Qustion: Based on a number of different observations, scientists have developed a theory that human activities contribute significantly to global warming. Which of the following is an observation that was used in the formulation of this theory? Need Assignment Help? • A. The climate of Mars has warmed over the same period as that of Earth. B. A large increase in greenhouse gases has occurred as industrial activity has increased. C. The average temperature of Earth has varied directly with the human population. D. Average sea level increases as average atmospheric temperature increases.