Intergovernmental Panel on Climate Change

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Intergovernmental Panel on Climate Change
Org typePanel

The Intergovernmental Panel on Climate Change (IPCC) is a scientific intergovernmental body,[1][2] set up at the request of member governments.[3] It was first established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), and later endorsed by the United Nations General Assembly through Resolution 43/53. Its mission is to provide comprehensive scientific assessments of current scientific, technical and socio-economic information worldwide about the risk of climate change caused by human activity, its potential environmental and socio-economic consequences, and possible options for adapting to these consequences or mitigating the effects.[4] It is chaired by Rajendra K. Pachauri.

Thousands of scientists and other experts contribute (on a voluntary basis, without payment from the IPCC) to writing and reviewing reports, which are reviewed by representatives from all the governments, with summaries for policy makers being subject to line-by-line approval by all participating governments. Typically this involves the governments of more than 120 countries.[5]

The IPCC does not carry out its own original research, nor does it do the work of monitoring climate or related phenomena itself. A main activity of the IPCC is publishing special reports on topics relevant to the implementation of the United Nations Framework Convention on Climate Change (UNFCCC),[4] an international treaty that acknowledges the possibility of harmful climate change. Implementation of the UNFCCC led eventually to the Kyoto Protocol. The IPCC bases its assessment mainly on peer reviewed and published scientific literature.[6] Membership of the IPCC is open to all members of the WMO and UNEP.[7]

The IPCC provides an internationally accepted authority on climate change,[8] producing reports which have the agreement of all the leading climate scientists and the consensus of every one of the participating governments. It has successfully provided authoritative policy advice with far-reaching implications for economics and lifestyles. In a context of unremitting opposition from fossil fuel interests, governments have been slow to implement the advice.[3] The 2007 Nobel Peace Prize was shared, in two equal parts, between the IPCC and Al Gore.[9]



The principles of the IPCC operation[10] are assigned by the relevant WMO Executive Council and UNEP Governing Council resolutions and decisions as well as on actions in support of the UNFCCC process.

The aims of the IPCC are to assess scientific information relevant to:[4]

  1. Human-induced climate change,
  2. The impacts of human-induced climate change,
  3. Options for adaptation and mitigation.


The chair of the IPCC is Rajendra K. Pachauri, elected in May 2002. The previous chair was Robert Watson. The chair is assisted by an elected bureau including vice-chairs, working group co-chairs and a secretariat.

The IPCC Panel is composed of representatives appointed by governments and organizations. Participation of delegates with appropriate expertise is encouraged. Plenary sessions of the IPCC and IPCC Working Groups are held at the level of government representatives. Non Governmental and Intergovernmental Organizations may be allowed to attend as observers. Sessions of the IPCC Bureau, workshops, expert and lead authors meetings are by invitation only.[11] Attendance at the 2003 meeting included 350 government officials and climate change experts. After the opening ceremonies, closed plenary sessions were held.[12] The meeting report[13] states there were 322 persons in attendance at Sessions with about seven-eighths of participants being from governmental organizations.[13]

There are several major groups:

The IPCC receives funding from UNEP, WMO, and its own Trust Fund for which it solicits contributions from governments. Its secretariat is hosted by the WMO, in Geneva.

Assessment reports

Assessment reports:
First (1990)
1992 sup.
Second (1995)
Third (2001)
Fourth (2007)
Fifth (2014)

The IPCC has published four 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. Drafts of these reports are made available for comment in open review processes to which anyone may contribute.

The IPCC published its first assessment report in 1990, a supplementary report in 1992, a second assessment report (SAR) in 1995, and a third assessment report (TAR) in 2001. A fourth assessment report (AR4) was released in 2007 and a fifth is due to be issued in 2014.

Each assessment report is in three volumes, corresponding to Working Groups I, II and III. Unqualified, "the IPCC report" is often used to mean the Working Group I report, which covers the basic science of climate change.

Scope and preparation of the reports

The IPCC does not carry out research nor does it monitor climate related data. The responsibility of the lead authors of IPCC reports is to assess available information about climate change drawn mainly from the peer reviewed and published scientific/technical literature.[14] The IPCC reports are a compendium of peer reviewed and published science. 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:[15]

Review comments are in an open archive for at least five years.

There are several types of endorsement which documents receive:

The Panel is responsible for the IPCC and its endorsement of Reports allows it to ensure they meet IPCC standards. The Panel's approval process has been criticized for changing the product of the experts who create the Reports. On the other hand, not requiring Panel re-endorsement of Reports has also been criticized, after changes required by the approval process were made to Reports.


