Final answer:
Long-term climate changes on Earth are influenced by variations in Earth's orbit, known as Milankovitch cycles, which include precession, eccentricity, and obliquity. These cycles affect the distribution of sunlight reaching Earth and contribute to natural climate change patterns over tens of thousands to millions of years. They cannot explain recent rapid climate changes.
Step-by-step explanation:
Variations in Earth's orbit that influence long-term climate changes include three significant factors: the wobbling of Earth's axis of rotation (precession), the shape of Earth's orbit (eccentricity), and the tilt of Earth's axis of rotation (obliquity). All of these Milankovitch cycles affect climate change over various time scales.
Eccentricity modifies the earth's distance to the sun, impacting solar radiation receipts and completing a cycle roughly every 100,000 years with longer cycles also present. The obliquity or tilt of Earth's axis fluctuates, affecting seasonal contrasts in sunlight distribution, contributing to climate trends over about 41,000-year cycles with a longer 1.2 million-year cycle as well. Lastly, precession—Earth's axial wobble—affects the seasonal timing of when each hemisphere points towards the sun, with a cycle of about 26,000 years.
These Milankovitch cycles can amplify or dampen climate effects depending on their individual and collective phases. For example, they are thought to be primarily responsible for the periodic ice age cycles experienced by Earth over the past several million years. It's important to note, however, that these cycles operate over very long time scales and therefore cannot explain recent, more rapid changes in Earth's climate.