Microbes in soil play a key role in the global carbon cycle by metabolizing organic matter and releasing over 60 Pg of carbon per year. Since the composition and activities of microbes are strongly influenced by changes in environmental conditions such as temperature, water availability, oxygen penetration, and carbon supply, global climate change may exert climate-microbial feedbacks to accelerate or alleviate GHG emission. In this chapter, we review the direct effects of elevated CO2 together with the indirect effects of temperature rise and precipitation change, and on soil microbial composition and process rates. Furthermore, we suggest several topics that should be addressed in order to better understand the implications of microbial feedback to the future climate.