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.

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 report

The IPCC first assessment report 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 1992

The 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:

Each of the last three parts was completed by a separate working group, and each has a Summary for Policymakers (SPM) that represents a consensus of national representatives. The SPM of the WG I report contains headings:

  1. Greenhouse gas concentrations have continued to increase
  2. Anthropogenic aerosols tend to produce negative radiative forcings
  3. 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).
  4. 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)
  5. Climate is expected to continue to change in the future (increasing realism of simulations increases confidence; important uncertainties remain but are taken into account in the range of model projections)
  6. There are still many uncertainties (estimates of future emissions and biogeochemical cycling; models; instrument data for model testing, assessment of variability, and detection studies)

Chapter 8

Chapter 8 of the Second Assessment Report stated that "these results indicate that the observed trend in global mean temperature over the past 100 years is unlikely to be entirely natural in origin. More importantly, there is evidence of an emerging pattern of climate response to forcings by greenhouse gases and sulphate aerosols in the observed climate record. Taken together, these results point towards a human influence on global climate."[16]

A week after the report was released, The Wall Street Journal published a letter from physicist Frederick Seitz denouncing the IPCC report, in particular the conclusions of Chapter 8. Seitz wrote, "I have never witnessed a more disturbing corruption of the peer-review process than the events that led to this IPCC report".[17][18] Seitz's comments were vigorously opposed by the presidents of the American Meteorological Society and University Corporation for Atmospheric Research, who wrote about a "systematic effort by some individuals to undermine and discredit the scientific process that has led many scientists working on understanding climate to conclude that there is a very real possibility that humans are modifying Earth's climate on a global scale. Rather than carrying out a legitimate scientific debate... they are waging in the public media a vocal campaign against scientific results with which they disagree".[19] The position of the lead author of Chapter 8, Benjamin D. Santer, was supported by fellow IPCC authors and senior figures of the American Meteorological Society and University Corporation for Atmospheric Research.[19] In 1997, Paul Edwards and IPCC author Stephen Schneider published a paper rebutting criticisms of the IPCC report.[20]

Debate over value of a statistical life

The Second Assessment Report was controversial in its treatment of the economic value of human life.[21][22][23][24][25][26] In environmental economics, it is customary to value the health impacts of climate change on the basis of willingness to pay for risk reduction. An advantage of this method is that health risks of climate change are treated like any other health risk. Some have commented on the difficulty of calculating the costs of climate change impacts such as human mortality.[27][28][29] For example, in calculations based on risk reduction, the value of a statistical life is assessed to be much higher in rich countries than in poor countries.

This information was presented in the full Second Assessment Report, however, dispute arose over the Report's Summary for Policymakers. The Summary for Policymakers (SPM) is prepared with the input of government delegates and IPCC experts. Governments were unhappy with the cost-benefit valuation of human life, and this was implied in the SPM. David Pearce, the IPCC convening lead author who oversaw the relevant chapter of the Report, officially dissented on this summary, commenting that:[30]

The relevant chapter [of the Report] values of statistical life based on actual studies in different countries. Whether the values used remain as in Chapter 6 or whether a common global average is used makes no difference to the results. What the authors of Chapter 6 did not accept, and still do not accept, was the call from a few [government] delegates for a common valuation based on the highest number for willingness to pay.

Michael Grubb, a lead author for several IPCC reports,[31] later commented:[32]

Many of us think that the governments were basically right. The metric [used by Pearce] makes sense for determining how a given government might make tradeoffs between its own internal projects. But the same logic fails when the issue is one of damage inflicted by some countries on others: why should the deaths inflicted by the big emitters — principally the industrialised countries — be valued differently according to the wealth of the victims' countries?

