Global warming has been a progression since the mid-20th century. We used to think that the sun was one of the main reasons for global warming, but we have been taking pictures of the sun since 1978 so that can’t be the case. Humans are the main cause of global warming. We have increased the “greenhouse effect” — warming that results when the atmosphere traps heat radiating from Earth toward space”(climate.nasa.gov). Another problem is that we are slowly destroying the ozone layer which blocks a large percentage of the sun light that is let into our atmosphere. In turn we are allowing more UV light to enter our atmosphere which can have very negative side effects on not only plants and animals but human life as well. There are many different greenhouse gases like water vapor, carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. Humans emit carbon dioxide every single day just by breathing. However, the main source of carbon emissions comes from all the coal, fossil fuels, and oils we burn on a daily basis. We also cut down lots of trees every year and those are essential to lowering the amount of carbon dioxide in the air since trees and plants use carbon dioxide for photosynthesis which allows them to grow and survive. The most important feedback mechanism to the greenhouse effect is water vapor. Regarding methane it is a “hydrocarbon gas produced both through natural sources and human activities, including the decomposition of wastes in landfills, agriculture, and especially rice cultivation, as well as ruminant digestion and manure management associated with domestic livestock”. Nitrous Oxide is a very strong greenhouse gas, it is used in many different things, but it is mainly used in things like fertilizers that farmers use for their crops or in biomass burnings.