Evidence from Wavelet Lag Coherence for Negligible Solar Forcing of Climate at Multi-year and Decadal Periods

Abstract

Abstract. We examine possible links between solar cycle irradiance variations the large atmospheric circulation systems that affect whole planet's climate. In particular we examine the putative mechanism of solar forcing mediated by changes in induced stratospheric conditions over the polar regions. We test this hypothesis by examining causal links between time series of solar irradiance based on both amplitude and length of the 11-year solar sunspot cycle and indices of Arctic Oscillation AO and ENSO activity. We use a wavelet lag coherence method based on wavelet filtering to examine the significance and magnitude of the phase coherence of the pairs of series in lag-period space. Hence we study the non-linear phase dynamics of weakly interacting oscillating systems. The method clearly shows no link between AO or SOI with solar irradiance at all scales from biannual to decadal. We conclude that the 11-year cycle sometimes seen in climate proxy records is unlikely to be driven by solar forcing.

Influence of solar magnetic activity on the North American temperature record

“…What that data lacks in duration compared to the Central England Temperature record (Johnson, 2009a(Johnson, , 2010a it more than makes up for in breadth of geophysical location. We note that our results are in accord with other investigators (Friis-Christensen and Lassen, 1991;Lean and Rind, 1998;Echer et al, 2009) and contrast with those who have found negligible evidence of solar forcing on Earth's climate (Moore et al, 2006(Moore et al, , 2007Lockwood and Fröhlich, 2007;Li et al, 2009). Most authors, when speaking of the influence of solar forcing on Earth's climate, are actually discussing the effect of changing some model parameters in a simulation of meteorological systems (Shindell et al, 2003;Wagner and Zorita, 2005), whereas here we are discussing a correlation found between independent instrumental observations from the historical record.…”

“…The amount of influence which the solar magnetic cycle has on Earth's climate continues to be a matter of debate (Lean and Rind, 1998;Wagner and Zorita, 2005;Moore et al, 2006Moore et al, , 2007Lockwood and Fröhlich, 2007;Echer et al, 2009;Li et al, 2009;Sitnov, 2009). The intriguing coincidence of the Maunder Minimum (Eddy, 1976;Luterbacher et al, 2001), a period of exceptionally low solar activity as indicated by a dearth of sunspots observed from 1645 and 1715, and the coldest years of the Little Ice Age (Grove, 2001;Mann, 2002), a period of exceptionally low temperatures as observed in Europe, North America, and elsewhere (Kreutz et al, 1997;Johnson et al, 2001;Holmgren et al, 2001) ending in the middle of the 19th century, suggests that the temperature on Earth might display a dependence on the level of solar magnetic activity.…”

Edge adapted wavelets, solar magnetic activity, and climate change

“…Here we find the linear trend holds up until about 1990, after which the observed temperature increases without relation to the magnetic activity. We note that our results are in accord with other investigators [27,28,10] and contrast with those who have found negligible evidence of solar forcing on Earth's climate [29,30,31].…”

“…The properties of our transform menagerie are summarized in Table 2. Let us first consider the responses of the EAWT, the AAWT, and the CCWT to a succession of test signals y k of duration N t = 300 with squared amplitudes A 2 k = [1, 2, 3, 4] and periods P k = [5,30,150,300]. In Figure 10 we display the IIP for each test signal.…”

Recent fire activity in the boreal eastern interior of North America is below that of the past 2000 yr

“…We used the Paul wavelet (order 4) as it is not very localized in frequency space and allows signals that are relatively aperiodic to be included in the analysis (Moore et al. ). The statistical significance level (90%) of the WTC against red noise backgrounds was estimated using Monte Carlo methods with n = 1000 iterations.…”