Abstract
The present study conducted investigations using modern methods of time series analysis to clarify whether the increase of the atmospheric carbon dioxide is related to the observable change of the climate in recent years. The cause-and-effect relationship among the solar activity, atmospheric carbon dioxide in the global scale and global air temperature was investigated through correlation analysis and spectral analysis using time series datasets of them. It was confirmed that the average global air temperature is increasing, and that the air temperature and atmospheric carbon dioxide are significantly correlated with each other. The results of the spectral analysis showed that the variations of the air temperature and atmospheric carbon dioxide have an obvious one-year cycle (seasonal cycle), and that the spectral intensity of the one-year cycle in the air temperature is greater in the polar regions than in low latitudes, while that in the atmospheric carbon dioxide tends to be lower in southward regions.
