOs.

The IPCC Bureau selects authors from government nominations. Lead authors review climate change information from published sources. They prioritize peer-reviewed sources but may also use non-peer-reviewed sources like government reports, NGO studies, industry journals, or model results if they are high quality.

Authors write drafts of the full report, divided into chapters. They also create a technical summary and a summary for policymakers. Each chapter has many authors who write and edit the material. A typical chapter includes two coordinating lead authors, ten to fifteen lead authors, and many contributing authors. Coordinating lead authors organize the work and ensure it meets formatting rules. They report to the Working Group co-chairs. Lead authors write sections of chapters and invite contributing authors to add text, graphs, or data. Review editors check that authors respond to comments during two review stages: the first is open to experts, and the second includes government representatives.

The IPCC Bureau tries to choose authors with a range of views, expertise, and geographic backgrounds. This ensures the team includes experts from both developed and developing countries. It also aims for a balance between men and women and between experienced and new participants.

Scientists who work on IPCC reports do not get paid. They work voluntarily and rely on their regular jobs for income. The work is time-consuming and can affect their other research. This has raised concerns that the process might discourage scientists from joining. Over 3,000 authors have helped write IPCC reports since the organization began.

Expert reviewers give feedback on drafts at different stages. Reviewers come from member governments and observer groups. Anyone with relevant expertise can become a reviewer.

The review process usually has three stages. First, experts review the first draft of the chapters. Next, governments and experts review the revised draft of the chapters and the first summary for policymakers. Finally, governments review the final version of the summary for policymakers. Comments and responses are kept in an open archive for at least five years. Government representatives and authors review the summary line by line to ensure it accurately reflects the report. This final review happens during meetings of the working group or the IPCC Panel.

Documents receive different types of approval:
– Approval: Material is discussed and agreed on line by line. Working Groups approve their summaries for policymakers, and the Panel approves the synthesis report summary.
– Adoption: Sections are approved individually, not line by line. The Panel adopts the full synthesis report and overview chapters of methodology reports.
– Acceptance: Material is not discussed line by line but still provides a complete, objective, and balanced view. Working Groups accept their reports, and the Panel accepts summaries after approval.

• The First Assessment Report (FAR) was published in 1990. It gave an overview of climate change science, discussed uncertainties, and showed evidence of warming. It stated that human activity increases greenhouse gases, leading to Earth’s warming. This report led to the creation of the United Nations Framework Convention on Climate Change (UNFCCC).
• The Second Assessment Report (SAR) was published in 1995. It supported the findings of the first report, showing clear human influence on the global climate. This report helped shape the Kyoto Protocol under the UNFCCC.
• The Third Assessment Report (TAR) was completed in 2001. It showed more evidence that human activity caused most of the global warming in the past 50 years. The report included a graph showing global temperatures since 1000 AD, called the "hockey stick" due to the sharp recent rise. It also explained how adapting to climate change can reduce some negative effects.
• The Fourth Assessment Report (AR4) was published in 2007. It gave strong confidence in climate change, stating, "Warming of the climate system is unequivocal." This report raised global awareness of climate change. The IPCC shared the Nobel Peace Prize in 2007 for this work.
• The Fifth Assessment Report (AR5) was published in 2013 and 2014. It confirmed the reality of climate change and warned about its impacts.

Other reports

The IPCC also creates other types of reports. It writes Special Reports on topics suggested by governments or observer groups. From 1994 to 2019, the IPCC published 14 special reports. Now, usually more than one working group works together to create a special report. The process for preparing and approving these reports is the same as for assessment reports.

During the fifth assessment cycle, the IPCC created two special reports. It finished the Special Report on Renewable Energy Sources and Climate Change Mitigation in 2011. Working Group III prepared this report. The report studied ways to use different types of renewable energy to replace fossil fuels. It noted that the cost of most renewable technologies had decreased. It said the cost might decrease even more with future technology improvements. The report stated that renewable energy could increase access to energy. It reviewed 164 scenarios showing how renewable energy could help reduce climate change. In more than half of these scenarios, renewable energy would provide more than 27% of the primary energy supply by mid-century. This would be more than double the 13% share in 2008. In scenarios with the highest renewable energy use, it would contribute 77% by 2050.

