The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) to assess the "risk of human-induced climate change". The Panel is open to all members of the WMO and UNEP.

The fact that the IPCC reports are widely cited [1] [2] as supporting material is ample evidence of the respect they have earned within the climate science community [3] [4]. The reports have been highly influential in forming national and international responses to climate change; they are the baseline for the debate. At the same time, a few of the scientists whose work is summarized in these reports have accused the IPCC of bias.

Authors for the IPCC reports are chosen from a list of experts prepared by governments, and participating organisations and the Working Group/Task Force Bureaux, and other experts as appropriate, known through their publications and works ([5], 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).

Contents

1 Aims 2 Activities 3 Publications 3.1 IPCC Third Assessment Report: Climate Change 2001 3.1.1 Debate over Climate Change 2001 3.1.1.1 Economic growth estimates 3.1.1.2 Physical modeling 3.2 IPCC Second Assessment Report: Climate Change 1995 3.2.1 Debate over Climate Change 1995 3.3 IPCC supplementary report, 1992 3.4 IPCC First Assessment Report: 1990 4 Criticism of IPCC 4.1 Christy 4.2 Schneider 4.3 Landsea 4.4 Stott 4.5 Mörner on sea level 4.6 IPCC processes 4.7 Criticism by non scientists 4.7.1 Inhofe 5 External links

Aims

The stated aims of the IPCC are threefold:

1. assess scientific information on climate change
2. assess the impacts of climate change
3. formulate response strategies

It says:

"The role of the IPCC is to assess on a comprehensive, objective, open and transparent basis the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. The IPCC does not carry out research nor does it monitor climate related data or other relevant parameters. It bases its assessment mainly on peer reviewed and published scientific/technical literature." [6]

The IPCC is led by government scientists, but also involves several hundred academic scientists and researchers. It synthesises the available information about climate change and global warming, has published four major reports reviewing the latest climate science, as well as more specialized reports.

The current head of IPCC is Rajendra K. Pachauri, elected in May 2002; previously Robert Watson headed the IPCC.

Activities

The IPCC is currently (August 2004) in the process of preparing the fourth assessment report or AR4 [7]. The working Group I report is due to be finalised during the first quarter of 2007, Working Group II and Working Group III reports in mid-2007. If it is decided to prepare one the AR4 Synthesis Report (SYR) would be finalised during the last quarter of 2007. Documentation on the scoping meetings for the AR4 are available [8] as are the outlines for the WG I report [9] and a provisional author list [10].

While the preparation of the assessment reports is the major IPCC function, it also supports other activities, such as the National Greenhouse Gas Inventories Programme [11] and the Data Distribution Centre [12].

Publications

The IPCC reports are a summary of current 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.

The IPCC published a 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. Each of the assessment reports is in three volumes from the working groups I, II and III. Unqualified, "the IPCC report" is often used to mean the WG I report.

IPCC Third Assessment Report: Climate Change 2001

The most recent IPCC report is Climate Change 2001, the Third Assessment Report (TAR) WG I report. The lead editor was John Houghton.

The "headlines" from the summary for policymakers in the WG I report [13] 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 kilometres 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 feedbacks 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 [14].)
4. There is new and stronger evidence that most of the warming observed over the last 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 SRES scenarios

In its last report, IPCC stated that 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 metres over the same period. The wide range in predictions is based upon several different 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 emssions, while the most pessimistic is a "business as usual" scenario. The more realistic scenarios fall in between.

IPCC predictions are based on the same models used to establish the importance of the different factors in global warming. These models need data about anthropogenic emissions of greenhouse gases and aerosols. These data are predicted from economic models based on 35 different scenarios. Scenarios go from pessimistic to optimistic, and predictions of global warming depend on the kind of scenario considered.

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 available data is not sufficient to determine the real importance of greenhouse gases in climate change. Sensitivity of climate to greenhouse gases may be over-estimated or under-estimated estimated because of some 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.

Debate over Climate Change 2001

Economic growth estimates

Castles and Henderson asserted that the IPCC has been using inflated economic growth rates, which result in increased emission estimates. [15] This was incorrect because IPCC growth and emissions rates were based upon several factors and not only GDP, as rebutted by Nebojsa Nakicenovic et al.

Physical modeling

A few participants in IPCC Working Group I (Science) do not agree with the IPCC reports (of the 120 lead authors, 2 have complained [16]).

