Climate change is one of the de_ning issues of our time. It is now more certain than ever based onrnmany lines of evidence that humans are changing the earth's climate. The atmosphere and oceans havernwarmed, accompanied by the sea level rise, strong decline in arctic sea ice, and other climate relatedrnchanges. The evidence is clear however, due to the nature of science, not every single detail is everrntotally settled or completely certain nor has every pertinent question yet been answered. Scienti_crnevidence continues to be gathered around the world and assumptions and _ndings about climate changernare continually analyzed and tested. Some areas of active debate and ongoing research include the linkrnbetween the ocean heat content and the rate of warming estimate of how much warming to expectrnin the future and the connection between climate change extreme weather events. The focus of thisrnstudy is aimed to provide a brief over view of climatology at the lower and middle atmosphere, thernatmospheric variables the signi_cance of the composition of the atmosphere and their inuence on lifernon the earth's surface and will extremely deal with the climate system, climate system components,rnobserved climate variability and changes. It also focuses on the e_ect of greenhouse gases, the carbonrncycle and atmospheric carbon dioxide, aerosols, their direct and indirect climatic e_ects in the middlernand lower atmosphere.