The greenhouse effect is a. reduced by photosynthesis, which removes co2 from the atmosphere b. made worse by photosynthesis, which adds co2 to the atmosphere c. reduced by the burning of fossil fuels, which removes oxygen from the atmosphere d. reduced by the addition of co2 to the atmosphere, since co2 removes excess heat from the earth's surface and reflects it back into space e. of little concern, since it is part of the normal cycle for the planet