The Intergovernmental Panel on Climate Change (IPCC) is a scientific body tasked to evaluate the risk of climate change caused by human activity. The panel was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP), two organizations of the United Nations.
The IPCC does not carry out research, nor does it monitor climate or related phenomena. A main activity of the IPCC is publishing special reports on topics relevant to the implementation of the UN Framework Convention on Climate Change (UNFCCC), 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. The IPCC is only open to member states of the WMO and UNEP. IPCC reports are widely cited in almost any debate related to climate change. National and international responses to climate change generally regard the UN climate panel as authoritative.
The summary reports (i.e. Summary for Policymakers), which draw the most media attention, include review by participating governments in addition to scientific review.
The stated aims of the IPCC are to assess scientific information relevant to:
The history of the IPCC is described in a . The IPCC has been chaired by Rajendra Pachauri since 2002.
|The four SRES scenario families of the Fourth Assessment Report vs. associated changes in global-mean temperature until 2100|
more economic focus
more environmental focus
rapid economic growth
1.4 - 6.4 °C
global environmental sustainability
1.1 - 2.9 °C
2.0 - 5.4 °C
local environmental sustainability
1.4 - 3.8 °C
The Fourth Assessment Report (AR4) was completed in early 2007. 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 and revised on 5 February 2007. There was also a 2 February 2007 press release. The full WGI report was published in March. The key conclusions of the SPM were that:
In IPCC statements "most" means greater than 50%, "likely" means at least a 66% likelihood, and "very likely" means at least a 90% likelihood.
An outline of chapters in the WGI report (as of November 3, 2005) and a list of the report's authors (as of March 10, 2005) were made available before publication of the SPM.
The Summary for Policymakers for the Working Group II report was released on April 6, 2007. The Summary for Policymakers for the Working Group III report was released on May 4, 2007. The AR4 Synthesis Report (SYR) was released on November 17, 2007.
The Third Assessment Report (TAR) consists of four reports, three of them from its working groups:
The "headlines" from the Summary for Policymakers in The Scientific Basis were:
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.
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.
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. 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. See the discussion under Special Report on Emissions Scenarios.
MIT professor Richard Lindzen, one of the scientists in IPCC Working Group I, has expressed disagreement with the IPCC reports. He expressed his unhappiness about those portions in the Executive Summary based on his contributions in May 2001 before the U.S. Senate Committee on Commerce, Science and Transportation:
The Summary for Policymakers of the WG1 reports does include caveats on model treatments: 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.
These statements are in turn supported by the executive summary of chapter 8 of the report, which includes:
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:
A December 20, 1995, Reuters report quoted British scientist Keith Shine, one of IPCC's lead authors, discussing the Policymakers' Summary. He said: "We produce a draft, and then the policymakers go through it line by line and change the way it is presented.... It's peculiar that they have the final say in what goes into a scientists' report". It is not clear, in this case, whether Shine was complaining that the report had been changed to be more skeptical, or less, or something else entirely.
Solid-state physicist Frederick Seitz, president emeritus of Rockefeller University and past president of the National Academy of Sciences, has publicly denounced the IPCC report, writing "I have never witnessed a more disturbing corruption of the peer-review process than the events that led to this IPCC report". He opposed it in the Leipzig Declaration of S. Fred Singer's Science and Environmental Policy Project.
In turn, 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
S. Fred Singer disseminated a letter about Chapter 8, asserting that :
Benjamin D. Santer, Convening Lead Author of Chapter 8 of 1995 IPCC Working Group I Report, replied :
The Second Assessment Report was the first and last to include a chapter on the economic impacts of climate change, of which impacts on human mortality are an important part. As is customary in environmental economics, health impacts of climate change are valued on the basis of willingness to pay for risk reduction. The advantage of this method is that health risks of climate change are treated like any other health risk. The disadvantage of this method is that health risks in different parts of the world are valued differently. Specifically, the value of a statistical life is much higher in rich countries than in poor countries. The chapter authored by David Pearce, Amrita Achanta, Bill Cline, Sam Fankhauser, Rajendra Pachauri, Richard Tol, and Pier Vellinga faithfully reflected the state of the art of the literature, but the chapter was attacked: the IPCC was accused of blasphemy and David Pearce's offices were occupied. This chapter is the only instance in which the authors of the chapter officially denounced the policy makers' summary for inaccuracy.
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.
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 BAU increase of global mean temperature during the [21st] century of about 0.3 oC per decade. They judge that: global mean surface air temperature has increased by 0.3 to 0.6 oC 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.
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. Attendance at the 2003 meeting included 350 government officials and climate change experts. After the opening ceremonies, closed plenary sessions were held. The meeting report states there were 322 persons in attendance at Sessions with about seven-eighths of participants being from governmental organizations.
