by Craig D. Idso, Robert M. Carter, S. Fred Singer, and Willie Soon:
Introduction
The United Nations’ Intergovernmental Panel on Climate Change (IPCC) released a final version of the Summary for Policymakers (SPM) of its Fifth Assessment Report on September 27, 2013. It differs in important ways from a draft SPM dated June 2013 that circulated widely in the preceding months.
As discussed below, the new SPM reveals the IPCC has retreated from at least 11 alarmist claims promulgated in its previous reports or by scientists prominently associated with the IPCC. The SPM also contains at least 13 misleading or untrue statements, and 11 further statements that are phrased in such a way that they mislead readers or misrepresent important aspects of the science.
Two weeks before the IPCC released its report, an alternative perspective was presented by a different group of scientists, the Nongovernmental International Panel on Climate Change (NIPCC) (Idso et al., 2013). Unlike the IPCC, NIPCC’s charter is to investigate the causes and consequences of climate change “in the round,” or from all perspectives, rather than to search only for evidence of a human impact on climate. The NIPCC report, titledClimate Change Reconsidered II: Physical Science contradicts many of the IPCC’s findings.
The IPCC has retreated from at least 11 alarmist claims promulgated in its previous reports or by scientists prominently associated with the IPCC. The SPM also contains at least 13 misleading or untrue statements, and 11 further statements that are phrased in such a way that they mislead readers or misrepresent important aspects of the science.
In the discussion that follows, IPCC quotations are identified by their page number in the SPM using the same numbering method (e.g., SPM-3) used in the SPM itself. Chapters in the NIPCC report providing evidence contrary to the IPCC’s claims are referenced as “NIPCC, Chapter X.” The NIPCC report and its Summary for Policymakers are available online at www.climatechangereconsidered.org.
1. IPCC Retreats
Eleven statements made in the 2013 SPM apparently retreat from more alarmist positions struck in earlier Assessment Reports or in related research literature. These repositionings are to be welcomed when they move the IPCC’s commentary closer to scientific reality.
1. “The rate of warming over the past 15 years (1998-2012; 0.05 deg. C/decade) is smaller than the trend since 1951 (1951-2012; 0.12 deg. C/decade)” (SPM-3).
The IPCC concedes for the first time that a 15 year-long period of insignificant warming has occurred since 1998 despite a 7% rise in carbon dioxide.
The IPCC concedes for the first time that a 15 year-long period of no significant warming occurred since 1998 despite a 7% rise in carbon dioxide (CO2). It also acknowledges that on a longer (more climatic) time scale the rate of global warming has decelerated since 1951, despite an accompanying 80 ppm or 26% increase in carbon dioxide (312 to 392 ppm).
The statement represents a significant revision in IPCC thinking, because their concern about dangerous warming rests upon the assumption that temperature increases will proceed in parallel fashion with CO2 increases, and not just sometimes or in a stepped fashion. NIPCC, in contrast, has documented that temperatures in the geologic time scale, the twentieth century, and the early twenty-first centuries have not changed in parallel with CO2 levels (NIPCC, Chapter 4).
2. “Continental-scale surface temperature reconstructions show, with high confidence, multi-decadal intervals during the Medieval Climate Anomaly (950-1250) that were in some regions as warm as in the late 20th century” (SPM-4).
IPCC-related scientists have previously argued that the magnitude of the late twentieth century global warming exceeded that of the Medieval Warm Period (MWP). The notorious “hockey stick” featured in the IPCC’s Third Assessment Report, and still visible in the Fourth Assessment Report, appeared to erase the MWP from the historical temperature record by showing little temperature change for thousands of years followed by a sharp rise in the twentieth century.
From an independent survey of paleoclimatic data records, NIPCC found the MWP to have been of near-global extent, and that the magnitude of warming was often similar to or exceeded that observed for the twentieth century from thermometer data (NIPCC, Chapter 4).
3. “It is very likely that the annual mean Antarctic sea ice extent increased … (by) 1.2-1.8% per decade between 1979 and 2012” (SPM-6).
IPCC-related scientists have repeatedly argued that greenhouse gas forcing would cause surface warming and ice melting in both north and south polar regions. There is no a priorireason to suggest that increasing atmospheric CO2 would cause Antarctic sea ice extent to increase, and in fact, this circumstance contradicts the IPCC’s climate model projections. It is a welcome advance that the IPCC now acknowledges the facts relevant to this matter (NIPCC, Chapter 5).