In 2011, the IPCC also released the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. This report was created by Working Groups I and II. It was the first time two working groups worked together on a special report. The report explained how climate change has changed extreme weather patterns. It also showed how policies to avoid or prepare for extreme weather events can reduce their effects. Policies to respond to and recover from these events can also help societies become more resilient.

During the sixth assessment cycle, the IPCC created three special reports. This was the most ambitious cycle in IPCC history. The UNFCCC set a goal of keeping global warming below 2°C (36°F) and trying to keep it at 1.5°C (34.7°F) after the Paris Agreement in 2015. At the time, there was little understanding of what a 1.5°C warming meant. There was also little scientific research on how the impacts of 1.5°C would differ from 2°C. The UNFCCC asked the IPCC to prepare a report on global warming of 1.5°C. The IPCC released the Special Report on Global Warming of 1.5°C (SR15) in 2018. The report stated that it was possible to keep warming below 1.5°C during the 21st century. However, this would require large reductions in emissions and rapid, widespread changes in society. The report showed that warming of 2°C would have much more severe effects than 1.5°C. This means that every degree of warming matters. SR15 had a major impact on the public and media, placing the 1.5°C target at the center of climate activism.

In 2019, the IPCC released two more special reports that studied different parts of the climate system. The Special Report on Climate Change and Land examined how land use affects the climate. It looked at emissions from activities like farming and forestry, not from energy or transport. It also studied how climate change is affecting land. All three IPCC working groups and the Task Force on National Greenhouse Gas Inventories worked on this report. The report found that climate change is increasing pressure on land used for living and growing food. It said that keeping warming below 2°C will only be possible if emissions are reduced in all sectors, including land and food.

The Special Report on the Ocean and Cryosphere in a Changing Climate studied how the ocean and frozen parts of the planet interact with climate change. (The cryosphere includes systems like ice sheets, glaciers, and permafrost.) Working Groups I and II prepared this report. It emphasized the need to address changes in the ocean and cryosphere. It also showed how adaptation can support sustainable development.

The IPCC has a National Greenhouse Gas Inventories Programme. It creates methods and software for countries to report their greenhouse gas emissions. The IPCC's Task Force on National Greenhouse Gas Inventories (TFI) has managed this program since 1998. Japan's Institute for Global Environmental Strategies hosts the TFI's Technical Support Unit.

The IPCC released its first Methodology Report, the IPCC Guidelines for National Greenhouse Gas Inventories, in 1994. The Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories updated this report. Two "good practice reports" complete these guidelines: the Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories and Good Practice Guidance for Land Use, Land-Use Change and Forestry. Parties to the UNFCCC and its Kyoto Protocol use the 1996 guidelines and the two good practice reports for their annual inventory submissions.

The 2006 IPCC Guidelines for National Greenhouse Gas Inventories further updated these methods. They include many "default emission factors" to estimate emissions for specific activities. The IPCC created this version at the request of the UNFCCC. The UNFCCC approved it for use at its 2013 Climate Change Conference, COP19, in Warsaw. The IPCC added more details in its 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories.

The TFI has begun preparing a methodology report on short-lived climate forcers (SLCFs). It will finish this report during the next assessment cycle, the seventh.

Challenges and controversies

The IPCC reports have faced criticism from different groups. Some people say the reports overstate the dangers of climate change, while others believe they understate the risks. The IPCC's method of reaching agreement has faced challenges from inside and outside the organization.

Some scientists argue that IPCC reports are too cautious in their climate risk assessments. In 2012, it was reported that some scientists criticized the IPCC for consistently underestimating how quickly global warming is happening and its effects. These scientists believe this leads to findings that are the "simplest version that everyone agrees on." Similar concerns were raised by scientists who noticed that recent IPCC reports focused more on lower temperature goals, like 1.5°C, while giving less attention to higher temperatures, such as 2°C, which may be more likely based on current emissions.

David Biello, writing in Scientific American, explains that the need to gain agreement among government representatives leads the IPCC to provide cautious estimates of global warming's effects. Science editor Brooks Hanson wrote in 2010 that the IPCC has underestimated how fast climate change is happening and overestimated how well societies can reduce greenhouse gas emissions.

