Anthropogenic and Solar Influence on Temperature over Bulgaria

Abstract

The Sun is the main source of energy for all Earth’s geosystems, including climate, weather, mean sea level, winds, precipitation, and etc., mainly through Total Solar Irradiance (TSI), whose variations during solar activity cause various changes on the Earth surface. Climate processes, interactions between atmosphere-and ocean system, various local, regional and global hydrological cycles are the main mediator between solar activity and a number of geophysical processes on the Earth surface. The temperature at the Earth surface is widely used climate index, whose variations consist of significant seasonal oscillations, trend and long-term cycles. The global warming due to greenhouse gases grout produces significant temperature rise in the last decades, while the solar activity cycles drive periodic oscillations of the temperature. The variations of temperature over Bulgaria, due to anthropogenic and solar influences, is investigated by means of several long time series of meteorological observations. The changes of seasonal components of temperature and long-term oscillations are analyzed in narrow frequency bands by means of the Partial Fourier Approximation (PFA). These temperature variations are compared with the corresponding cycles of solar activity. The determined linear trends of temperature rise in the last decades are associated with the anthropogenic factors of the global warming.