History repeats” goes a popular adage. Thus, by understanding monsoons in the ancient climates that are analogous to what is expected in the future, we can develop more confidence in the prediction of 21st century climate and be prepared accordingly. Monsoons of the distant past are inferred through indirect measurements, called proxies. Proxies suggest that monsoon strength has varied in step with periodic oscillations in the Sun-Earth geometry. These oscillations with periods 23 ky, 41 ky, and 100 ky (years – y, 1000 years - ky) modulate the solar radiation reaching the Earth. The growth and decay of ice sheets and the rise and fall of greenhouse gas concentrations in the atmosphere through the ice ages also modulate the monsoons. An emerging theory of monsoons known as “energetics of monsoons” can decipher the impact of these climate drivers and the ensuing feedbacks. We find that long-term monsoon evolution is determined by only two variables: the net energy flux into the atmosphere and water vapor. Furthermore, we have shown that the energy released by the oceans plays a crucial role in determining the local rainfall over the oceans. The anthropogenic global warming will enhance the moisture content in the atmosphere and lead to an increase in the monsoon rainfall
