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aerosols due to human activities continue to alter the atmosphere "Reshaping the Theory of Cloud Formation" by R. J. Charlson et in ways that are expected to affect the climate." This statement —al., Science, June 15, 2001.) reflects a false certainty. Whether or not human emissions will If, as the UN IPCC states quite clearly and correctly, an ability affect climate is obviously a matter of great debate. What fol- to project future climate requires an understanding of the effect of lows, however, are some incredible omissions. aerosols, then we simply do not have that ability. Yet the IPCC The role of aerosols is explained as follows: "A negative radia- does project future climates, based on various scenarios. tive forcing, which can arise from an increase in some types of How does the UN IPCC deal with our profound lack of under- aerosols (microscopic airborne particles), tends to cool the sur- standing of aerosol forcings? The answer lies in an incredible face... Characterisation of these climate forcing agents and _ footnote on page 13, specifically footnote 11. In the preceding their changes over time...is required to understand past climate text, the IPCC says this: "The globally averaged surface tempera- changes in the context of natural variations and to project what _ ture is projected to increase by 1.4 to 5.8°C...over the period climate changes could lie ahead. Figure 3 shows current esti- 1990 to 2100. These results are for the full range of 35 SRES sce- mates of the radiative forcing due to increased concentrations of —_ narios, based on a number of climate models." Footnote 11 atmospheric constituents and other mechanisms." amends this 1.4 to 5.8°C projection as follows: "This range does This text states quite clearly and correctly that an ability to not include uncertainties in the modelling of radiative forcing, predict future climate (if that is even possible) requires an __e.g., aerosol forcing uncertainties." understanding of the effect of aerosols. The So the UN IPCC has simply ignored the last sentence says that "current estimates of the very large aerosol uncertainties. No reason is radiative forcing" of aerosols are shown in given—but if these uncertainties were includ- figure 3. This sentence is false. In fact, not ed, some of the scenarios would yield projec- only are the estimated uncertainties in aerosol tions of future cooling, not warming. Perhaps forcings not shown, they are also excluded the UN IPCC does not want to admit the pos- from the projections of future climate. These Human greenhouse sibility that there may be no warming at all, or are major omissions. Icey actual cooling. Figure 3 shows estimated forcings for five gas (GHG) EMISSIONS In any case, it is clear that the entire issue classes of aerosols. For four of these classes area tiny fraction of of aerosol uncertainty has been omitted from where is also a vertical error bar which the natural emissions. the WGI SPM, and the language of the key legend explains "indicates a range of estimates, figure has been changed. Far worse, howev- guided by the spread in the published values of er, is that the effect of this uncertainty has frames a pss weaning’ The fact that the vast | = dlr smd inthe moe "Level of Scientific Understanding". not to see this as scientific fraud. One class is labelled "low" and the other four are labelled "very low". No explanation of these uncertainty levels is provided. However, in the UN IPCC's 1995 Second Assessment Report, an earlier version of this same figure appears as figure 2.16 on page 117. Here it is explained that the levels "low" and "very low" are "our subjective confidence that the actual forcing lies within this error bar". In fact, the "The rate of increase of atmospheric levels are headed "Level of CO), concentration has been about 1.5 Confidence", not "Level of Scientific Understanding". ppm (0.4%) per year over the past two decades. During the 1990s In plain language, this means that the chances that the aerosol the year-to-year increase varied from 0.9 ppm (0.2%) to 2.8 ppm forcings actually lie within the error bars are very low in most _—_ (0.8%). A large part of this variability is due to the effect of cli- majority of all greenhouse gas emissions are natural is ignored. Natural GHG Emissions Human greenhouse gas (GHG) emis- sions are a tiny fraction of natural emis- sions. The fact that the vast majority of all greenhouse gas emissions are natural is ignored. The discussion of GHG emissions on UN IPCC WGI SPM page 7 contains these three sequential paragraphs: cases. Conversely, it is very likely that the actual forcings lie out- mate variability (e.g., El Nifio events) on CO, uptake and release side these error bars. What, then, is the likely range for these by land and oceans. forcings? We are not told. In fact, the very issue, which was at "The atmospheric concentration of methane (CH,) has least alluded to in the IPCC SAR, has now been entirely omitted. increased by 1060 ppb (151%) since 1750 and continues to The truth is that the possible range of forcings is very large, increase. The present CH, concentration has not been exceeded much larger than the error bars show. Therefore, the range of | during the past 420,000 years. The annual growth in CHy aerosol forcings is much larger than the ranges for the greenhouse concentration slowed and became more variable in the 1990s, gases, which are shown to have a "high" level of scientific under- compared with the 1980s. Slightly more than half of current standing. If the correct error bars for aerosols were shown—bars CH, emissions are anthropogenic (e.g., use of fossil fuels, cattle, that display the likely range of forcings—they would be seen to _ rice agriculture and landfills). In addition, carbon monoxide (CO) overwhelm the greenhouse gas forcings. emissions have recently been identified as a cause of increasing In short, we simply do not understand aerosol forcing. In fact, a CH, concentration. recent paper in the journal Science claims that the range of "The atmospheric concentration of nitrous oxide (N,O) has possible forcings is as much as twice the very large range that is increased by 46 ppb (17%) since 1750 and continues to increase. not shown in the TAR. This indicates that our understanding of | The present N,O concentration has not been exceeded during at aerosol forcing is diminishing as research proceeds. (See __ least the past thousand years. About a third of current N,O Human greenhouse gas (GHG) emissions are a tiny fraction of natural emissions. majority of all greenhouse gas emissions are natural is ignored. NEXUS ¢ 27 The fact that the vast OCTOBER — NOVEMBER 2002 www.nexusmagazine.com