Final answer:
The current climate change is unusual compared to earlier climate changes in Earth's history. Earlier changes showed similar patterns and rates, but recent changes cannot be explained by natural causes alone. Human activities, especially the combustion of fossil fuels, explain most of the observed warming.
Step-by-step explanation:
The current climate change is unusual compared to earlier climate changes in Earth's history based on observations and evidence. Earlier changes showed similar patterns and rates, indicating that climate change is not solely driven by human activities. The historical record shows that climate variations prior to the Industrial Revolution can be explained by natural causes such as changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas concentrations.
However, recent changes in climate cannot be explained by natural causes alone. Research indicates that human activities, especially the combustion of fossil fuels, explain most of the observed warming, especially since the mid-20th century. The scientific consensus is clear that humans are changing the global climate by increasing the effects of the greenhouse effect through alterations of the carbon cycle.