4. The June draft of the SPM contained the statement that “Models do not generally reproduce the observed reduction in surface warming trend over the last 10-15 years”(Section D-1, Draft SPM-10).
Though this statement was removed from the final, published version of the SPM, it remains patently true, as does the fact that IPCC’s climate models have failed to project the lack of warming over the last 15 (now 17) years.
The termination of the late-twentieth century warming phase has two alternative explanations, both of which are referred to on page SPM-10. These are that the now prolonged period of temperature stasis reflects a statistical fluctuation; or, alternatively, that the cessation of warming has been caused by the accumulation of heat in the deep ocean. The IPCC clearly remains ambivalent about which, if either, of these two explanations is correct, and fails to explain how heat can be transferred to the deep ocean without first passing through the shallow ocean, which has not warmed since at least 2003 (Pielke, 2008).
The IPCC fails to explain how heat can be transferred to the deep ocean without first passing through the shallow ocean, which has not warmed since at least 2003.
These confusions aside, IPCC-related scientists have hitherto argued consistently that their computer models provide realistic estimates of future temperature with a reliability that is adequate for use in policy formulation. This is clearly not the case (NIPCC, Chapter 1).
5. “There are … differences between simulated and observed trends over periods as short as 10 to 15 years (e.g., 1998 to 2012)” (SPM-10); “there remains low confidence in the representation and quantification of [cloud and aerosol) processes in models” (SPM-11); and “most models simulate a small downward trend in Antarctic sea ice extent, albeit with larger inter-model spread, in contrast to the small upward trend in observations”(SPM-11).
These statements, which appear in the published version of the SPM, indirectly point to the same conclusion reached under 4 above, i.e., that the IPCC’s models are inadequate to simulate many aspects of the climate system, not just temperature. The IPCC relies heavily on modeling to lend theoretical support to its hypothesis of dangerous CO2-forced warming. The statements listed above represent a significant reduction in confidence of IPCC model projections.
In contrast, NIPCC scientists have consistently been critical of the presumption that climate models are adequate for use in serious forecasting exercises, while at the same time recognizing their undoubted heuristic value.
6. “The reduced trend in radiative forcing (between 1998 and 2012) is primarily due to volcanic eruptions and the timing of the downward phase of the 11-year solar cycle” (SPM-10).
This statement marks the first time the IPCC has acknowledged that solar factors may play a determinative role in short-term climate variability.
This is a critically important concession to the views of the many independent scientists who have concluded that solar effects play a bigger role in controlling climate than does CO2 (NIPCC, Chapter 3).
7. “Equilibrium climate sensitivity** is likely in the range 1.5 deg. C to 4.5 deg. C …”(SPM-11) and “No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies”(SPM-11, fn 16).
The IPCC’s Fourth Assessment Report allocated a range of 2.0 deg. C to 4.5 deg. C for ECS. By now reducing the ECS lower limit to 1.5 deg. C, the IPCC has conceded that less certainty exists than in 2007. Indeed, the climate sensitivity of atmospheric CO2 is now as uncertain as it was in 1979 when a National Academy of Sciences report first established the same range of 1.5 to 4.5 deg. C (Charney et al., 1979). In other words, no refinement has been made in 34 years in determining how much warming is likely to result from a doubling of atmospheric CO2.
In other words, no refinement has been made in 34 years in determining how much warming is likely to result from a doubling of atmospheric CO2.
The decision not to designate a “best estimate” for ECS is unique in IPCC’s history, and a further indication of growing uncertainty. It probably reflects the publication of a number of recent papers (e.g., Aldrin et al., 2012; Ring et al., 2012; Lewis, 2013) in which sensitivity has been estimated from observations to be between 1.2 and 2.0 deg. C, a range that extends below IPCC’s newest estimates.
8. “The transient climate response*** is likely in the range of 1.0 deg. C to 2.5 deg. C … and extremely unlikely greater than 3 deg. C” (SPM-12).
