Water vapor in the earth's upper atmosphere plays a crucial role in the radiative balance, hydrological process, and climate change. Based on the latest moderate-resolution imaging spectroradiometer (MODIS) data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor content declined from 2003 to 2012 (slope b=-0.0149, R=0.893, P=0.0005). The decreasing trend over the ocean surface (b=-0.0170, R=0.908, P=0.0003) is more explicit than that over terrestrial surface (b=-0.0100, R=0.782, P=0.0070), more significant over the Northern Hemisphere (b=-0.0175, R=0.923, P=0.0001) than that over the Southern Hemisphere (b=-0.0123, R=0.826, P=0.0030). In addition, the analytical results indicate that water vapor content are decreasing obviously between latitude of 36°N and 36°S (b=0.0224, R=0.892, P=0.0005), especially between latitude of 0°N and 36°N (b=0.0263, R=0.931, P=0.0001), while the water vapor concentrations are increasing slightly in the Arctic regions (b=0.0028, R=0.612, P=0.0590). The decreasing and spatial variation of water vapor content regulates the effects of carbon dioxide which is the main reason of the trend in global surface temperatures becoming nearly flat since the late 1990s. The spatio-temporal variations of water vapor content also affect the growth and spatial distribution of global vegetation which also regulates the global surface temperature change, and the climate change is mainly caused by the earth's orbit position in the solar and galaxy system. A big data model based on gravitational-magmatic change with the solar or the galactic system is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatio-temporal variations of global water vapor content, vegetation and temperature at large spatio-temporal scale. This comprehensive examination of water vapor changes promises a holistic understanding of the global climate change and potential underlying mechanisms.