Final answer:
The global climate in the past has changed primarily due to plate tectonics and Milankovitch cycles, affecting the Earth's climate system over millennia. Since the Industrial Revolution, human activities have led to global warming by increasing greenhouse gases, enhancing the greenhouse effect.
Step-by-step explanation:
The global climate has changed in the past due to various natural factors. The two correct factors from the options provided that have contributed to climate change in the past are plate tectonics and Milankovitch cycles. Plate tectonics influence climate over millions of years by affecting the position and shape of the continents and the oceans, helping determine the flow of ocean and air currents, thus impacting the Earth's climate system. On the other hand, the Milankovitch cycles describe changes in Earth's orbit around the sun that impact its climate. These cycles range from 19,000 to 100,000 years and correspond with patterns of climate change, such as the ice ages. Volcanic eruptions can also impact climate by releasing aerosols and gases that may cool the Earth's surface, a phenomenon known as the haze-effect. However, this is usually a short-term effect compared to the extensive timescales of plate tectonics and orbital changes.
Since the Industrial Revolution, global warming largely due to human activities, notably the burning of fossil fuels, has caused a steady increase in greenhouse gases like carbon dioxide. This has led to an enhancement of the greenhouse effect, which traps heat in the Earth's atmosphere, contributing to a rise in the average temperature of the Earth's climate system. Unlike the past natural variations in climate, the recent rapid warming cannot be explained by natural factors alone, and the consensus among scientists is that human actions are the primary cause.