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 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.
There are several major groups:
The IPCC receives funding from UNEP, WMO, and its own Trust Fund for which it solicits contributions from governments.
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 .
In April 2006, the IPCC released the IPCC Fourth Assessment Report or AR4. Reports of the workshops held so far are available at the IPCC website.
While the preparation of the assessment reports is a major IPCC function, it also supports other activities, such as the Data Distribution Centre and the National Greenhouse Gas Inventories Programme , required under the UNFCCC. This involves publishing default emission factors, which are factors used to derive emissions estimates based on the levels of fuel consumption, industrial production and so on.
The IPCC also often answers inquiries from the UNFCCC Subsidiary Body for Scientific and Technological Advice (SBSTA).
There are generally three stages in the review process :
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.
Authors for the IPCC reports are chosen from a list of researchers prepared by governments, and participating organisations and the Working Group/Task Force Bureaux, and other experts as appropriate, known through their publications and works (4.2.1,2). The composition of the group of Coordinating Lead Authors and Lead Authors for a section or chapter of a Report is intended to reflect the need to aim for a range of views, expertise and geographical representation (ensuring appropriate representation of experts from developing and developed countries and countries with economies in transition).
In January 2005 Christopher Landsea resigned from work on the IPCC AR4, saying that he viewed the process "as both being motivated by pre-conceived agendas and being scientifically unsound" because of Kevin Trenberth's public contention that global warming was contributing to recent hurricane activity . Roger A. Pielke who published Landsea's letter writes: "How anyone can deny that political factors were everpresent in the negotiations isn't paying attention", but notes that the actual report "Despite the pressures, on tropical cyclones they figured out a way to maintain consistency with the actual balance of opinion(s) in the community of relevant experts." He continues "So there might be a human contribution (and presumably this is just to the observed upwards trends observed in some basins, and not to downward trends observed in others, but this is unclear) but the human contribution itself has not been quantitatively assessed, yet the experts, using their judgment, expect it to be there. In plain English this is what is called a 'hypothesis' and not a 'conclusion.' And it is a fair representation of the issue.
The third assessment report (TAR) prominently featured a graph labeled "Millennial Northern Hemisphere temperature reconstruction" from a paper by Michael E. Mann, Raymond S. Bradley and Malcolm K. Hughes (MBH98) often referred to as the "Hockey Stick Graph". This graph differed from a schematic in the first assessment report which depicted larger global temperature variations over the past 1000 years, and higher temperatures during the Medieval Warm Period than the present day. (The schematic was not an actual plot of data.) The appearance of MBH98 in the TAR was widely construed as demonstrating that the current warming period is exceptional in comparison to temperatures between 1000 and 1900. The methodology used to produce this graph was criticized in an article by Stephen McIntyre and Ross McKitrick. In a 2006 letter to Nature, Bradley, Hughes and Mann 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.
On February 1, 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. 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 rise was above the top of the range of the IPCC projection.
An example of scientific research which has indicated that previous estimates by the IPCC, far from overstating dangers and risks, has actually understated them (this may be due, in part, to the expanding human understanding of climate, as well as to the conservative bias, noted above, which is built into the IPCC system,) 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 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.
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 Ramstorf, professor of physics and oceanography at Potsdam University as saying:
In his December 2006 book, Hell and High Water: Global Warming, and in an interview on Fox News on January 31, 2007, energy expert Joseph Romm noted that the IPCC Fourth Assessment Report is already out of date and omits recent observations and factors contributing to global warming, such as the release of greenhouse gases from thawing tundra.
Political influence on the IPCC has been documented by the release of a memo by ExxonMobil to the Bush administration, and its effects on the IPCC's leadership. The memo led to strong Bush administration lobbying, evidently at the behest of ExxonMobil, to oust Robert Watson, 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.
Interestingly, 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.
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,
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. However, there has generally been a steady evolution of key findings and levels of scientific confidence from one assessment report to the next.
The submission deadlines for the Fourth Assessment Report (AR4) differed for the reports of each Working Group. Deadlines for the Working Group I report were adjusted during the drafting and review process in order to ensure that reviewers had access to unpublished material being cited by the authors. The final deadline for cited publications was July 24, 2006. The final WG I report was released on April 30, 2007 and the final AR4 Synthesis Report was released on November 17, 2007.
Rajendra Pachauri, the IPCC chair, admitted at the launch of this report that since the IPCC began work on it, scientists have recorded "much stronger trends in climate change", like the unforeseen dramatic melting of polar ice in the summer of 2007, and added, "that means you better start with intervention much earlier".