_____________________________________________________________________________________________________ 1 Geo Systems Infrastructure, Mumbai, India. *Corresponding author: E-mail: vinay78pandey@gmail.com; Chapter 6 Print ISBN: 978-93-91473-26-6, eBook ISBN: 978-93-91473-34-1 Determining the Atmospheric Variation and Future Climate Change: An Approach Based on Paleoclimate Studies Vinay Kumar Pandey 1* DOI: 10.9734/bpi/ciees/v7/11774D ABSTRACT After the industrial revolution in 18 th century, Carbon dioxide (CO2) concentration has been increases rapidly and predicted the impact of global warming. Atmosphere is made up of various gasses and overall compositions of gasses are constant for the development of the ecosystem. Minor variation in the atmospheric composition, impacted the Earth weather and climate pattern. As increase in CO2 and other greenhouse gases absorbed the sun radiation and increase the temperature of earth. During the Paleo-climatic studies it was observed that climate change happened several times in geological past. Atmospheric concentration varies due to various natural reasons. The CO2 concentration was much higher and oxygen was very low during early atmospheric condition. The concentration of CO2 were varies from 7000 part per million (PPM) to 350 PPM, Oxygen (O2) varies 1% to 35%, sea level 450 m high to (-)50 m low from present sea level and Earth average temperature varies between 29°C to 11°C. Sun brightness was varying 95% to 100% compared to present. Earth had faced various warm and cold phases during the geological past. Presently we are (human) living in small time cycle of Earth and its need of study regarding the future climate of earth. Regarding this, trying to discuss Paleo-climatic variation throughout the Geological time, affecting factors and observed that average atmospheric concentration of CO2, O2, Earth’s average temperature and sea level was much higher than present level. Based on observed data, prepared the impact of CO2 & O2 on flora, fauna & natural disaster. Also prepared the line diagram and suggested that atmospheric concentration of CO2, O2, Earth’s average temperature and sea level would be increased naturally in future and affect the ecosystem by various natural way. Keywords: Climate change; Paleo-climate; geological time; atmospheric variation; greenhouse effect. 1. INTRODUCTION Human life evolved only in 315000 years back and development of human society is still going on. Human have natural tendency to know everything in details, accordingly exploring the ecosystem. Every life species has been surviving in a specific weather condition and change according to climatic condition called evolution. Earth was originated approximate 4600 million years (Ma)/ 4.6 billion years (Ga) ago and was very hot with no or little oxygen in the atmosphere. Later on, due to specific location of Earth in solar system and geological activities, atmosphere and organic activities started. Life evolution is very complex and time taken process also depends on atmospheric composition, Earth mean temperature, sea level, vegetation and greenhouse effect of Earth. Various researchers such as Hasiung J [1], Cronin TM [2], Hansen J [3], McInherney FA el al. [4], Hulme Mike [5], Harvey C [6], Ivany LC el at [7] Raible CC et. Al., [8] and others, have tried to discuss the role of atmospheric variation and climate change. The Intergovernmental Panel on Climate Change (IPCC) was set up by the World Meteorological Organization