Third assessment report

The Third Assessment Report (TAR) consists of four reports, three of them from its working groups:

The "headlines" from the Summary for Policymakers[37] in The Scientific Basis were:

  1. An increasing body of observations gives a collective picture of a warming world and other changes in the climate system (The global average surface temperature has increased over the 20th century by about 0.6 °C; Temperatures have risen during the past four decades in the lowest 8 kilometers of the atmosphere; Snow cover and ice extent have decreased)
  2. Emissions of greenhouse gases and aerosols due to human activities continue to alter the atmosphere in ways that are expected to affect the climate (Anthropogenic aerosols are short-lived and mostly produce negative radiative forcing; Natural factors have made small contributions to radiative forcing over the past century)
  3. Confidence in the ability of models to project future climate has increased (Complex physically based climate models are required to provide detailed estimates of feedback and of regional features. Such models cannot yet simulate all aspects of climate (e.g., they still cannot account fully for the observed trend in the surface-troposphere temperature difference since 1979) and there are particular uncertainties associated with clouds and their interaction with radiation and aerosols. Nevertheless, confidence in the ability of these models to provide useful projections of future climate has improved due to their demonstrated performance on a range of space and time-scales.[38])
  4. There is new and stronger evidence that most of the warming observed over the past 50 years is attributable to human activities
  5. Human influences will continue to change atmospheric composition throughout the 21st century
  6. Global average temperature and sea level are projected to rise under all IPCC Special Report on Emissions Scenarios

The TAR estimate for the climate sensitivity is 1.5 to 4.5 °C; and the average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100, and the sea level is projected to rise by 0.1 to 0.9 meters over the same period. The wide range in predictions is based on scenarios that assume different levels of future CO2 emissions. Each scenario then has a range of possible outcomes associated with it. The most optimistic outcome assumes an aggressive campaign to reduce CO2 emissions; the most pessimistic is a "business as usual" scenario. Other scenarios fall in between.[citation needed]

IPCC uses the best available predictions and their reports are under strong scientific scrutiny. The IPCC concedes that there is a need for better models and better scientific understanding of some climate phenomena, as well as the uncertainties involved. Critics assert that the data is insufficient to determine the real importance of greenhouse gases in climate change. Sensitivity of climate to greenhouse gases may be overestimated or underestimated because of flaws in the models and because the importance of some external factors may be misestimated. The predictions are based on scenarios, and the IPCC did not assign any probability to the 35 scenarios used.[citation needed]

Economic growth estimates debate

Castles and Henderson asserted that the IPCC's use of market exchange rates in the Special Report on Emissions Scenarios to convert GDP measures into a common currency is inappropriate, and that, for most countries a Purchasing Power Parity conversion would yield higher estimates of income. It follows that the rate of growth implied by an assumption of income convergence is higher if exchange rate conversions are used. They imply that this is likely to produce biased projections of emissions.[39] Nebojsa Nakicenovic et al. claim that this is incorrect because, provided an internally consistent procedure is used, projections of emissions are unaffected by the choice of index number used to measure GDP.[40] See the discussion under Special Report on Emissions Scenarios.

Physical modeling debate

MIT professor Richard Lindzen, one of the lead authors of the IPCC Working Group I Report, has criticised the IPCC Summary for Policymakers document before the U.S. Senate Committee on Commerce, Science and Transportation. Taking Chapter 7, Physical Processes, on which he worked, he said that it "found numerous problems with model treatments – including those of clouds and water vapor", the chapter was summarized in the single sentence "Understanding of climate processes and their incorporation in climate models have improved, including water vapor, sea-ice dynamics, and ocean heat transport."[41]

Sir John Houghton, former Chair of the IPCC Working Group I Report, has commented on Lindzen's criticisms of the IPCC:,[42] saying that Lindzen, having previously expressed satisfaction with the report, had "gone on to express his view that the conclusions of the Policymakers Summary did not faithfully represent the chapters. But he has never provided any supporting evidence for that statement." He emphasized that the Policymaker's Summaries were "agreed unanimously at intergovernmental meetings involving over 200 government delegates from around 100 countries...after several days of scientific debate (only scientific arguments not political ones are allowed) the main purpose of which is to challenge the scientific chapter authors regarding the accuracy, clarity and relevance of the summary and most especially its consistency with the underlying chapters."

Fourth assessment report

The four SRES scenario families[43][44][45] of the Fourth Assessment Report vs. associated changes in global-mean temperature until 2100
more economic focusmore environmental focus
(homogeneous world)
rapid economic growth
(groups: A1T/A1B/A1Fl)
1.4 – 6.4 °C
global environmental sustainability 
1.1 – 2.9 °C
(heterogeneous world)
regionally oriented
economic development

2.0 – 5.4 °C
local environmental sustainability
1.4 – 3.8 °C

The Fourth Assessment Report (AR4) was completed in early 2007.[46] Like previous assessment reports, it consists of four reports, three of them from its working groups.