By reducing the bottom of the range of TCR to 1.0 deg. C, the IPCC’s estimate of human-caused warming for the rest of the twenty-first century now overlaps with those many independent scientists who put the response in the range of 0.3 to 1.2 deg. C. (NIPCC, Chapter 1, Section 1.1.5). In setting the top of the range at 3.0 deg. C, the IPCC’s estimate now falls within the range of natural climate variation over the last 6 million years. Because it falls within the warm natural temperature limit that planet Earth has attained recently, any such change (should it actually happen) is unlikely to be “dangerous” (NIPCC, Chapter 1).
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** Equilibrium climate sensitivity (ECS) is the amount of warming expected to result from a doubling of atmospheric CO2 as the climate system tends towards equilibrium (>1,000 years).*** Transient climate response (TCR) is the amount of warming expected to result from a doubling of atmospheric CO2 after 70 years, given a rate of CO2 increase of 1% per year.
9. “It is very unlikely the Atlantic Meridional Overturning Circulation will undergo an abrupt transition or collapse in the 21st century for the scenarios considered” (SPM-17).
The IPCC also indicated in its 2007 report that it was unlikely that the AMOC would collapse because of fresh water input to the ocean from melting ice. However, this did not prevent IPCC-related scientists and environmental lobbyists from arguing in the interim that increasing greenhouse gases might cause major and deleterious changes in ocean circulation. The reiteration of IPCC’s view of low risk, and its agreement in that regard with NIPCC (NIPCC, Chapter 9), is therefore both welcome and important.
10. “Global mean sea level rise for 2081-2100 will likely be in the ranges of 0.26 to 0.55 m for RCP2.6, 0.32 to 0.63 m for RCP4.5, 0.33 to 0.63 m for RCP6.0 and 0.45-0.82 m for RCP8.5” (SPM-18).
The lowest estimate of a 26 cm rise by 2100 is significantly above the 18 cm rise suggested by many independent scientists (based upon an extrapolation of the last century rate of increase as measured by tide gauges). However, the highest estimate of 82 cm by 2100 falls well below the 1.4 m promulgated by IPCC-related scientists like Rahmstorf (2007) and others.
By admitting it has “low confidence” in predictions of more frequent or more extreme droughts and tropical cyclones, IPCC is specifically revoking its previous more alarmist claims.
Overall, these sea-level projections are still high when compared to currently observed trends and the best estimates reported by NIPCC (NIPCC, Chapter 6); at the same time, they are lower than the alarmist forecasts often cited by reporters and environmental advocacy groups.
11. “Low confidence” that damaging increases will occur in either drought or tropical cyclone activity (SPM-23, Table SPM.1).
Many papers by IPCC-related scientists, and also previous Assessment Reports, argued that carbon dioxide forcing would result in dangerous increases in the magnitude or frequency of extreme climatic events including cyclones and droughts. By admitting it has “low confidence” in predictions of more frequent or more extreme droughts and tropical cyclones, IPCC is specifically revoking its previous more alarmist claims.
NIPCC presents extensive evidence that extreme weather events have not become more frequent or intense in the late twentieth and early twenty-first centuries, and also summarizes the theoretical reasons as to why dangerous weather events should actually be less frequent or intense in a modestly warmer world (NIPCC, Chapter 7).
2. Misleading or Untrue Statements
The following 13 statements by the IPCC are written in such a way that although they may be technically true, or nearly true, they are misleading of the actual state of affairs.
1. “Probabilistic estimates of quantified measures of uncertainty in a finding are based on statistical analysis of observations or model results, or both, and expert judgment”(SPM-2).
The IPCC’s use of numeric percentage confidence limits has been widely criticized, as outlined further below. Regarding the “statistical analysis of … model results” we make the following comments.
Weather forecasting methods make successful use of probabilistic ensemble averaging to provide a numerical range of uncertainties for individual forecasts. IPCC’s climate models, however, are not run in this mode, and their ensemble averages are based upon a statistically inadequate and inconsistent number of runs, generally less than five. As discussed by Singer (2013), the chaoticity of modeling can only be overcome by using a large number of runs.
It is obvious also that different climate models in CMIP5 use different parameterizations and adopted forcings in calculating both the present and future climate. No meaningful statistical probability can be derived by averaging such an inhomogeneous set of model outputs, not only in a statistical sampling sense but also from the structural and methodological point of view.
