Mechanism of Interaction Between Global Terrestrial Net Emissions of Carbon Dioxide and Water Cycle

Under the background of climate change and the utilization of human water and land resources, it is crucial to clarify the interaction mechanism between global carbon emissions and water cycle for the sustainable development of water resources and ecosystems. Taking the carbon water cycle in natural and social systems as the main line, based on causal discovery algorithm and spatial analysis technology, this study constructed a causal chain of “net terrestrial carbon dioxide emissions (NCE), atmospheric carbon dioxide, net terrestrial long-wave radiation, surface temperature, and precipitation/evapotranspiration”, improved the carbon sink coefficient and carbon emission coefficient, and further clarified the mechanism of interaction between carbon emissions and water cycle. The results indicate that the increase of global NCE from 2000 to 2019 is the main factor contributing to the increase of atmospheric carbon dioxide concentration (54.06%); the increase of atmospheric carbon dioxide concentration will cause the sharp increase of net terrestrial long-wave radiation and the obvious rise of temperature, which will accelerate the global water cycle. Global carbon emissions and water cycle have significant interaction mechanisms; the carbon sink coefficient in the equator and the middle and high latitudes of the Northern Hemisphere show a significant decrease trend (10.68%). However, the carbon emission coefficient in the middle and high latitudes of the Northern Hemisphere is the opposite. At present, the carbon sink capacity of the ecosystem is not enough to offset carbon emissions.