The second alternative is correct.
The greenhouse effect is a natural phenomenon caused by the concentration of gases in the atmosphere, which form a layer that allows the passage of solar rays and the absorption of heat. This process is responsible for keeping the Earth at a suitable temperature, ensuring the necessary heat.
However, the scientific community has constantly warned that the greenhouse effect has been intensified through human action, through burning and emission of pollutant gases from fossil fuels. In this context, the Earth would be overheating harmful to the environment and in the long run could have dangerous consequences for human life.