A particularly active critic, MIT physicist Richard Lindzen, 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 does not reflect the full document... For example, I worked on Chapter 7, Physical Processes. This chapter dealt with the nature of the basic processes which determine the response of climate, and found numerous problems with model treatments – including those of clouds and water vapor. The chapter was summarized with the following sentence: 'Understanding of climate processes and their incorporation in climate models have improved, including water vapour, sea-ice dynamics, and ocean heat transport.'"

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. [17].

These statements are in turn supported by the executive summary of chapter 8 of the report, which includes:

• Coupled models can provide credible simulations of both the present annual mean climate and the climatological seasonal cycle over broad continental scales for most variables of interest for climate change. Clouds and humidity remain sources of significant uncertainty but there have been incremental improvements in simulations of these quantities.

• Confidence in the ability of models to project future climates is increased by the ability of several models to reproduce the warming trend in 20th century surface air temperature when driven by radiative forcing due to increasing greenhouse gases and sulphate aerosols. However, only idealised scenarios of only sulphate aerosols have been used.

IPCC Second Assessment Report: Climate Change 1995

Climate Change 1995, the IPCC Second Assessment Report (SAR) was finished in 1996. It is split into four parts:

• A synthesis to help interpret UNFCCC article 2.
• The Science of Climate Change (WG I)
• Impacts, Adaptations and Mitigation of Climate Change (WG II)
• Economic and Social Dimensions of Climate Change (WG III)

Each of the last three parts was completed by a separate working group, and each has a Summary for Policymakers (SfP) that represents a consensus of national representatives. The SfP 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)

Debate over Climate Change 1995

Most scientists involved in climate research believe that the IPCC reports accurately summarise the state of knowledge. A few scientists have objected and made public comments to that effect, in fact so few that no-one can find any suitable quote to add in here.

The report formed the basis of negotiations over the Kyoto Protocol.

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.

Dr. 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 his Science and Environmental Policy Project.

In turn, Seitz's comments were vigourously 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 [18].

IPCC supplementary report, 1992

The 1992 supplementary report was an update, requested in the context of the negotiations on the Framework Convention on Climate Change 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.

IPCC First Assessment Report: 1990

The IPCC first assessment report was completed in 1990, and served as the basis of the United Nations Framework Convention on Climate Change (UNFCCC).

The executive summary of the policymakers summary of the WG I report includes:

• We are certain of the following: there is a natural greenhouse effect...; emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases: CO₂, methane, CFCs and nitrous oxide. These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface. The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it.

• We calculate with confidence that: ...CO₂ has been responsible for over half the enhanced greenhouse effect; long-lived gases would require immeadiate reductions in emissions from human activities of over 60% to stabilise their concentrations at today's levels...

• Based on current models, we predict: under [BAU] increase of global mean temperature during the [21st] century of about 0.3 ^oC per decade (with an uncertainty range of 0.2 to 0.5 ^oC per decade); this is greater than that seen over the past 10,000 years; under other ... scenarios which assume progressively increasing levels of controls, rates of increase in global mean temperature of about 0.2 ^oC [to] about 0.1 ^oC per decade.

• There are many uncertainties in our predictions particularly with regard to the timing, magnitude and regional patterns of climate change, due to our incomplete understanding of: sources and sinks of GHGs; clouds; oceans; polar ice sheets.

• Our judgement is that: global mean surface air temperature has increased by 0.3 to 0.6 ^oC over the last 100 years...; The size of this warming is broadly consistent with predicion of climate models, but it is also of the same magnitude as natural climate variability. Thus the observed increase could be largely due to this natural variability; alternatively this variability and other human factors could have offset a still larger human-induced greenhouse warming. The unequivocal detection of the enhanced greenhouse effect is not likely for a decade or more.

In 1991, the SEPP (The Science & Environmental Policy Project) surveyed IPCC contributors and researchers, along with a comparison group of global warming skeptics who had not contributed. [19]

Criticism of IPCC

Christy

Dr. John Christy, professor of Atmospheric Science and Director of the Earth System Science Center at the University of Alabama in Huntsville, and a key contributor to the 1995 IPCC report, participated with the lead authors in the drafting sessions, and in the detailed review of the scientific text. He wrote in the Montgomery Advertiser on February 22, 1998 that much of what passes for common knowledge in the press regarding climate change is "inaccurate, incomplete or viewed out of context."

