Interrelation between variations in the global surface air temperature and solar activity based on observations and reconstructions

Abstract

The key problem of climatic research is related tothe diagnostics of the relative role of natural andanthropogenic factors in modern climate changes. Inthis case, the necessary tools are 3D numerical modelsof the climate with interacting atmosphere, ocean,active layer of soil, cryosphere, and biosphere. Solarand volcanic activities are among the significant factorsinfluencing climatic variations. In this work, we ana-lyzed the interrelation between variations in the globalsurface temperature and solar radiation based on theannual observation and reconstruction data for the 17–20th centuries and the results of numerical experimentswith our 3D global climatic model IAP RAS CM.We used two versions of reconstructions of interan-nual variations in solar radiation [1] (1610–1994) and[2] (1680–1992) without taking other factors intoaccount. Numerical experiments using the IAP RASCM were performed [3–5] for both versions of thereconstructions. It is worth noting that the results of thecomparative analysis of the reconstruction data [1] and[2] reveal notable quantitative differences. For exam-ple, a decrease in the solar constant (with respect to thepresent value) during the Maunder Minimum was equalto 0.24% according to the data in [1] and 0.3% accord-ing to the data in [2]. In the analysis, we also applied thedata of annual global surface air temperature (AGSAT)based on instrumental measurements [6] (1861–2004).The results of numerical experiments using the IAPRAS CM are presented in Fig. 1. According to themodel calculations, the increase in AGSAT by the endof the 20th century (with respect to the Maunder Mini-mum) and in the beginning of the 18th century is ~0.45 Kand ~0.60 K based on reconstructions [1] and [2],respectively. The corresponding values of warming(with respect to the Dalton Minimum) at the boundarybetween the 18th and 19th centuries are equal to 0.55and 0.40 K. These estimates are close to those obtainedusing the global climatic models ECHAM3/LSG [7]and GISS [8]. In the second half of the 20th century, theincrease in the AGSAT in the IAP RAS CM is equal to0.10–0.15 K or 1/6–1/4 of the corresponding warmingbased on observations for that period [6, 9]. The resultsof the calculations indicate that variations in solar activ-ity have made a notable (although not crucial) contribu-tion to global warming in recent decades.We used different methods, in particular, methods ofwavelet and cross wavelet analysis [10, 11] (see also[12]), to carry out a more detailed study of the peculiar-ities of variations in the solar activity and temperatureregime of the earth’s climatic system and their corre-lated variations. Figure 2 shows results of the waveletanalysis of solar radiation based on the data in [1, 2]and the analysis of AGSAT based on the instrumentalmeasurement data [6] (1681–2004). Significant cycleswith periods approximately equal to 11, 50, and 100 yrare characteristic of the time series of solar activityreconstruction. A longer cycle with a period of approx-imately 170–190 yr can also be distinguished.Location and depth of spectral minima are alsoimportant characteristics along with the spectral max-ima. In particular, according to the data in [1], a clear min-imum in solar activity was found at periods of ~140 yr. Inaddition, a weaker minimum at periods two timessmaller (~70 yr) can be distinguished. Close minima(~130–140 and ~65–70 yr) were found in the spectra ofsolar activity from the data in [2]. They are clearer thanthose obtained from the data in [1].Spectral characteristics of AGSAT differ significantlyfrom those obtained for solar activity. The ~50-yr-longcycle is similarly to the spectrum of solar activity. How-ever, it is less significant (with respect to the tempera-