Mass industrialization across the U.S. was made possible by burning fossil fuels.  This reliance on dirty energy has played a lasting role across the country.  Burning fossil fuels releases large amounts of Co2 into the atmosphere, creating the industrial pollution that chokes cities today.  The Co2 in the atmosphere has been rising with the growing number of products and processes that rely on them.  Co2 is a major green house gas and the Earth needs it to survive, but it’s also a main contributor to global warming.  Scientists use glaciers to measure the levels of Co2 in the atmosphere dating back to over 800,000 years ago.  Co2 levels haven’t been this high in 400,00 years.  The main contributors to the increased levels of Co2 are deforestation and burning fossil fuels.  The Co2 in the atmosphere increases about 2 parts per million a year.