Many of the misconceptions about climate change, Christy contends, originated from the IPCC's six-page executive summary. It was the most widely read and quoted of the three documents published by the IPCC's Working Group, but, Christy said, it had the "least input from scientists and the greatest input from non-scientists."[20]

Schneider

Dr. Stephen Schneider, an outspoken believer in catastrophic global warming, criticized the IPCC's assumptions in the journal Nature on May 3, 2001. In his article, Schneider asks, "How likely is it that the world will get 6 degrees C hotter by 2100?" That, he said, "depends on the likelihood of the assumptions underlying the projections."

The assumptions, he wrote, are "'storylines' about future worlds from which population, affluence and technology drivers could be inferred." These storylines, he wrote, "gave rise to radically different families of emission profiles up to 2100 - from below current CO emissions to five times current emissions."

Schneider says that he "strongly argued at the time that policy analysts needed probability estimates to assess the seriousness of the implied impacts." In other words, how likely is it that temperatures would go up by 5.8 degrees Celsius, or 1.4 degrees Celsius, which represent the IPCC's respective upper and lower bounds?

But as Schneider wrote, the group drafting the IPCC report decided to express "no preference" for each temperature scenario.

In effect, this created the assumption that the higher bound of 5.8 degrees Celsius appeared to be just as likely as the lower of 1.4 degrees Celsius. "But this inference would be incorrect," said Schneider, "because uncertainties compound through a series of modeling steps."

Schneider's own calculations, which cast serious doubt on the IPCC's extreme prediction, broadly agree with an MIT study published in April of 2001. It found that there is a "far less" than one percent chance that temperatures would rise to 5.8 degrees C or higher, while there is a 17 percent chance the temperature rise would be lower than 1.4 degrees.[21]

Landsea

In January of 2005 Christopher Landsea resigned from work on the IPCC AR4, saying:

"I personally cannot in good faith continue to contribute to a process that I view as both being motivated by pre-conceived agendas and being scientifically unsound. As the IPCC leadership has seen no wrong in Dr. Trenberth's actions and have retained him as a Lead Author for the AR4, I have decided to no longer participate in the IPCC AR4." [22].

Stott

Emeritus professor of biogeography Philip Stott points out in an interview [23] that the used computer models are still inadequate to make predictions about the change of climate. He criticises the IPCC for not having a risk assement, meaning that there is no assement about the likelihood of a scenario really taking place. With regard to the temperature cuve Stott remarks that "in 1200AD Europe was 2 degrees centigrade [Celsius] warmer that it is today", a statement which is not supported by any version of the temperature record of the past 1000 years. In general the expertise of Stott is dubious: "Stott does not appear to have had a single paper published in a scientific journal in the fields in which he most frequently applies this 'expertise', e.g. climate change or tropical ecology." [24]

Stott has also been quoted in a BBC online interview [25], talking about a fundamental "contradiction" of the Kyoto Protocol: "that climate is one of the most complex systems known, yet that we can manage it by trying to control a small set of factors, namely greenhouse gas emissions. Scientifically, this is not mere uncertainty: it is a lie."

Mörner on sea level

Nils-Axel Mörner has been critical of the IPCC TAR sea level chapter. [26]

Mörner, at the time president of the INQUA Commission on Sea Level Changes and Coastal Evolution "reviewed" the IPCC TAR in 2000. Morner disagrees with the IPCC estimate of 0.09 to 0.88 metres between 1990 and 2100 and prefers his own figure of 10 cm ±10 cm.". Morner believes that "All handling by IPCC of the Sea Level questions have been done in a way that cannot be accepted and that certainly not concur with modern knowledge of the mode and mechanism of sea level changes."

IPCC processes

Meteorologist and professor Richard Lindzen also has said that "picking holes in the IPCC is crucial" [27].

"It is strange that the climate reconstruction of Mann has passed both peer review rounds of the IPCC without anyone ever really having checked it. I think this issue will be on the agenda of the next IPCC meeting in Peking in May." (Rob van Dorland, Royal Netherlands Meteorological Institute, 27 January 2005)

"The IPCC is monolithic and complacent, and it is conceivable that they are exaggerating the speed of change." (John Maddox, a former highly-respected editor of the journal Nature, quoted by David Adam in The Guardian, 28 January 2005)

Criticism by non scientists

Inhofe

U.S. Senator James M. Inhofe(R-Oklahoma), Chairman, Committee on Environment and Public Works has been critical of the IPCC. He has made a number of scientifically illiterate speeches that clearly demonstrate his ignorance of the science.

