Figure Captions

Fig. 1. Atmospheric carbon dioxide, temperature and methane levels for the last 420,000 years as reconstructed from the Vostok ice core, Antarctica (after Petit et al., 1999). Note the remarkable coincidence of timing of variations in atmospheric temperature (middle curve) and the two greenhouse gases. In terms of cause and effect, however, it is apparent at higher resolution that the changes in temperature precede the changes in carbon dioxide by about 800 years (e.g. Mudelsee, 2001).

Fig. 2. Reconstruction of paleo-atmospheric carbon dioxide levels for the last 1800 years inferred from stomatal density in fossil pine needles (Tsuga heterophylla), northwestern USA (after Kouwenberg, 2005, Fig. 5.4). Black line: 3-point running average, based on 305 needles per data point; grey shading: error estimate. Open diamonds and squares indicate, respectively, measurements from the Taylor Dome and Law Dome ice cores, Antarctica. The ice core data represent generalized averages, and appear not to preserve the decadal-centennial changes in atmospheric carbon dioxide indicated by the stomatal measurements.

Fig. 3. Atmospheric carbon dioxide levels for the last 60 million years, reconstructed from leaf stomata, boron isotopes, paleosols, alkenones and the GEOCARB III geochemical model; wide bars at ~1, 22 and 50 million years BP are estimates from the Green River (nahcolite), Beypazari and Searles Lake trona deposits (after Lowenstein and Demicco, 2006, Fig. 1). Despite the variability inherent in estimates using such a wide range of methods, the data indicate enhanced levels of ~1500 ppm in the early Cenozoic, 60 million years ago, declining to a few hundred ppm by 20 million years ago. Modern biota therefore live in a carbon dioxide-impoverished environment compared with their recent ancestors.

Fig. 4. Incremental increase in forcing caused by addition of carbon dioxide to the atmosphere up to a value of 1200 ppm; (inset: data plotted with non-zeroed y-axis, to clarify incremental warming over the 200-500 ppm range). Note that an increase of 4.5 w/m² equates to a temperature increase of ~1⁰ C. Note also the logarithmic relationship between increasing carbon dioxide and total downward radiation flux. Forcing estimated using MODTRANS modelling (graphs courtesy W. Eschenbach).

Fig. 5. Instrumentally measured changes in global temperature for 1861-2000 (thin line), fitted with a cyclic modelled trend of period 64 years (bold line, with error bars for 2000-2030) (after Klyashtorin and Lyubushin, 2003, Fig. 5). Projection of climatic cycling into the 21^st century indicates a predicted cooling trend.

Fig. 6. Combined annual land surface-air and sea surface global temperature anomalies (⁰C) for 1861-2001 relative to a 1961-1990-average baseline, and plotted with the estimated two standard error uncertainty (after IPCC, 2001, Fig. 2). Also plotted, without error bars, is the estimated curve of atmospheric carbon dioxide values over the same period. Note the lack of correspondence between the two curves, and especially that cooling accompanied the marked increase in carbon dioxide emissions between 1950 and 1970.

Fig. 7. Climatic cycling over the last 16,000 years as indicated by averaged 20-year oxygen isotope ratios from the GISP2 Greenland ice core (after NSIDC User Services, 1997 and Davis and Bohling, 2001). Trend lines A-E all extend up to the end of the 20^th century, fitted through the data for the last 16 000, 10 000, 2000, 700 and 100 years, respectively. The trends are indicative of both warming and cooling, depending upon the chosen starting point, and all except E are statistically significant.

Fig. 8. Combined annual land surface-air and sea surface global temperature anomalies (⁰C) for 1980-2005 relative to a 1961-1990-average baseline (data from Climate Research Unit, University of East Anglia). Though a warming of perhaps 0.3⁰ C is recorded between 1980 and 1998 (a marked El Nino year), no warming has occurred in the seven subsequent years despite continued large increases in human-sourced atmospheric carbon dioxide.

Fig. 9. Lower tropospheric temperature anomaly since 1979 as measured by satellite-mounted microwave sounding units (MSU; from http://vortex.nsstc.uah.edu/data/msu/t2lt/tltglhmam_5.2). When the warming effect of El Ninos, and the cooling effect of the El Chichon and Pinatubo volcanic eruptions, are discounted, little if any greenhouse-forced warming is apparent for the last 25 years (Gray, 2006). Note also that these tropospheric measurements agree with the ground-based thermometer series (Figure 8) in recording no significant warming since 1998, and probably none since 1982.

Fig. 10. Oxygen isotope time series for the last 5,000 years, GISP2 Greenland ice core (light line; same dataset as Fig. 7), fitted with a moving average (dark line; after a slide by Andre Illarianov, 2004). The Late 20^th Century Warm Period represents the latest of a regular millennial cycle of similar warm periods (grey stripes). The Late 20^th Century Warm Period may have equalled the magnitude of the Mediaeval Warm Period, but it has not yet attained the warmth of either of the preceding Roman or Minoan Warm Periods.

Fig. 11. Rate of temperature change for the last 48 000 years, in ⁰ C/century, based on the analysis of oxygen isotope ratios from the GISP2 ice core (same dataset as Fig. 7; after a slide by Andre Illarianov, 2004). Note that during the last 9000 years of the Holocene, temperature change occurred regularly at rates between +2.5⁰ and -2.5⁰ C/century. Earlier, during the last glaciation, rates of change as high as 15⁰ C/century are indicated.

Robert Ferguson, President

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