  Soil has been recognized as an indirect driver of global warming by
regulating atmospheric greenhouse gases. However, in view of the higher heat
capacity and CO2 concentration in soil than those in atmosphere, the direct
contributions of soil to greenhouse effect may be non-ignorable. Through field
manipulation of CO2 concentration both in soil and atmosphere, we demonstrated
that the soil-retained heat and its slow transmission process within soil may
cause slower heat leaking from the earth. Furthermore, soil air temperature was
non-linearly affected by soil CO2 concentration with the highest value under
7500 ppm CO2. This study indicates that the soil and soil CO2, together with
atmospheric CO2, play indispensable roles in fueling the greenhouse effect. We
proposed that anthropogenic changes in soils should be focused in understanding
drivers of the globe warming.
