Anthropogenic climate change refers to the long-term alteration of the Earth’s climate system as a direct result of human activities such as fossil fuel burning, deforestation, industrial emissions, intensive agriculture, and land-use changes. Unlike natural climatic variations which occur over geological timescales, anthropogenic climate change is accelerated and intensified within a few centuries, particularly since the Industrial Revolution. Scientists around the world have identified numerous indicators that provide strong evidence of human-induced climate change. These indicators are drawn from observations of the atmosphere, cryosphere, hydrosphere, and biosphere, and together they paint a coherent picture of how human actions are altering the balance of the Earth’s climate system. Each indicator serves as both a symptom and a measurement tool, allowing researchers and policymakers to assess the scale of the problem and the urgency of mitigation strategies. One of the most direct indicators of anthropogenic climate change is the increase in atmospheric greenhouse gas concentrations. Carbon dioxide, methane, and nitrous oxide are the three major long-lived greenhouse gases released primarily from human activities. The burning of coal, oil, and natural gas for energy is the largest source of carbon dioxide emissions, while methane is released through agriculture, livestock, and fossil fuel extraction. Nitrous oxide is mostly emitted from the use of nitrogen-based fertilizers. Measurements from ice cores demonstrate that current concentrations of these gases are unprecedented in at least 800,000 years. For instance, atmospheric carbon dioxide levels have exceeded 420 parts per million, far above the pre-industrial level of about 280 parts per million. This sharp increase, closely correlated with industrial development and