Chapter 11 The Current Solar Minimum and Its Consequences for Climate David Archibald Summa Development Limited Chapter Outline 1. Introduction 277 2. The Current Minimum 278 3. Summary 287 1. INTRODUCTION A number of cycles in solar activity have been recognized, including the Schwabe (11 years), Hale (22 years), Gleissberg (88 years), de Vries (210 years), and Bond (1,470 years) cycles. There is nothing to suggest that cyclic behavior in solar activity has ceased for any reason. Therefore, predicting when the next minimum should occur should be as simple as counting forward from the last one. The last major minimum, the Dalton Minimum from 1798 to 1822, was two solar cycles long e Solar Cycles 5 and 6. Recent Gleissberg minima appear to be the decade 1690e1700, Solar Cycle 13 from 1889 to 1901, and Solar Cycle 20 from 1964 to 1976. A de Vries cycle event, herein termed the Eddy Minimum, has started exactly 210 years after the start of the Dalton Minimum. Friis-Christensen and Lassen theory, using methodology pioneered by Butler and Johhnson at Armagh, can be used to predict the temperature response to the Eddy Minimum for individual climate stations with a high degree of confidence. The latitude of the US-Canadian border is expected to lose a month from its growing season with the potential for un-seasonal frosts to further reduce agricultural productivity. Evidence-Based Climate Science. DOI: 10.1016/B978-0-12-385956-3.10011-7 Copyright Ó 2011 Elsevier Inc. All rights reserved. 277 278 PART j IV Solar Activity 2. THE CURRENT MINIMUM As recently as 2008, there was a wide range in estimated amplitudes for Solar Cycle 24, from Dikpati at 190 and Hathaway at 170 respectively to Clilverd (2005) at 42 and Badalyan et al. (2001) at 50. This enormous divergence in projections of solar activity generated very little interest from the climate science community, despite the large impact it would have on climate (Archibald, 2006, 2007). The basis of Clilverd’s prediction was a model for sunspot number using low-frequency solar oscillations, with periods of 22, 53, 88, 106, 213, and 420 years modulating the 11-year Schwabe cycle. The model predicts a period of quiet solar activity lasting until approximately 2030 fol- lowed by a recovery during the middle of the century to more typical solar activity cycles with peak sunspot numbers around 120. The graphs in Figs. 1e15 show data related to solar activity. Additional data may be found in Archibald (2010). The Eddy Minimum (Fig. 1) has started 210 years after the start of the Dalton Minimum, consistent with it being a de Vries Cycle event. The graph in Fig. 2 shows that Solar Cycles 3 and 4, leading up to the Dalton Minimum, are very similar in amplitude and morphology to Solar Cycles 22 and 23, leading up to the current minimum. The two data sets are aligned on the month of transition between Solar Cycles 4 and 5 and between Solar Cycles 23 and 24. In the absence of a significant change in Total Solar Irradiance over the solar cycle, modulation of the Earth’s climate by the changing flux in galactic cosmic 200 180 Projected 160 Dalton Eddy Minimum Minimum 140 120 100 80 60 4 5 24 25 40 20 0 1701 1731 1761 1791 1821 1851 1881 1911 1941 1971 2001 2031 FIGURE 1 Solar cycle amplitude 1701e2045. Chapter j 11 The Current Solar Minimum 279 180 Solar Cycle 3 Solar Cycle 23 compared to Solar Cycle 4 160 Aligned on month of minimum Solar Cycle 22 140 Solar Cycle 4 120 100 Solar Cycle 23 80 Dalton Minimum 60 Solar Cycle 5 Solar Cycle 6 Solar Cycle Amplitude 40 May 2010 20 0 1777 1781 1785 1789 1793 1797 1801 1805 1809 1813 1817 FIGURE 2 Similarity between precursor cycles. 1.8 Maunder Sporer Minimum Dalton 1.6 Minimum Minimum Decreasing Galactic 1.4 Cosmic Rays 1.2 1.0 0.8 0.6 Modern Little Ice Age 0.4 Warm Period 0.2 0.0 1425 1485 1545 1605 1665 1725 1785 1845 1905 1965 FIGURE 3 Be10 from the Dye 3 ice core, Greenland Plateau. rays was proposed by Svensmark and Friis-Christensen (1997). The Dye 3 Be10 record (Fig.3) shows a correlation between spikes in Be10 and cold periods for the last 600 years. It also shows a steep decline in Be10 in the Modern Warm Period, suggesting a solar origin for this warming. Usokin et al. (2005) found 280 PART j IV Solar Activity 12 Interplanetary Magnetic Field smoothed 27 day average 10 1970s cooling period 8 6 nanoTeslas 4 2 Solar Cycle 20 Solar Cycle 21 Solar Cycle 22 Solar Cycle 23 0 1966 1970 1973 1977 1980 1984 1987 1991 1994 1998 2001 2005 2009 FIGURE 4 Interplanetary Magnetic Field 1966e2010. 