Carbon is a very common element, present in plants, animals, the atmosphere, ocean, and rocks. It naturally moves between these forms by many processes, learn about some here.
The greenhouse effect is a warming of the earth's surface and lower atmosphere caused by substances which let the sun's energy through to the ground but impede the passage of energy from the earth back into space.
It was the atmospheric part of ENSO - (called the "Southern Oscillation" or "SO"), that first attracted the attention of scientists. It is one of several persistent patterns of high and low pressures around the globe.