From a Senate floor statement on July 28, 2003:[28]

• According to the U.N.'s Intergovernmental Panel on Climate Change, Kyoto will achieve "stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system."

  What does this statement mean? The IPCC offers no elaboration and doesn't provide any scientific explanation about what that level would be. Why? The answer is simple: thus far no one has found a definitive scientific answer.

• The first IPCC Assessment Report in 1990 found that the climate record of the past century was "broadly consistent" with the changes in Earth's surface temperature, as calculated by climate models that incorporated the observed increase in greenhouse gases.

  This conclusion, however, appears suspect considering the climate cooled between 1940 and 1975, just as industrial activity grew rapidly after World War II. It has been difficult to reconcile this cooling with the observed increase in greenhouse gases.

• After its initial publication, the IPCC's Second Assessment report in 1995 attracted widespread international attention, particularly among scientists who believed that human activities were causing global warming. In their view, the report provided the proverbial smoking gun.

  The most widely cited phrase from the report — actually, it came from the report summary, as few in the media actually read the entire report — was that "the balance of the evidence suggests a discernible human influence on global climate." This of course is so vague that it's essentially meaningless. …

The statement is, of course, not vague at all. It reflects the scientific view that, at that time, it was not possible to definitively attribute the observed warming to human influence, but that the probabilities were in favour of human influence.

• The Third Assessment Report Policymaker's Summary was politicized and radically differed from an earlier draft. For example the draft concluded the following concerning the driving causes of climate change:

  "From the body of evidence since IPCC (1996), we conclude that there has been a discernible human influence on global climate. Studies are beginning to separate the contributions to observed climate change attributable to individual external influences, both anthropogenic and natural. This work suggests that anthropogenic greenhouse gases are a substantial contributor to the observed warming, especially over the past 30 years. However, the accuracy of these estimates continues to be limited by uncertainties in estimates of internal variability, natural and anthropogenic forcing, and the climate response to external forcing."

  The final version looks quite different, and concluded instead: "In the light of new evidence and taking into account the remaining uncertainties, most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations."

  This kind of distortion was not unintentional, as Dr. Lindzen explained before the EPW Committee. He said, "I personally witnessed coauthors forced to assert their 'green' credentials in defense of their statements."

  In short, some parts of the IPCC process resembled a Soviet-style trial, in which the facts are predetermined, and ideological purity trumps technical and scientific rigor.

• The predictions in the summary went far beyond those in the IPCC's 1995 report. In the Second Assessment, the IPCC predicted that the earth could warm by 1 to 3.5 degrees Celsius by the year 2100. The "best estimate" was a 2-degree-Celsius warming by 2100. Both are highly questionable at best.

  In the Third Assessment, the IPCC dramatically increased that estimate to a range of 1.4 to 5.8 degrees Celsius, even though no new evidence had come to light to justify such a dramatic change.

This is of course complete nonsense, as shown by http://www.grida.no/climate/ipcc_tar/wg1/008.htm.

• In fact, the IPCC's median projected warming actually declined from 1990 to 1995. The IPCC 1990 initial estimate was 3.2°C, then the IPCC revised 1992 estimate was 2.6°C, followed by the IPCC revised 1995 estimate of 2.0°C.

  What changed? As it turned out, the new prediction was based on faulty, politically charged assumptions about trends in population growth, economic growth, and fossil fuel use.

  The extreme-case scenario of a 5.8-degree warming, for instance, rests on an assumption that the whole world will raise its level of economic activity and per capita energy use to that of the United States, and that energy use will be carbon intensive. This scenario is simply ludicrous. This essentially contradicts the experience of the industrialized world over the last 30 years. Yet the 5.8 degree figure featured prominently in news stories because it produced the biggest fear effect.

  Moreover, when regional climate models, of the kind relied upon by the IPCC, attempt to incorporate such factors as population growth "the details of future climate recede toward unintelligibility," according to Jerry Mahlman , Director of NOAA's Geophysical Fluid Dynamics Laboratory.

External links

• The IPCC web site
  • IPCC organisation
  • Second Assessment Synthesis Report (pdf)
  • Second Assessment Summary for Policymakers from the Working Group 1 (Science) Report.
• Third Assessment Report
• The IPCC Controversy - from the SEPP
• climate change - What is the IPCC by Jean-Marc Jancovici
• Climate Change - News and information on climate change, alternative energy, global warming and energy efficiency Includes frequent IPCC press releases