300 250 Solar Cycle 23 1970s Cooling Period 200 Projection 150 Solar Flux Units Flux Solar 100 50 F10.7 Flux 1948 - 2020 0 1948 1953 1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008 2013 2018 FIGURE 5 F10.7 flux 1948e2020. that the level of solar activity during the past 70 years is exceptional, and the previous period of equally high activity occurred more than 8,000 years ago. The strength of the Interplanetary Magnetic Field (Fig. 4) has fallen to levels below that of previous solar cycle transitions. What is also interesting in Chapter j 11 The Current Solar Minimum 281 40 aa Index 35 1970s 1868 - 2010 Cooling Period 30 25 20 15 10 Increasing Solar Activity 5 Little Ice Age Modern Warm Period 0 1868 1888 1908 1928 1948 1968 1988 2008 FIGURE 6 The aa Index 1868e2010. 7500 Oulu Neutron Count 23/24 Solar 1964 - 2009 Minimum 21/22 Solar 22/23 Solar 7000 1970s Cooling Minimum Minimum Period 6500 6000 5500 5000 Monthly Average Counts per Minute Data: Sodankyla Geophysical Observatory 4500 1964 1968 1972 1976 1980 1984 1988 1992 1996 2000 2004 2008 FIGURE 7 Oulu, Finland neutron monitor count 1960e2010. this data is the flatness of this solar magnetic indicator during the 1970s cooling period. The F10.7 index (Fig. 5) is a measure of the solar radio flux near the peak of the observed solar radio emission. Emission from the Sun at radio wavelengths 282 PART j IV Solar Activity FIGURE 8 The correlation between solar cycle length and mean annual temperature at Armagh, Northern Ireland. 1.6 1.4 Archangel, Russia rsq = 0.38 1.2 1.0 Correlation = 0.6 degrees/annum 0.8 0.6 0.4 Degrees Celsius 0.2 0.0 -0.2 -0.4 9 9.5 10 10.5 11 11.5 12 12.5 13 Solar Cycle Length Years FIGURE 9 Archangel, Russia e solar cycle length relative to average annual temperature. Chapter j 11 The Current Solar Minimum 283 10.5 Providence, Rhode Island 10.0 rsq = 0.38 9.5 9.0 8.5 Correlation = 0.62 degrees/annum Degrees Celsius 8.0 7.5 7.0 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 Solar Cycle Length Years FIGURE 10 Providence, Rhode Island e solar cycle length relative to average annual temperature. 8.5 Hanover, New Hampshire 8.0 rsq = 0.53 7.5 7.0 6.5 Correlation = 0.73 degrees/annum Degrees Celsius 6.0 5.5 5.0 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 Solar Cycle Length Years FIGURE 11 Hanover, New Hampshire e solar cycle length relative to average annual temperature. 284 PART j IV Solar Activity 12.0 11.5 West Chester, Pennsylvania rsq = 0.29 11.0 10.5 10.0 Degree Celsius 9.5 Correlation = 0.5 degrees/annum 9.0 8.5 8.0 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 Solar Cycle Length Years FIGURE 12 West Chester, Pennsylvania e solar cycle length relative to average annual temperature. 8.5 Portland, Maine 8.0 rsq = 0.49 7.5 7.0 6.5 Degree Celsius 6.0 Correlation = 0.70 degrees/annum 5.5 5.0 9.0 9.5 10.0 10.5 11.0 11.5 12.0 12.5 13.0 Solar Cycle Length Years FIGURE 13 Portland, Maine e solar cycle length relative to average annual temperature. is due primarily to diffuse, non-radiative heating of coronal plasma trapped in the magnetic fields overlying active regions. It is the best indicator of overall solar activity levels and is not subject to observer bias in the way that the counting of sunspots is. The graph above shows the F10.7 flux from 1948 with Chapter j 11 The Current Solar Minimum 285 300 200 17 23 15 21 19 100 0 -100 Solar Cycle Amplitude 20 S.C. 24 S.C. 25 16 22 -200 18 Eddy Minimum -300 1914 1924 1934 1944 1954 1964 1974 1984 1994 2004 2014 2024 2034 2044 FIGURE 14 The ability to look forward using a model of solar activity. 4 Parana River Streamflow 3 2 1 Sunspot Number 0 -1 -2 -3 -4 1909 1919 1929 1939 1949 1959 1969 1979 1989 FIGURE 15 The correlation between the de-trended time series for the Parana River stream flow and sunspot number. a projection to 2020. Note the lower activity of the 1970s cooling period. Activity over the next 10 years is projected to be much lower again.