Solar-geomagnetic activity influence on Earth's climate

A long uninterrupted homogeneous data set on the annual mean Sea Surface Temperature (SST) anomaly records as a representative of the Earth's climatic parameter has been analyzed in conjunction with 158 year long time series on the annual sunspot indices, RzRz and geomagnetic activity indices, aaaa for the period 1850–2007. The 11-year and 23-year overlapping means of global (δtg)(δtg) as well as northern (δtn)(δtn) and southern (δts)(δts) hemispheric SST anomalies reveal significant positive correlation with both RzRz and aaaa indices. RzRz, aaaa and δtgδtg depict a similar trend in their long-term variation and both seem to be on increase after attaining a minimum in the early 20th century (∼1905)(∼1905). Whereas the results on the power spectrum analysis by the Multi-Taper Method (MTM) on δtgδtg, RzRz and aaaa reveal periodicities of ∼79–80∼79–80 years (Gleissberg's cycle) and ∼9–11∼9–11 years (Schwabe solar cycle) consistent with earlier findings, MTM spectrum analysis also reveals fast cycles of 3–5 years. A period of ∼4.2∼4.2 years in aaaa at 99% confidence level appears recorded in δtgδtg at ∼4.3∼4.3 years at 90% confidence level. A period of ∼3.6–3.7∼3.6–3.7 years at 99% confidence level found in δtgδtg is correlating with a similar periodic variation in sector structure of Interplanetary Magnetic Field (IMF). This fast cycle parallelism is new and is supportive of a possible link between the solar-modulated geomagnetic activity and Earth's climatic parameter i.e. SST.

Research highlights► Instrumental records of temperature anomalies analyzed in conjunction with sunspot, Rz and geomagnetic, aa indices. ► Significant positive correlation exists between Rz and aa when they are referred to long-term trends. ► Besides the 79 year and 11 year cycle the present investigation has also revealed fast cycle periods of 3–5 years in SST and aa. ► Geomagnetic activity could be a possible link through which solar activity may influence the Earth's climate. ► The Sun has a significant role to play in the long-term and short-term climate change.