Intergovernmental Panel on Climate Change

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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.

Its reports are widely cited and have been highly influential in forming national and international responses to climate change, yet some of the scientists whose work is summarized in these reports have accused the IPCC of bias.

Contents

Aims

The aims of the IPCC are threefold:

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

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.

Publications

As a summary of current peer reviewed and published science, each IPCC report notes areas where the science has improved since the previous report (except the first one, of course), 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 Fourth Assessment Report: AR4

Main article: IPCC Fourth Assessment Report Work on the fourth assessment report (AR4) is well underway [2].

The Working Group I report was published on February 2, 2007 [3]. Its key conclusions were that [4]:

  • Global warming is occurring
  • The probability that this is caused by natural climatic processes is less than 5%
  • The probability that this is caused by human emissions of greenhouse gases is over 90%
  • World temperatures will probably rise by 1.8 to 4�C (3.25 to 7.2�F) during the 21st century and that:
  • Sea levels will probably rise by 28 to 43cm (11 to 17 inches)
  • It is more than 66% certain that there will be an increase in droughts, tropical cyclones and extreme high tides.
  • Both past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rise for more than a millennium.

Working Group II and Working Group III reports are scheduled for early April and early May, respectively. The AR4 Synthesis Report (SYR) is expected to be finalised during the last quarter of 2007.

Author lists and a chapter outline of the WGI report are available [5].

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 headlines from the summary for policymakers in the WG I report [6] 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)
  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

Debate over Climate Change 2001

Castles and Henderson asserted that the IPCC has been using inflated economic growth rates, which result in increased emission estimates. [7] 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.

A few participants in IPCC Working Group I (Science) do not agree with the IPCC reports (of the 120 lead authors, 2 have complained [8]). 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 United States Senate Commerce Committee:

"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. [9].

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.

But all the confidence in chapter 8 is undermined by the numerous unknowns in chapter 7. As the basic science is not understood, models are incomplete and do not reflect reality well. Indeed, descriptions of models include numerous uncertainties and magic numbers used to make the model behave as experimenters expect.[10][11][12]

Supporting Lindzen's claim, that the brief summary's dismissive confidence in the science needed for models seems poorly supported, is in the more detailed WG1 Chapter 7 "Physical Climate Processes and Feedback" Executive Summary:

  • While improved parametrizations have built confidence in some areas, recognition of the complexity in other areas has not indicated an overall reduction or shift in the current range of uncertainty of model response to changes in atmospheric composition.[13]

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 oC 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. Some scientists and scientific organizations have objected and made public comments to that effect.

Politicians such as Bill Clinton and Al Gore (author of Earth in the Balance) have endorsed the report, saying that "the science is settled". Actually, the SAR states that the science has significant problems. This is even visible in the SAR SfP [14] section 4, including that effects due to human activity can't be quantified. This was confirmed when the 2001 TAR reported even more "signficant progress" and showed more or new uncertainties.

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.

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, and the United Nations Conference on Environment and Development (Rio de Jaeiro, 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 Earths 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 stabailise their concentrations at todays levels...
  • Based on current models, we predict: under [BAU] increase of global mean temperature during the [21st] century of about 0.3 oC per decase (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 cliamte 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.

External Links

References

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