New book finds at least 63% of global warming was due to the Sun

A chapter in the book, Global Warming - Impacts and Future Perspective, published in September 2012, finds that at least 63% of the global warming of the past 400 years was due to an increase in solar activity. According to the authors, "The sudden increases of solar activity that occurred after the 1724 and 1924 solar dynamo transitions have been accompanied by sudden increases of average surface temperature of 0.2ºC and 0.34ºC after 1724 and 1924, respectively. Therefore, out of the total increase in global temperature of ~ 0.8ºC during the past 400 years, less than 0.3ºC may be of non-solar origin, in agreement with previous results." The authors predict a decrease in solar activity during the 21st century will result in global cooling of 0.64ºC over the next 100 years.

[note quote above was edited for clarity]

FIGURE 3.

Solar dynamo transitions in (a) sunspot number maxima (stars) and geomagnetic index at minima (diamonds). The black diamonds indicates the polar cycles at which the transitions occur and the horizontal green line the transition point (93.4 spot, 10.4 nT) level [1]. The letter D indicates the short type Dalton Minimum. The green and black triangles are the predictions from [11] (upper black),[2] (green) and [3] (lower black), respectively. (b): SSC Index and Flare Index (blue line). (c): total solar irradiance, TSI. In (b) and (c) the horizontal green lines are at the average value along the Regular Oscillations episode and the black numbers are the conventional numbering of the strongest maxima occurring after 1924.

FIGURE 7.

Solar dynamo transitions in global surface temperature. The dashed black line is the yearly averages of paleodata [46] in the interval 1610-1849 to which ground based data [47,48] from 1850 onward are pasted (dashed black line) The dashed blue line is satellite UAH MSU lower troposphere temperature data [49] and the thick line are the smoothed values (see text). The vertical lines indicate the dates of occurrence of the four historically documented solar dynamo transition (cf. black diamonds in Figure 3a). The projections of IPCC [50] for the forthcoming twenty years are shown for two cases: one on which the emissions of greenhouse gases would continue at the same rate as today (full) and the other on which it would remain in the actual level (dashed black line).

FIGURE 8.

The secular oscillation in the temperature data of Figure 7. and in TSI of Figure 3c, this last scaled to fit temperature prior 1800.

Solar Dynamo Transitions as Drivers of Sudden Climate Changes

Silvia Duhau¹ and Ernesto A. Martínez²

^[1] Departamento de Física, Facultad de Ingeniería, Universidad de Buenos Aires and Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina

^[2] Dirección General de Cultura y Escuelas, Buenos Aires, Argentina

8. Conclusions

The sudden increases of solar activity that occurred after the 1724 and 1924 solar dynamo transitions, has been accompanied by a sudden increases of average surface temperature of 0,2ºC, and 0.34º after 1724 and 1924, respectively. Therefore, of the total increases of the average temperature level, that was of ~ 0.8ºC along the last 400 years, less than 0.3 º may be of non solar origin, in agreement with previous results [15]

A solar dynamo transition to a new Grand Episode of lower solar activity is occurring, that would be settled at sunspot cycle #24 [1, 14, 15]. It would be alike [37] to the 1724-1924 Regular Oscillations episode. In fact sunspot cycle maximum #24, that would occur at 2013.5, is being the weakest of the last 100 hundred years [13], being alike to sunspot cycle maximum #12 occurring at 1883.

While greenhouse gases emission continued increasing at present, there is a hiatus in temperature increases since 10 years ago. This may be the first indication of the impact of the current solar dynamo transition on climate cooling. However, at latitudes above the 64° (North and South) temperature it is still increasing fast as much as there is a acceleration of the ice-melting since 1980 [52-54] and some models indicates that the ice feedback albedo mechanism due to this acceleration is appreciable at the poles [56] and also at height latitudes [57]. This may indicates that this feedback mechanism is still not well represented in IPCC climate models, since they underestimate Arctic sea ice thinning by a factor of 4 and fail to capture the recent sea ice kinematic acceleration [54]. Or it may indicate that a heating source that mainly operates at the polar cap and high latitudes is still missing in those models, and, as suggested in [9, 10] this source may be solar storms, which after the mid-1970s have duplicated their average intensity and frequency as compared with those occurring at the XIX century.

Natural sources of climate changes has been reviewed here, and from present knowledge of them it was concluded that in the long term (time scales above the semi-secular) the main sources of climate change along the past century were greenhouse gases and solar activity, and that the same would happen along the current, XXI century. The episode of Regular Oscillations in solar activity that is starting by now would endure for the rest of the present millennium [37]. If this prediction and the principal source of polar and high latitudes atmosphere heating were solar storms, the sudden decreases of the geoeffectiveness of solar storms to a 50 % of its values prevailing along the XX century Gran Maximum will lead to global temperature to decreases from the present average level of ~0.2°C to the same level that along the 1724-1924 Regular Oscillation episode, that is -0.44°C. The time that it will take to the climate system to react to current decreases of solar activity sensitively depends on the ice-albedo feedback mechanism that is still not well known. An estimation of this time is possible by observing that is has taken ~150 for the recovering from the Little Ice Age [51, 52]. The fact that the principal solar source of atmosphere heating at the poles and high latitudes has already decreased to its values prevailing prior 1924, allows us estimating that the expected decreases in 0.64°C would occurs in about 100 years. Solar storms has decreased yet to values alike to that prevailing at the XIX century, but TSI will decreases substantially only by sunspot cycle maximum #25 (that will occur at ~2024), a appreciable decreases of temperature would be observed only by 2030.

In the case that the main source of heating of the last 100 years were greenhouse gases [which this paper argues is not the case], the solar activity decreases would contribute with a cooling of only ~0.3°C, and taking into account the projections of temperature from climate models [50], the sudden decreases of solar activity that is going on would mitigate the impact of greenhouse gases on global warming only by the forthcoming 20 years.