What is the difference in the rate of carbon exchange (in gigatons per year of carbon) between photosynthesis and respiration in the marine environment?

Weathering of rocks proceeds faster in a warmer climate because rainfall amounts tend to be greater. By providing calcium ions, weathering promotes limestone formation and removal of carbon dioxide from the atmosphere; hence, a perturbation of the earth's climate toward the warm side would favor decreasing atmospheric carbon dioxide concentrations, which would tend to return the climate to its original state. In this way, the carbonate-silicate cycle serves as a negative feedback on the temperature of the earth system.