Working Group I dealt with the "Physical Science Basis of Climate Change." The Working Group I Summary for Policymakers (SPM) was published on 2 February 2007[47] and revised on 5 February 2007.[48] There was also a 2 February 2007 press release.[49] The full WGI report[50] was published in March. The key conclusions of the SPM were that:[47]

An outline of chapters in the WGI report (from 2005)[51] and a list of the report's authors (as of 10 March 2005 (2005 -03-10))[52] were made available before publication of the SPM.

The Summary for Policymakers for the Working Group II[53] report was released on 6 April 2007.[54] The Summary for Policymakers for the Working Group III report[55] was released on 4 May 2007. The AR4 Synthesis Report (SYR) was released on 17 November 2007.

People from over 130 countries contributed to the IPCC Fourth Assessment Report over the previous 6 years. These people included more than 2500 scientific expert reviewers, more than 800 contributing authors, and more than 450 lead authors.[56]

Of these, the Working Group 1 report (including the summary for policy makers) included contributions by 600 authors from 40 countries, over 620 expert reviewers, a large number of government reviewers, and representatives from 113 governments.[57]

Fifth assessment report

The IPCC is currently starting to outline its Fifth Assessment Report (AR5) which will be finalized in 2014. As it has been the case in the past, the outline of the AR5 will be developed through a scoping process which involves climate change experts from all relevant disciplines and users of IPCC reports, in particular representatives from governments. As a first step, experts, governments and organizations involved in the Fourth Assessment Report have been asked to submit comments and observations in writing. These submissions are currently being analysed by members of the Bureau. The scoping meeting of experts to define the outline of the AR5 took place on 13–17 July 2009. The outline was submitted to the 31st Session of the IPCC held in Bali, Indonesia, 26–29 October 2009.[58]

Special reports

In addition to climate assessment reports, the IPCC is publishing 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.[59]

Special report on renewable energy sources and climate change mitigation (SRREN)

This report assesses existing literature on the future potential of renewable energy for the mitigation of climate change. It covers the six most important renewable energy technologies, 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.[60][59]

Special Report on managing the risks of extreme events and disasters to advance climate change adaptation (SREX)

The report 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 SREX.[61][59]

Methodology reports

Within IPCC the National Greenhouse Gas Inventory Program develops methodologies to estimate emissions of greenhouse gases.[62] 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:

Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories

The 1996 Guidelines for National Greenhouse Gas Investories provide the methodological basis for the estimation of national greenhouse gas emissions inventories.[63] 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 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.[clarification needed][64] 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.[65]


The 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.[4]

In April 2006, the IPCC released the IPCC Fourth Assessment Report or AR4.[66] Reports of the workshops held so far are available at the IPCC website.[67]

The AR4 Synthesis Report (SYR) was finalized in November 2007. Documentation on the scoping meetings for the AR4 are available[72] as are the outlines for the WG I report [73] PDF (11.5 KB) and a provisional author list [74] PDF (108 KB).

While the preparation of the assessment reports is a major IPCC function, it also supports other activities, such as the Data Distribution Centre[75] and the National Greenhouse Gas Inventories Programme,[76] 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 Prize

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.[77]


Various criticisms have been raised, both about the specific content of IPCC reports, as well as about the process undertaken to produce the reports. On 13 March 2010, an open letter, signed by over 250 scientists in the United States, was sent to U.S. federal agencies that "None of the handful of mis-statements (out of hundreds and hundreds of unchallenged statements) remotely undermines the conclusion that 'warming of the climate system is unequivocal' and that most of the observed increase in global average temperatures since the mid-twentieth century is very likely due to observed increase in anthropogenic greenhouse gas concentrations."[78] In 2010, an independent investigation into the IPCC recommended that the body focus more on explaining the science behind any changes in global temperature, and less on lobbying activities.[79]

Projected date of melting of Himalayan glaciers

A 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 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.[80]

Watson criticism

Former IPCC chairman Robert Watson has said "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".[81] 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".[82]

Emphasis of the "hockey stick" graph

Figure 1(b) from the Intergovernmental Panel on Climate Change Third Assessment Report
Comparison of MBH99 40 year average from proxy records, as used in IPCC TAR 2001 (blue), with 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).[83] Also shown, Moberg et al. 2005 low frequency signal (black).

