Final answer:
The correct statement regarding Earth's past and future climate is that Earth's climate is changing as a result of both natural and human processes.
Step-by-step explanation:
The correct statement regarding Earth's past and future climate is A. Earth's climate is changing as a result of both natural and human processes.
Scientific evidence indicates that Earth's climate has constantly changed throughout its existence, with periods of both warmer and cooler climates. The study of past climates, known as paleoclimatology, provides evidence of these variations. While natural causes like changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas concentrations have influenced climate in the past, recent changes cannot be solely attributed to natural causes. Research suggests that human activities, especially the combustion of fossil fuels, are the primary cause of current climate change.