In Earth’s history before the Industrial Revolution, Earth’s climate changed due to natural causes not humans. In most cases, global climate has changed because of differences in sunlight. Tiny movements in Earth’s orbit changed when and where sunlight hits the Earth. Differences in the Sun have increased and decreased the amount of solar energy reaching Earth. Volcanic activity has also, in the past, increased greenhouse gases over millions of years which has contributed to global warming. These natural causes still happen today, but their effect is too small or they happen too slowly to explain the increased heat in current decades. We know this because scientists keep track of the natural and human activities that effect climate with satellites
