Anytime you conserve energy you are contributing less to the greenhouse effect.
Power companies burn coal and other fossil fuels to generate electricity.
Cars emit toxins into the air. This type of energy consumption contributes to the global warming by releasing greenhouse gasses into the atmosphere. Purchase energy efficient appliances when old appliances fail. Use compact fluorescent lights - they not only save electricity, they last longer and save money in the long run. Don't leave lights on when it's not necessary.