Ice core data. Note length of glacial cycles averages ~100,000 years. Blue curve is temperature, green curve is CO₂, and red curve is windblown glacial dust (loess).

An average of several samples of δ¹⁸O, a proxy for temperature, for the last 600,000 years

Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the orbit (see Milankovitch cycles).

These orbital changes alter the amount of sunlight reaching the Earth by up to 25% at mid-latitudes. That has a huge effect. The term "forcing" is a physical process which definitely affects the Earth's climate.