Karma isn't the only thing! The Carbon Cycle is the cycle by which carbon is exchanged, transferred, and used among Earth's different spheres. Here is an extremely simplified explanation:

Animals absorb carbon dioxide through the plants that they eat. The carbon is then released through decaying plants and animals into the soil, which is when the decomposers break down the remaining matter all while releasing carbon dioxide back into the atmosphere. Also, plants and trees release carbon dioxide into the atmosphere as a product of respiration, as so do humans. Plants then use the carbon dioxide in the atmosphere to perform photosynthesis. Like I said, extremely simplified.

Unfortunately, carbon dioxide is a Greenhouse gas. "Atmospheric CO2 is currently increased by .5 percent every year, and the increase is expected to continue." Global warming is caused when the amount of energy escaping the atmosphere is less than the amount of energy that is being reached by the earth from the sun.

There are so any ways that you can decrease your carbon footprint. Dont know what your footprint is? Check out this websites:
http://www.carbonfootprint.com/calculator.aspx
http://green.msn.com/tools/calculator.aspx


Reference:

Barry W. Barker (2003). Environmental Studies: Concepts, Connections, and Controversies. 2nd ed. Iowa, United States: Kendall/Hunt. 37-38.

Picture: http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/earth_system/carbon_cycle_NASA.jpg