Internal variability refers to natural fluctuations or variations in a system that are not caused by external factors such as human activity. In the context of climate change, internal variability refers to changes in temperature and other atmospheric conditions that occur due to complex interactions between different components of the Earth's atmosphere, oceans, land surfaces, and ice. These natural variations can cause short-term fluctuations in global temperatures, but they do not negate the long-term warming trend caused by human activities such as burning fossil fuels and deforestation.