Roger A. Pielke Sr. claims that the Working Group I report of IPCC AR4 (2007) contains at least three significant errors - with error meaning "an inaccurate or flawed analysis of the available, scientifically legitimate knowledge available in time of the deadline of AR4". Thus the issue is not whether the statements about the climate are in hindsight wrong or right, but if the assessment provides a reliable account of the knowledge at the time of the assessment. The deadline was in mid 2006.
One error refers to an incomplete account of the drivers of climate change (absorbing aerosols and land-use changes), another relates to a figure caption, and the third to the attribution of recent warm years only to elevated greenhouse gas levels.
On page 2 of the 2007 IPCC Statement for Policymakers (SPM) there is a title "Human and Natural Drivers of Climate Change". The Statement, however, only focuses on a limited subset of these drivers and essentially ignores the findings in the 2005 NRC (US National Research Council) report.
In the SPM IPCC writes "Changes in the atmospheric abundance of greenhouse gases and aerosols, in solar radiation and in land surface properties alter the energy balance of the climate system. These changes are expressed in terms of radiative forcing." and in the IPCC glossary to the WG1 report (page 11), that "For the purposes of this report, radiative forcing is further defined as the change relative to the year 1750 and, unless otherwise noted, refers to a global and annual average value."
However, as summarized in a 2005 US-National Research Council (NRC) report "Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties "Despite all these advantages, the traditional global mean TOA radiative forcing concept has some important limitations, which have come increasingly to light over the past decade. The concept is inadequate for some forcing agents, such as absorbing aerosols and land-use changes, that may have regional climate impacts much greater than would be predicted from TOA [top of the atmosphere] radiative forcing. Also, it diagnoses only one measure of climate change—global mean surface temperature response—while offering little information on regional climate change or precipitation. These limitations can be addressed by expanding the radiative forcing concept and through the introduction of additional forcing metrics. In particular, the concept needs to be extended to account for (1) the vertical structure of radiative forcing, (2) regional variability in radiative forcing, and (3) nonradiative forcing."
The omission of this perspective the 2007 IPCC SPM has misled policymakers and others to conclude that these other heterogeneous climate are secondary to the global average radiative forcings. A number of peer reviewed papers that support this broader perspective, and were available prior tot he cut-off deadline of IPCC 2007 report, that were ignored in that IPCC report are summarized in Pielke (2008). Marland et al. (2003) also provides a recommendation for a broader view that was available for the 2007 IPCC WG1 assessment but this perspective was not discussed in the 2007 IPCC SPM.
The Figure SPM.2 caption in the 2007 IPCC WG1 Statement for Policymakers on page is in error. It reads "Global average radiative forcing (RF) estimates and ranges in 2005. The actual radiative forcings in 2005 must be less than given in Figure SPM.2. IPCC writes otherwise in their footnote, but the caption itself is clearly incorrect. See http://pielkeclimatesci.wordpress.com/2010/06/23/comment-on-an-error-in-a-figure-caption-in-the-statement-for-policymakers-in-the-wg1-2007-ipcc-report/ for more detail.
The conclusion that the “eleven of the… twelve years (1995–2006) rank among the 12 warmest years in the instrumental record of global surface temperature" (since 1850)” and this is due predominately to human added greenhouse gases [Figure SPM.2 and associated text] ignored peer reviewed studies which found a major effect on the land portion of the temperature record due to human caused landscape change (e.g. Marshall et al 2004), as well significant biases and remaining uncertainties in the land portion of the observational record (e.g. Pielke et al 2007). A discussion of a set of remaining uncertainties and biases in the land surface temperature trend record in the U.S. Climate Change Science Program (CCSP) report [which was used in the completion of the 2007 IPCC report] was inappropriately excluded as reported in Pielke (2005) and http://pielkeclimatesci.wordpress.com/2009/11/26/e-mail-documentation-of-the-successful-attempt-by-thomas-karl-director-of-the-u-s-national-climate-data-center-to-suppress-biases-and-uncertainties-in-the-assessment-surface-temperature-trends/.
National Research Council, 2005: Radiative forcing of climate change: Expanding the concept and addressing uncertainties. Committee on Radiative Forcing Effects on Climate Change, Climate Research Committee, Board on Atmospheric Sciences and Climate, Division on Earth and Life Studies, The National Academies Press, Washington, D.C., 208 pp.
Marland, G., R.A. Pielke, Sr., M. Apps, R. Avissar, R.A. Betts, K.J. Davis, P.C. Frumhoff, S.T. Jackson, L. Joyce, P. Kauppi, J. Katzenberger, K.G. MacDicken, R. Neilson, J.O. Niles, D. Dutta S. Niyogi, R.J. Norby, N. Pena, N. Sampson, and Y. Xue, 2003: The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy. Climate Policy, 3, 149-157.
Marshall, C.H. Jr., R.A. Pielke Sr., L.T. Steyaert, and D.A. Willard, 2004: The impact of anthropogenic land-cover change on the Florida peninsula sea breezes and warm season sensible weather. Mon. Wea. Rev., 132, 28-52. http://pielkeclimatesci.wordpress.com/files/2009/10/r-272.pdf
Pielke Sr., R. A., 2005: Public Comment on CCSP Report "Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences". 88 pp including appendices.
Pielke Sr., R.A., C. Davey, D. Niyogi, S. Fall, J. Steinweg-Woods, K. Hubbard, X. Lin, M. Cai, Y.-K. Lim, H. Li, J. Nielsen-Gammon, K. Gallo, R. Hale, R. Mahmood, S. Foster, R.T. McNider, and P. Blanken, 2007: Unresolved issues with the assessment of multi-decadal global land surface temperature trends. J. Geophys. Res., 112, D24S08, doi:10.1029/2006JD008229. http://pielkeclimatesci.wordpress.com/files/2009/10/r-321.pdf
Pielke Sr., R. A., 2008: A Broader View of the Role of Humans in the Climate System is Required In the Assessment of Costs and Benefits of Effective Climate Policy. Written Testimony for the Subcommittee on Energy and Air Quality of the Committee on Energy and Commerce Hearing “Climate Change: Costs of Inaction” – Honorable Rick Boucher, Chairman. June 26, 2008, Washington, DC., 52 pp.