The third assessment report (TAR) prominently featured[84] a graph labeled "Millennial Northern Hemisphere temperature reconstruction" from 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 differed from a schematic in the 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 vineyards in England.[83])

The appearance of MBH99 in the Third Assessment Report was widely construed as demonstrating that the current warming period is exceptional in comparison to temperatures between 1000 and 1900. Criticism of the graph in a much disputed paper by Soon and Baliunas was picked up by US Republican senator James Inhofe. He called global warming a "hoax" in a Senate speech, and this became a focus of political debate. The methodology used to produce the "hockey stick graph" was criticized in a paper by Stephen McIntyre and Ross McKitrick.[85]

A National Academy of Sciences inquiry requested by the United States Congress agreed that there were some statistical failings, but these had little effect on the graph, which was generally correct. The graph has been validated by more than 12 reconstructions producing broadly similar results.[86] In a 2006 letter to Nature, Mann, Bradley and Hughes pointed out that their original article had said that "more widespread high-resolution data are needed before more confident conclusions can be reached" and that the uncertainties were "the point of the article."[87]

Conservative nature of IPCC reports

Some critics have contended that the IPCC reports tend to underestimate dangers, understate risks, and report only the "lowest common denominator" findings.[88]

On 1 February 2007, the eve of the publication of IPCC's major report on climate, a study was published suggesting that temperatures and sea levels have been rising at or above the maximum rates proposed during the last IPCC report in 2001.[89] 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.[90][91]

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."[92]

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.[93]

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 Pachauri, who was seen at the time as more mild-mannered and industry-friendly.[94][95]

IPCC processes

In 2005, the UK House of Lords Select Committee on Economic Affairs (of which Nigel Lawson, the noted climate sceptic, was a member) produced a report on the economics of climate change. It commented on the IPCC process:

We have some concerns about the objectivity of the IPCC process, with some of its emissions scenarios and summary documentation apparently influenced by political considerations. There are significant doubts about some aspects of the IPCC's emissions scenario exercise, in particular, the high emissions scenarios. The Government should press the IPCC to change their approach. There are some positive aspects to global warming and these appear to have been played down in the IPCC reports; the Government should press the IPCC to reflect in a more balanced way the costs and benefits of climate change. The Government should press the IPCC for better estimates of the monetary costs of global warming damage and for explicit monetary comparisons between the costs of measures to control warming and their benefits. Since warming will continue, regardless of action now, due to the lengthy time lags.

The Economics of Climate ChangePDF

The Stern Review ordered by the UK government, whose findings were released in October 2006, made a stronger argument in favor of urgent action to combat human-made climate change than previous analyses, including some by IPCC. The conclusions of the Stern Review have been contested, however.[96]

The structural elements of the IPCC processes have been criticized in other ways, with the design of the processes during the formation of the IPCC making its reports prone not to exaggerations, but to underestimating dangers, under-stating risks, and reporting only the "least common denominator" findings which by design make it through the bureaucracy. As noted by Spencer Weart, Director of the Center for History of Physics at the American Institute of Physics,

The Reagan administration wanted to forestall pronouncements by self-appointed committees of scientists, fearing they would be 'alarmist.' Conservatives promoted the IPCC's clumsy structure, which consisted of representatives appointed by every government in the world and required to consult all the thousands of experts in repeated rounds of report-drafting in order to reach a consensus. Despite these impediments the IPCC has issued unequivocal statements on the urgent need to act.[97]

Climatologist Judith Curry, who supports the scientific conclusions of the IPCC reports generally, has publicly criticized aspects of the IPCC's process, expressions of certainty, and treatment of dissent.[98]

Outdatedness of reports

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

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.[100] 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,[101] and added, "that means you better start with intervention much earlier".[102]

Burden on participating scientists

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.[103] Concerns have been raised that the large uncompensated time commitment and disruption to their own research may discourage qualified scientists from participating.[104]

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.[105]

Proposed organizational overhaul

In February 2010, in response to controversies regarding claims in the Fourth Assessment Report,[106][107] 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.[108][109] Other recommendations included that the panel employ a full-time staff and remove government oversight from its processes to avoid political interference.[110]

InterAcademy Council review

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.[111][112] The IAC panel, chaired by Harold Tafler Shapiro, convened on 14 May 2010 and released its report on 1 September 2010.[105][113]

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.[114]

The panel also advised that the IPCC avoid appearing to advocate specific policies in response to its scientific conclusions.[115] 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".[116]

Endorsements of the IPCC

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

See also


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Further reading

External links

Awards and achievements
Preceded by
Grameen Bank
Muhammad Yunus
Nobel Peace Prize Laureate
with Al Gore

Succeeded by
Martti Ahtisaari