The questions in the public sphere — which is my natural subject matter — are whether we’re facing a meltdown or whether it’s all a big hoax. I’m not claiming these are the right questions — I’m claiming these are the questions being debated. You may rightfully think they are false alternatives but the public sphere never was one for avoiding logical fallacies. Recently, I read about James Hansen’s trip to Copenhagen and how he had to have a police escort because of death threats. Recently as well, Steven Mosher has informed us that Steven McIntyre’s safety has been in question.
I’m interested in how we got to this state of things. How is it that the questions are either “Are Deniers Misrepresenting The Science to Delay Action?” or “Are Scientific Fraudsters Perpetrating a Hoax?”
A good place to start is with what each side is saying: What is the position and arguments and evidence produced in the AGW dominant scientific paradigm? What is the position and arguments and evidence of the critics, whether they be skeptics, contrarians or denialists?
I’m going to try taking it one step at a time. A first step is to review the most recent Assessment Report of the IPCC to get an idea of what the IPCC says about the state of the climate in 2007 and then review what the critics say about it.
First, what is the IPCC? (note: all the following is adapted from the IPCC website)
ETA: Tomorrow, besides a post on the modeling forecasts, I’m going to add a post on the origins of the IPCC, which I believe is key to understanding the politicization of climate science. But I want to start with a general overview of what the main debates really are about by laying part of the framework. Since AGW is the dominant scientific paradigm, it is the focal point for debate and analysis. An analysis of the origins of the IPCC and the “discovery of global warming” will then set the stage for the politicization of the science and the development of the battle lines.
- The IPCC was established by the UNEP and WMO to “provide the world with a clear scientific view on the current state of climate change and its potential environmental and socio-economic consequences.”
- The Working Group selects from a list of nominations received from governments and participating organizations the IPCC authors, contributors, reviewers and other experts who will produce the assessment reports.
- The work on the assessment reports is voluntary and the authors etc. are supposed to reflect “a range of views, expertise and geographical background”.
- The IPCC “does not conduct any research nor does it monitor climate related data or parameters.” The authors are expected to “assesses the most recent scientific, technical and socio-economic information produced worldwide relevant to the understanding of climate change.”
- Each chapter in the assessment report has two coordinating lead authors (CLAs), who are responsible for coordinating the chapter, while lead authors (LAs)create the content. There are also contributing authors (CAs) who may offer specific technical information covered in the chapters.
- According to the IPCC, there is a multi-stage review process during which scientists and governments review the documents. Hundreds of scientists and government officials review the documents for accuracy and soundness of the information contained within it. Review editors take all comments into account and review comments are kept archived for a period of 5 years.
- Funding: “The IPCC is funded by regular contributions from its parents’organizations WMO and UNEP, the UNFCCC and voluntary contributions by its member countries.”
Next, onto the 2007 Synthesis Report, which includes the following in the Introduction:
Where uncertainty is assessed qualitatively, it is characterised by providing a relative sense of the amount and quality of evidence (that is, information from theory, observations or models indicating whether a belief or proposition is true or valid) and the degree of agreement (that is,the level of concurrence in the literature on a particular finding). This approach is used by WG III through a series of self-explanatory terms such as: high agreement, much evidence; high agreement, medium evidence; medium agreement, medium evidence; etc.
Where uncertainty is assessed more quantitatively using expert judgement of the correctness of underlying data, models or analyses, then the following scale of confidence levels is used to express the assessed chance of a finding being correct: very high confidence at least 9 out of 10; high confidence about 8 out of 10; medium confidence about 5 out of 10; low confidence about 2 out of 10; and very low confidence less than 1 out of 10. (27)
This is the guide to how the IPCC reports assess uncertainty. This is important to determine if it is under- or over-representing the data.
What does the report claim about the science of climate change?
- Warming is unequivocal and is evident from observations of increases in global air and ocean temperatures, widespread melting of snow and ice and rising global average sea levels.
- 11 of the last 12 years (1995-2006) were the hottest on record for the instrumental record of global average temperature;
- The 100 year linear trend is 0.73 deg C (0.56-0.92), which is larger than in the AR4 of 0.6 deg C (04-0.8), The linear trend for the last 5o years (1956-2005) is 0.13 deg C (0.10- 0.16), which is twice that of 1906 – 2005.
- Average arctic temperatures have increased the most, at twice that of the average rate of the last 100 years.
- Land regions have warmed faster than oceans. Oceans have taken up 80% of the heat added to the system.
- Lower to mid troposphere temperatures show similar rates of warming to the surface temperatures.
- Global average sea levels have risen by an average of 3.1 mm (2.4 – 3.8) per year from 1993 to 2003 and 1.8 mm (1.3-2.3) per year from 1961 to 2003.
- Since 1978, annual average Arctic sea ice extent has shrunk by 2.7% per decade (2.1 – 3.3) with summer decreases of 7.4% (5.0 – 9.8). Maximum areal extent of seasonally frozen ground has decreased by about 7% in the Northern Hemisphere since 1900. Temperatures in the top of the Arctic permafrost have generally increased by up to 3 deg C since 1980s.
From the chapter on Causes of Change:
- Changes in the atmospheric concentrations of GHGs and aerosols, land cover and solar radiation alter the energy balance of the climate system and are drivers of climate change. They affect the absorption, scattering and emission of radiation within the atmosphere and at the Earth’s surface. The resulting positive or negative changes in energy balance due to these factors are expressed as radiative forcing, which is used to compare warming or cooling influences on global climate. (37)
- The atmospheric concentrations of CO2 and CH4 in 2005 exceeded by far the natural range over the last 650,000 years. Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution.(37)
- There is very high confidence that the global average net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W/m2. (37)
- The combined radiative forcing due to increases in CO2, CH4 and NO is +2.3 [+2.1 to +2.5] W/m2 and its rate of increase during industrial era is very likely to have been unprecedented in more than 10,000 years (Figures 2.3 and 2.4). The CO2 radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years.(37-38)
- Anthropogenic contributions to aerosols (primarily sulphate, organic carbon, black carbon, nitrate and dust) together produce a cooling effect, with a total direct radiative forcing of -0.5 [-0.9 to -0.1] W/m2 and an indirect cloud albedo forcing of -0.7 [-1.8 to -0.3] W/m2. Aerosols also influence precipitation.(38)
- In comparison, changes in solar irradiance since 1750 are estimated to have caused a small radiative forcing of +0.12 [+0.06 to +0.30] W/m2, which is less than half the estimate given in the TAR. (38)
- The equilibrium climate sensitivity is a measure of the climate system response to sustained radiative forcing. It is defined as the equilibrium global average surface warming following a doubling of CO2 concentration. Progress since the TAR enables an assessment that climate sensitivity is likely to be in the range of 2 to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values. (38)
- Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG concentrations. This is an advance since the TAR’s conclusion that “most of the observed warming over the last 50 years is likely to have been due to the increase in GHG concentrations” (39)
- is likely that increases in GHG concentrations alone would have caused more warming than observed because volcanic and anthropogenic aerosols have offset some warming that would otherwise have taken place. (39)
I’ll deal with forecasts in a separate post but for now, I wanted to lay out the AGW side and then examine the critics and their response.
This is probably boring material to most readers, but I want to open it up for comments on the main points and issues. Since many of the readers here are skeptics, tips on good pages to read for the critical / skeptic take on the 2007 Synthesis Report are appreciated.
What are the main issues with the report’s findings? What are things to consider?
I have a few issues having to do with the process itself and how the participants are selected and how the document is constructed and vetted, but that’s all for now.
The next post will be on SRES projections and then the Reviewer Comments and what they contain and how they were dealt with.