Climate scientist James E. Hansen argues that the IPCC's cautious approach seriously underestimates the risk of sea-level rise, which could flood many low-lying areas, such as southern Florida. In January 2024, he told the Guardian that the world is now entering a 1.5°C temperature range. He added that reaching this milestone shows that the United Nations and the IPCC's approach may not be accurate.

Roger A. Pielke Sr. stated that humans are changing the climate in many ways beyond carbon dioxide's effects. He said the IPCC has been too cautious in recognizing these changes. Stefan Rahmstorf, a professor at the University of Potsdam, argued in 2007 that the IPCC's conservative risk assessments are actually a strength, as they avoid overstating climate change risks.

IPCC reports aim to inform governments about scientific knowledge on climate change. They summarize thousands of scientific studies at a given time. Individual studies may differ from IPCC reports, especially those published after an IPCC report is released. This can lead to criticism that the IPCC is either too alarmist or too cautious. New findings are considered only in the next assessment report.

A 2002 memo from ExxonMobil to the U.S. government led to efforts to replace Robert Watson, a climate scientist, as IPCC chair. The government wanted to replace him with Rajendra Pachauri, who was seen as more friendly to industries.

Governments are the main members of the IPCC and its primary audience. They have a formal role in shaping, reviewing, and approving reports. For example, governments help review and approve the Summary for Policymakers in each report. However, some activists argue that governments misuse this role to influence report outcomes.

In 2023, pressure from Brazil and Argentina, countries with large beef industries, caused the IPCC to remove text recommending plant-based diets. An earlier draft of the report had stated that plant-based diets could reduce greenhouse gas emissions by up to 50% compared to Western diets. This draft was leaked online in March 2023.

The IPCC faced intense media scrutiny in 2009 before the Copenhagen climate conference. This involved the leak of emails from climate scientists, many of whom had contributed to the 2007 Fourth Assessment Report. An error in this report about Himalayan glaciers melting by 2035 added to the pressure. Scientific groups supported the overall findings of the Fourth Assessment Report but suggested the IPCC should review its methods.

Public debate after the 2009 release of the Fourth Assessment Report led to scrutiny of the IPCC for alleged bias and inaccuracies. In 2010, the U.N. Secretary-General and the IPCC chair asked the InterAcademy Council (IAC) to review the IPCC's processes. The IAC recommended improving the IPCC's management, conflict-of-interest policies, review processes, and communication strategies. Most of these recommendations were implemented by 2012, including a protocol to address errors in reports. However, the IPCC did not adopt a proposal to hire a full-time executive secretary.

Michael Oppenheimer, a long-time IPCC participant, said the IPCC's consensus method has some limitations. He suggested smaller, focused studies on specific issues instead of large-scale assessments. Others believe the IPCC should include minority opinions and improve statements about uncertainties.

Some criticism has come from experts who work with the IPCC. For example, John Christy, a contributing author, explained in 2007 that it is difficult to reach scientific agreement on the exact impact of human activity on climate change. He noted that contributing authors have limited influence over editing decisions. Christopher Landsea, a hurricane researcher, said he could not continue contributing to the IPCC process due to concerns about pre-conceived agendas and scientific accuracy.

Endorsements and awards

The IPCC reports are the standard for climate science. Many scientists agree with the IPCC's findings. Other scientific groups and experts have also supported these reports. Official statements from several scientific organizations back the IPCC's work. For example:

• The Third Assessment Report from 2001 was supported by the Canadian Foundation for Climate and Atmospheric Sciences, the United States National Research Council, and the European Geosciences Union.
• The Fourth Assessment Report from 2007 was supported by the International Council for Science (ICSU) and the Network of African Science Academies.

In December 2007, the IPCC received the Nobel Peace Prize. This award honored their work to share information about human-caused climate change and to help create solutions to address this issue. They shared the prize with former U.S. Vice President Al Gore for his efforts on climate change and his documentary An Inconvenient Truth.

In October 2022, the IPCC and IPBES won the Gulbenkian Prize for Humanity. These two groups received the award because they "create scientific knowledge, warn society, and help leaders make better choices to fight climate change and protect biodiversity."